Angiotensin II activates at least two tyrosine kinases in rat liver epithelial cells. Separation of the major calcium-regulated tyrosine kinase from p125FAK.

摘要: In rat liver epithelial cell lines (WB or GN4), angiotensin II (Ang II) stimulates cytosolic tyrosine kinase activity, in part, through a calcium-dependent mechanism. other types, selected hormones that activate Gi- Gq-coupled receptors stimulate the soluble kinase, p125FAK. Immunoprecipitation of p125FAK from Ang II-activated GN4 cells demonstrated doubling activity. However, an additional (or kinases) representing majority total activity was detected when remaining lysate, immunodepleted p125FAK, reimmunoprecipitated with anti-phosphotyrosine antibody. Cytochalasin D pretreatment blocks G-protein receptor-dependent phosphorylation Swiss 3T3 cells. While cytochalasin decreased Tyr(P) content 65-75-kDa substrates II-treated cells, it did not diminish 115-130-kDa substrates, again suggesting activation at least two pathways To search for enzymes, we used molecular techniques to identify 20 sequences these lines. None major enzyme activated by II. Specifically, JAK2, which had been shown others be stimulated smooth muscle Finally, purified Tyr(P)-containing kinases using anti-Tyr(P) and ATP affinity resins; 80% migrated as single 115-120-kDa tyrosine-phosphorylated protein immunologically distinct summary, activates separate cells; presumably novel, referred kinase.