Stimulation of K+ transport systems by Ha-ras

M. Meyer, K. Maly, F. Uberall, J. Hoflacher, H. Grunicke

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The expression of Ha-ras in quiescent NIH3T3 cells carrying a glucocorticoid-inducible human Ha-ras gene (Val-Gly mutation at codon 12) stimulates total 86Rb+ influx. This effect is predominantly due to an elevated 86Rb+ uptake through an ouabain-resistant, furosemide-sensitive system. The ouabain-sensitive Na+/K+-ATPase is less affected. The transport which is resistant to both inhibitors is not altered by Ha-ras. Overexpression of the Ha-ras proto-oncogene causes only a marginal increase in total 86Rb+ uptake. The stimulation of the furosemide-sensitive influx by Ha-ras is paralleled by an increase in mean cell volume which can be inhibited by furosemide. A rapid stimulation of the furosemide-sensitive Rb+ influx is also observed after addition of bombesin to growth-arrested cells. Furosemide inhibits the mitogenic response after expression of Ha-ras or addition of bombesin. Both the Ha-ras and the bombesin-induced stimulation of the furosemide-sensitive Rb+ transport can be blocked by protein kinase C depletion or the protein kinase C inhibitor staurosporine. In contrast to bombesin-induced phosphatidylinositol-4,5-bisphosphate hydrolysis which is down-modulated by Ha-ras, the stimulation of the furosemide-sensitive Rb+ influx by bombesin is elevated in Ha-ras-expressing cells. This is in accordance with the increased mitogenic activity of bombesin in Ha-ras-expressing cells.

Original languageEnglish (US)
Pages (from-to)8230-8235
Number of pages6
JournalJournal of Biological Chemistry
Issue number13
StatePublished - 1991
Externally publishedYes


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