title: Stabilization of cell polarity by the C. elegans RING protein PAR-2.
abstract: Asymmetric localization of PAR proteins is a hallmark of polarized cells, but the mechanisms that create PAR asymmetry are not well understood. In the C. elegans zygote, PAR asymmetry is initiated by a transient actomyosin contraction, which sweeps the PAR-3/PAR-6/PKC-3 complex toward the anterior pole of the egg. The RING finger protein PAR-2 accumulates in a complementary pattern in the posterior cortex. Here we present evidence that PAR-2 participates in a feedback loop to stabilize polarity. PAR-2 is a target of the PKC-3 kinase and is excluded from the anterior cortex by PKC-3-dependent phosphorylation. The RING domain of PAR-2 is required to overcome inhibition by PKC-3 and stabilize PAR-2 on the posterior cortex. Cortical PAR-2 in turn prevents PAR-3/PAR-6/PKC-3 from returning to the posterior, in a PAR-1- and PAR-5-dependent manner. Our findings suggest that reciprocal inhibitory interactions among PAR proteins stabilize polarity by reinforcing an initial asymmetry in PKC-3.
authors.affiliation: Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Yingsong
authors.initials: Y
authors.lastname: Hao
authors.forename: Lynn
authors.initials: L
authors.lastname: Boyd
authors.forename: Geraldine
authors.initials: G
authors.lastname: Seydoux
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology*; D015536:Down-Regulation; D005246:Feedback; D005260:Female; D017238:Genes, Helminth; D008297:Male; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D015053:Zygote / Q000166:cytology / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; C087977:par-2 protein, C elegans; C115015:PKC-3 protein; D011493:Protein Kinase C