Calcium Signaling

Question 1

what are cytoplasmic Ca2+ ion buffers

Answer 1

Cytoplasmic Ca2+ buffers are proteins that bind to free Ca2+ in the cell.

Question 2

functions of cytoplasmic Ca2+ ion buffers

-how do they affect cytoplasmic calcium signals

Answer 2

1. They restrict the spatial spread of free Ca2+ in order to localize it and control pathways
2. Store Ca2+ until it can be properly transported.

Question 3

routes by which extracellular Ca2+ moves out of ER/SR (sarcoplasmic) into the cytoplasm

Answer 3

1. recognition of Ca2+ in the cytoplasm by ryanodine receptors
2. Triggers release of Ca2+ from ER/SR into cytoplasm
3. Positive feedback mechanism –> more Ca2+ release
4. IP3 receptors respond to IP3 to activate Ca2+ channels and stimulate Ca2+ influx into cytoplasm from the ER/SR.

Question 4

routes (pumps/exchangers) by which Ca2+ is moved out of the cytoplasm into the extracellular space

Answer 4

1. Plasma membrane Ca2+ ATPase (PMCa ATPase)
   - a pump in the cell membrane
2. or by Na/Ca exchangers (3 Na entry: 1 Ca exit)

Question 5

routes (pumps) by which Ca2+ is moved out of the cytoplasm into the the lumen of ER/SR

Answer 5

Sarco/Endoplasmic reticulum Ca2+ ATPase (SERCa ATPase)

Question 6

Important sources of Ca2+

Answer 6

(where it comes from)

-can overlap with sinks

Question 7

Important sink of Ca2+

Answer 7

(where it goes to)

-can overlap with sources

Question 8

EF hands

- example?

Answer 8

helix-loop-helix domains with 2 perpendicular alpha helices connected by a short loop that coordinates with Ca2+

-Calmodulin: protein made of 4 EF hands

Question 9

C2 domains

-example?

Answer 9

structural domains on proteins that coordinates with Ca2+ and target the protein to the plasma membrane

• Protein Kinase A (PKA),
• PKC
• Synaptotagmin

Question 10

parvalbumin

Answer 10

cytoplasmic buffers: restricts spread of Calcium

Question 11

calsequestrin

Answer 11

high capacity ER/SR lumen buffers that store large quantities of calcium