title: Partitioning-defective protein 6 (Par-6) activates atypical protein kinase C (aPKC) by pseudosubstrate displacement.
abstract: Atypical protein kinase C (aPKC) controls cell polarity by modulating substrate cortical localization. Aberrant aPKC activity disrupts polarity, yet the mechanisms that control aPKC remain poorly understood. We used a reconstituted system with purified components and a cultured cell cortical displacement assay to investigate aPKC regulation. We find that aPKC is autoinhibited by two domains within its NH(2)-terminal regulatory half, a pseudosubstrate motif that occupies the kinase active site, and a C1 domain that assists in this process. The Par complex member Par-6, previously thought to inhibit aPKC, is a potent activator of aPKC in our assays. Par-6 and aPKC interact via PB1 domain heterodimerization, and this interaction activates aPKC by displacing the pseudosubstrate, although full activity requires the Par-6 CRIB-PDZ domains. We propose that, along with its previously described roles in controlling aPKC localization, Par-6 allosterically activates aPKC to allow for high spatial and temporal control of substrate phosphorylation and polarization.
authors.affiliation: Institute of Molecular Biology and Department of Chemistry, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Chiharu
authors.initials: C
authors.lastname: Graybill
authors.forename: Brett
authors.initials: B
authors.lastname: Wee
authors.forename: Scott X
authors.initials: SX
authors.lastname: Atwood
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Prehoda
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D020816:Amino Acid Motifs; D000818:Animals; D020134:Catalytic Domain; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D004789:Enzyme Activation / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D046912:Multiprotein Complexes; D025521:Tumor Suppressor Proteins; C081435:l(2)gl protein, Drosophila; C115015:PKC-3 protein; C532584:Par-6 protein, Drosophila; D011493:Protein Kinase C