Exam 3: Ch 14 Secretory Pathway & Vesicle Budding Flashcards Preview

Cellular and Molecular Biology > Exam 3: Ch 14 Secretory Pathway & Vesicle Budding > Flashcards

Flashcards in Exam 3: Ch 14 Secretory Pathway & Vesicle Budding Deck (50):
1

the secretory pathway carries both...

soluble and membrane proteins from the ER to their destination on the cell surface or the lysosome

2

soluble proteins delivered to the lysosome include

lysosomal digestive enzymes like...

proteases, phosphatases, lipases

3

endocytic pathway

used to take up substances from the cell surface and move them into the interior of the cell

ingest nutrients that are too big to be transported (ex. LDL and iron)

remove receptor proteins from the cell surface to down-regulate their activity

4

unifying principle that governs all protein trafficking in secretory and endocytic pathways

transport of membrane and soluble proteins from 1 membrane bound compartment to the next is mediated by transport vesicles

these vesicles collect "cargo" proteins in buds, then deliver them by fusing with the target membrane

5

when transport vesicles bud from one membrane and fuse to the next, does the same face of the membrane remain oriented toward the cytosol?

yes

therefore, the protein being transported retains its original orientation

6

stage 1 of secretory pathway

proteins are translocated to the ER where they properly fold and receive modifications like N/O-linked carbohydrates and disulfide bonds

7

stage 2 of the secretory pathway

the properly folded proteins are transported via anterograde vesicles to the Golgi that fuse to form cis-golgi

retrograde vesicles moves proteins back to the ER

cis-golgi --> medial-golgi --> trans-goli (cisternal maturation)

retrograde vesicles move golgi proteins from trans to cis

8

trans-golgi network (TGN)

major branch point in secretory pathway

here, proteins are loaded into different vesicles and trafficked to different destinations

9

destinations of proteins from the TGN

plasma membrane --> secretion

storage

lysosome

10

exocytosis

process where a vesicle to and fuses with a plasma membrane and releases its contents

11

late endosome

a compartment where secretory proteins destined for the lysosome end up first

12

where are secretory proteins never released

cytosol

they are always associated with some kind of membrane bound intermediate

13

combining pulse-chase labeling and autoradiography (radiolabeled aa)

after injection of labeled aa in pancreas of hamsters, they were killed and pancreatic cells visualized to detect the location of labeled protein

14

vesicular stomatitis virus procedure (VSV)

temperature sensitive mutant G protein from VSV transfected into cells that then produce G protein on rough ER

at restrictive temp of 40 degrees C, no transport occurs

at permissive temp of 32 degrees C, transport occurs through secretory pathway to cell surface

15

microscopy of GFP labeled VSV G protein

hybrid gene of GFP + VSVG

when cells transcribe gene, fluorescent microscope used to observe

protein moves to golgi, then cell surface

16

endoglycosidase D

carbohydrate cleaving enzyme

distinguish glycosylated proteins in ER (resistant to cleavage) from those that enter cis-Golgi

deglycosylated protein moves faster on SDS gel

17

temperature (hot or cold) sensitive secretion (sec) mutants in coding region

yeast mutants that secrete proteins at a permissive temp, but not at a higher nonpermissive temp

at nonpermissive temp, see which proteins build up and where

18

what is budding of vesicles driven by

combination of soluble protein complexes onto the membrane to form a protein vesicle coat

19

cytosolic portions of integral membrane proteins interact with the vesicle coat to...

uptake appropriate cargo proteins into forming vesicle

causes curvature

20

v-SNARE

vesicle SNARE proteins in protein coat accessible in uncoated vesicle (when pinched off)

binds to t-SNARE in target memb. to bring the membranes close together, allowing bilayers to fuse

21

t-SNARE

found on target membrane (target SNARE)

v-SNARE binds and allows membranes to fuse

22

classic coat proteins

COPII vesicles transport proteins from ER to golgi (anterograde)

COPI vesicles transport proteins retrograde between golgi compartments, and from cis-golgi to ER

clathrin vesicles transport proteins from plasma membrane and trans-golgi to endosomes (ex. cholesterol)

23

is the formation of vesicles energy dependent?

yes

24

why is movement in golgi retrograde

vesicles stay stationary as golgi matures

25

do some vesicles move on microtubules?

yes

26

GTPase switch proteins control...

assembly of vesicle coat proteins (ex. ARF protein, Sar1)

Sar1-ATP helps coat proteins bind, hydrolysis to GDP causes release

27

Sar1 / ARF protein mutants that cant hydrolyze GTP-GDP

protein coats form, but never disassemble

28

how does the vesicle coat select the right cargo proteins?

cargo proteins have sorting signals

29

___ GTPases control docking of vesicles on target membranes

Rab

has an anchor that allows tethering to vesicle memb. (Rab-GTP)

Rab-GTP interacts with a Rab effector in target membrane to dock vesicle

then Rab-GTP --> Rab-GDP = release

30

VAMP (v-SNARE) and syntaxin (t-SNARE) binding mechanism in secreted protein exocytosis

VAMP incorporated into secretory vesicles as they bud from trans-Golgi

when protein coat disassembles, VAMP exposed, binds to syntaxin after Rab-GTP tethering to memb.

forms SNARE complex

31

dissociation of SNARE complexes after membrane fusion is driven by ___ hydrolysis

ATP

32

anterograde transport from ER to golgi uses which vesicle type

COPII

vesicles contain proteins destined to golgi, cell surface, or lysosomes, and v-SNARES

33

retrograde transport from cis-Golgi to ER uses which vesicle type

COPI

retrieves v-SNARES, membrane, and missorted ER proteins

34

KDEL sorting signal

found on proteins destined to ER from golgi

proteins carried by COPI vesicles

35

golgi processes post-translational modifications to what proteins

glycoproteins

contains enzymes like glycosidases and glycosyltransferases (add n/o-linked carbohydrates)

add mannose-6-phosphate in cis-golgi

36

vesicles that bud from trans-golgi to final destinations have two layers

outer layer of clathrin (trimeric)

inner layer of adapter protein (AP) complexes, 3 kinds

37

AP proteins

determine which cargo proteins are included in vesicle bud

bind cytosolic face of membrane proteins

38

trans golgi proteins going to the lysosome through late endosome contain

clathrin and AP1

39

trans golgi proteins going to lysosome by bypassing late endosome contain

AP3

MAYBE clathrin

40

______ is required for pinching off clathrin vesicles

Dynamin, a cytosolic protein

forms around neck of bud and hydrolyzes GTP-->GDP

41

do COPI and COPII need dynamic to pinch off?

no

42

mannose 6-phosphate residues target proteins to ______

lysosomes

trans-golgi has mannose 6-phosphate receptors

43

some mannose 6-phosphate glycoproteins are ___-proteins initially synthesized as...

pro-proteins

pre-pro-proteins like lysosomal proteases

44

there are receptors for M6P proteins in the ____ golgi

trans

bind to clathrin/AP1 vesicles --> late endosome --> lysosome

45

lysosomal storage disease (genetic)

degradative enzyme is defective in active site of M6P or in sorting/transport process

absence of one or more lysosomal enzymes results in buildup of glygolipids in lysosomes

46

secretory cells like pancreatic beta cells (insulin) use 2 types of secretory vesicle

regulated transport vesicles

unregulated transport vesicles (constitutive)

47

proprotein

long lived inactive precursor proteins

need further proteolytic processing to generate mature active proteins

48

which proteins undergo proteolytic processing after leaving trans-golgi

lysosomal pro-enzymes (happens in late endosome)

pro-insulin (happens in vesicles after leaving trans golgi)

49

how do epithelial cells get to either the apical or basolateral region

sorting pathways in the trans golgi

different transport vesicles to apical or basolateral surfaces

50

transcytosis

when epithelial cells destined for the apical side of the membrane move across the cell and fuse