Osteoclast Cytosolic Calcium, Regulated by Voltage-Gated Calcium Channels and Extracellular Calcium, Controls Podosome Assembly and Bone Resorption

• Published in: The Journal of cell biology Vol. 111; no. 6; pp. 2543 - 2552
• Main Authors: Miyauchi, Akimitsu, Hruska, Keith A., Greenfield, Edward M., Duncan, Randall, Alvarez, Jose, Barattolo, Raniero, Colucci, Silvia, Zambonin-Zallone, Alberta, Teitelbaum, Steven L., Teti, Anna
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Rockefeller University Press 01.12.1990; The Rockefeller University Press
• Subjects: 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester - pharmacology; Aerospace Medicine; Animals; Biological and medical sciences; Bone Resorption; Bones; Calcium; Calcium - metabolism; Calcium - pharmacology; Calcium - physiology; Calcium Channel Blockers - pharmacology; Calcium Channels - drug effects; Calcium Channels - physiology; Cell membranes; Cells; Cells, Cultured; Chickens; Cytoskeleton - drug effects; Cytoskeleton - ultrastructure; Cytosol - metabolism; Dantrolene - pharmacology; Depolarization; Dihydropyridines; Egtazic Acid - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Kinetics; Lanthanum - pharmacology; Membrane Potentials - drug effects; Microfilaments; Osteoclasts; Osteoclasts - physiology; Osteoclasts - ultrastructure; Physiological regulation; Potassium - pharmacology; Skeleton and joints; Space life sciences; Vertebrates: osteoarticular system, musculoskeletal system; Non-Nasa Center; Nasa Discipline Musculoskeletal; Vertebrata; Regulation(control); Calcium; Resorption; Ionic channel; Osteoclast; Chicken; Bone; Aves; Fluorescence microscopy; NASA Discipline Musculoskeletal; Non-NASA Center
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.111.6.2543

The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5× 10-6 M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10-5 M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggest the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.