Differences in the Cyclic AMP-Dependent Phosphorylation of Plasma Membrane Proteins of Differentiated and Undifferentiated L6 Myogenic Cells |
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Authors: | ROBERT E SCOTT THOMAS P DOUSA |
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Institution: | Department of Pathology and Anatomy, Mayo Clinic, Rochester, Minnesota 55901, USA;Department of Physiology and Medicine, Mayo Clinic, Rochester, Minnesota 55901, USA |
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Abstract: | Differences in the cyclic AMP-dependent plasma membrane phosphorylation system of undifferentiated and differentiated L6 myogenic cells have been detected. Endogenous plasma membrane protein phosphorylation in undifferentiated L6 myoblasts was stimulated more than three fold by 5 × 10?5 M cyclic AMP, whereas no statistically significant cyclic AMP-dependent phosphorylation of endogenous plasma membrane proteins was observed in differentiated L6 cells. In undifferentiated cells cyclic AMP promoted the phosphorylation of several proteins, the most prominent of which had a molecular weight of 110,000. In differentiated cells cyclic AMP did not selectively promote the phosphorylation of specific plasma membrane proteins. Both differentiated and undifferentiated L6 cells, however, contain a cyclic AMP-dependent protein kinase capable of catalyzing the phosphorylation of exogenous substrates, such as histone f2b. Therefore, the data show that differentiation in L6 cells is associated with a selective change in the activity of a plasma membrane cyclic AMP-dependent protein kinase which employs endogenous membrane proteins as substrate. |
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