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

Exam 3: Ch 14 Secretory Pathway & Vesicle Budding Flashcards

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1
Q

the secretory pathway carries both…

A

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

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2
Q

soluble proteins delivered to the lysosome include

A

lysosomal digestive enzymes like…

proteases, phosphatases, lipases

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3
Q

endocytic pathway

A

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

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4
Q

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

A

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

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5
Q

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

A

yes

therefore, the protein being transported retains its original orientation

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6
Q

stage 1 of secretory pathway

A

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

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7
Q

stage 2 of the secretory pathway

A

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

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8
Q

trans-golgi network (TGN)

A

major branch point in secretory pathway

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

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9
Q

destinations of proteins from the TGN

A

plasma membrane –> secretion

storage

lysosome

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10
Q

exocytosis

A

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

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11
Q

late endosome

A

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

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12
Q

where are secretory proteins never released

A

cytosol

they are always associated with some kind of membrane bound intermediate

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13
Q

combining pulse-chase labeling and autoradiography (radiolabeled aa)

A

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

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14
Q

vesicular stomatitis virus procedure (VSV)

A

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

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15
Q

microscopy of GFP labeled VSV G protein

A

hybrid gene of GFP + VSVG

when cells transcribe gene, fluorescent microscope used to observe

protein moves to golgi, then cell surface

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16
Q

endoglycosidase D

A

carbohydrate cleaving enzyme

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

deglycosylated protein moves faster on SDS gel

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17
Q

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

A

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

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18
Q

what is budding of vesicles driven by

A

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

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19
Q

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

A

uptake appropriate cargo proteins into forming vesicle

causes curvature

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20
Q

v-SNARE

A

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

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21
Q

t-SNARE

A

found on target membrane (target SNARE)

v-SNARE binds and allows membranes to fuse

22
Q

classic coat proteins

A

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
Q

is the formation of vesicles energy dependent?

A

yes

24
Q

why is movement in golgi retrograde

A

vesicles stay stationary as golgi matures

25
Q

do some vesicles move on microtubules?

A

yes

26
Q

GTPase switch proteins control…

A

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

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

27
Q

Sar1 / ARF protein mutants that cant hydrolyze GTP-GDP

A

protein coats form, but never disassemble

28
Q

how does the vesicle coat select the right cargo proteins?

A

cargo proteins have sorting signals

29
Q

___ GTPases control docking of vesicles on target membranes

A

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
Q

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

A

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
Q

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

A

ATP

32
Q

anterograde transport from ER to golgi uses which vesicle type

A

COPII

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

33
Q

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

A

COPI

retrieves v-SNARES, membrane, and missorted ER proteins

34
Q

KDEL sorting signal

A

found on proteins destined to ER from golgi

proteins carried by COPI vesicles

35
Q

golgi processes post-translational modifications to what proteins

A

glycoproteins

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

add mannose-6-phosphate in cis-golgi

36
Q

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

A

outer layer of clathrin (trimeric)

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

37
Q

AP proteins

A

determine which cargo proteins are included in vesicle bud

bind cytosolic face of membrane proteins

38
Q

trans golgi proteins going to the lysosome through late endosome contain

A

clathrin and AP1

39
Q

trans golgi proteins going to lysosome by bypassing late endosome contain

A

AP3

MAYBE clathrin

40
Q

______ is required for pinching off clathrin vesicles

A

Dynamin, a cytosolic protein

forms around neck of bud and hydrolyzes GTP–>GDP

41
Q

do COPI and COPII need dynamic to pinch off?

A

no

42
Q

mannose 6-phosphate residues target proteins to ______

A

lysosomes

trans-golgi has mannose 6-phosphate receptors

43
Q

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

A

pro-proteins

pre-pro-proteins like lysosomal proteases

44
Q

there are receptors for M6P proteins in the ____ golgi

A

trans

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

45
Q

lysosomal storage disease (genetic)

A

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
Q

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

A

regulated transport vesicles

unregulated transport vesicles (constitutive)

47
Q

proprotein

A

long lived inactive precursor proteins

need further proteolytic processing to generate mature active proteins

48
Q

which proteins undergo proteolytic processing after leaving trans-golgi

A

lysosomal pro-enzymes (happens in late endosome)

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

49
Q

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

A

sorting pathways in the trans golgi

different transport vesicles to apical or basolateral surfaces

50
Q

transcytosis

A

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

Cellular and Molecular Biology (34 decks)

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