Regulation of intracellular levels of calmodulin and tubulin in normal and transformed cells.
Transformation of mammalian tissue culture cells by oncogenic viruses results in a 2-fold increase in the intracellular concentration of calmodulin quantitated by radioimmunoassay. The two pairs of companion cell lines used in this study were the Swiss mouse 3T3/simian virus 40-transformed 3T3 cells and the normal rat kidney (NRK)/Rous sarcoma virus-transformed NRK cells. The increased intracellular levels of calmodulin in the transformed cells are due to a greater increase in the rate of synthesis (3-fold) relative to the change in the rate of degradation (1.4-fold). On the other hand, no increases were observed in tubulin levels as quantitated by a colchicine-binding assay. The lack of change in tubulin concentration was accounted for by a 2-fold increase in the rate of degradation that is compensated by a similar increase in the rate of synthesis. The consequence of such changes in both transformed cell types is a 2-fold increase in the calmodulin-to-tubulin protein ratio relative to that in their nontransformed counterparts.
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002460:Cell Line; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D007668:Kidney; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D051379:Mice; D051381:Rats; D013539:Simian virus 40 / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D014404:Tubulin / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D013462:Sulfur Radioisotopes; D014404:Tubulin; D008715:Methionine