Untitled

Phospholipase C activates 2 signaling pathways

Ligand binds to G-protein coupled receptor

Change in confirmation of receptor

G protein associates w/ the receptor

Displacement of GDP by GTP on G alpha sub-unit

Gq alpha sub-unit activates membrane bound enzyme phospholipase C

activated phospholipase C propagates signal by hydrolyzing/cleaving inositol phospholipid (IP)

IP is split into 2 signaling molecules: diacylglycerol (DAG) & IP3 (inositol 1,4,5-trisphosphate)

lipid DAG stays anchored in cell membrane where it eventually recruits & activates protein kinase C w/ Ca2+

IP3 is the (water-soluble sugar phosphate) 2nd messenger that diffuses into the cytosol & binds a ligand-gated calcium channel (IP3 receptor channel) on ER membrane

Changes confirmation of receptor

Opens Ca2+ channels that are embedded in the ER membrane

Ca2+ stored inside the ER rushes out into the cytosol

Ca2+ & DAG activates protein kinase C (PKC)

phospholipase C chops the sugar-phosphate head off the IP

This causes a sharp rise in the cytosolic [] of free Ca2+, which is normally kept very low

PKC phosphorylates a set of intracellular proteins which levetually leads to muscle contraction

PKC needs to bind to Ca2+ to become active