Competence induction by PDGF requires sustained calcium influx by a mechanism distinct from storage-dependent calcium influx.
The significance and mechanism of extracellular calcium influx in the stimulation by PDGF of cell replication was investigated in density-arrested C3H 10T1/2 mouse fibroblasts. PDGF consistently stimulated a biphasic increase in the [Ca2+]i composed of a rapid transient release of calcium from intracellular storage sites followed by a sustained elevation, significantly greater than prestimulated levels, which was dependent upon the [Ca2+]e and persisted for at least 1 h. The percentage of cells incorporating [3H]-TdR into DNA after stimulation with PDGF+insulin was closely correlated with the magnitude of the sustained [Ca2+]i increase and to the [Ca2+]e. Selective inhibition of the sustained [Ca2+]i increase, by blocking calcium influx with La3+, completely inhibited progression to S phase without affecting the release of calcium from intracellular storage sites. Progression to S phase was inhibited by La3+ or the omission of added extracellular calcium only during PDGF exposure and not during treatment with insulin. PDGF-induced calcium influx was completely inhibited by La3+ whereas storage-dependent calcium influx (SDCI) induced by thapsigargin was unaffected. Pretreatment with TPA, forskolin, dibutyryl-cAMP, dibutyryl-cGMP, nifedipine, and TMB-8 had no effect on PDGF-induced calcium influx. These data suggest that the induction of replicative competence by PDGF is dependent upon the maintenance of a sustained increase in the intracellular calcium concentration due to the influx of extracellular calcium through a calcium influx pathway distinct from SDCI.
University of Hawaii at Manoa, Cancer Research Center of Hawaii, Honolulu.
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Estacion
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Mordan
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002451:Cell Compartmentation; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D003260:Contact Inhibition / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects; D004357:Drug Synergism; D005110:Extracellular Space / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D051379:Mice; D008809:Mice, Inbred C3H; D009543:Nifedipine / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015220:Calcium Channels; D007328:Insulin; D010982:Platelet-Derived Growth Factor; D005576:Colforsin; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D003994:Bucladesine; D007811:Lanthanum; D009543:Nifedipine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium