IP3 /Ca2+/Protein Kinase C pathway

What primary messengers and where use the IP3 /Ca2+/Protein Kinase C pathway

Glucagon- liver

Epinephrine- liver

Components of the IP3 /Ca2+/Protein Kinase C pathway

7TM helix receptor

G-protein complex (alphaq, beta, gamma)

Phospholipase C

Diacylglycerol (DAG)

inositol- 1,4,5-triphosphate (IP3)

Protein Kinase C (PKC)

Step 1

When a ligand binds to the receptor, the G-protein releases the GDP and binds GTP. The GTP-bound a-subunit (Galphaq ) dissociates from the receptor and stimulates Phospholipase C

Step 2

Phospholipase C hydrolyzes phosphotidylinositol-4,5-bisphosphate (PIP2) to diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (IP3).

Step 3

IP3 directly causes a rapid release of Ca2+ by opening IP3-regulated calcium ion channels in the endoplasmic reticulum (or sarcoplasmic reticulum in muscle cells)

Step 4

DAG and IP3 activate PKC which will phosphorylate the target proteins (on Ser and Thr)