INSULIN-INDUCED STIMULATION OF PROTEIN-PHOSPHORYLATION IN NEUROSPORA-CRASSA CELLS

1) Insulin stimulated the phosphorylation of at least 14 discrete proteins in Neurospora crassa cells. Specific proteins were phosphorylated at serine, threonine, and tyrosine residues, as determined by phosphoamino acid analysis of discrete spots on two-dimensional gels. 2) Insulin stimulated the phosphorylation by [gamma-P-32]ATP of at least six discrete proteins in solubilized N. crassa membrane preparations at serine and tyrosine residues. 3) A phosphotyrosine-containing protein of 38 kDa, pI 7.0-7.2, reacted by both immunoblotting and immunoprecipitation with antiserum to P2, a peptide from the human insulin receptor that contains an autophosphorylated tyrosine residue. In N. crassa cells, therefore, as in mammalian cells, insulin induces a variety of protein phosphorylations, some of which may be part of an evolutionarily conserved signal transduction pathway.