The Crumbs3-Pals1 complex participates in the establishment of polarity in mammalian epithelial cells.
In Drosophila, the Crumbs-Stardust-Discs-lost complex is required during the establishment of polarized epithelia. Embryos that lack a component of this complex or overexpress Crumbs exhibit defects in epithelial morphogenesis. We recently cloned a novel mammalian epithelial Crumbs isoform, Crumbs3 (CRB3). CRB3 exists in a complex at tight junctions (TJs) with Pals1 and PATJ, the mammalian homologues of Stardust and Discs lost, respectively. Here, we observe that overexpression of CRB3 leads to delayed TJ formation in MDCK epithelial cell monolayers and disruption of polarity in MDCK cysts cultured in collagen. Both phenomena require the last four residues of CRB3. Next, we expressed, in MDCK cells, a dominant-negative Myc-Lin-2-Pals1 chimeric protein, where the PDZ domain of Lin-2 was replaced with that of Pals1. TJ and apical polarity defects were also observed in these cells. Collectively, this suggests that the CRB-Pals1 interaction is important for formation of TJs and polarized epithelia. These results provide insight into the function of the mammalian Crumbs complex during TJ formation and epithelial polarization.
Roh
Michael H
MH
Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109-0650, USA.
Fan
Shuling
S
Liu
Chia-Jen
CJ
Margolis
Ben
B
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003094:Collagen / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D005136:Eye Proteins; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D062725:Tight Junction Proteins; D019108:Tight Junctions / Q000378:metabolism / Q000502:physiology; D014162:Transfection
C472002:CRB3 protein, human; D005136:Eye Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C107903:PATJ protein, human; D020033:Protein Isoforms; D062725:Tight Junction Proteins; D003094:Collagen; D004247:DNA; D005982:Glutathione Transferase; D002118:Calcium