title: An Arg-Gly-Asp peptide stimulates Ca2+ efflux from osteoclast precursors through a novel mechanism.
abstract: We examined the effect of a peptide containing the Arg-Gly-Asp (RGD) sequence on 45Ca2+ efflux from osteoclast precursors. 45Ca(2+)-loaded osteoclast precursors were treated with GRGDSP (170 microM) 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 micrograms/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 Ca(2+)-adenosinetriphosphatase (Ca(2+)-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 Ca(2+)-ATPase.
authors.affiliation: Renal Division, Jewish Hospital, Washington University Medical Center, St. Louis, Missouri 63110.
authors.forename: K
authors.initials: K
authors.lastname: Yamakawa
authors.forename: R
authors.initials: R
authors.lastname: Duncan
authors.forename: K A
authors.initials: KA
authors.lastname: Hruska
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016227:Benzoquinones; D002645:Chickens; D005260:Female; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D047029:Lactams, Macrocyclic; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010010:Osteoclasts / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D017828:Rifabutin / Q000031:analogs & derivatives; D013234:Stem Cells / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D016227:Benzoquinones; D007529:Isoflavones; D007546:Isoquinolines; D047029:Lactams, Macrocyclic; D009842:Oligopeptides; D010446:Peptide Fragments; D011809:Quinones; D017828:Rifabutin; D014638:Vanadates; C020754:herbimycin; C047981:arginyl-glycyl-aspartic acid; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; C058161:glycyl-arginyl-glycyl-aspartyl-seryl-proline; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C