Tight junction protein Par6 interacts with an evolutionarily conserved region in the amino terminus of PALS1/stardust.
Tight junctions are the structures in mammalian epithelial cells that separate the apical and basolateral membranes and may also be important in the establishment of cell polarity. Two evolutionarily conserved multiprotein complexes, Crumbs-PALS1 (Stardust)-PATJ and Cdc42-Par6-Par3-atypical protein kinase C, have been implicated in the assembly of tight junctions and in polarization of Drosophila melanogaster epithelia. These two complexes have been linked physically and functionally by an interaction between PALS1 and Par6. Here we identify an evolutionarily conserved region in the amino terminus of PALS1 as the Par6 binding site and identify valine and aspartic acid residues in this region as essential for interacting with the PDZ domain of Par6. We have also characterized, in more detail, the amino terminus of Drosophila Stardust and demonstrate that the interaction mechanism between Stardust and Drosophila Par6 is evolutionarily conserved. Par6 interferes with PATJ in binding PALS1, and these two interactions do not appear to function synergistically. Taken together, these results define the molecular mechanisms linking two conserved polarity complexes.
Wang
Qian
Q
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-2216, USA.
Hurd
Toby W
TW
Margolis
Ben
B
D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D004247:DNA / Q000737:chemistry; D004285:Dogs; D029721:Drosophila Proteins / Q000737:chemistry*; D004331:Drosophila melanogaster / Q000378:metabolism; D051528:Guanylate Kinases; D006801:Humans; D015151:Immunoblotting; D026901:Membrane Transport Proteins / Q000737:chemistry*; D051379:Mice; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry*; D017354:Point Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism*; D014162:Transfection; D014633:Valine / Q000737:chemistry; D015027:Zebrafish; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
D029721:Drosophila Proteins; D026901:Membrane Transport Proteins; D011506:Proteins; D018179:Receptors, Thrombin; C105295:protease-activated receptor 3; D001224:Aspartic Acid; D004247:DNA; C115015:PKC-3 protein; D011493:Protein Kinase C; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; C444479:sdt protein, Drosophila; D020764:cdc42 GTP-Binding Protein; D014633:Valine