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2 Feb 2011
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LECTURE 7 โ€“ Feb. 1. 2010
Intracellular vesicular transport part 1 and Molecular mechanisms
Each cisternae has different [enzymes]โ€
Remove or add sugarsโ€
Proteins today all synthesize into ER lumen or
Golgi has series of membrane stacks/pancakes โ€“ there are resident proteins in each stack
Vesicle tracking
Synthesis of membrane lipids
๎€In the smooth ER
๎€Ceramide โ€“ more minor component โ€“ made in ER โ€“ transported to other
compartments in vesicles
oSynthesized in ER, transported into golgi, where it is modified to produce
๎€Sphingomyelin
๎€Glycolipids โ€“ sugars attached to fat โ€“ happens in Golgi
๎€Found in luminal leafletโ€
๎€Likely to find in extraplasmic leaflet ?
Do not need to memorize the chemical pathway
๎€Enzymes labelled in green โ€“ in cytosol โ€“ or are transmembrane membranes with
acive sites in cytosol
๎€OCCURS IN CYTOSOL *** cytosolic leaflet will grow,
๎€Made by ER expansionโ€
oPlasma membrane expands โ€“ lipids from ER
oNew lipids in cytosolic leaflet of ERโ€
Newly synthesized lipids inserted into cytosolic leaflet โ€“ luminal leaflet a bit smaller โ€“ not
stable โ€“ so some lipids in cytsolic leaflet flipped into other leaflet
๎€Rapidly flipped to other leafletโ€
๎€Scramblaseโ€
oSo random distribution in ER membrane
๎€By vesicular transportโ€
Asymmetry of lipid bilayer โ€“ from LEC1
๎€Synthesized on luminal face of Golgiโ€
๎€Signallingโ€
๎€These for lec1
Negatively charge on outside surface of cell โ€“ cell is dying โ€“ so important to maintain
asymmetry
Intracellular vesicle that fuse and deliver these lipids
Delivery of randomly distributed lipids โ€“ flippase at plasma membrane that grabs
onto lipids like phsoptidyserine and flips them from outside to inside
๎€Flippase (ABC transport)โ€
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๎€Energy from ATP hydrolysisโ€
๎€Know the phsoptidyserine example *****
oScavenger cells survey body looking for dead or dying cells to digest
oWhen cell dies, exposes phosophidylserine โ€“ recognized by scavenger cells
oCannot maintain asymmetric membrane โ€“ so sick cell โ€“ must be killed
2. formation and fusion of vesicles (part a)
Vesicular transport
๎€Budding with cargoโ€
oBuds from donor membrane, containing cargo
๎€Fusion to targetโ€
๎€Release cargoโ€ as it fuses โ€“ thus deliver cargo
๎€Vesicle โ€“ ball with lipid bilayer, studded with transmembrane proteins and
proteins that stick out, and contains cargo
Know overview of intracellular vesicular transport โ€“ know the arrows, come from, go to,
detailsโ€ฆetc
***********
- blue is a retrieval pathway
Transport vesicles
๎€Vesicles in process of buding, eventually buds off, moves to target, fuses, and
delivers cargo
๎€Transmemebrane proteinsโ€
๎€Soluble proteins โ€“ bound by transmembrane cargo receptorsโ€
๎€Imagine target compartment is the plasma membrane, donor is Golgi
oThe transmembrane proteins now on cytosolic
oN-terminal luminal now outside
oCargo now outside cell
Vesicle formation depends on protein coats
๎€Repeated subunits of protein that stick together, curve membrane and cause
vesicle to form
๎€Select cargo for vesicleโ€
๎€Give curvature to vesicleโ€
๎€Promote vesicle buddingโ€
COPI-coated vesicles
๎€Cop one is how it is pronounced
๎€From Golgi to ERโ€
๎€Light blue ones in the diagram
๎€Between different Golgi cisternae
COP2
๎€From ER to Golgiโ€
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Document Summary

Intracellular vesicular transport part 1 and molecular mechanisms. Proteins today all synthesize into er lumen or. Golgi has series of membrane stacks/pancakes there are resident proteins in each stack. ceramide more minor component made in er transported to other compartments in vesicles: synthesized in er, transported into golgi, where it is modified to produce. glycolipids sugars attached to fat happens in golgi. Do not need to memorize the chemical pathway. enzymes labelled in green in cytosol or are transmembrane membranes with acive sites in cytosol. occurs in cytosol *** cytosolic leaflet will grow, made by er expansion : plasma membrane expands lipids from er, new lipids in cytosolic leaflet of er . Newly synthesized lipids inserted into cytosolic leaflet luminal leaflet a bit smaller not stable so some lipids in cytsolic leaflet flipped into other leaflet. scramblase : so random distribution in er membrane.

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