title: Atypical PKC phosphorylates PAR-1 kinases to regulate localization and activity.
abstract: The establishment and maintenance of cellular polarity are essential biological processes that must be maintained throughout the lifetime of eukaryotic organisms. The Par-1 protein kinases are key polarity determinants that have been conserved throughout evolution. Par-1 directs anterior-posterior asymmetry in the one-cell C. elegans embryo and the Drosophila oocyte. In mammalian cells, Par-1 may regulate epithelial cell polarity. Relevant substrates of Par-1 in these pathways are just being identified, but it is not yet known how Par-1 itself is regulated. Here, we demonstrate that human Par-1b (hPar-1b) interacts with and is negatively regulated by atypical PKC. hPar-1b is phosphorylated by aPKC on threonine 595, a residue conserved in Par-1 orthologs in mammals, worms, and flies. The equivalent site in hPar-1a, T564, is phosphorylated in vivo and by aPKC in vitro. Importantly, phosphorylation of hPar-1b on T595 negatively regulates the kinase activity and plasma membrane localization of hPar-1b in vivo. This study establishes a novel functional link between two central determinants of cellular polarity, aPKC and Par-1, and suggests a model by which aPKC may regulate Par-1 in polarized cells.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Hurov
authors.forename: Janis L
authors.initials: JL
authors.lastname: Watkins
authors.forename: Helen
authors.initials: H
authors.lastname: Piwnica-Worms
mesh_terms: D015153:Blotting, Western; D016764:Cell Polarity / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D010748:Phosphopeptides / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism* / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary; D013912:Threonine / Q000378:metabolism*; D014162:Transfection
chemical_list: D010748:Phosphopeptides; D013912:Threonine; D017346:Protein Serine-Threonine Kinases; C115015:PKC-3 protein; D011493:Protein Kinase C