M&R Session 5 (Lecture 5.2) Flashcards
What is the advantage and disadvantage of having a large inward gradient of Ca2+?
Advantage : Changes [Ca2+]i occur rapidly with little ion movement
Disadvantage : Ca2+ overload leads to loss of regulation and cell death
Describe the feedback mechanism of calcium in relation to PMCA?
1) Ca2+ i rises
2) Ca2+ binds to calmodulin
3) Ca2+-calmodulin complex binds to PMCA
4) With the expense of ATP, Ca2+ is removed from the cell
(PMCA - high affinity, low capacity)
What is a low affinity, high capacity transporter?
NCX (3 Na+ in, 1 Ca2+ out) antiporter which is electrogenic (reverses in depolarisation)
Name some calcium buffers/binding proteins.
Calreticulin, calbindin, calsequestrin, parvalbumin
Name a ligand gated CC? Name its agonists.
NMDA receptor with glutamate or glycine activating it.
What does the SERCA pump do?
Sequesters Ca2+ back into SER at the expense of ATP.
What stimulates GPCRs?
Hormones, NTs, Ions, Odourants, Taste
What type of receptors is the IP3R?
Ligand gated for IP3 causing Ca2+ release
What is CICR and what receptore mediates this?
Calcium induced Calcium release via the Ryanodine receptor
What are the minor and major ways of calcium recycling?
1) Minor - NCX
2) Major - SERCA
What role do mitochondria play in calcium regulation?
1) Uptake of calcium when intracellular [Ca2+] is high via uniporter.
2) Calcium signalling, buffering and role in cell death.
How is calcium returned to basal levels?
1) Terminate the signal
2) Ca2+ removal
3) Ca2+ store refilling
How is capacitative Ca2+ entry done?
Via SOC (store operated channel) on pm, is signalled via a depleted SER which causes influx of Ca2+ into the cell and loaded into SER via SERCA.
Via specific proteins e.g. STIM (stromal interaction molecule - a calcium sensor on ER membrane) and ORAI (pm channel)
