Phospholipase C beta and membrane action of calcitriol and estradiol.
We have shown that estrogens and calcitriol, the hormonally active form of vitamin D, increase the concentration of intracellular calcium ([Ca2+]i) within 5 s by mobilizing calcium from the endoplasmic reticulum and the formation of inositol 1,4, 5-trisphosphate and diacylglycerol. Because the activation of effectors as phospholipase C (PLC) coupled to G-proteins is the early event in the signal transduction pathway leading to the inositol 1,4,5-trisphosphate formation and to [Ca2+]i increase, we described different PLC isoforms (beta1, beta2, gamma1, and gamma2, but not beta4) in female rat osteoblasts using Western immunoblotting. The data showed that phospholipase C beta was involved in the mobilization of Ca2+ from the endoplasmic reticulum of Fura-2-loaded confluent osteoblasts by calcitriol and 17beta estradiol, and PLC gamma was ineffective. The data also showed that only a PLC beta1 linked to a Pertussis toxin-insensitive G-protein and a PLC beta2 coupled to a Pertussis toxin-sensitive G-protein are involved in the effects of calcitriol and 17beta estradiol on the mobilization of Ca2+ from intracellular Ca2+ stores. In conclusion, these results may be an important step toward understanding membrane effects of these steroids and may be an additional argument in favor of membrane receptors to steroid hormones.
Le Mellay
V
V
CNRS, URA 583, Université Paris V, 78 350 Jouy-en-Josas, France.
Grosse
B
B
Lieberherr
M
M
D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D015151:Immunoblotting; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000276:immunology / Q000378:metabolism*; D007700:Kinetics; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D037342:Pertussis Toxin; D054799:Phospholipase C beta; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions / Q000378:metabolism; D010738:Type C Phospholipases / Q000276:immunology / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000906:Antibodies; D004075:Diglycerides; D007527:Isoenzymes; D010566:Virulence Factors, Bordetella; D004958:Estradiol; D015544:Inositol 1,4,5-Trisphosphate; D037342:Pertussis Toxin; D000469:Alkaline Phosphatase; D009597:4-Nitrophenylphosphatase; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C518035:Plcb1 protein, rat; C518038:Plcb2 protein, rat; C518044:Plcb4 protein, rat; D019204:GTP-Binding Proteins; D002117:Calcitriol; D002118:Calcium