MITOSIS-SPECIFIC PHOSPHORYLATION OF VIMENTIN BY PROTEIN-KINASE-C COUPLED WITH REORGANIZATION OF INTRACELLULAR MEMBRANES

Using two types of anti-phosphopeptide antibodies which specifically r ecognize vimentin phosphorylated by protein kinase C (PKC) at two dist inct PKC sites, we found that PKC acted as a mitotic vimentin kinase. Temporal change of vimentin phosphorylation by PKC differed from chang es by cdc2 kinase. The mitosis-specific vimentin phosphorylation by PK C was dramatically enhanced by treatment with a PKC activator, 12-O-te tradecanoylphorbol-13-acetate (TPA), while no phosphorylation of vimen tin by PKC was observed in interphase cells treated with TPA. By contr ast, the disruption of subcellular compartmentalization of interphase cells led to vimentin phosphorylation by PKC. Cytoplasmic and nuclear membranes are fragmented and dispersed in the cytoplasm and some bind to vimentin during mitosis. Thus, targeting of activated PKC, coupled with the reorganization of intracellular membranes which contain phosp holipids essential for activation, leads to the mitosis-specific phosp horylation of vimentin. We propose that during mitosis, PKC may phosph orylate an additional subset of proteins not phosphorylated in interph ase.