L1-4: General Extra Content Flashcards
1
Q
+ Are IRS and AKT essential for glucose signalling? Evidence:
A
- Knockout and knockdown studies have shown both to be absolutely necessary
2
Q
+ Effect of overexpression of constitutively active AKT on insulin signalling:
A
- Overexpression able to largely mimic the effects of insulin
- As such the pathway was independently activated without the initial substrate
3
Q
+ How does insulin signalling influence specific SNARE proteins?
A
- e.g. Synip and CDP138 are direct substrates for Akt and regulate GLUT4 vesicle fusion
4
Q
+ Which part of GLUT4 targeting at PM is independent of PI3K activation?
A
- Activated insulin receptor recruits APS at pTyr (high affinity)
- APS recruits a complex including c-CBL, CAP etc -> triggers RTK phosphorylation of c-CBL -> recruitment of CRK and C3G in complex
- Activation of TC10 -> exocyst recruitment (tethering complex)
5
Q
+ Where specifically in PM is TC10 found?
A
- In lipid rafts
6
Q
+ Evidence for importance of both PI3K-independent and APS signalling in GLUT4 trafficking/translocation:
A
- Disruption to individual components of these pathways has been found to inhibit GLUT4 exocytosis and glucose uptake
- e.g. pharmacological inhibitors
- e.g. siRNA-mediated knockdown
7
Q
+ By what 2 mechanisms is GLUT4 endocytosed?
A
- Clathrin-mediated endocytosis
- Cholesterol-dependent endocytosis
- In both cases, the GLUT4 is internalised into a sorting endosome compartment
- Balance of the two varies between adipocytes and muscle cells
8
Q
+ Why are GSVs difficult to study?
A
- It is difficult to tag the GSV itself; the proteins enriched in these vesicles are widely observed elsewhere
- e.g. GLUT4 has been fond in electron microscopy studies in all endosomal compartments
- The organisation of TGN is poorly defined/not well understood
- The dynamic and circular nature of the system means it is hard to isolate effects on one stage of the process
