1,25(OH)2-vitamin D3 stimulation of phospholipases C and D in muscle cells involves extracellular calcium and a pertussis-sensitive G protein.
The steroid hormone 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] activates in chick myoblasts the breakdown of phosphoinositides by phospholipase C and the hydrolysis of phosphatidylcholine by phospholipase D. Extracellular Ca2+ requirement and GTP-binding protein mediation of 1,25(OH)2D3-dependent activation of phospholipases C and D were investigated in cells prelabelled with [3H]glycerol or [3H]arachidonic acid. Generation of diacylglycerol by phospholipase C and phosphatidylethanol by phospholipase D were shown to be dependent on extracellular calcium, since both responses were suppressed by EGTA and the Ca(2+)-channel blockers nifedipine and verapamil, and were mimicked by the calcium ionophore A23187. The G-protein activators guanosine 5'-O-(3-thiotriphosphate) and AlF4- strongly enhanced diacylglycerol and phosphatidylethanol release in myoblasts while guanosine 5'-O-(2-thiodiphosphate), which inhibits G-protein-mediated signals, abolished 1,25(OH)2D3-dependent diacylglycerol and phosphatidylethanol release. Bordetella pertussis toxin pretreatment suppressed the hormone action. These results suggest that 1,25(OH)2D3-stimulation of phosphoinositide-specific phospholipase C and phospholipase D in chick myoblasts is mediated by a pertussis-sensitive GTP-binding protein(s) and the influx of extracellular calcium.
Departamento de Biologia y Bioquimica, Universidad Nacional del Sur, Bahia Blanca, Argentina.
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Morelli
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Boland
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de Boland
D017607:Aluminum Compounds / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002642:Chick Embryo; D004075:Diglycerides / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D005990:Glycerol / Q000378:metabolism; D020404:Glycerophospholipids; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D009132:Muscles / Q000187:drug effects / Q000201:enzymology*; D037342:Pertussis Toxin; D010712:Phosphatidic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D017607:Aluminum Compounds; D002121:Calcium Channel Blockers; D004075:Diglycerides; D020404:Glycerophospholipids; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D019269:Phosphatidylinositol 4,5-Diphosphate; D010566:Virulence Factors, Bordetella; C051521:phosphatidylethanol; D016718:Arachidonic Acid; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D010738:Type C Phospholipases; D010739:Phospholipase D; D019204:GTP-Binding Proteins; D002117:Calcitriol; D005990:Glycerol; D005459:Fluorides; D002118:Calcium; C032311:aluminum fluoride