An Arg-Gly-Asp peptide stimulates Ca2+ efflux from osteoclast precursors through a novel mechanism

K. Yamakawa, R. Duncan, K. A. Hruska

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We examined the effect of a peptide containing the Arg-Gly-Asp (RGD) sequence on 45Ca2+ efflux from osteoclast precursors. 45Ca2+-loaded osteoclast precursors were treated with GRGDSP (170 μM) for 10 min after 30 min of basal perfusion with a bicarbonate-containing buffer. GRGDSP significantly increased fractional efflux of Ca2+ from treated cells compared with vehicle-treated cells (P < 0.01) or cells treated with up to 200 μg/ml of a control peptide containing GRGESP. The effect of RGD was sustained for 15 min after the peptide was removed from the perfusate, but control levels of Ca2+ efflux returned by 1 h. The Ca2+ efflux effect of GRGDSP was most likely due to activation of the plasma membrane Ca2+-adenosinetriphosphatase (Ca2+-ATPase) pump, as indicated by its inhibition with vanadate and a calmodulin antagonist, N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide, and the absence of an effect of Na+/Ca2+ exchange inhibition. An inhibitor of cyclic, nucleotide-dependent protein kinases, N-[2-(methylamino)ethyl]-5-isoquinoline-sulfonamide (0.1 mM), failed to inhibit GRGDSP-stimulated Ca2+ efflux. However, genistein and herbimycin A, inhibitors of protein-tyrosine kinases, blocked Ca2+ efflux stimulated by GRGDSP. The results indicate that RGD sequences of matrix proteins may stimulate Ca2+ efflux from osteoclasts through activation of protein-tyrosine kinases and suggest that GRGDSP-stimulated Ca2+ efflux is mediated via the plasma membrane Ca2+-ATPase.

Original languageEnglish
Pages (from-to)F651-F657
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Issue number4 35-4
StatePublished - Apr 1994


  • Genistein
  • Herbimycin A
  • N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide
  • N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide
  • Protein kinases
  • RGD proteins
  • Synthetic peptides


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