Regulation of phospholipase C-beta activity by phosphatidic acid: isoform dependence, role of protein kinase C, and G protein subunits.
Phosphatidic acid (PA) stimulates phospholipase C-beta(1) (PLC-beta(1)) activity and promotes G protein stimulation of PLC-beta(1) activity. The isoform dependence for PA regulation of PLC-beta activity as well as the role of PA in modulating regulation of PLC-beta activity by protein kinase C (PKC) and G protein subunits was determined. As compared to PLC-beta(1), the phospholipase C-beta(3) (PLC-beta(3)) isoform was less sensitive to PA, requiring greater than 15 mol % PA for stimulation. PLC-beta(3) bound weakly to PA. PKC had little effect on PA stimulation of PLC-beta(3) activity. PKC, however, inhibited PA stimulation of PLC-beta(1) activity through a mechanism dependent on the mol % PA. Stimulation by 7.5 mol % PA was completely inhibited by PKC. Increasing the PA and Ca(2+) concentration attenuated PKC inhibition. The binding of PLC-beta(1) to PA containing phospholipid vesicles was also reduced by PKC, in a manner dependent on the mol % PA. PA increased the stimulation of PLC-beta(1) activity by G alpha q but had little effect on the stimulation by beta gamma subunits. These results demonstrate that PA stimulation of PLC-beta activity is tightly regulated, suggesting the existence of a distinct PA binding region in PLC-beta(1). PA may be an important component of a receptor mediated signaling mechanism that determines PLC-beta(1) activation.
Litosch
Irene
I
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, Florida 33101, USA. ilitosch@med.miami.edu
D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D010712:Phosphatidic Acids / Q000494:pharmacology*; D054799:Phospholipase C beta; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000737:chemistry*; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D021122:Protein Subunits / Q000737:chemistry*; D010738:Type C Phospholipases / Q000737:chemistry / Q000378:metabolism*
D007527:Isoenzymes; D008051:Lipid Bilayers; D010712:Phosphatidic Acids; D021122:Protein Subunits; C496628:PRKCA protein, human; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins