Binding to PKC-3, but not to PAR-3 or to a conventional PDZ domain ligand, is required for PAR-6 function in C. elegans.
PAR-6 is a conserved protein important for establishment and maintenance of cell polarity in a variety of metazoans. PAR-6 proteins function together with PAR-3, aPKC and CDC-42. Mechanistic details of their interactions, however, are not fully understood. We studied the biochemical interactions between C. elegans PAR-6 and its binding partners and tested the requirements of these interactions in living worms. We show that PB1 domain-mediated binding of PAR-6 to PKC-3 is necessary for polarity establishment and PAR-6 cortical localization in C. elegans embryos. We also show that binding of PAR-6 and PAR-3 is mediated in vitro by a novel type of PDZ-PDZ interaction; the betaC strand of PAR-6 PDZ binds the betaD strand of PAR-3 PDZ1. However, this interaction is dispensable in vivo for PAR-6 function throughout the life of C. elegans. Mutations that specifically abolish conventional ligand binding to the PAR-6 PDZ domain also failed to affect PAR-6 function in vivo. We conclude that PAR-6 binding to PKC-3, but not to PAR-3 nor to a conventional PDZ ligand, is required for PAR-6 cortical localization and function in C. elegans.
Li
Jin
J
Department of Molecular Biology and Genetics, 107 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
Kim
Heon
H
Aceto
Donato G
DG
Hung
Jeffrey
J
Aono
Shinya
S
Kemphues
Kenneth J
KJ
D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008024:Ligands; D054731:PDZ Domains; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases
D029742:Caenorhabditis elegans Proteins; D008024:Ligands; C512642:par-6 protein, C elegans; C097238:PAR-3 protein, C elegans; D017346:Protein Serine-Threonine Kinases; C115015:PKC-3 protein; D011493:Protein Kinase C