| Abstract | Protamine sulfate (PS), a specific blocker of PDGF action, inhibited the proliferative response of tsKSV-NRK cells to a reactivated, temperature-sensitive viral Ki-RAS protein, but it did not affect the proliferative response of tsASV-NRK cells to a reactivated pp60v-src protein kinase. The inhibition by PS of the proliferation response of tsKSV-NRK cells to reactivated Ki-RAS protein was overcome by serum growth factors, notably EGF, and concentrated serum-free conditioned medium from cultured NRK cells infected with wild-type KSV, but not by a combination of PDGF and insulin. These observations suggest that the viral Ki-RAS protein, but not pp60v-src, stimulates proliferation exclusively by inducing the host cells to produce PDGF or PDGF-like mitogenic factors. |
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