Involvement of calmodulin in 1alpha,25-dihydroxyvitamin D3 stimulation of store-operated Ca2+ influx in skeletal muscle cells.
The steroid hormone 1alpha,25-dihydroxyvitamin D(3) (1, 25-(OH)(2)D(3)) rapidly modulates Ca(2+) homeostasis in avian skeletal muscle cells by driving a complex signal transduction mechanism, which promotes Ca(2+) release from inner stores and cation influx from the outside through both L-type and store-operated Ca(2+) (SOC) channels. In the present work, we evaluated the involvement of calmodulin (CAM) in 1,25-(OH)(2)D(3) regulation of SOC influx in chick skeletal muscle cells. Treatment with 10(-9) m 1,25-(OH)(2)D(3) in Ca(2+)-free medium resulted in a rapid but transient Ca(2+) rise correlated with the sterol-induced inositol 1,4,5-trisphosphate (IP(3)) production. The SOC influx stimulated by the hormone was insensitive to both CAM antagonists (fluphenazine, trifluoperazine, chlorpromazine, compound 48/80) and the CAM-dependent protein kinase II (CAMKII) inhibitor KN-62 when added after the sterol-dependent Ca(2+) transient, but it was completely abolished when added prior to the IP(3)-induced mobilization of Ca(2+) from endogenous stores. Moreover, in cells microinjected with antisense oligonucleotides directed against the CAM mRNA the sterol-stimulated SOC influx was reduced up to 60% respect to uninjected cells. The present results suggest that the 1, 25-(OH)(2)D(3)-induced (IP(3)-mediated) cytosolic Ca(2+) transient is required for CAM, activation which in turn activates SOC influx in a mechanism that seems to include CAMKII.
Vazquez
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G
Departamento de Biologia, Bioquimica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000 Bahia Blanca, Argentina.
de Boland
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AR
Boland
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D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008845:Microinjections; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors; D015398:Signal Transduction
D015220:Calcium Channels; D002147:Calmodulin; D004791:Enzyme Inhibitors; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D015544:Inositol 1,4,5-Trisphosphate; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002117:Calcitriol; D002118:Calcium