Cellular signaling events elicited by v-abl associated with growth factor independence in an interleukin-3-dependent cell line

A temperature-sensitive mutant of the v-abl oncoprotein has previously been shown to have markedly reduced tyrosine protein kinase activity in interleukin 3 (IL-3)-dependent cells grown at restrictive (39 °C), compared to permissive (32 °C) temperatures. Transfection of this mutant v-abl into the IC2.9 cell line, generated the IC.DP subclone which was dependent on IL- 3 for survival at 39 °C, but not at 32 °C. Furthermore, IC.DP cells cultured at 32 °C exhibited IL-3-independent thymidine incorporation, which was not apparent at 39 °C. Switching cells from the restrictive to the permissive temperature resulted in an increase in cellular inositol-1,4,5- trisphosphate, choline phosphate and diacylglycerol levels in the IC.DP cell line. These increases were only observed after a lag period of 4 h. Within 2 h of switching IC.DP cells previously maintained at 32 to 39 °C, there was a significant decrease in all three metabolites. Temperature switches had no effect upon these metabolites in the parent IC2.9 cell line. Down-regulation of protein kinase C inhibited v-abl-stimulated DNA synthesis in IC.DP cells cultured at 32 °C IC.DP cells cultured at 32 °C were found to have a constitutively activated Na⁺/H⁺ antiport, although this activation was inhibited by the down-modulation of protein kinase C. These data indicate a role for phospholipid hydrolysis and protein kinase C activation in V-ABL- mediated abrogation of IL-3 dependence.