J. Biol. Chem., Vol. 265, Issue 16, 9022-9026, 06, 1990
Kinetic evidence of a rapid activation of phosphatidylcholine hydrolysis by Ki-ras oncogene. Possible involvement in late steps of the mitogenic cascade
M Lopez-Barahona, PL Kaplan, ME Cornet, MT Diaz-Meco, P Larrodera, I Diaz- Laviada, AM Municio and J Moscat
Medicina y Cirugia Experimental, Hospital General Gregorio Maranon, Madrid, Spain.
A novel phospholipase C specific for phosphatidylcholine has been shown to
be activated by several agonists. Also, recent evidence suggests that
transformation mediated by the ras oncogene possibly involves the
activation of this novel phospholipid degradative pathway which would
account for the increased diacylglycerol levels associated with
transformation. Here we use a mutant of Ki-ras which is temperature-
sensitive for transformation to investigate the kinetics of activation of
the phosphodiesterase-mediated turnover of phosphatidylcholine. Upon shift
to the permissive temperature, products of the activated
phosphatidylcholine-specific phospholipase C were detected by 30 min and
reached maximal levels by 1-2 h. These results suggest that the product of
the ras oncogene rapidly activates the phosphodiesteratic hydrolysis of
phosphatidylcholine. Furthermore, the fact that at least 4 h are required
for serum to activate this phospholipase C strongly suggests that the ras
oncogene product might be involved in late steps of the mitogenic signaling
cascade.