Vesicular Transport

3 vesicular transport pathways

1. biosynthetic

2. retrieval

3. endosomal

biosynthetic pathway refers to cargo being made in the cell and its vesicular transport “forward,” post-ER - and - pathways

secretory, endosomal-lysosomal

retrieval pathway refers to return of cargo to the -

original donor compartment

endosomal pathway refers to - vesicles bringing cargo into the cell from -

endocytic, extracellular space

biosynthetic pathway refers to the delivery of newly synthesized proteins, carbohydrates, and lipids to - or - of cells, and proteins can be - along the way

appropriate cell compartments, exterior, modified

endocytic pathway refers to - from extracellular space, - and -

metabolites, PM receptors, bound ligands

retrieval pathway refers to the recycling of - back to the PM or golgi or the retrieval of molecules “accidentally” packaged into -

transport receptors, vesicles

in the endocytic pathway, endocytic vesicles fuse with -, which will evolve into -

early endosomes, lysosomes

endosomes are the compartment where - and - cargo can meet

inside, outside

proteins made on RER are sent to the golgi, then the PM or extracellular space via -pathways

they can also be sent to lysosomes via -

biosynthetic secretory, endosomes

retrieval pathway - or - molecules, ensuring that ER and golgi - or endocytosed - are returned to these compartments

redistributes, recycles, resident proteins, PM receptors

biosynthetic cargo is delivered from the RER to golgi to PM/lysosomes via -

fusion of exocytic vesicles with the PM delivers proteins in the vesicle membrane into the - and releases soluble biosynthetic cargo into the -

vesicular transport

PM, extracellular space

endocytosis delivers outside cargo into the cell via -

endocytic vesicles

this image depicts endocytosis or exocytosis?

exocytosis

this image depicts endocytosis or exocytosis?

Endocytosis

vesicular transport steps

1. - form in regions of cytosolic side

2. budding of membrane containing soluble cargo or membrane proteins → -

3. - and - of vesicle to target compartment

4. - of vesicle and target compartment = - of soluble cargo or membrane proteins

protein coated pits, vesicle, binding, recognition, fusion, delivery

3 major types of protein coats

1. COPII

2. COPI

3. clathrin

COPII coats vesicles budding from - en route to -

ER, golgi

COPI coats vesicles budding from - to -, for -

golgi, RER, retrieval

clathrin coats

1. endocytic vesicles budding from -

2. transport vesicles moving between - and -

3. secretory retrieval vesicles moving back to -

PM, golgi, endosomes, golgi

what is the red? blue? green?

COPII, COPI, clathrin

clathrin “coat” protein subuntis assemble into -

triskelions self-assemble into hexagons and pentagons, creating final - structure that encloses the - into a coated pit

triskelion, basket-like, plasma membrane

coat assembly causes local - of the membrane “bud” leading to the assembly of a -

curvature, protein coated vesicle

general steps of protein coated vesicle formation

1. cargo receptors in membrane of - compartment bind -

2. adaptor proteins bind and bridge - to -

3. local - of membrane

4. membrane-bending and fission protein proteins use - to regulate rate at which vesicles - from donor membrane and bud

donor, cargo molecule, outer coat proteins, membrane cargo receptors, curving, GTPase, pinch off

CRG stands for

coat recruitment GTPases

CRGs regulate where and when - form

donor vesicles

the region of membrane where vesicle formation initiates and the type of protein coat assembled are regulated by - and their corresponding -

CRGs, GEFs

how do CRGs work?

1. CRG is - into regions of donor membrane where the - is concentrated

2. - is loaded onto CRG by CRG-GEF

3. insertion of - into membrane

4. membrane bound CRG recruits -

inserted, CRG-GEF, GTP, CRG amphipathic helix, cargo adaptors

essentially, - starts the vesicle formation

CRG

CRGs add another level of - specificity, based on the location of the - in the donor membrane

consequently, only membrane proteins and their bound cargo in the vicinity of the - wil be - in the vesicle bud

vesicle cargo, CRG-GEF, CRG, taken-up

coat disassembly occurs when the CRG GTPase hydrolyzes - to -

GTP, GDP

v and t SNAREs have characteristic - domains, whose complementary pairs specifically interact by -

helical, wrapping around each other

v-SNAREs are typically a - chain on the -

single polypeptide helical, vesicle

t-SNAREs are composed of - proteins on the -

2 or 3 helical, target membrane

SNAREs form tight interactions that bring the two membranes very - allowing for - of vesicle and target membrane

close together, fusion

based on this photo, which membrane is the vesicle membrane and target membrane?

top is vesicle, bottom is target membrane

Rab GTPases help specify and regulate - and -

vesicle-target recognition, blocking

How do Rab GTPases work?

1. membrane-bound Rab GEFs activate - on both - and - membrane

2. cytosolic Rab is - into respective membrane via a -

3. on the target membrane, Rab GTP recruits -

4. Rab effector will recognise corresponding - on the donor vesicle

5. results in vesicle and target membranes being pulled - and - can interact

cytosolic Rabs, target, donor, inserted, lipid tail, Rab effector, Rab GTP, closer, SNAREs