Vesicle Trafficking Flashcards
Protein transfer to nucleus, peroxicsome, ER, or mitochrondria targeting?
All post translationally modified except ER
Transport to nucleous
Nuclear pores for large particles-both directions
mRNA goes through here
Small can diffuse
Nuclear pore structure
Lamin scaffolding and intermediate filaments on inside
Proteins on outside attached to fibril grab proteins and bring in
Nuclear signal sequence+pathway into cell
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
Nuclear export
Exportin binds to R
Monomeric GTP
+
3 uses
Guanine nucleotide exchapge protein-GDP to GTP
GDP bound-inactive
GTP-conformatiational change-active state
GAP-hydrolyzes GTP
Ran, Arf/Sar-1, Rab
Transport to peroxisomes
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
Zellweger syndrome
No transport of enzymes into peroxisomes (empty peroxisomes)
-no signal in all peroxisomal proteins to send to peroxisome
SRP
N terminus of sec pathway proteins bind to SRP while being synthesized on site ribosomes
- SRP binding causes pause in translation
- SRP bound ribosome attached to SRP receptor in ER membrane-GTP hydrolysis and conformational change-create protein directly into the ER-
- SRP and SRP receptor dispalced and recycled
SRP from inside ER
- signal petide is remoed
- Hydroyxlaton of lys, pro
- disulfide bonds form
- Chaperones fold
- glycosylation and initial step of oligosaccharide processing
Glycosylation
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
Vesicuar Transport
Benefit+steps
Transport of cargo without crossing a membrane
Form vesicle, select cargo (look at glycosylation pattern), have address (SNARES)
Where do coat proteins come from
from cytosol (not on PM) -recruited by binding to specific receptors that recognize specific signals on cargo proteins
How assemble COP-1/2
Guanine nucleotide exchange protein-make GTP from GDP
ARF-COP1
SAR-1=COP2
GAP-GTPase that hydroyzes GTP to inactive state
Coatmaer coated vesicele formation
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
Where use a particular transport protein
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
v/t SNARES
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
Botulinum and tetanus effect on cell
Cleave snares
Summary of formation and fusion of vesicles
(7 steps) DRAW
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
KDEL
Sequence for misrouted proteins
COP1
Brings things from late endosome back to trans golgi, to cis golgi, to ER
Transport to lysosome
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
I-cel disease
No M6P modification of mannose on lysosomal protein b/c no phoshotransferase that is needed
-empty lysosomes
all would-be lysosomal contents are excreted
Constitutive vs regulated secretory
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+????
Legionairre’s disease
Phagosome hijcaks host vessicles-becomes like RER
-block delivery to lysosome and can replicate
????
Where does intracellular receptor go after disassocation
Lysosome, recycle, or transcytosis
in clathrin pit
Early endosome
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
Late endosome
With M6P lysosomal enzymes from TGN
Eventually can become lysosome
Adaptins
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
Structure of transport vesicle
Cargomolecules attache dto cargo recepttors
- attached to adoptions
- attached to clathrin
- then dynamic cuts off the last bit of cytoplasm to make free vesicle
Virsuses
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
Which proteins bind to SRP
lysoomal, resident golgi, PM, regulated sec proteins
NOT NUCLEAR
Lysomal protein facts
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
Endocytosis facts
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
