Cyclic adenosine 3',5'-monophosphate-independent phosphorylation of externally oriented plasma membrane proteins in transformed and nontransformed mouse embryo cell lines.

Thirty transformed and nontransformed mouse embryo cell lines were analyzed to determine if increased plasma membrane phosphorylation is a characteristic of all transformed cell lines. Nontransformed, virally and chemically transformed, and smooth surface-transformed cell lines derived from Swiss, BALB/c, AKR, or C3H mice were studied. Cyclic AMP-independent phosphorylation of plasma membrane proteins was comparable in nontransformed and simian virus 40 (SV40)-transformed Balb/3T3 cells, in nontransformed and 3-methylcholanthrene (MCA)-transformed C3H/10T 1/2 cells, and in nontransformed and MCA-transformed AKR-2B cells. In contrast, increased plasma membrane phosphorylation was observed in MCA- and smoooth surface-transformed Balb/3T3 cells and in SV40-transformed Swiss 3T3 cells compared to the respective nontransformed parent cell lines. These observations suggest that increased cyclic AMP-independent phosphorylation of externally oriented plasma membrane proteins is not a universal marker for the transformed phenotype.