Type I protein kinase A is localized to interphase microtubules and strongly associated with the mitotic spindle

We show here that type I protein kinase A is localized to microtubules duri ng the entire cell cycle in epithelial (hepatoma, cervical carcinoma) and n onepithelial (myoblast) cell lines, The association of the type I alpha reg ulatory subunit is very strong in all phases of mitosis, from prophase to c ytokinesis, In interphase, the association appears weaker, reflecting perha ps a more dynamic molecular interaction. This regulatory subunit appears to recruit catalytic subunits as the latter are also associated with microtub ules, BW1J hepatoma cells, stably transfected with either wild-type or muta nt I alpha regulatory subunit, are enriched in aberrant mitoses with multip olar spindles and in mono- or multinucleated giant cells, This suggests tha t type I protein kinase A could have a role in centrosome duplication and/o r segregation, sister chromatid separation, or cytokinesis. (C) 2001 Academ ic Press.