Open AccessTyrosine phosphorylation is a signal for the trafficking of pp85, an 85-kDa phosphorylated polypeptide associated with phosphatidylinositol kinase activity.
Author(s) -
B Cohen,
Monique Yoakim,
Helen PiwnicaWorms,
Thomas M. Roberts,
Brian Schaffhausen
Publication year - 1990
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.87.12.4458
Subject(s) - phosphorylation , phosphoprotein , cytosol , tyrosine , biochemistry , tyrosine phosphorylation , phosphatidylinositol , protein phosphorylation , biology , blot , kinase , chemistry , protein kinase a , enzyme , gene
A family of 85/86-kDa (85K/86K) polypeptides closely linked to phosphatidylinositol kinase activity is found in polyoma middle-sized tumor antigen (MTAg)/pp60c-src complexes. MTAg and the 85-kDa phosphoprotein (pp85) could be reassociated in solution, or on blots, after denaturation with SDS. Results from such experiments focus attention on phosphorylation in controlling intracellular sorting and activation of pp85. Tyrosine phosphorylation seems important for recruitment of pp85 from cytosol to membrane. By blotting, pp85 is substantially cytosolic, whereas that recognized by anti-phosphotyrosine antibody is almost exclusively in membranes. Tyrosine phosphorylation also determined association of pp85 with MTAg. Manipulation of MTAg tyrosine phosphorylation, for example, by expressing MTAg using baculovirus vectors in the absence or presence of pp60c-src, dramatically affects reassociation. Finally, tyrosine phosphorylation appears to be involved in release of pp85 from MTAg, since vanadate increased its rate of dissociation.