Store-operated calcium entry induced by activation of Gq-coupled alpha1B adrenergic receptor in human osteoblast

• Published in: Biochemical and biophysical research communications 2013-07, Vol.437 (2), p.239-244
• Main Authors: Kodama, Daisuke, Togari, Akifumi
• Format: Article
• Language: English
• Subjects: Adult; Calcium - metabolism; Cells, Cultured; Gq protein-coupled α1-adrenergic receptor; GTP-Binding Protein alpha Subunits, Gq-G11 - metabolism; Humans; Male; Osteoblast; Osteoblasts - cytology; Osteoblasts - metabolism; Receptors, Adrenergic, alpha-1 - metabolism; Store-operated Ca2+ channel; Sympathetic nervous system
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2013.06.047

•Noradrenaline-induced Ca2+ response was abolished by removal of extracellular Ca2+.•Neither voltage-dependent Ca2+ channel nor Na+/Ca2+ exchanger was involved.•Store-operated Ca2+ channel has a critical role in α1B-adrenoceptor-mediated signal. Recent studies have revealed that the sympathetic nervous system is involved in bone metabolism. We previously reported that noradrenaline (NA) suppressed K+ currents via Gi/o protein-coupled alpha1B-adrenergic receptor (α1B-AR) in human osteoblast SaM-1 cells. Additionally, it has been demonstrated that the intracellular Ca2+ level ([Ca2+]i) was increased by NA via α1B-AR. In this study, we investigated the signal pathway of NA-induced [Ca2+]i elevation by using Ca2+ fluorescence imaging in SaM-1 cells. NA-induced [Ca2+]i elevation was suppressed by pretreatment with a PLC inhibitor, U73122. This suggested that the [Ca2+]i elevation was mediated by Gq protein-coupled α1B-AR. On the other hand, NA-induced [Ca2+]i elevation was completely abolished in Ca2+-free solution, which suggested that Ca2+ influx is the predominant pathway of NA-induced [Ca2+]i elevation. Although the inhibition of K+ channel by NA caused membrane depolarization, the [Ca2+]i elevation was not affected by voltage-dependent Ca2+ channel blockers, nifedipine and mibefradil. Meanwhile, NA-induced [Ca2+]i elevation was abolished following activation of store-operated Ca2+ channel by thapsigargin. Additionally, the [Ca2+]i elevation was suppressed by store-operated channel inhibitors, 2-APB, flufenamate, GdCl3 and LaCl3. These results suggest that Ca2+ influx through store-operated Ca2+ channels plays a critical role in the signal transduction pathway of Gq protein-coupled α1B-AR in human osteoblasts.