title: Ahnak protein activates protein kinase C (PKC) through dissociation of the PKC-protein phosphatase 2A complex.
abstract: We have previously reported that central repeated units (CRUs) of Ahnak act as a scaffolding protein networking phospholipase Cgamma and protein kinase C (PKC). Here, we demonstrate that an Ahnak derivative consisting of four central repeated units binds and activates PKC-alpha in a phosphatidylserine/1,2-dioleoyl-sn-glycerol-independent manner. Moreover, NIH3T3 cells expressing the 4 CRUs of Ahnak showed enhanced c-Raf, MEK, and Erk phosphorylation in response to phorbol 12-myristate 13-acetate (PMA) compared with parental cells. To evaluate the effect of loss-of-function of Ahnak in cell signaling, we investigated PKC activation and Raf phosphorylation in embryonic fibroblast cells (MEFs) of the Ahnak knock-out (Ahnak(-/-)) mouse. Membrane translocation of PKC-alpha and phosphorylation of Raf in response to PMA or platelet-derived growth factor were decreased in Ahnak null MEF cells compared with wild type MEFs. Several lines of evidence suggest that PKC-alpha activity is regulated through association with protein phosphatase 2A (PP2A). A co-immunoprecipitation assay indicated that the association of PKC-alpha with PP2A was disrupted in NIH3T3 cells expressing 4 CRUs of Ahnak in response to PMA. Consistently, Ahnak null MEF cells stimulated by PMA showed enhanced PKC-PP2A complex formation, and add-back expression of Ahnak into Ahnak null MEF cells abolished the PKC-PP2A complex formation in response to PMA. These data indicate that Ahnak potentiates PKC activation through inhibiting the interaction of PKC with PP2A.
authors.affiliation: Department of Life Science, Ewha Womans University, 11-1 Daehyun-dong, Seodaemoon-Gu, Seoul 120-750, Korea.
authors.forename: In Hye
authors.initials: IH
authors.lastname: Lee
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Lim
authors.forename: Suhyeon
authors.initials: S
authors.lastname: Yoon
authors.forename: Je Kyung
authors.initials: JK
authors.lastname: Seong
authors.forename: Duk Soo
authors.initials: DS
authors.lastname: Bae
authors.forename: Sue Goo
authors.initials: SG
authors.lastname: Rhee
authors.forename: Yun Soo
authors.initials: YS
authors.lastname: Bae
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism; D051966:Phospholipase C gamma / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C489572:Ahnak protein, mouse; D002273:Carcinogens; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D010718:Phosphatidylserines; D014280:Triglycerides; C057439:1,3-dioleoyl-2-stearoylglycerol; D048490:raf Kinases; D051571:Protein Kinase C-alpha; D054648:Protein Phosphatase 2; D051966:Phospholipase C gamma; D013755:Tetradecanoylphorbol Acetate