title: Pleckstrin Homology (PH) Domain Leucine-rich Repeat Protein Phosphatase Controls Cell Polarity by Negatively Regulating the Activity of Atypical Protein Kinase C.
abstract: The proper establishment of epithelial polarity allows cells to sense and respond to signals that arise from the microenvironment in a spatiotemporally controlled manner. Atypical PKCs (aPKCs) are implicated as key regulators of epithelial polarity. However, the molecular mechanism underlying the negative regulation of aPKCs remains largely unknown. In this study, we demonstrated that PH domain leucine-rich repeat protein phosphatase (PHLPP), a novel family of Ser/Thr protein phosphatases, plays an important role in regulating epithelial polarity by controlling the phosphorylation of both aPKC isoforms. Altered expression of PHLPP1 or PHLPP2 disrupted polarization of Caco2 cells grown in 3D cell cultures as indicated by the formation of aberrant multi-lumen structures. Overexpression of PHLPP resulted in a decrease in aPKC phosphorylation at both the activation loop and the turn motif sites; conversely, knockdown of PHLPP increased aPKC phosphorylation. Moreover, in vitro dephosphorylation experiments revealed that both aPKC isoforms were substrates of PHLPP. Interestingly, knockdown of PKCζ, but not PKCι, led to similar disruption of the polarized lumen structure, suggesting that PKCζ likely controls the polarization process of Caco2 cells. Furthermore, knockdown of PHLPP altered the apical membrane localization of aPKCs and reduced the formation of aPKC-Par3 complex. Taken together, our results identify a novel role of PHLPP in regulating aPKC and cell polarity.
authors.affiliation: From the Markey Cancer Center and.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Xiong
authors.affiliation: From the Markey Cancer Center and.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: From the Markey Cancer Center and.
authors.forename: Yang-An
authors.initials: YA
authors.lastname: Wen
authors.affiliation: From the Markey Cancer Center and tianyan.gao@uky.edu.|Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536-0509.
authors.forename: Tianyan
authors.initials: T
authors.lastname: Gao
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D018938:Caco-2 Cells; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology / Q000235:genetics; D016764:Cell Polarity / Q000502:physiology*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051744:Protein Kinase C-epsilon / Q000235:genetics / Q000378:metabolism*; D000099293:Protein Kinase C-lambda
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010749:Phosphoprotein Phosphatases; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D000099293:Protein Kinase C-lambda; C509689:PARD3 protein, human; C115084:Pard3 protein, mouse; C497256:Prkce protein, mouse; C497255:PRKCE protein, human; C400601:PHLPP1 protein, human; C519282:PHLPP1 protein, mouse; C541572:PHLPP2 protein, human
keywords: Akt PKB; PHLPP; atypical PKC; cell polarity; dephosphorylation; phosphatase; protein kinase C (PKC); protein phosphorylation