Coated Vesicles

Clathrin is a protein that makes up clathrin coating. Essential for vesicle formation.
Clathrin coating comes from the Golgi and plasma membrane,
Clathrin structures consist of multiple triskelions.

Endocytosis is transporting material in the cell membrane into the cell via vesicles. It uses Clathrin, Adaptin, BAR, PIP, Dynamin, Auxillin.

Consists of 3 small and large subunits. Form basket like framework.

A protein required for Clathrin to bind to the membrane. Will bind to transmembrane proteins and cargo receptors.

Phosphoinositides are a kind of phospholipid that regulates coat formation.
Regulates protein transport, transmembrane has binding sites for PIP.
PIP recognizes a sequence of transmembrane proteins that need to be shipped off.

Binds to head groups of phospholipids.
Triggers bending of membrane, crescent shaped.
Polymerizes actin filaments
BAR and clathrin stimulate Actin to protrude around the vesicle.

Pinches, squeezes the neck of vesicle

Must decoat before it binds to an organelle. Auxillin will activate ATPase of heat shock proteins which will decoat vesicle.

Intracellular trafficking, transportation of material from organelle to organelle via vesicles.

COP1 coated vesicles packages bud from the Golgi

COP2 coated vesicles packages bud from the ER

GTP, membrane exchange, GEFs and GAPS.

ARF proteins and Sar1 proteins.
ARF proteins responsible for COP1 and clathrin coat assembly at Golgi.
Sar1 proteins responsible for COP2 assembly at ER membrane.

SAR/ARF proteins will be found inactive in the cytosol of the cell; they are bound to a GDP,
A GEF embedded in the ER binds to SAR/ARF, and it will exchange the GDP for a GTP.
GTP-bound SAR will expose its fatty acid tail and embed it into the lipid bilayer of ER.
This process recruits coat proteins to ER membrane to initiate budding.

Hydrolysis of recruitment GTPases ARF/SAR will result in change of conformation and disassemble of structure. SAR1/ARF fatty acid tail pops out of membrane.

Retromers are a kind of coating that helps transport receptors back into the golgi.

Acts as a fishing line for RAB bound to vesicles, and both interact and reel RAB unto the membrane with vesicle.

Help with docking and snare interactions.
Selectively binds proteins on the target membrane.
Directs vesicles to specific sites on the plasma membrane for endocytosis of organelles.

Vesicles have RAB GTPases in the cell cytosol, which will facilitate and regulate the docking of vesicles to target membranes. RAB needs to be active to associate with a vesicle. RAB GEF handles activation.

A family of protein that catalyzes the fusion of vesicle with target membrane. Vsnares are vesicle snares, Tsnares are target snares.
Snares wrap around each other until vesicle and membrane fuse together and form trans-SNARE complex.

A protein that will unravel the snares once fusion is completed.

Multiple RAB effectors, T snares and tethering proteins. Caused by GTP bound vesicle RABs recruiting multiple RABS and PIPs. (Rab5, Rab 7).

Occurs after RAB5 recruits a RABGEF7.
RABGEF7 recruits RAB7 and that buds off in the form of vesicle with a new RAB7 domain. Receptors are recycled back to golgi this way.