Notes taken during lecture

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2 Feb 2011
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LECTURE 8 Feb.1.2011
Sorting and packaging
Depending on cell can have one Golgi or more if cell involved in secretion, can have 100
Golgi apparatus
ER sends transport vesicles to ER, fuse together, form cis Golgi structure
Sorting mechanism that occurs in transGolgi network
Bud from ER exit sites
Bound by cargo receptors
Resident ER protein stays in ER
Chaperone proteins responsible for holding misfolded or unfolded protein in ER
Know specific names of these chaperones
Cargo from ER to cisGolgi network
COPII-coated vesicles
oVesicular tubular cluster attached by motor proteins to microtubule
migrate towards Golgi
oShed COPII coat
oSNAREs involved in vesicle fusion
oTransport vesicles
oVesicular tubular cluster becomes the cis Golgi network
Retrograde transport recovering the proteins that should be in ER, but somehow left
Escaped ER-resident proteins
Proteins involved in vesicle budding from ER
oV-SNAREs, Rab-GTPAses, etc.
Retrieval of ER-resident proteins
Soluble with KDEL signal
oSignal that brings it back into ER if it escapes
oBound by KDEL receptor
oFour amino acids
KKXX pointing to the Y receptor attached to blue labelled COPI coat
oSignal bound by COPI coats
KDEL receptor recognizes the Er-resident proteins in Golgi returns them to ER
KDEL receptor coming back towards ER releases it to the ER and then goes back
to Golgi, empty
Receptor doesnt want to bind to KDEL in ER, but does in the Golgi
pH is how this is regulated
High affinity for KDEL
ER low affinity for KDEL
Higher pH at ER and decreases towards the Golgi
oYounger compartment, higher pH
oER younger than Golgi
o5 for early endosome
o3 for lysosome
o6 for Golgi
o7 for ER
Binds KDEL in acidic pH; releases in neutral pH
Cycle between ER and Golgi, but transport to ER at slower rate
Not v. good explanation
Protein complex so big that cannot fit in vesicle so not transported anywhere
Prevent packaging into transport vesicles
Transport of proteins in the Golgi apparatus
Stacking structure of Golgi
Vesicles fuse to cis face, leave the trans face
Some proteins move through, some dont and stay in the pancake
Little vesicles move in between the cisternae
Kept close to Golgi cisternae by tethering proteins
Vesicular transport model
Move forward from one Golgi cisterna to next
Return escaped ER-resident proteins and Golgi enzymes
Second model
Move Golgi enzymes and ER resident proteins back
Both models may occur
Rapidly by transport vesicles
Slowly via cisternal maturation
Vesicle trafficking from TGN
Proteins sorted into different vesicles
Transport of proteins to lysosomes
Degradation of macromolecules
Lysosome in cell, fuse with vacuoles (food vacuole, phagosome)
Mannose 6 phosphate tag and receptor
Work together
Cis-Golgi network: mannose phosphorylated = M6P
EX question Er signal sequence with M6P tag, where does it end up?