Lecture 1: Membrane trafficking Flashcards
Functions of polarised cells
- Have different functions at different cell regions
- Define inside vs outside
- Transmit signals from one end to the other
How does membrane trafficking send proteins to different domains
- Exocytosis
directly to the target domain - Exocytosis to any domain then endocytosis followed by recycling to the target domain
How does membrane trafficking determine where proteins end up
- Some trafficking routes are polarized
- Proteins are organized at sorting stations
- Different routes are balanced by retrieval pathways
What are 3 methods of Constitutive Secretion
- Signal mediated diversion to lysosomes (M6P)
- Signal mediated diversion to secretory vesicles
- Constitutive secretory pathway
How does Secretion release concentrated cargo ?
- Clathrin-coated vesicles can return membrane back to the Golgi
- This shrinks the vesicle and makes the cargo more concentrated
How does regulated secretion release material in response to a signal ?
- Regulated secretion
vesicles are fully- formed but do not fuse with the plasma membrane until a signal is received - e.g. Mast cell releasing stored histamine
Regulated secretion often delivers extra membrane material . What for ? and through what?
For
a. Cytokinesis
b. phagocytosis
c. Plasma membrane repair
Through
Endosomes (a&b)
Lysosomes (c)
What are the 3 options of endocytose cell membrane?
- Recycling to the same domain of the plasma membrane
- Transcytosis to the other domain of the plasma membrane
- Degradation in the lysosome
What are the types of membrane changes during vesicle trafficking ?
- Vesicle forms from the donor membrane into the cytoplasm
- Vesicle fusion: vesicle merges with a target membrane
- Vesicle forms from a donor membrane away from the cytoplasm
What’s an example of vesicle forming from the donor membrane into the cytoplasm (types of membrane changes during vesicle trafficking)
Clathrin mediated vesicle formation
- Cathrin coats assemble on cargo prots; the bud, then vesicle forms, the coated membrane vesicle is released and then the vesicle is uncoated
What’s an example of Vesicle fusion: vesicle merges with a target membrane (types of membrane changes during vesicle trafficking)
Vesicles coats are selective of cargo and specifically targeted
Eg Clathrin(from extracellular to Golgi), COPI(from glogi to ER), COPII (from ER to Golgi),retromer (from early endoscope to Golgi)
What’s an example of Vesicle forms from a donor membrane away from the cytoplasm(types of membrane changes during vesicle trafficking)
- ESCRT proteins
- Vesicles can form away from the cytoplasm (into lumen or extracellular space)
- Vesicle formation machinery is in the cytoplasm
Which protein helps mediate vesicle fusion?
SNARE proteins
* Both t-SNAREs & v- SNAREs are required
* t-SNARES and v-SNARES must be on opposite membranes
How many of the following are examples of vesicle formation into the cytoplasm?
* COPII-mediated secretory vesicle formation at the ER
* ESCRT-mediated vesicle formation
* clathrin-mediated endocytic vesicle formation
* any process mediated by SNARE proteins
a) 0
b) 1
c) 2
d) 3
c
the first and the 3rd are true
In ESCRT the structure goes out of the cell to the lumen,
In SNARE the vesicle is fusing , not forming
What does PI(3,4)P2 mean
PI-phosphatidlinositide
3,4 -phosphrylation site positions
p2- total number of phosphorylation sites
