NEGATIVE CORRELATION WITH LIVER-CELL DIVISION OF A 38 KILODALTON PROTEIN WHOSE PHOSPHORYLATION IS ENHANCED BY RAS AND G-PROTEINS

We showed earlier that the phosphorylation of a 38 kDa protein (p38) f rom rat liver plasma membrane is stimulated by ras or endogenous G-pro teins. We have now estimated the level of expression of p38 in liver t issues from embryos at different stages of development, regenerating l iver and also in tumor cell lines of hepatic origin. Our results indic ate that the expression of p38 is negatively correlated with cell divi sion. It is suggested that the phosphorylation of p38, an event which is regulated by ras proteins and G-proteins, could be involved in sign al transduction processes associated with the inhibitory regulation of cell division.