细胞科学
Cell Science
（ 8.1-2-3）
蔡国平
§ 8 C y t o p las m ic m e m b r an e s y s t e m s,
C y t o p l a s m i c Me m b r a n e S y s t e m o r C y t o m e m b r a n e s
I n t e r n a l Me m b r a n e o r E n d o m e m b r a n e S y s t e m ( E M S )
i n c l u d e s, n u c l e a r e n v e l o p e s,e n d o p l a s m i c r e t i c u l u m
( E R ),G o l g i c o m p l e x ( G C ),l y s o s o m e s a n d a v a r i e t y o f
v e s i c l e s o r v a c u o l e s, A l t h o u g h e a c h o f t h e s e
m e m b r a n o u s o r g a n e l l e s h a s i t s o w n d i s t i n c t s t r u c t u r e
a n d f u n c t i o n,t a k e n t o g a t h e r t h e y f o r m a n
e n d o m e m b r a n e s y s t e m i n w h i c h t h e i n d i v i d u a l
c o m p o n e n t s f u n c t i o n a s p a r t o f a c o o r d i n a t e d u n i t,
S e v e r a l o t h e r m e m b r a n o u s o r g a n e l l e s i n
c y t o p l a s m — m i t o c h a n d r i a,p e r o x i s o m e s,a n d
c h l o r o p l a s t s — a r e n o t p a r t o f t h i s i n t e r c o n n e c t e d
s y s t e m,
―!
!!―
8, 1, T h e d y n a m i c n a t u r e o f t h e e n d o m e m b r a n e
s y s t e m
A d y n a m i c,i n t e g r a t e d n e t w o r k i n w h i c h m a t e r i a l s
a r e s h u t t l e d b a c k a n d f o r t h f r o m o n e p a r t ( t h e m e m b r a n e
o f d o n o r o r g a n e l l e s ) o f t h e c e l l t o a n o t h e r ( t h e
m e m b r a n e o f a c c e p t o r c o m p a r t m e n t ) b y t r a n s p o r t
v e s i c l e s, R e p e a t e d c y c l e o f b u d d i n g a n d f u s i o n o f
t r a n s p o r t v e s i c l e s m o v e m a t e r i a l s a l o n g p a t h w a y s a n d
t r a c k s f o r m e d b y c y t o s k e l e t o n t h r o u g h t h e c e l l,
Sever al distinct pathway s f or tr ans por t of m aterials
thr ough the endom e m br ane s y s te m,
(1 ) Bios y nt het ic pathway, along this pathway,
m aterials are s y nthesize d in E R or GC,m odi f ied and
incor por ated into the E R,GC,ly s oso m es and a variety of
vacuoles dur ing pas s age and tr ans por t f ro m E R to the GC,
and to vario us des tination or ganelles (p las m a m e m br ane,
and or ganelles o f E MS etc.).
(2 ) Secr etory pathwa y, m aterials s y nthesi zed in E R or
GC are des tined to be dis char ged to extracellular s pace
f ro m the c ell (S ecretion) –b y two t y pes,
Constitutive s ec r etion to f or m both E CM and the pla s m a
m e m br ane its el f in a conti nual batch m ann er for m o s t cells,
Regulated s ec r etion, f ir s t s tor ed in s e cretor y gr anules,in
the perip heral area and then discha r ged hor m on es,dige s tive
enzy m e s and neur otr ans m itter s etc,only in response to an
appr opr iate s ti m ulus.
* Lip id s,ca rb oh ydrates and th e m os t pr ot ein s
sy nt hesized in th e cell are all tran sp or te d th ro ugh th e cell
alon g th e a bo ve two path ways,
(3 ) Endo c yt ic path way, by th is path way,m at erials m ov e
fr om th e su rf ac e of th e ce ll to co m par tments,su ch as
end os ome s and lys os ome s etc,within the cytop lasm,
Like t o tru cks tran sp or t,it requ ire defi ned traf fic
pattern s ( path ways and ve hi cles) and is spec ifi ca lly
tar geted usi ng specifi c addr esses or so rti ng sig nals,
8.2 a few ap pro ach es to stu dy of endo membran es
* Autoradiography and * The use of GFP
Palade& Ja m i eson,in the aut o radiog raph ic experi m e nt o f
pancre atic t iss ue,using this app roach,it w as p roved that ER is
the site of synth es is of se c retory pro teins an d then
―pulse - ch as e‖ experi m e nt first defin ed the biosy n thetic
(secreto ry) pathw ay an d tied a nu m b er o f se e m ingly se parat e
m em branous com partm ents int o an integrated func tional un it,
* Bio chem ical a nalysis of subcellular fra ctions
Vesicles are isol ated fro m endo m e m b ranes b y ce ll
fractionatio n and th e n their c o m p osit ion and fu n ctional
prep erties ca n b e d et ermin ed by bioch e m ic al an alysis and
i m m un o - electro m i crosc opy,Fo r e xa m ple,en zy m ati c a ct iviti es
and t he c ap ac ities of tr ansportin g newly synth esized p rote ins o f
the m i croso m e s and th e role o f G olgi co m ple x in the ste pwise
assem bly of com plex car bohydrates,
* The use of gene tic m utants i n stu dy of EMS
A secr etion st udy in yeast using tem pera ture - sensiti ve m utants,
8.3 S truct ues a nd funcion s of the ma jor orga nell es of EMS
8.3,1 The endo pla smic re ticul um (ER)
1,Outl ine
E arly it is ca lled ergastop las ma,it was sh own in pan creatic
ce lls as b as ephilic and rela t ed to pr otein synt he sis dep endi ng on
physiologic al condition, 1952,K Porter obs ervate its n etwork
ultrastru ctur e on in vitro fibro blasts,and refered a s th e
endoplasm ic re ticum (ER),
1) Structure and com positi on
It comp rises a va ry compl ex syste m of thin er m e m br anes (5 - 6
n m ) that enclose a sp a ce or lu m e n or Cister n al spa ce,with a
dyna m i c c h anged - sh ape with phys iolog ic st ate:,fl attened sac s,
vesicles a nd tub ules ( ? 40 - 70 nm ) with branchs
It is div ided into t wo b road ca te gro ries or p arts,Rough
endopl as m i c r eticulu m(RER) atta c hed riboso m e s and a s m oot h
endopl as m i c reti culu m(SER) with out riboso m e s,the fo r m er is
typically e xtensive fla ttened s ac s stacks,th e later is ty pically
tubul es and for m interconnec ting s ystem,
I ts m embr ane co m pos ition, highe r am ount of protein s,less
ch ole s terol tha n pla s ma me mbran e,23 PL s pe r protein,
Eg, for R at liver ce ll,Protein ~ 60-70%,PL ~30-40% ( PC
55%,PE 20-25%,PS 5 -10%,PI 5 -10% an d Sph 4-7%,
In ER,the re are 30-40 en z y me s,am ong th em,M arke r
en z y me s, are c y toc hrome p 450,gluc os e-6-pho s ph ata s e,
内质网膜 上特异的 Ca 2+ － A T P a s e 能把胞内游离 Ca 2+ 泵入内质网腔内，同时又存在
IP 3 受体和 R y a n o d i n e 受体钙通道，在 IP 3 或 R y a n o d i n e 作用下，相应的钙通道被打
开,C a 2+ 释放到胞浆。
I n m any cas es wher e both SE R and RER are f ound
togat her,diff eren t ty pes of cell s contai n m a r k edly diff eren t
a m ount s o f either SE R or RER,dependi ng on the cell
activi ties,For exa mple,
R ER, The pan cre as,s alivar y gland s and unmatural egg c ells
or retinal rod ce lls,e xtens ivel y s y nthe s izing membran es,s e cret
a large amoun ts of proteins,these c ells h ave exte ns ive regions
of R ER.
SE R, In many t y pes of c ells,s u ch a s tho s e found in s k ele tal
mus cle,the tubule s of th e kidne y or s t eroid-pr oduc ing
end oc ri ne glands ( s uch as tes ticular mes en ch y mic c ells or
corpus luteum ce lls ) and th e c ells ( as hep atoc y t es,that are
ac tive in lipi d metab olism ),there is an ext ens ive netw ork of
SE R tubules with a grea tl y reduc ed R ER cis ternae, The
hete rogene ous nature of th e SE R,i.e.,its s pec if ic enzy mic
con tent,v aries con s iderabl y fr om ce ll to ce ll,eve n though its
app ea ranc e ma y be fair l y s imi lar.
2) The F unct ion of ER
ER f ir s t m ake s the c ell an app roach to s epa rate new ly
s y nthe s ize d cy tos olic proteins f ro m the non-cy tos olic
m ate ri als, B ut m ore i m portantly,ER play s a ce ntral role
in s y nthe s is of m ac ro m olec ules u s ed to build organe lles,
includ ing proteins,lipid,a nd c o m ple c arbohy drates etc,.
T he fu nction s of the RE R are simi lar among dif fer ent
ty pe s of ce ll s,the y includ e th e s y nth es is of pr oteins to be
se creted,l y so somal pr oteins,int egral memb rane pr oteins,and
memb rane li pids,In the RE R lum en,the pr oteins fo ld and
oli gom erize,disulf fi de bond s are fo rm ed,th e T he a ddit ion of
suga rs (N- li nked oli go sa cc h arid es gl ycos y lati on) to
as paragine residue s of pr oteins begin s in th e RE R,and
additi on of glycol ipi d anchors (g l y cos y lpho spha ti d y li nositol,
GP I) to s ome pla sma m embr ane pr oteins,
The funct ions of S ER varies f r o m cell to cell,inc lude,
T he s y nthe s i s of fatt y ac ids,pho s pholipid s,ch ole s terol
an d ce ramide oc cu rs in SE R an d the s y nthe s is of s teroid
hormone s in the en doc rine ce lls of the gona d an d ad rena l
co rtex.
De toxifica tion in the liv er of a wide v arie ty of or g an ic
co mpoun ds,s uc h as ba rbiturate s,an d eth an ol, It i s c arried
out by a s ys tem of ox y ge n-trans ferring en z y mes
( oxy ge na s es ),inc luding c ytoc hrome p450 s, T h es e en z y mes
are ab le to oxidiz e thous an d s of dif feren t h y dropho bic
molec ule s an d co nv ert the m to more hydrop hilic b y
hy drox y lation,s ulfury lation or urona tory l ation,more rea dil y
ex cre ted de rivative s, T he ef fe cts are not alw a ys po s itive,For
ex amp le,the ha rmle s s be nz o [ ? ] py rene i s co nv erte d into a
pote nt ca rcinog en by the ox y ge na s e s of SE R,
Glucose is r eleased into the bloo dstream fr o m glucose
6 - phosph a te in the liver ce lls by glucose 6 - pho s phatase,
The glucose 6 - pho s phate is converted fr om glucose 1 -
pho s phate that is rel ea s ed fr o m l ar ge re serves of glycog en
granu les by phosphoryl ase on t he outs ide o f SER
m em branes,w hen the nee d for c hem ica l e ner gy arise,
Seques tration and regulated release of calciu m ions
bou n d to calciu m - bind i ng p rot eins within the ciste rnal
space,There ar e a p ar ticular SE R s arc opla sm i c r eticulu m in
the skele tal m u scle c ells,
内质网膜上特异的 Ca
2+
－ A TPase 能把胞内游离 Ca
2+
泵入内质网腔内，同时又存在 IP
3
受体和 R y anodine 受体钙通道，在 IP
3
或 R y anodine 作用下，相应的钙通道被打开,Ca
2+
释放到胞浆。
8.3,2 Gol gi complex (a pp ara tu s)
1,Outl in e
18 98,Camill o G ol gi (Italian,Nob el Pr ize in
19 06) fo und a dark stain ed Saccat e Ne twor k
Sy stem th at w as as Golg i ap paratu s or Golg i
Co m pl ex (GC) n ea r th e cell nu cle us in nerv e
tis su e so aked f or sever al d ays in an
os m iu m - co nt ainin g stain, But it wa sn ’t un til th e
GC wa s cl ea rly id entif ied by ele ctro n m ic ro scopy
and part ic ul arly fr ee ze - etc hi ng tec hn iq ue in many
di ff erent ce lls th at its exis t ence wa s veri fied
bey on d r ea so nab le do ub t,
1) Structure o f GC
The GC co ns is ts of f latte ne d,dis klike,
m e m brano us ci s terna e (0.5-1.0 ? m ) with dila ted
rim s an d a s s oc iate d v es icles an d tubu le,ap pe aring
a ch arac teris tic m orpholo gy, Few er tha n eig ht
Go lgi cis terna e are arrange d in an orderly cu rved
s ha llow bow l-sta ck with the cis f ac e ( f or m ing f ac e)
clo s ed to the ER an d the opp os ite t r ans face
( m atu ring f ac e),An indiv idua l ce ll m ay co nta in
f ro m f ew to s ev eral thou s an d s ta ck s pe r ce ll,
de pe ndin g on the ce ll ty pe s, Ve s icle s bud f ro m a
pe ripheral tu bula r dom ain o f c is terna e.
The G C is di vi ded in to th e s everal co m p art me nt s
po laris ed str uctu rally and bi o che m i cally alon g an
axis f ro m the cis face to th e tra ns face,
cis Golg i networ k ( CGN 5 - 6n m ),in tercon nected
networ k o f tu bu les,a sor tin g selectively state
cis cistern ae
cistern ae m eddi al c ist ernae
stack tra ns cistern ae
tra ns Golg i networ k (TGN7.5 - 10 nm ),a n etwo rk of
tu bu les and v esicles,a n assi gn ation state,
A se t of pr ocess ing pla nts tha t pa ss
from ci s to tran s ciste rn ae,cargo ar e
modi fied se q uenti al ly in spec ific way s,
e.g.p rotein - trim ming by prot eoly t ic
en z ym es,hy drox yl at io n of ly sine and
prol ine r es idu es of colla gen,
gl yco syla tio n by a se ries of stepwise
enz yma ti reactio ns,
Ther e a re reg io n al b io chemi cal d if fer ences acr o ss th e
cist ern ae stack,
cis cist ern ae,red u ced o smiu m tetr o x id e
m edi al cist ern ae,Nicot in am id e aden in e din u cleot id e
p h o s p h a t a s e ( N A D P a s e ),
M a n n o s i d a s e I I,
tr a n s cist ern ae, Thiaminep y ro p h o sp h atase ( TP P ase),
N u c l e o s i d e d i p h o s p h a t a s e ( e, g, U D P a s e ),
Cy tid in e m o n o p h o sp h atase ( CMP ase),
L y s o s o m a l e n z y m e s ( t r a n s f a c e ),
The re g io n al b io che m i cal d if fer en tiat io n acr o ss th e
cist ern ae st ack t akes th e res p o n si b ility for th e st epwi se
p ro cedu es in carg o - pr o cess,
Mark er,Redu ced o smiu m tetr o x id e,
T h i a m i n e p y r o p h o s p h a t a s e ( T P P a s e ),
N u c l e o s i d e d i p h o s p h a t a s e ( e, g, U D P a s e ),
T he GC looks like to be a tr ans itional organelle
betwee n the E R and plas m a m e m brane,undergoing a
progr es s ive dif f erentiatione:
T he dif f erence o f thickness f ro m ci s f ac e to tr ans
f ace m e m branes in the cis ternae s tack is s i m ilar to the
one betwee n the E R (5- 6n m ) and plas m a m e m brane
(7,5-10nm ).
T he prot ein and lipid com po s ition of the G C tends
to to be inter m ediate betwee n that of the E R and
plas m a m e m brane,in co m p arison to E R,the GC have
an elevate d choles terol and s phingom y elin level and a
lowered uns aturated f atty acids,being m ore like the
plas m a m e m brane.
3,The fo rma tio n of the GC - th e rela tio nship of ER
an d GCs,and vesicula r trans po rt w ith in t he GC,
The G Cs lo cate d near th e nu cleus and us ually are
asso ciate d to ER,Th e vesicl es bu dd ed fr om th e ap ical
edges of RE R (h ave been devo id of rib osom es,
th erefo re a lso cons id ered as S ER ) fo r 10 - 20 m in,th en
m ov e and rea ch th e GC,fin all y fo rm th e no vel part s of
cis (f or m i ng ) face o f GC by f us io n of the vesicl es,su ch
as in th e pancr eas e,Thes e vesicles ( coated wi th a
br ist l y lay er of appl i ed pr ot ein s in so m e ca s es) c an be
th ou ght of as a ty pe of tran sit io nal el ements betw een
th e two or ganelles, I n so me cells,th ere i s evid ence of
di rect con tin ui ties be tw ee n th e ca vi ties of th e ER and
th os e of th e G C alo ng th e m i crot ub ul es us ually an d its
asso ciation with m ot or pr ot ein s (dyn ein,ki nesin,
m yo sin ) even sp ec tri n,
Th e qu es tio n is how the m ov ement of carg o thr ough the
GC is carried ou t,There are two contr astin g vi ew s,
* Up un til the m id - 19 80 s,maturatio n m o del w as
generally acepted — each cis cistern a ―matur es‖ int o a
tra ns cistern a changin g in itself co m po sit ion or ca rgo as it
pr ogress ed fr om the cis to tra ns end of the sta ck, E.g,
algal c ells secret the external scale s,
* An alt ernate m o del,stabl e entiti es m od el pr op os ed
that the ci stern ae st ack re main in place as a stabl e en tit ies
held tog ather by a p r otein s ca ff old, The Carg os on ly m ov e
thr ough the G C by bu dd ing - fus ion cycle s of vesicles fr om
on e ciste rn a membr ane to a neigh bo ring cistern a
mem br ane so on along t he stack,ca rg o is m od ifi ed as
vesicles p ro gr essed,Ja mes Ro thma n’ s vesicle tr an sp or t
experim ent us ing a ce ll - fr ee sys tem,
Whic hev er,the GC is a dy na m ic and ordered
organe lle,On one han d,the GC is bein g it s elf tr ans itory
in natu re,i.e.,the m ate ri als o f whic h they are m ade are
con tinually ar ri ving and dep arting,althou gh the organe l
itse lf pers i s ts, For the f or m ation of G C s tac k,thi s is a
proce s s,in that m e m brane s are gradua lly bein g m odif ie d
f ro m an ER ty pe to one with cha racteris tics o f the
plasm a m e m brane, On the ano ther han d,it is als o
i m portant to kee p the s table and regiona l dif fer entia tion
of the GC s tac k,and to preve nt itse lf s tr uctu ral and
f unc tional co m pone nts f ro m di ffu s iing or dis patc hing
into othe r organe lles, How to do it? At the lea s t,the
protein loca ting topolog ica lly o r s ele ctive ly s orting and
the m e m branous ve s icle tr ans port play a k ey role.
4,T he functions of Golgi complex
T he T he GC functions as a proc es s ing factor y in which
newly s y nthe s ize d prot eins and lipi ds (i ncluding the
membr ane components and ca rgo) fr om the E R are rece ived
fi rst and are fur ther processe d and modi fi ed before the y
moves on to their target des tination, A s the y move,the gl y
cosy lation of prot eins and lipi ds, Sugars are add ed b y
gly co s y ltr ans feras es loc ate d in particular Golgi cis ternae,N-
linked oligosa cc h arides are fur ther gl y co s y lated,O-l inked
oligosa cc haride s are produced,and GAG cha in s are adde d to
core prot eins to for m prot eoglyc ans, Amino ac ids o r the
s ugars modi fi ed,s uc h a s s ulf ation of s ug ars of prot eoglyc ans
and of s ele cte d t y rosines on the prot eins, And port ions of the
peptides ma y be removed to make it a ctivate d,
Th e G C part icipate s in all t hre e m aj or m ac r o m olec ul ar pathw ays:
bi osyn t het ic path w ay,se c r e t o r y pathw ay- c ons t itutive se c r e t ion and
r e gul at e d sec r e t ion,e nd oc yt ic pat hw ay,bu t it plays a key r ole
T he GC is als o the s ite of s y nthes is of the co m plex
poly s acc harides,which m ak es up the m atrix of the plant
cell wall,In addition,gly colipids and s phingo m y elin are
s y nthes ized within the GC,
T he GC f unctions a c argo tr ans port s tation and editor-
dispa tch centre,in which m aterials are packe d,
conce ntr ated,tagged,s tepwis e s ort ed and chec k ed up, T he
GC is a tr ans port line by which m aterials enter the s t ack at
the cis f a ce and m ove by ves icle tr ans port toward the
oppos ite or trans face,Once the cargo reach the tr ans
Golgi network (T GN) at the end of the s tack,they are
ready to be s ort ed and targeted f or deliver y to its ultim ate
cellular or extracellular des tination,and f inally export
f ro m the G C,
8.3.3 L yso somes
1,Outlin e
* Lysos om es ar e mem br ane - bo und or ganelles act as
ce ll` s dig estive or ganelles,tha t contain a div erse ar ray
of ac id hy dr olases ca pable of dig esting vir tually ever y
typ e of bio logical macro m olecule i nto
low - m ole cu lar - we igh t pr od u cts that can b e trans po rted
ac ro ss th e lysos om al m em br ane int o th e c yto sol,
* The lyso som e e nzym es a re a cid hy dr olases,pH 4.6
* Morp holog ica l he terog eneity of lys osomes and size
range fro m 20 n m to ov er 1 ? m,
* Their ident ify ing by dem o nst ratin g t he pr es ence of
ac id p ho sph ata se,
用电镜细胞化学技术显示其中含有的酸性磷酸酶，
M：线粒体,L：溶酶体（朴英杰）
323-1
2,Structure an d t y pe s of ly s os o m es
Ly s os om e m em brane co nta ins a proton trans porter (V-
ty pe H
+
-A TPas e),an d two groups of ac idic,high ly
gly co s yla ted inte gral protein s,ca lled Igp-A an d Igp-B,to
protec t the m e m brane f ro m atta ck by the en clo s ed
en zy m e s,an d a s eries o f trans port ca rr iers f or low -
m ole cu lar-weigh t produc ts tha t ca n be trans ported ac ros s
the ly s os o m al m em b rane into the c y tos ol.
The V-t y pe H
+
-ATPas e an d a C l
-
ch an ne l protein in the
ly s os o m e m e m brane,toga the r the y trans port HC l an d
m ain tain the inte rior pH 4.6, All of the ly s os o m al en zy m e s
are ac id hy drol y as es,wh ich provide s dou ble protec tion
ag ain s t unc ontrolle d d ige s tion.
There are m ore tha n 50 di f ferent hy drol y tic en z y m es in
the ly s os o m es, Take n toga the r,ly s os o m al en zy m e s ca n
hy drol y ze vi rtually e ve r y t y pe of bio m ac ro m ole cu les,
L y s o s o m a l e n z y m e s ( s h o w e d i n t a b l e )
Ly soso m es are dy nami c org anelle s that are cap able of
rapid fusion and fi ss ion, Three t yp es of lysosome,
Prim ary lysosome, rough l y sp herica l and do not co ntai n
ob vio us parti culate or m em brane deb ris,
Secondary lysosome, lar ger and i rr egu lar ly heteroge neo us
shape,app e ar to result fr om the fu si on of prim ary lysosomes
with ot her m em brano us org a nelles,con tai n partic ulates and
m em branes in the pro ces s of being di geste d,Th e low - MW
deg rade d precursors are sm all enough to pe netrat e the
lysosomal m em brane th roug h the channels, Accordin g t o
their res ou rce,ther e ar e t wo cl ass es of sec on dary lysoso m e,
Ph a go l ysos ome are derived fr om ph a go c yto s is rou te in
speci ali zed cel l s,such as m acr op hag es,Kup ff er cellc i n the
liver etc, ph a go c ytic cel ls,tha t take up lar ge partic les,
includ e bacter ia,cel l deb ris,and aged cel ls,in ph ag ocy tic
vauole (phagosomes ),wh ich th en fuse with lysosom es,
res ulting in dig est ion of their ―preys‖,
Au tophag ol ysos ome ar e derived from autop ha gy ro ute in the
m ost ce ll s,by this wa y,the gradu al tur no ver of t he ce ll ’ s ow n
com ponent s is ca rried ou t,fir st th e or ganell es to be scr appe d ar e
encl osed in m embrane derived fro m ER,the re sult ing aut ophag ic
vacuole ( autop hago som e) then fuse s with a lysosom e,
Residu al bodies, a ce rta in am ou nt of undi gest ible m at eria ls
or re si du e s rema in within the lysosome,re sult ing in the
form at ion of the re sid ual bo dies, In som e ca se s,som e residual
bodies m ay ar e disch ar ged by exocyto si s,In the ce lls of
verte brate s,the re si dual bodies,ca ll ed as li po fusci n,or pigme nt
gran ule can not be el im inat ed ou t of the ce ll s,and ac cum ulat e
within the cyto plas m,wh ic h beco m e a m aj or chara ct er is ti c of the
aged proces s,
So m e c ytoso li c pro te ins ar e se le ctively tra nspo rte d into
lysosome s direc tl y or in direc tl y (b y ot her or ga ne ll es ) for
degradati on, So m e of thes e pro te ins contai n ce rta in sig nals o n
thei r s urfac e,c al le d KFE RQ ( L ys.,Ph e.,Gl u.,Ar g,and Gln,),
3,Th e form ation of lysosome and En docytosis
Th e lysoso me s a re for med by t he fusion o f transpo rt vesicles
budded fro m th e T GN with end oso mes,whi ch contain mol ecul es
taken up by endocytosis at t he plasm a m em brane,
Th e en d oso me s ar e the vesi cles,whic h ar e matur ed gr a duall
fro m e arly endoso mes into late en doso me s,a nd do not play the
digesting r ole,M ate ri als f ro m o utside th e cell is tak e n up in
clathri n - c oa ted end ocyt ic vesicl es,which bu d fro m the plas ma
me mbrane and th en fu se with e arl y end oso mes,T h e me mbran e
co mponents ar e r ecycl ed to th e p lasa me mbrane and th e early
endoso mes gradu ally mature into t he lat e en d oso me s,wh ich a re
the pr ecurs ors to lys o so me s,Dur ing end oso me ma t urat ion,its
intern al pH is low erin g to about 5.5,w hich plays a k ey role in
the d elive ry of lys oso mal en zy me t arg eted by M - 6 - p hosp hate t o
the lu me n of endoso me fro m its r eceptor on intern al membran e
of the T G N vesi cles,while the receptor s are re cycl e d to the
Golgi,The late end oso mes then mature into l ysoso me s a s they
acqui re a f ull co mpl e ment o f aci d hyd rolas es,and dig est th e
m olecules taken up by endocytosis originall y,
So th e fo rmatio n of ly soso m es r epresent s an
in tersectio n betwe en th e se cretor y path way and
endo cyto sis path way,th ro ug h th e fo rmer,ly so so mal
pr ot eins ar e pr ecesse d,th ro ugh th e lat er,extr acellu lar
m ol ec ul es are take n up and endo so m es gr aduall y
m atur e,
Fo r so me ty pes of ce ll s,ly so some s fo r m i n
GER L or TGN,(?)
* L ys os om al enzy mes are s electi vely so rt in g,m os t
ly so somal hy drol as e are s or ting by addr essi ng
manno se - 6 - phos ph a te,M - 6 - P and its re cep to r, T here
are ot her path ways,acid ph os ph atase (b y re cy clin g),
and gl ycocerebr os id ase etc,sp ec if ic ly so soma l
m em br ane pro tein (m em br ane flo w),
* The mem br anes o f ly so so m es and endo cyti c v esic les
cont ain so m e sign als to facilitate th eir sp ec if ic fus io n,
动物细胞溶酶体系统示意图
P720
4,Functions of l y s o s omes
1) intr ac ellula r dige s tion
(1) he teropha gy,
In ma ny protists,l y s o s omes dige s t food matterthat i s
inges ted b y pha goc yto s is,W he rea s in mammals an d other
an imals,lys os ome s pl a y a ke y role in munologica l de fense.
(2) Autopha gy, ha ve a gre at va riet y of de s tructive ac tiviti es
* impor tant s ca ve nge r s of the bod y,for individual protein or
whole organe lles,
* organe lles rene w,
* tiss ue s reorgani s ation ( the de s truction of ECM of bone an d
ca rti lage during n ormal turnove r or remod eling of the s tructure.
The trans for mation of e r y throblas t into the mature red blood
ce ll,During m eta morphor s is in an amphibia n or the
s cu lpturi ng of toe an d fingers in a mammalian and av i an limb.)
* nutrient co mpens a tion b y it s elf ce llular au tol y s is ( e, g,i n
s tarving ce lls)
2) T urnover of m acro m olecule by r ece ptor -m e diated
pinocy tosis ( including se lective f us ion o f pinoso m es
with ly s os o m es ) involving in the s o m e s ecretion and
exocy tosis of the cell,not being subje ct to des tr ucture:
the prot eins of blood seru m
thy rog lobin- th y rox ine
insulin
antigens opsonic r eac tion in t he m acrophage s,
3) T he acros o m al reaction of the s per m dur ing f ertil ization
383
324-2
324-1
5,Pla nt c e ll v a c uo le s
A te m po rary s to reh ou s e of nu trien t c o m po n e nt s
or to xi c c o m po un ds,
To m a in ta in tu rgo r pre s s ure -- th e to no pl a s t,
Intra c e llu la r di ge s tio n lik e th e ly s os om e s o f a n
a ni m a l c e ll,a c id e hydrola s e s,
H
+
-ATP a s e -- - pH a dj us t
In s o m e c e ll s such as th e sto r age p ar ench y m a of
dev elo pi ng s e eds,up to 50 % of
s y n t h e s i z e d n e w l y p r o t e i n s
a r e t a r g e t e d t o t h e v a c u o l e s f o r s t o r a g e
6,Disor ders inv ol vi ng in ly so so m e fun ction s
1) resu ltin g f ro m defects in ly so so m al fun ction
(1) Lyso so m s destr uctu re,sil ic os is,asbe sto sis,and
rh eumatoid arth rit is resu lts,in part,fr om th e rele ase
of lys os oma l enzym es into the extracellular s pace,
T o develo p th e dr ug s pr ot ec tin g lo sos omes,e.g,
cort iso ne,Al - reagents etc,
(2) Genetic diseases,
―S to rage di seases‖ la ckin g on e or m ul tip le of
ly so soma l enzy me s,resu lt in th e bu ild up with in
tis su es of part icular macro m o lecules,w hi ch are a
su bs t rate of ly so so ma l en zymes no rmally,Fo r
exa m pl e,Gauch er’s di seas e i n Jewish at 1/ 25 00,
th at is ca us ed by deficie ncy of gl ucocere br os i dase,a
ly so so m al e nzyme,
I - ce ll dis ea se (M 6P)
Pompe dise as e ( ? - glucosidas e,glycogen)
T ay - Sachas dides e ( ? - N - hexo sa m inidas e A,GM
2,
i n brain)
2) T he a berrant interaction betwee n lys oso m e and
ph agocyti c be cteria e,g,Mycoba cte riu m t ub er cl osi s
inh ibi t the fu sio n of lys oso m e and ph a g ocyti c ves icles,Or
los s of lysoso m al en zy m e ac ti vit y,e,g,Coxie lla b u rnetii (Q
fever) inh ibi t the aci dization of ph agosome s,res ult ing i n
los s of lysoso m al en zy m e act ivi ty, Some vir us’ s envelop
pr otein s are eli m ina ted int o cy tos ol fro m ph agoso me s b y
the acidi c envir onm ent of ph agosome s,faci lit ate its
repro du ction,
Cell Science
（ 8.1-2-3）
蔡国平
§ 8 C y t o p las m ic m e m b r an e s y s t e m s,
C y t o p l a s m i c Me m b r a n e S y s t e m o r C y t o m e m b r a n e s
I n t e r n a l Me m b r a n e o r E n d o m e m b r a n e S y s t e m ( E M S )
i n c l u d e s, n u c l e a r e n v e l o p e s,e n d o p l a s m i c r e t i c u l u m
( E R ),G o l g i c o m p l e x ( G C ),l y s o s o m e s a n d a v a r i e t y o f
v e s i c l e s o r v a c u o l e s, A l t h o u g h e a c h o f t h e s e
m e m b r a n o u s o r g a n e l l e s h a s i t s o w n d i s t i n c t s t r u c t u r e
a n d f u n c t i o n,t a k e n t o g a t h e r t h e y f o r m a n
e n d o m e m b r a n e s y s t e m i n w h i c h t h e i n d i v i d u a l
c o m p o n e n t s f u n c t i o n a s p a r t o f a c o o r d i n a t e d u n i t,
S e v e r a l o t h e r m e m b r a n o u s o r g a n e l l e s i n
c y t o p l a s m — m i t o c h a n d r i a,p e r o x i s o m e s,a n d
c h l o r o p l a s t s — a r e n o t p a r t o f t h i s i n t e r c o n n e c t e d
s y s t e m,
―!
!!―
8, 1, T h e d y n a m i c n a t u r e o f t h e e n d o m e m b r a n e
s y s t e m
A d y n a m i c,i n t e g r a t e d n e t w o r k i n w h i c h m a t e r i a l s
a r e s h u t t l e d b a c k a n d f o r t h f r o m o n e p a r t ( t h e m e m b r a n e
o f d o n o r o r g a n e l l e s ) o f t h e c e l l t o a n o t h e r ( t h e
m e m b r a n e o f a c c e p t o r c o m p a r t m e n t ) b y t r a n s p o r t
v e s i c l e s, R e p e a t e d c y c l e o f b u d d i n g a n d f u s i o n o f
t r a n s p o r t v e s i c l e s m o v e m a t e r i a l s a l o n g p a t h w a y s a n d
t r a c k s f o r m e d b y c y t o s k e l e t o n t h r o u g h t h e c e l l,
Sever al distinct pathway s f or tr ans por t of m aterials
thr ough the endom e m br ane s y s te m,
(1 ) Bios y nt het ic pathway, along this pathway,
m aterials are s y nthesize d in E R or GC,m odi f ied and
incor por ated into the E R,GC,ly s oso m es and a variety of
vacuoles dur ing pas s age and tr ans por t f ro m E R to the GC,
and to vario us des tination or ganelles (p las m a m e m br ane,
and or ganelles o f E MS etc.).
(2 ) Secr etory pathwa y, m aterials s y nthesi zed in E R or
GC are des tined to be dis char ged to extracellular s pace
f ro m the c ell (S ecretion) –b y two t y pes,
Constitutive s ec r etion to f or m both E CM and the pla s m a
m e m br ane its el f in a conti nual batch m ann er for m o s t cells,
Regulated s ec r etion, f ir s t s tor ed in s e cretor y gr anules,in
the perip heral area and then discha r ged hor m on es,dige s tive
enzy m e s and neur otr ans m itter s etc,only in response to an
appr opr iate s ti m ulus.
* Lip id s,ca rb oh ydrates and th e m os t pr ot ein s
sy nt hesized in th e cell are all tran sp or te d th ro ugh th e cell
alon g th e a bo ve two path ways,
(3 ) Endo c yt ic path way, by th is path way,m at erials m ov e
fr om th e su rf ac e of th e ce ll to co m par tments,su ch as
end os ome s and lys os ome s etc,within the cytop lasm,
Like t o tru cks tran sp or t,it requ ire defi ned traf fic
pattern s ( path ways and ve hi cles) and is spec ifi ca lly
tar geted usi ng specifi c addr esses or so rti ng sig nals,
8.2 a few ap pro ach es to stu dy of endo membran es
* Autoradiography and * The use of GFP
Palade& Ja m i eson,in the aut o radiog raph ic experi m e nt o f
pancre atic t iss ue,using this app roach,it w as p roved that ER is
the site of synth es is of se c retory pro teins an d then
―pulse - ch as e‖ experi m e nt first defin ed the biosy n thetic
(secreto ry) pathw ay an d tied a nu m b er o f se e m ingly se parat e
m em branous com partm ents int o an integrated func tional un it,
* Bio chem ical a nalysis of subcellular fra ctions
Vesicles are isol ated fro m endo m e m b ranes b y ce ll
fractionatio n and th e n their c o m p osit ion and fu n ctional
prep erties ca n b e d et ermin ed by bioch e m ic al an alysis and
i m m un o - electro m i crosc opy,Fo r e xa m ple,en zy m ati c a ct iviti es
and t he c ap ac ities of tr ansportin g newly synth esized p rote ins o f
the m i croso m e s and th e role o f G olgi co m ple x in the ste pwise
assem bly of com plex car bohydrates,
* The use of gene tic m utants i n stu dy of EMS
A secr etion st udy in yeast using tem pera ture - sensiti ve m utants,
8.3 S truct ues a nd funcion s of the ma jor orga nell es of EMS
8.3,1 The endo pla smic re ticul um (ER)
1,Outl ine
E arly it is ca lled ergastop las ma,it was sh own in pan creatic
ce lls as b as ephilic and rela t ed to pr otein synt he sis dep endi ng on
physiologic al condition, 1952,K Porter obs ervate its n etwork
ultrastru ctur e on in vitro fibro blasts,and refered a s th e
endoplasm ic re ticum (ER),
1) Structure and com positi on
It comp rises a va ry compl ex syste m of thin er m e m br anes (5 - 6
n m ) that enclose a sp a ce or lu m e n or Cister n al spa ce,with a
dyna m i c c h anged - sh ape with phys iolog ic st ate:,fl attened sac s,
vesicles a nd tub ules ( ? 40 - 70 nm ) with branchs
It is div ided into t wo b road ca te gro ries or p arts,Rough
endopl as m i c r eticulu m(RER) atta c hed riboso m e s and a s m oot h
endopl as m i c reti culu m(SER) with out riboso m e s,the fo r m er is
typically e xtensive fla ttened s ac s stacks,th e later is ty pically
tubul es and for m interconnec ting s ystem,
I ts m embr ane co m pos ition, highe r am ount of protein s,less
ch ole s terol tha n pla s ma me mbran e,23 PL s pe r protein,
Eg, for R at liver ce ll,Protein ~ 60-70%,PL ~30-40% ( PC
55%,PE 20-25%,PS 5 -10%,PI 5 -10% an d Sph 4-7%,
In ER,the re are 30-40 en z y me s,am ong th em,M arke r
en z y me s, are c y toc hrome p 450,gluc os e-6-pho s ph ata s e,
内质网膜 上特异的 Ca 2+ － A T P a s e 能把胞内游离 Ca 2+ 泵入内质网腔内，同时又存在
IP 3 受体和 R y a n o d i n e 受体钙通道，在 IP 3 或 R y a n o d i n e 作用下，相应的钙通道被打
开,C a 2+ 释放到胞浆。
I n m any cas es wher e both SE R and RER are f ound
togat her,diff eren t ty pes of cell s contai n m a r k edly diff eren t
a m ount s o f either SE R or RER,dependi ng on the cell
activi ties,For exa mple,
R ER, The pan cre as,s alivar y gland s and unmatural egg c ells
or retinal rod ce lls,e xtens ivel y s y nthe s izing membran es,s e cret
a large amoun ts of proteins,these c ells h ave exte ns ive regions
of R ER.
SE R, In many t y pes of c ells,s u ch a s tho s e found in s k ele tal
mus cle,the tubule s of th e kidne y or s t eroid-pr oduc ing
end oc ri ne glands ( s uch as tes ticular mes en ch y mic c ells or
corpus luteum ce lls ) and th e c ells ( as hep atoc y t es,that are
ac tive in lipi d metab olism ),there is an ext ens ive netw ork of
SE R tubules with a grea tl y reduc ed R ER cis ternae, The
hete rogene ous nature of th e SE R,i.e.,its s pec if ic enzy mic
con tent,v aries con s iderabl y fr om ce ll to ce ll,eve n though its
app ea ranc e ma y be fair l y s imi lar.
2) The F unct ion of ER
ER f ir s t m ake s the c ell an app roach to s epa rate new ly
s y nthe s ize d cy tos olic proteins f ro m the non-cy tos olic
m ate ri als, B ut m ore i m portantly,ER play s a ce ntral role
in s y nthe s is of m ac ro m olec ules u s ed to build organe lles,
includ ing proteins,lipid,a nd c o m ple c arbohy drates etc,.
T he fu nction s of the RE R are simi lar among dif fer ent
ty pe s of ce ll s,the y includ e th e s y nth es is of pr oteins to be
se creted,l y so somal pr oteins,int egral memb rane pr oteins,and
memb rane li pids,In the RE R lum en,the pr oteins fo ld and
oli gom erize,disulf fi de bond s are fo rm ed,th e T he a ddit ion of
suga rs (N- li nked oli go sa cc h arid es gl ycos y lati on) to
as paragine residue s of pr oteins begin s in th e RE R,and
additi on of glycol ipi d anchors (g l y cos y lpho spha ti d y li nositol,
GP I) to s ome pla sma m embr ane pr oteins,
The funct ions of S ER varies f r o m cell to cell,inc lude,
T he s y nthe s i s of fatt y ac ids,pho s pholipid s,ch ole s terol
an d ce ramide oc cu rs in SE R an d the s y nthe s is of s teroid
hormone s in the en doc rine ce lls of the gona d an d ad rena l
co rtex.
De toxifica tion in the liv er of a wide v arie ty of or g an ic
co mpoun ds,s uc h as ba rbiturate s,an d eth an ol, It i s c arried
out by a s ys tem of ox y ge n-trans ferring en z y mes
( oxy ge na s es ),inc luding c ytoc hrome p450 s, T h es e en z y mes
are ab le to oxidiz e thous an d s of dif feren t h y dropho bic
molec ule s an d co nv ert the m to more hydrop hilic b y
hy drox y lation,s ulfury lation or urona tory l ation,more rea dil y
ex cre ted de rivative s, T he ef fe cts are not alw a ys po s itive,For
ex amp le,the ha rmle s s be nz o [ ? ] py rene i s co nv erte d into a
pote nt ca rcinog en by the ox y ge na s e s of SE R,
Glucose is r eleased into the bloo dstream fr o m glucose
6 - phosph a te in the liver ce lls by glucose 6 - pho s phatase,
The glucose 6 - pho s phate is converted fr om glucose 1 -
pho s phate that is rel ea s ed fr o m l ar ge re serves of glycog en
granu les by phosphoryl ase on t he outs ide o f SER
m em branes,w hen the nee d for c hem ica l e ner gy arise,
Seques tration and regulated release of calciu m ions
bou n d to calciu m - bind i ng p rot eins within the ciste rnal
space,There ar e a p ar ticular SE R s arc opla sm i c r eticulu m in
the skele tal m u scle c ells,
内质网膜上特异的 Ca
2+
－ A TPase 能把胞内游离 Ca
2+
泵入内质网腔内，同时又存在 IP
3
受体和 R y anodine 受体钙通道，在 IP
3
或 R y anodine 作用下，相应的钙通道被打开,Ca
2+
释放到胞浆。
8.3,2 Gol gi complex (a pp ara tu s)
1,Outl in e
18 98,Camill o G ol gi (Italian,Nob el Pr ize in
19 06) fo und a dark stain ed Saccat e Ne twor k
Sy stem th at w as as Golg i ap paratu s or Golg i
Co m pl ex (GC) n ea r th e cell nu cle us in nerv e
tis su e so aked f or sever al d ays in an
os m iu m - co nt ainin g stain, But it wa sn ’t un til th e
GC wa s cl ea rly id entif ied by ele ctro n m ic ro scopy
and part ic ul arly fr ee ze - etc hi ng tec hn iq ue in many
di ff erent ce lls th at its exis t ence wa s veri fied
bey on d r ea so nab le do ub t,
1) Structure o f GC
The GC co ns is ts of f latte ne d,dis klike,
m e m brano us ci s terna e (0.5-1.0 ? m ) with dila ted
rim s an d a s s oc iate d v es icles an d tubu le,ap pe aring
a ch arac teris tic m orpholo gy, Few er tha n eig ht
Go lgi cis terna e are arrange d in an orderly cu rved
s ha llow bow l-sta ck with the cis f ac e ( f or m ing f ac e)
clo s ed to the ER an d the opp os ite t r ans face
( m atu ring f ac e),An indiv idua l ce ll m ay co nta in
f ro m f ew to s ev eral thou s an d s ta ck s pe r ce ll,
de pe ndin g on the ce ll ty pe s, Ve s icle s bud f ro m a
pe ripheral tu bula r dom ain o f c is terna e.
The G C is di vi ded in to th e s everal co m p art me nt s
po laris ed str uctu rally and bi o che m i cally alon g an
axis f ro m the cis face to th e tra ns face,
cis Golg i networ k ( CGN 5 - 6n m ),in tercon nected
networ k o f tu bu les,a sor tin g selectively state
cis cistern ae
cistern ae m eddi al c ist ernae
stack tra ns cistern ae
tra ns Golg i networ k (TGN7.5 - 10 nm ),a n etwo rk of
tu bu les and v esicles,a n assi gn ation state,
A se t of pr ocess ing pla nts tha t pa ss
from ci s to tran s ciste rn ae,cargo ar e
modi fied se q uenti al ly in spec ific way s,
e.g.p rotein - trim ming by prot eoly t ic
en z ym es,hy drox yl at io n of ly sine and
prol ine r es idu es of colla gen,
gl yco syla tio n by a se ries of stepwise
enz yma ti reactio ns,
Ther e a re reg io n al b io chemi cal d if fer ences acr o ss th e
cist ern ae stack,
cis cist ern ae,red u ced o smiu m tetr o x id e
m edi al cist ern ae,Nicot in am id e aden in e din u cleot id e
p h o s p h a t a s e ( N A D P a s e ),
M a n n o s i d a s e I I,
tr a n s cist ern ae, Thiaminep y ro p h o sp h atase ( TP P ase),
N u c l e o s i d e d i p h o s p h a t a s e ( e, g, U D P a s e ),
Cy tid in e m o n o p h o sp h atase ( CMP ase),
L y s o s o m a l e n z y m e s ( t r a n s f a c e ),
The re g io n al b io che m i cal d if fer en tiat io n acr o ss th e
cist ern ae st ack t akes th e res p o n si b ility for th e st epwi se
p ro cedu es in carg o - pr o cess,
Mark er,Redu ced o smiu m tetr o x id e,
T h i a m i n e p y r o p h o s p h a t a s e ( T P P a s e ),
N u c l e o s i d e d i p h o s p h a t a s e ( e, g, U D P a s e ),
T he GC looks like to be a tr ans itional organelle
betwee n the E R and plas m a m e m brane,undergoing a
progr es s ive dif f erentiatione:
T he dif f erence o f thickness f ro m ci s f ac e to tr ans
f ace m e m branes in the cis ternae s tack is s i m ilar to the
one betwee n the E R (5- 6n m ) and plas m a m e m brane
(7,5-10nm ).
T he prot ein and lipid com po s ition of the G C tends
to to be inter m ediate betwee n that of the E R and
plas m a m e m brane,in co m p arison to E R,the GC have
an elevate d choles terol and s phingom y elin level and a
lowered uns aturated f atty acids,being m ore like the
plas m a m e m brane.
3,The fo rma tio n of the GC - th e rela tio nship of ER
an d GCs,and vesicula r trans po rt w ith in t he GC,
The G Cs lo cate d near th e nu cleus and us ually are
asso ciate d to ER,Th e vesicl es bu dd ed fr om th e ap ical
edges of RE R (h ave been devo id of rib osom es,
th erefo re a lso cons id ered as S ER ) fo r 10 - 20 m in,th en
m ov e and rea ch th e GC,fin all y fo rm th e no vel part s of
cis (f or m i ng ) face o f GC by f us io n of the vesicl es,su ch
as in th e pancr eas e,Thes e vesicles ( coated wi th a
br ist l y lay er of appl i ed pr ot ein s in so m e ca s es) c an be
th ou ght of as a ty pe of tran sit io nal el ements betw een
th e two or ganelles, I n so me cells,th ere i s evid ence of
di rect con tin ui ties be tw ee n th e ca vi ties of th e ER and
th os e of th e G C alo ng th e m i crot ub ul es us ually an d its
asso ciation with m ot or pr ot ein s (dyn ein,ki nesin,
m yo sin ) even sp ec tri n,
Th e qu es tio n is how the m ov ement of carg o thr ough the
GC is carried ou t,There are two contr astin g vi ew s,
* Up un til the m id - 19 80 s,maturatio n m o del w as
generally acepted — each cis cistern a ―matur es‖ int o a
tra ns cistern a changin g in itself co m po sit ion or ca rgo as it
pr ogress ed fr om the cis to tra ns end of the sta ck, E.g,
algal c ells secret the external scale s,
* An alt ernate m o del,stabl e entiti es m od el pr op os ed
that the ci stern ae st ack re main in place as a stabl e en tit ies
held tog ather by a p r otein s ca ff old, The Carg os on ly m ov e
thr ough the G C by bu dd ing - fus ion cycle s of vesicles fr om
on e ciste rn a membr ane to a neigh bo ring cistern a
mem br ane so on along t he stack,ca rg o is m od ifi ed as
vesicles p ro gr essed,Ja mes Ro thma n’ s vesicle tr an sp or t
experim ent us ing a ce ll - fr ee sys tem,
Whic hev er,the GC is a dy na m ic and ordered
organe lle,On one han d,the GC is bein g it s elf tr ans itory
in natu re,i.e.,the m ate ri als o f whic h they are m ade are
con tinually ar ri ving and dep arting,althou gh the organe l
itse lf pers i s ts, For the f or m ation of G C s tac k,thi s is a
proce s s,in that m e m brane s are gradua lly bein g m odif ie d
f ro m an ER ty pe to one with cha racteris tics o f the
plasm a m e m brane, On the ano ther han d,it is als o
i m portant to kee p the s table and regiona l dif fer entia tion
of the GC s tac k,and to preve nt itse lf s tr uctu ral and
f unc tional co m pone nts f ro m di ffu s iing or dis patc hing
into othe r organe lles, How to do it? At the lea s t,the
protein loca ting topolog ica lly o r s ele ctive ly s orting and
the m e m branous ve s icle tr ans port play a k ey role.
4,T he functions of Golgi complex
T he T he GC functions as a proc es s ing factor y in which
newly s y nthe s ize d prot eins and lipi ds (i ncluding the
membr ane components and ca rgo) fr om the E R are rece ived
fi rst and are fur ther processe d and modi fi ed before the y
moves on to their target des tination, A s the y move,the gl y
cosy lation of prot eins and lipi ds, Sugars are add ed b y
gly co s y ltr ans feras es loc ate d in particular Golgi cis ternae,N-
linked oligosa cc h arides are fur ther gl y co s y lated,O-l inked
oligosa cc haride s are produced,and GAG cha in s are adde d to
core prot eins to for m prot eoglyc ans, Amino ac ids o r the
s ugars modi fi ed,s uc h a s s ulf ation of s ug ars of prot eoglyc ans
and of s ele cte d t y rosines on the prot eins, And port ions of the
peptides ma y be removed to make it a ctivate d,
Th e G C part icipate s in all t hre e m aj or m ac r o m olec ul ar pathw ays:
bi osyn t het ic path w ay,se c r e t o r y pathw ay- c ons t itutive se c r e t ion and
r e gul at e d sec r e t ion,e nd oc yt ic pat hw ay,bu t it plays a key r ole
T he GC is als o the s ite of s y nthes is of the co m plex
poly s acc harides,which m ak es up the m atrix of the plant
cell wall,In addition,gly colipids and s phingo m y elin are
s y nthes ized within the GC,
T he GC f unctions a c argo tr ans port s tation and editor-
dispa tch centre,in which m aterials are packe d,
conce ntr ated,tagged,s tepwis e s ort ed and chec k ed up, T he
GC is a tr ans port line by which m aterials enter the s t ack at
the cis f a ce and m ove by ves icle tr ans port toward the
oppos ite or trans face,Once the cargo reach the tr ans
Golgi network (T GN) at the end of the s tack,they are
ready to be s ort ed and targeted f or deliver y to its ultim ate
cellular or extracellular des tination,and f inally export
f ro m the G C,
8.3.3 L yso somes
1,Outlin e
* Lysos om es ar e mem br ane - bo und or ganelles act as
ce ll` s dig estive or ganelles,tha t contain a div erse ar ray
of ac id hy dr olases ca pable of dig esting vir tually ever y
typ e of bio logical macro m olecule i nto
low - m ole cu lar - we igh t pr od u cts that can b e trans po rted
ac ro ss th e lysos om al m em br ane int o th e c yto sol,
* The lyso som e e nzym es a re a cid hy dr olases,pH 4.6
* Morp holog ica l he terog eneity of lys osomes and size
range fro m 20 n m to ov er 1 ? m,
* Their ident ify ing by dem o nst ratin g t he pr es ence of
ac id p ho sph ata se,
用电镜细胞化学技术显示其中含有的酸性磷酸酶，
M：线粒体,L：溶酶体（朴英杰）
323-1
2,Structure an d t y pe s of ly s os o m es
Ly s os om e m em brane co nta ins a proton trans porter (V-
ty pe H
+
-A TPas e),an d two groups of ac idic,high ly
gly co s yla ted inte gral protein s,ca lled Igp-A an d Igp-B,to
protec t the m e m brane f ro m atta ck by the en clo s ed
en zy m e s,an d a s eries o f trans port ca rr iers f or low -
m ole cu lar-weigh t produc ts tha t ca n be trans ported ac ros s
the ly s os o m al m em b rane into the c y tos ol.
The V-t y pe H
+
-ATPas e an d a C l
-
ch an ne l protein in the
ly s os o m e m e m brane,toga the r the y trans port HC l an d
m ain tain the inte rior pH 4.6, All of the ly s os o m al en zy m e s
are ac id hy drol y as es,wh ich provide s dou ble protec tion
ag ain s t unc ontrolle d d ige s tion.
There are m ore tha n 50 di f ferent hy drol y tic en z y m es in
the ly s os o m es, Take n toga the r,ly s os o m al en zy m e s ca n
hy drol y ze vi rtually e ve r y t y pe of bio m ac ro m ole cu les,
L y s o s o m a l e n z y m e s ( s h o w e d i n t a b l e )
Ly soso m es are dy nami c org anelle s that are cap able of
rapid fusion and fi ss ion, Three t yp es of lysosome,
Prim ary lysosome, rough l y sp herica l and do not co ntai n
ob vio us parti culate or m em brane deb ris,
Secondary lysosome, lar ger and i rr egu lar ly heteroge neo us
shape,app e ar to result fr om the fu si on of prim ary lysosomes
with ot her m em brano us org a nelles,con tai n partic ulates and
m em branes in the pro ces s of being di geste d,Th e low - MW
deg rade d precursors are sm all enough to pe netrat e the
lysosomal m em brane th roug h the channels, Accordin g t o
their res ou rce,ther e ar e t wo cl ass es of sec on dary lysoso m e,
Ph a go l ysos ome are derived fr om ph a go c yto s is rou te in
speci ali zed cel l s,such as m acr op hag es,Kup ff er cellc i n the
liver etc, ph a go c ytic cel ls,tha t take up lar ge partic les,
includ e bacter ia,cel l deb ris,and aged cel ls,in ph ag ocy tic
vauole (phagosomes ),wh ich th en fuse with lysosom es,
res ulting in dig est ion of their ―preys‖,
Au tophag ol ysos ome ar e derived from autop ha gy ro ute in the
m ost ce ll s,by this wa y,the gradu al tur no ver of t he ce ll ’ s ow n
com ponent s is ca rried ou t,fir st th e or ganell es to be scr appe d ar e
encl osed in m embrane derived fro m ER,the re sult ing aut ophag ic
vacuole ( autop hago som e) then fuse s with a lysosom e,
Residu al bodies, a ce rta in am ou nt of undi gest ible m at eria ls
or re si du e s rema in within the lysosome,re sult ing in the
form at ion of the re sid ual bo dies, In som e ca se s,som e residual
bodies m ay ar e disch ar ged by exocyto si s,In the ce lls of
verte brate s,the re si dual bodies,ca ll ed as li po fusci n,or pigme nt
gran ule can not be el im inat ed ou t of the ce ll s,and ac cum ulat e
within the cyto plas m,wh ic h beco m e a m aj or chara ct er is ti c of the
aged proces s,
So m e c ytoso li c pro te ins ar e se le ctively tra nspo rte d into
lysosome s direc tl y or in direc tl y (b y ot her or ga ne ll es ) for
degradati on, So m e of thes e pro te ins contai n ce rta in sig nals o n
thei r s urfac e,c al le d KFE RQ ( L ys.,Ph e.,Gl u.,Ar g,and Gln,),
3,Th e form ation of lysosome and En docytosis
Th e lysoso me s a re for med by t he fusion o f transpo rt vesicles
budded fro m th e T GN with end oso mes,whi ch contain mol ecul es
taken up by endocytosis at t he plasm a m em brane,
Th e en d oso me s ar e the vesi cles,whic h ar e matur ed gr a duall
fro m e arly endoso mes into late en doso me s,a nd do not play the
digesting r ole,M ate ri als f ro m o utside th e cell is tak e n up in
clathri n - c oa ted end ocyt ic vesicl es,which bu d fro m the plas ma
me mbrane and th en fu se with e arl y end oso mes,T h e me mbran e
co mponents ar e r ecycl ed to th e p lasa me mbrane and th e early
endoso mes gradu ally mature into t he lat e en d oso me s,wh ich a re
the pr ecurs ors to lys o so me s,Dur ing end oso me ma t urat ion,its
intern al pH is low erin g to about 5.5,w hich plays a k ey role in
the d elive ry of lys oso mal en zy me t arg eted by M - 6 - p hosp hate t o
the lu me n of endoso me fro m its r eceptor on intern al membran e
of the T G N vesi cles,while the receptor s are re cycl e d to the
Golgi,The late end oso mes then mature into l ysoso me s a s they
acqui re a f ull co mpl e ment o f aci d hyd rolas es,and dig est th e
m olecules taken up by endocytosis originall y,
So th e fo rmatio n of ly soso m es r epresent s an
in tersectio n betwe en th e se cretor y path way and
endo cyto sis path way,th ro ug h th e fo rmer,ly so so mal
pr ot eins ar e pr ecesse d,th ro ugh th e lat er,extr acellu lar
m ol ec ul es are take n up and endo so m es gr aduall y
m atur e,
Fo r so me ty pes of ce ll s,ly so some s fo r m i n
GER L or TGN,(?)
* L ys os om al enzy mes are s electi vely so rt in g,m os t
ly so somal hy drol as e are s or ting by addr essi ng
manno se - 6 - phos ph a te,M - 6 - P and its re cep to r, T here
are ot her path ways,acid ph os ph atase (b y re cy clin g),
and gl ycocerebr os id ase etc,sp ec if ic ly so soma l
m em br ane pro tein (m em br ane flo w),
* The mem br anes o f ly so so m es and endo cyti c v esic les
cont ain so m e sign als to facilitate th eir sp ec if ic fus io n,
动物细胞溶酶体系统示意图
P720
4,Functions of l y s o s omes
1) intr ac ellula r dige s tion
(1) he teropha gy,
In ma ny protists,l y s o s omes dige s t food matterthat i s
inges ted b y pha goc yto s is,W he rea s in mammals an d other
an imals,lys os ome s pl a y a ke y role in munologica l de fense.
(2) Autopha gy, ha ve a gre at va riet y of de s tructive ac tiviti es
* impor tant s ca ve nge r s of the bod y,for individual protein or
whole organe lles,
* organe lles rene w,
* tiss ue s reorgani s ation ( the de s truction of ECM of bone an d
ca rti lage during n ormal turnove r or remod eling of the s tructure.
The trans for mation of e r y throblas t into the mature red blood
ce ll,During m eta morphor s is in an amphibia n or the
s cu lpturi ng of toe an d fingers in a mammalian and av i an limb.)
* nutrient co mpens a tion b y it s elf ce llular au tol y s is ( e, g,i n
s tarving ce lls)
2) T urnover of m acro m olecule by r ece ptor -m e diated
pinocy tosis ( including se lective f us ion o f pinoso m es
with ly s os o m es ) involving in the s o m e s ecretion and
exocy tosis of the cell,not being subje ct to des tr ucture:
the prot eins of blood seru m
thy rog lobin- th y rox ine
insulin
antigens opsonic r eac tion in t he m acrophage s,
3) T he acros o m al reaction of the s per m dur ing f ertil ization
383
324-2
324-1
5,Pla nt c e ll v a c uo le s
A te m po rary s to reh ou s e of nu trien t c o m po n e nt s
or to xi c c o m po un ds,
To m a in ta in tu rgo r pre s s ure -- th e to no pl a s t,
Intra c e llu la r di ge s tio n lik e th e ly s os om e s o f a n
a ni m a l c e ll,a c id e hydrola s e s,
H
+
-ATP a s e -- - pH a dj us t
In s o m e c e ll s such as th e sto r age p ar ench y m a of
dev elo pi ng s e eds,up to 50 % of
s y n t h e s i z e d n e w l y p r o t e i n s
a r e t a r g e t e d t o t h e v a c u o l e s f o r s t o r a g e
6,Disor ders inv ol vi ng in ly so so m e fun ction s
1) resu ltin g f ro m defects in ly so so m al fun ction
(1) Lyso so m s destr uctu re,sil ic os is,asbe sto sis,and
rh eumatoid arth rit is resu lts,in part,fr om th e rele ase
of lys os oma l enzym es into the extracellular s pace,
T o develo p th e dr ug s pr ot ec tin g lo sos omes,e.g,
cort iso ne,Al - reagents etc,
(2) Genetic diseases,
―S to rage di seases‖ la ckin g on e or m ul tip le of
ly so soma l enzy me s,resu lt in th e bu ild up with in
tis su es of part icular macro m o lecules,w hi ch are a
su bs t rate of ly so so ma l en zymes no rmally,Fo r
exa m pl e,Gauch er’s di seas e i n Jewish at 1/ 25 00,
th at is ca us ed by deficie ncy of gl ucocere br os i dase,a
ly so so m al e nzyme,
I - ce ll dis ea se (M 6P)
Pompe dise as e ( ? - glucosidas e,glycogen)
T ay - Sachas dides e ( ? - N - hexo sa m inidas e A,GM
2,
i n brain)
2) T he a berrant interaction betwee n lys oso m e and
ph agocyti c be cteria e,g,Mycoba cte riu m t ub er cl osi s
inh ibi t the fu sio n of lys oso m e and ph a g ocyti c ves icles,Or
los s of lysoso m al en zy m e ac ti vit y,e,g,Coxie lla b u rnetii (Q
fever) inh ibi t the aci dization of ph agosome s,res ult ing i n
los s of lysoso m al en zy m e act ivi ty, Some vir us’ s envelop
pr otein s are eli m ina ted int o cy tos ol fro m ph agoso me s b y
the acidi c envir onm ent of ph agosome s,faci lit ate its
repro du ction,
