Protein kinase C-theta is specifically activated in murine erythroleukaemia cells during mitosis

Protein kinase C-theta is a member of the n-protein kinase C subfamily that in mitotic cells translocates to centrosomes and kinetochores. Although th is kinase is expressed in comparable amounts in murine erythroleukaemia cel ls during the interphase or metaphase, when localized in the mitotic struct ures, it selectively phosphorylates a 66 kDa protein, also associated to ch romosomes. Moreover, protein kinase C-theta immunoprecipitated from cells a t the metaphase results four times more active in the absence of lipid cofa ctors as compared with the kinase obtained from cells in the interphase, Th is activation is accomplished by interaction of protein kinase C-theta with a protein factor which also promotes an increased autophosphorylation of t he kinase. These findings indicate that in the mitotic phase of the cell cy cle, protein kinase C-theta recognizes a protein factor which operates as a positive modulator of the kinase activity in the absence lipids. (C) 1999 Federation of European Biochemical Societies.