Emerging Insights into the Role of Calcium Ions in Osteoclast Regulation

• Published in: Journal of bone and mineral research Vol. 14; no. 5; pp. 669 - 674
• Main Authors: Zaidi, Mone, Adebanjo, Olugbenga A., Moonga, Baljit S., Sun, Li, Huang, Christopher L.‐H.
• Format: Journal Article
• Language: English
• Published: Washington, DC John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR) 01.05.1999; American Society for Bone and Mineral Research
• Subjects: Animals; Biological and medical sciences; Calcitonin - physiology; Calcium - physiology; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Interleukin-6 - physiology; Membrane Potentials; Osteoclasts - physiology; Signal Transduction; Skeleton and joints; Vertebrates: osteoarticular system, musculoskeletal system; Osteoarticular system; Signal transduction; Regulation(control); Calcium ion; Cell death; Resorption; Osteoclast; Bone; Gene expression; Extracellular; Apoptosis
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1359/jbmr.1999.14.5.669

Osteoclasts are exposed to unusually high, millimolar, Ca2+ concentrations and can “sense” changes in their ambient Ca2+ concentration during resorption. This results in a sharp cystolic Ca2+ increase through both Ca2+ release and Ca2+ influx. The rise in cystolic Ca2+ is transduced finally into an inhibition of bone resorption. We have shown that a type 2 ryanodine receptor isoform, expressed uniquely in the osteoblast plasma membrane, functions as a Ca2+ influx channel, and possibly as a Ca2+ sensor. Ryanodine receptors are ordinarily microsomal membrane Ca2+ release channels. They have only recently been shown to be expressed a other sites, including nuclear membranes. At the latter site, ryanodine receptors gate nucleoplasmic Ca2+ influx. Nucleoplasmic Ca2+, in turn, regulates key nuclear processes, including gene expression and apoptosis. Here, we review potential mechanisms underlying the recognition, movement, and actions of Ca2+ in the osteoclast.