Hormonal regulation of phospholipase Cepsilon through distinct and overlapping pathways involving G12 and Ras family G-proteins.
PLCepsilon (phospholipase Cepsilon) is a novel PLC that has a CDC25 guanine nucleotide exchange factor domain and two RA (Ras-association) domains of which the second (RA2) is critical for Ras activation of the enzyme. In the present studies, we examined hormonal stimulation to elucidate receptor-mediated pathways that functionally regulate PLCepsilon. We demonstrate that EGF (epidermal growth factor), a receptor tyrosine kinase agonist, and LPA (lysophosphatidic acid), S1P (sphingosine 1-phosphate) and thrombin, GPCR (G-protein-coupled receptor) agonists, stimulate PLCepsilon overexpressed in COS-7 cells. EGF stimulated PLCepsilon in an RA2-dependent manner through Ras and Rap. In contrast, LPA, S1P and thrombin stimulated PLCepsilon by both RA2-independent and -dependent mechanisms. To determine the G-proteins that mediate the effects of these GPCR agonists, we co-expressed constitutively active G-proteins with PLCepsilon and found that G(alpha12), G(alpha13), Rho, Rac and Ral stimulate PLCepsilon in an RA2-independent manner; whereas TC21, Rap1A, Rap2A and Rap2B stimulate PLCepsilon in an RA2-dependent manner similar to H-Ras. Of these G-proteins, we show that G(alpha12)/G(alpha13) and Rap partly mediate the effects of LPA, S1P and thrombin to stimulate PLCepsilon. In addition, the stimulation by LPA and S1P is also partly sensitive to pertussis toxin. These studies demonstrate diverse hormonal regulation of PLCepsilon by distinct and overlapping pathways.
Kelley
Grant G
GG
Department of Medicine, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA. kelleyg@upstate.edu
Reks
Sarah E
SE
Smrcka
Alan V
AV
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D006728:Hormones / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D008246:Lysophospholipids / Q000037:antagonists & inhibitors; D037342:Pertussis Toxin / Q000494:pharmacology; D054801:Phosphoinositide Phospholipase C; D017434:Protein Structure, Tertiary; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000819:agonists; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors; D010738:Type C Phospholipases / Q000737:chemistry / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*; D020741:rho GTP-Binding Proteins
D006728:Hormones; D007527:Isoenzymes; D008246:Lysophospholipids; D043562:Receptors, G-Protein-Coupled; C060506:sphingosine 1-phosphate; D037342:Pertussis Toxin; D020794:Receptor Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C423320:phospholipase C epsilon; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D013110:Sphingosine