Cellular Logistics: Vesicular Traffic - Molecular Mechanisms

Question 1

What TWO pathways do proteins pass through in Eukaryotic cells?

Answer 1

• Secretory
• Endocytic

Question 2

What happens to proteins in the Secretory Pathway?

Answer 2

Initially targeted to the ER and then transported in vesicles via the Golgi to the plasma membrane

Question 3

What happens to proteins in the Endocytic Pathway?

Answer 3

Plasma membrane and extracellular proteins are endocytosed and transported in vesicles to endosomes or lysosomes

Question 4

What are the general features of vesicular trafficking?

Answer 4

• Vesicles bud from a parent/donor organelle and fuse with a target membrane
• Membrane orientation is maintained
• Membrane integrity is maintained

Question 5

What are Coat Proteins involved in during vesicular trafficking in the secretory and endocytic pathways?

Answer 5

Involved in the budding of vesicles and the recruitment of cargo

Question 6

What are SNARE Proteins involved in during vesicular trafficking in the secretory and endocytic pathways?

Answer 6

Involved in membrane fusion

Question 7

What are Small GTPases involved in during vesicular trafficking in the secretory and endocytic pathways?

Answer 7

Regulate both the budding and docking of vesicles

Question 8

What are Cargo Receptors involved in during vesicular trafficking in the secretory and endocytic pathways?

Answer 8

Recruit soluble cargo proteins to vesicles

Question 9

TRUE OR FALSE:
For any given transport step in the secretory or endocytic pathway, the particular set of proteins involved is generally the same

Answer 9

False.
Particular sets of proteins are generally different
E.g. ER to Golgi involves different coat proteins and GTPases than Golgi to Lysosome

Question 10

What are the THREE types of Coated Vesicles?

Answer 10

1. COPII
2. COPI
3. Clathrin

Question 11

Which trafficking step does COPII mediate?

Answer 11

Rough ER to cis-Golgi

Question 12

Which trafficking step does COPI mediate?

Answer 12

Retrograde transport:
cis-Golgi to rough ER and within Golgi

Question 13

Which trafficking step does Clathrin mediate?

Answer 13

Plasma membrane and trans-Golgi to endosome

Question 14

How does vesicle coat assembly occur?

Answer 14

Reversible polymerisation of soluble coat proteins on the membrane

Question 15

Where does the vesicle coat assemble?

Answer 15

Cytosolic face of the membrane

Question 16

What is the diameter of a typical coated vesicle?

Answer 16

~50nm

Question 17

How is vesicle coat assembly / disassembly regulated?

Answer 17

Regulated by small GTPases

Question 18

Which GTPase regulates vesicle coat assembly / disassembly for COPII vesicles?

Answer 18

Sar1

Question 19

Which GTPase regulates vesicle coat assembly / disassembly for COPI & Clathrin vesicles?

Answer 19

ARF

Question 20

TRUE OR FALSE:
GTP hydrolysis is required for vesicle coat disassembly

Answer 20

True