Vesicle Trafficking

Question 1

Protein transfer to nucleus, peroxicsome, ER, or mitochrondria targeting?

Answer 1

All post translationally modified except ER

Question 2

Transport to nucleous

Answer 2

Nuclear pores for large particles-both directions

mRNA goes through here

Small can diffuse

Question 3

Nuclear pore structure

Answer 3

Lamin scaffolding and intermediate filaments on inside

Proteins on outside attached to fibril grab proteins and bring in

Question 4

Nuclear signal sequence+pathway into cell

Answer 4

Binds to importin (a/b complex) in cytoplasm

• transported through pore
• RanGTP binds to importin b-release of protein
• Ran GTP and importin b transported back to cyto where changes to Ran GDP by Ran GTPase+importin B release

Question 5

Nuclear export

Answer 5

Exportin binds to R

Question 6

Monomeric GTP
+
3 uses

Answer 6

Guanine nucleotide exchapge protein-GDP to GTP

GDP bound-inactive

GTP-conformatiational change-active state

GAP-hydrolyzes GTP

Ran, Arf/Sar-1, Rab

Question 7

Transport to peroxisomes

Answer 7

Start by synthesis by free cytosolic ribosomes

Phospholipids and membrane proteis are also imported to peroxisomes forom ER

Targeted by amino acid signal-never cleaved

Catalase-major peroxisome protein-degrades H2O2 into H2O

Add heme to each monoer-provent from going tback to cytosol

Question 8

Zellweger syndrome

Answer 8

No transport of enzymes into peroxisomes (empty peroxisomes)

-no signal in all peroxisomal proteins to send to peroxisome

Question 9

SRP

Answer 9

N terminus of sec pathway proteins bind to SRP while being synthesized on site ribosomes

1. SRP binding causes pause in translation
2. SRP bound ribosome attached to SRP receptor in ER membrane-GTP hydrolysis and conformational change-create protein directly into the ER-
3. SRP and SRP receptor dispalced and recycled

Question 10

SRP from inside ER

Answer 10

1. signal petide is remoed
2. Hydroyxlaton of lys, pro
3. disulfide bonds form
4. Chaperones fold
5. glycosylation and initial step of oligosaccharide processing

Question 11

Glycosylation

Answer 11

Oligosacchirde with 9 manses added co-translationally from membrane lipid donor to specific residues
-modifed by compartment-specific enzymes-deduce how far protein has proressed by event of mods

Question 12

Vesicuar Transport

Benefit+steps

Answer 12

Transport of cargo without crossing a membrane

Form vesicle, select cargo (look at glycosylation pattern), have address (SNARES)

Question 13

Where do coat proteins come from

Answer 13

from cytosol (not on PM)
-recruited by binding to specific receptors that recognize specific signals on cargo proteins

Question 14

How assemble COP-1/2

Answer 14

Guanine nucleotide exchange protein-make GTP from GDP
ARF-COP1
SAR-1=COP2

GAP-GTPase that hydroyzes GTP to inactive state

Question 15

Coatmaer coated vesicele formation

Answer 15

Bind to donar membrane of one submit that is GTP binding protein (after activated)

• lipid tail of Sar1 is exposed when GTP is bound, inserts into membrane and then other COP2 subunits bind
• other cargo/cargo receptors bind to these additional subunits-load cargo

Question 16

Where use a particular transport protein

Answer 16

COP2-ER to cis golgi
Cop1-Retrograde-from trans to cis golgi or golgi to ER

Clahtrin-cell surface to early endosome, trans golgi to late endosome, late endosome to trans golgi

Question 17

v/t SNARES

Answer 17

Mediate vesicle targeting and fusion

v is snares on vesicle, t is snares on target

Lock and key

Rabs (GTP binding protein) inolved in vesicle tageting by binding effectors when GTP bound

Different snares are use in different transport steps

Question 18

Botulinum and tetanus effect on cell

Answer 18

Cleave snares

Question 19

Summary of formation and fusion of vesicles

(7 steps) DRAW

Answer 19

GTP binding protein, inner coat, SNARE, and cargo recruitment

COat completed with outer layer coat proteins that deform membrane

Scission from surface and uncaring to expose SNAREs

Tether may mediate initial attachment, likely recognized in part by Rab

Docking-vSNARE interacts with tsnare and then fusion

Question 20

KDEL

Answer 20

Sequence for misrouted proteins

COP1

Brings things from late endosome back to trans golgi, to cis golgi, to ER

Question 21

Transport to lysosome

Answer 21

Mannose 6 phosphate

Packaged into clathrin vesicles-sent to late endosome

Ligand-receptor dissociates at acidic pH when inside lysosome (merged PM’s)-removes phosphate

Receptor recycls

There is also an ATP dependent H+ pump on lysosome

Question 22

I-cel disease

Answer 22

No M6P modification of mannose on lysosomal protein b/c no phoshotransferase that is needed
-empty lysosomes

all would-be lysosomal contents are excreted

Question 23

Constitutive vs regulated secretory

Answer 23

Constituative
-unregulated membrane fusion-no sorting information

Regulated-Hormone or NT comes in from ECM and causes intracellular pathway that results in secretion of secretory vesicle

• greatly concentrated
• prohormones are processed
• Ca2+????

Question 24

Legionairre’s disease

Answer 24

Phagosome hijcaks host vessicles-becomes like RER
-block delivery to lysosome and can replicate
????

Question 25

Where does intracellular receptor go after disassocation

Answer 25

Lysosome, recycle, or transcytosis in clathrin pit

Question 26

Early endosome

Answer 26

Where surface receptors and cargo go after internalization to get sorted out Acidic pH - cargo dissocaites - some receptors return to PM - Transport some stuff to lysosome

Question 27

Late endosome

Answer 27

With M6P lysosomal enzymes from TGN Eventually can become lysosome

Question 28

Adaptins

Answer 28

Bind both chalthrin and receptors for vesicle cargo Mutation in receptor tail can interfere with receptor binding to adoption -cargo can be bound to receptor but will not be incorporated into vesicles

Question 29

Structure of transport vesicle

Answer 29

Cargomolecules attache dto cargo recepttors - attached to adoptions - attached to clathrin - then dynamic cuts off the last bit of cytoplasm to make free vesicle

Question 30

Virsuses

Answer 30

Envoloped and brough to endosome - capsid disassembles and results in RNA that can replicate itself or result in proteins/capsid proteins - which allow for more viruses to be made - also RNA can result in viral proteins being expressed on PM

Question 31

Which proteins bind to SRP

Answer 31

lysoomal, resident golgi, PM, regulated sec proteins NOT NUCLEAR

Question 32

Lysomal protein facts

Answer 32

Transported from ER to Golgi in COP2 vesicles Sorted from secretory proteins in TGN Get mannose 6 P marker BUT DO NOT BIND TO M6P receptor in cis golgi

Question 33

Endocytosis facts

Answer 33

Mutationsin LDL repceptors tail can prvent LDL internalization pH changes reg dissociation of internalized ligands from receptors Early endosome is major sorting station after endocytosis But NOT ALL INTERNALIEED RECEPTORS ARE RECYCLED TO PM