BIOL 3450 Lecture 10: 01 February - Chapter 14 – Vesicular Trafficking
01 February 2019
BIOL 3450
Chapter 14 – Vesicular Trafficking
Cis Golgi – vesicles may bud off here if retrograde
o Medial Golgi
o Trans Golgi – where vesicles bud off → directly to lysosome or cytoplasm
Coated Proteins
o COPI – retrograde; Golgi to ER
o COPII – anterograde; ER to Golgi
o Clathrin –
SNARES
o V – located on vesicles
o T – target proteins
Protein Sorting at Trans Golgi Network
o Proteins destined for sites other than ER or Golgi complex are all processed same up to
this point
▪ Synthesis and folding in ER
▪ Sequential glycosylation in Golgi
o Once they reach TGN, they must be sorted to different destinations
o Mechanism
▪ Cell surface protein and exoplasmic receptor
▪ Upon ligand binding to exoplasmic receptor, may bind lipid raft → formation of
clathrin coated pit on cytoplasmic side
▪ Clathrin coated vesicles uncoat after vesicle formation → clathrin becomes
available in monomeric form to coat other proteins
▪ Now is endosome (endocytosis) → fused with lysosomal proteins and turned into
lysosome eventually (Degradation of material taken in from plasma membrane)
• If cell wants to scavenge receptor through pH trips → can dissociate
ligand from receptor to recycle receptor back to cell surface
o Cargo is degraded in lysosome → gradual acidification (when
reaching low pH, they are called late endosome)
o Turns into lysosome and degrades contents
o Secretory pathway and formation of clathrin coated vesicles → specific for packing
proteins (mannose 6 phosphate) → packaged into mannose 6 phosphate receptor which
are packaged in receptors which eventually turn into lysosome
▪ Or packaged in secretory vesicles
Document Summary
Cis golgi vesicles may bud off here if retrograde. Chapter 14 vesicular trafficking: medial golgi, trans golgi where vesicles bud off directly to lysosome or cytoplasm. Coated proteins: copi retrograde; golgi to er, copii anterograde; er to golgi, clathrin . Snares: v located on vesicles, t target proteins. Sorting of proteins destined for apical and basolateral plasma membranes of polarized cells. Ldl uptake via endocytosis: ldl receptors (multiple) lead to vesicle formation clathrin coated pit loaded with. Delivery of plasma membrane proteins to lysosomal interior for degradation. Clathrin coated vesicle fuses with late endosomal structure. Instead of single membrane department, multivesicular body (vesicles within vesicles) protects; lysosomes can also be packaged in these complexes until ph is low enough to form lysosomal compartment. Gtp proteins: sar1, arf, both involved in vesicle formation. Receptor mediated endocytosis: clathrin coated vesicles. Late endosomes plasma membrane proteins; forming multivesicular bodies to prevent plasma membrane proteins from becoming part of late endosome.
