[Phospholipid metabolism regulated by heterotrimeric G proteins].
Phosphoinositide-specific phospholipase C (PI-PLC) catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate to inositol 1,4,5-trisphosphate (IP3) and diacylglycerol. IP3 induces the release of Ca2+ from intracellular stores, and diacylglycerol acts as the physiological activator of protein kinase C. Several distinct PI-PLC enzymes have been identified from various cells. Based on the primary sequences, PI-PLC isozymes are divided into three families: PLC-beta, PLC-gamma, and PLC-delta. Substantial evidence has strongly suggested that G proteins regulate PI-PLC in various cell-stimulation systems and that there might be two distinct pathways (pertussis toxin-sensitive and pertussis toxin-insensitive). Recently, it has become apparent that beta-type PLC isoforms are activated by the heterotrimeric G protein subfamily Gq. Careful studies using in vitro and in vivo reconstitution systems have further suggested that the alpha-subunits of Gq/11/16 specifically regulate PLC-beta 1 and PLC-beta 3 and that the beta gamma -subunits of the Gi subfamily interact with PLC-beta 2, which are considered to be responsible for the pertussis toxin-insensitive and the pertussis toxin-sensitive pathways, respectively. In this paper, involvement of G proteins in the regulation of phospholipase A2 and phosphatidylcholine-specific PLC and PLD is also discussed.
Homma
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Department of Biosignal Research, Tokyo Metropolitan Institute of Gerontology, Japan.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D010739:Phospholipase D / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
D010743:Phospholipids; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D002118:Calcium