title: PKC epsilon-related kinase associates with and phosphorylates cytokeratin 8 and 18.
abstract: A 40-kD protein kinase C (PKC)epsilon related activity was found to associate with human epithelial specific cytokeratin (CK) polypeptides 8 and 18. The kinase activity coimmunoprecipitated with CK8 and 18 and phosphorylated immunoprecipitates of the CK. Immunoblot analysis of CK8/18 immunoprecipitates using an anti-PKC epsilon specific antibody showed that the 40-kD species, and not native PKC epsilon (90 kD) associated with the cytokeratins. Reconstitution experiments demonstrated that purified CK8 or CK18 associated with a 40-kD tryptic fragment of purified PKC epsilon, or with a similar species obtained from cells that express the fragment constitutively but do not express CK8/18. A peptide pseudosubstrate specific for PKC epsilon inhibited phosphorylation of CK8/18 in intact cells or in a kinase assay with CK8/18 immunoprecipitates. Tryptic peptide map analysis of the cytokeratins that were phosphorylated by purified rat brain PKC epsilon or as immunoprecipitates by the associated kinase showed similar phosphopeptides. Furthermore, PKC epsilon immunoreactive species and CK8/18 colocalized using immunofluorescent double staining. We propose that a kinase related to the catalytic fragment of PKC epsilon physically associates with and phosphorylates cytokeratins 8 and 18.
authors.affiliation: Stanford University School of Medicine, Gastroenterology Division, California 94305.
authors.forename: M B
authors.initials: MB
authors.lastname: Omary
authors.forename: G T
authors.initials: GT
authors.lastname: Baxter
authors.forename: C F
authors.initials: CF
authors.lastname: Chou
authors.forename: C L
authors.initials: CL
authors.lastname: Riopel
authors.forename: W Y
authors.initials: WY
authors.lastname: Lin
authors.forename: B
authors.initials: B
authors.lastname: Strulovici
mesh_terms: D003599:Cytoskeleton / Q000201:enzymology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007527:Isoenzymes / Q000276:immunology / Q000378:metabolism*; D007633:Keratins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D046911:Macromolecular Substances; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000276:immunology / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D014407:Tumor Cells, Cultured / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010748:Phosphopeptides; D007633:Keratins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C497255:PRKCE protein, human; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon