Mammalian PAR-1 determines epithelial lumen polarity by organizing the microtubule cytoskeleton.
Epithelial differentiation involves the generation of luminal surfaces and of a noncentrosomal microtubule (MT) network aligned along the polarity axis. Columnar epithelia (e.g., kidney, intestine, and Madin-Darby canine kidney [MDCK] cells) generate apical lumina and orient MT vertically, whereas liver epithelial cells (hepatocytes and WIFB9 cells) generate lumina at cell-cell contact sites (bile canaliculi) and orient MTs horizontally. We report that knockdown or inhibition of the mammalian orthologue of Caenorhabditis elegans Par-1 (EMK1 and MARK2) during polarization of cultured MDCK and WIFB9 cells prevented development of their characteristic lumen and nonradial MT networks. Conversely, EMK1 overexpression induced the appearance of intercellular lumina and horizontal MT arrays in MDCK cells, making EMK1 the first known candidate to regulate the developmental branching decision between hepatic and columnar epithelial cells. Our experiments suggest that EMK1 primarily promotes reorganization of the MT network, consistent with the MT-regulating role of this gene product in other systems, which in turn controls lumen formation and position.
Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, 1300 York Ave., Box 233, New York, NY 10021, USA.
David
D
Cohen
Patrick J
PJ
Brennwald
Enrique
E
Rodriguez-Boulan
Anne
A
Müsch
D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D016764:Cell Polarity; D048429:Cell Size; D003599:Cytoskeleton / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology* / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D007668:Kidney / Q000166:cytology; D008565:Membrane Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D009024:Morphogenesis / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism
D029742:Caenorhabditis elegans Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C489440:EMK1 protein, Canis familiaris; C409406:PAR-1 protein, C elegans; D017346:Protein Serine-Threonine Kinases