Vesicular Transport

Question 1

Describe the anterograde movement of transport

Answer 1

ER–> golgi–> plasma membrane or lysosomes

Question 2

Describe the retrograde movement of transport

Answer 2

plasma membrane endosome–> golgi–> golgi compartments–>ER

Question 3

Describe endocytosis

Answer 3

plasma membrane buds, early endosome forms, golgi compartments bind and late endosome forms, lysosome

Question 4

Vesicular transport involves

Answer 4

Cargo selection
Vesicle budding
Vesicle Transport
Vesicle targeting
Vesicle fusion and cargo delivery

Question 5

Cargo selection uses a _____ ________ to bind to the cargo which in turn binds with the ______ _______ and a vesicle buds off. The adaptor proteins are shed to create a __________ _______

Answer 5

cargo receptor, adaptor protein, transporter vesicle

Question 6

Mechanism used for vesicle transport

Answer 6

cytoskeletal proteins with motor proteins attached (myosin protein on actin, dyneins and kinesins on microtubules), Rab GTPs bind the motor proteins to the vesicles.

Question 7

Rab proteins

Answer 7

GTPases that connect vesicles to motor proteins on cytoskeleton for transport. They also bind Rab effectors on the target surface to make a primary connection (highly specific). GTP form marks vesicles

Question 8

SNAREs

Answer 8

Proteins that mediate the the fusion of the vesicle and target membranes, v and t.

Question 9

The three coat proteins and which vesicles they correspond to

Answer 9

1. Clathrin- exo and endocytotic vesicles from membrane to golgi or trans Golgi network to endosomes
2. COP1- golgi to ER or golgi to other golgi compartments
3. COP2- ER to golgi

Question 10

ER chaperone proteins- where are they and what do they do?

Answer 10

in lumen of ER, they hold unfolded proteins, keeping them from getting exported in COP2 coated vesicles

Question 11

Folded ER proteins need a ______ _______ with a _______ tail that will bind the COP2 protein

Answer 11

cargo receptor, cytoplasmic

Question 12

Sar 1-GTP

Answer 12

a Rab-GTP like protein that allows the association of COP2 coat proteins with the ER membrane. It embeds in the ER membrane with its amphipathic helix domain (when associated with GTP).

Question 13

COP 1 proteins

Answer 13

allow vesicles with proteins that have escaped inappropriately to be ushered back to the ER. The proteins must have the KDEL signal sequence

Question 14

KDEL

Answer 14

ER retention signal sequence. Proteins with this can be taken up with COP1 coated vesicles and transported back to the ER (retrieval pathway)

Question 15

How do you mark membrane cargo receptors for coat proteins/vesicle to recognize?

Answer 15

phosphorylate cytoplasmic side, have an amino acid motif, or ubiquitination

Question 16

Monoubiquitination of integral membrane proteins occurs in …

Answer 16

early endosomes (clathrin will bind)

Question 17

YxxPHI aa motif occurs in…

Answer 17

plasma membrane or TransGN

Question 18

Describe the LDL uptake process in a cell

Answer 18

LDL binds to LDL receptors and clathrin associates, endocytosis occurs, and with high [acid], the LDL dissociates from the receptor. It goes into a lysosome and gets hydrolyzed–>available for use

Question 19

Hyper-cholesterolemia

Answer 19

less cholesterol is taken up by cells, caused by LDL receptor mutation (clathrin cannot bind)

Question 20

Vesicle budding is driven by ______ _______ which assemble in specific geometric shapes to create a curve.

Answer 20

coat proteins

Question 21

Vesicle fission is assisted by …

Answer 21

dynamin and its associated proteins (it bring the membrane so close they fuse)

Question 22

Phosphoinositides (PI3, PI4, PI4,5, etc)

Answer 22

hydroxyl on inositol sugar is phosphorylated on membrane- a distinguishing mark on a target organelle used to guide a vesicle and it’s specific Rab to the surface

Question 23

Describe the process of vesicle recognition

Answer 23

PI kinase phosphrylates the specific PI, which then recruits a specific Rab GEF. This will transfer GDP off and GTP onto the incoming Rab protein of the vesicle, allowing it to embed/tether into the target membrane.

Question 24

_____ promote fusion of vesicles to target

Answer 24

SNAREs (via scissor sort of alpha helix which is energetically favorable)

Question 25

How do you break up SNAREs after fusion?

Answer 25

ATP, accessory proteins, and NSF cause dissociation

Question 26

Botulism toxin does what to inhibit Ach transfer to muscle cells?

Answer 26

it cleaves SNAREs so that vesicles with ACh cannot fuse–> muscle paralysis

Question 27

What is the Golgi’s main function?

Answer 27

it is a sorting station. The cis-golgi receives protein-filled vesicles from ER and the TGN sorts/modifies and ships to lysosomes, plasma membrane, or secretory vesicles

Question 28

What are two characteristics of the Golgi?

Answer 28

It is made of membranous stacks very closed spaced to each other.
It is located mostly near the nucleus (perinuclear)

Question 29

Enzymatic functions of the Golgi

Answer 29

CGN: phosphorylate oligosaccharides on on lysosomal proteins
the Cisterna: removal of Man and addition of glycans
TGN: sulfation of tyrosines and carbs

Question 30

Storage granules

Answer 30

dense homogenous protein material formed after “distillation” of a via movement from the Golgi to the vesicle

Question 31

An ________ ________ pathway will regulate some protein secretion of vesicles. Otherwise they are __________ expressed

Answer 31

intracellular signaling, constitutively