Soluble alpha v beta 3-integrin ligands raise [Ca2+]i in rat osteoclasts and mouse-derived osteoclast-like cells.
We evaluated the possible involvement of intracellular Ca2+ concentration ([Ca2+]i) changes in the action of alpha v beta 3-ligands, known to regulate osteoclast function. Rat osteoclasts or mouse osteoclast-like cells, as examined by microfluorimetry and fura 2, showed a transient [Ca2+]i increase when perfused with (all 0.1 microM) vitronectin, osteopontin, polypeptide echistatin, fibronectin, and Arg-Gly-Asp-Asp and Arg-Gly-Asp-Ser peptides (10(-4) M) but not with laminin, collagen I, collagen IV, or [Ala24]echistatin, in which Ala was substituted for Arg in the Arg-Gly-Asp complex. The threshold for echistatin was 10 pM, the 50% effective concentration was 1 nM, and the median [Ca2+]i increase was 420 nM above the resting level (217 +/- 22 nM) at saturating concentration of 0.1 microM. Echistatin did not cause Mn2+ influx, and 10 microM nifedipine, 10 nM omega-conotoxin, 5 mM Ni2+, or Cd2+ did not prevent [Ca2+]i change. However, extracellular Ca2+ was needed for the [Ca2+]i increase, probably enabling ligand-integrin interaction. Polyclonal and monoclonal (LM609) antibody as well as depletion of [Ca2+]i stores with 5 microM thapsigargin and Ca(2+)-free medium abolished the [Ca2+]i increase, after restoring extracellular Ca2+. Furthermore, the LM609 antibody induced a Ca2+ signal in the presence or absence of extracellular Ca2+, suggesting that the alpha v beta 3-ligand interaction is mediated at least partially by Ca2+ mobilized from intracellular stores.
Zimolo
Z
Z
Department of Bone Biology and Osteoporosis Research, Merck Research Laboratories, West Point 19486.
Wesolowski
G
G
Tanaka
H
H
Hyman
J L
JL
Hoyer
J R
JR
Rodan
G A
GA
D000818:Animals; D000911:Antibodies, Monoclonal; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D007106:Immune Sera; D016023:Integrins / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D007425:Intracellular Membranes / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D009994:Osmolar Concentration; D010010:Osteoclasts / Q000378:metabolism*; D010455:Peptides; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D012995:Solubility; D014757:Viper Venoms / Q000737:chemistry / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D007106:Immune Sera; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D010455:Peptides; D014757:Viper Venoms; C057986:echistatin; D002118:Calcium