title: Protein kinase C ζ is a positive modulator of canonical Wnt signaling pathway in tumoral colon cell lines.
abstract: The colonic epithelium is a continuously renewing tissue with a dynamic turnover of cells. Wnt pathway is a key regulator of its homeostasis and is altered in a large proportion of colon cancers. Protein kinase C (PKC) family of serine/threonine kinases are also involved in colon tumor formation and progression; however, the molecular role played by them in the Wnt pathway, is poorly understood. Reciprocal coimmunoprecipitation and immunofluorescence studies revealed that PKCζ interacts with β-catenin mainly in tumoral colon cells, which overexpressed this PKC isoform. The pharmacological inhibition, the small interference RNA-mediated knockdown of PKCζ or the expression of a dominant-negative form of it in tumoral SW480 cells, blocked in a dose-dependent manner the constitutive transcriptional activity mediated by β-catenin, the cell proliferation and the expression of the Wnt target gene c-myc. Remarkably, the PKCζ stably depleted cells exhibited diminished tumorigenic activity in grafted mice. We show that PKCζ functions in a mechanism that does not involve β-catenin degradation since the effects produced by PKCζ inhibition were also obtained in the presence of proteosome inhibitor and in cells expressing a β-catenin degradation-resistant mutant. It was found that PKCζ activity regulates the nuclear localization of β-catenin since PKCζ inhibition induces a rapid export of β-catenin from the nucleus to the cytoplasm in a Leptomycin B sensitive manner. Taken together, our results indicate that the atypical PKCζ plays an important role in the positive regulation of canonical Wnt pathway.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México, Av. Universidad 3000, Mexico, 04510, Mexico.
authors.forename: Luis Bernardo
authors.initials: LB
authors.lastname: Luna-Ulloa
authors.forename: José G
authors.initials: JG
authors.lastname: Hernández-Maqueda
authors.forename: Paula
authors.initials: P
authors.lastname: Santoyo-Ramos
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Castañeda-Patlán
authors.forename: Martha
authors.initials: M
authors.lastname: Robles-Flores
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D003106:Colon / Q000378:metabolism; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D005799:Genes, Dominant; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*; D000099221:Protein Kinase C zeta
chemical_list: D008156:Luciferases; D011493:Protein Kinase C; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051176:beta Catenin; D000099221:Protein Kinase C zeta; C495270:CTNNB1 protein, human