title: A role for the centrosome and PAR-3 in the hand-off of MTOC function during epithelial polarization.
abstract: BACKGROUND
  The centrosome is the major microtubule organizing center (MTOC) in dividing cells and in many postmitotic, differentiated cells. In other cell types, however, MTOC function is reassigned from the centrosome to noncentrosomal sites. Here, we analyze how MTOC function is reassigned to the apical membrane of C. elegans intestinal cells.
  
  
  RESULTS
  After the terminal intestinal cell division, the centrosomes and nuclei move near the future apical membranes, and the postmitotic centrosomes lose all, or nearly all, of their associated microtubules. We show that microtubule-nucleating proteins such as γ-tubulin and CeGrip-1 that are centrosome components in dividing cells become localized to the apical membrane, which becomes highly enriched in microtubules. Our results suggest that centrosomes are critical to specify the apical membrane as the new MTOC. First, γ-tubulin appears to redistribute directly from the migrating centrosome onto the lateral then apical membrane. Second, γ-tubulin fails to accumulate apically in wild-type cells following laser ablation of the centrosome. We show that centrosomes localize apically by first moving toward lateral foci of the conserved polarity proteins PAR-3 and PAR-6 and then move together with these foci toward the future apical surface. Embryos lacking PAR-3 fail to localize their centrosomes apically and have aberrant localization of γ-tubulin and CeGrip-1.
  
  
  CONCLUSIONS
  These data suggest that PAR proteins contribute to apical polarity in part by determining centrosome position and that the reassignment of MTOC function from centrosomes to the apical membrane is associated with a physical hand-off of nucleators of microtubule assembly.
authors.affiliation: Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Feldman
authors.forename: James R
authors.initials: JR
authors.lastname: Priess
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002503:Centromere / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000196:embryology; D007834:Lasers; D008854:Microscopy, Electron; D008868:Microtubule Proteins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D022101:Microtubule-Organizing Center / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D009154:Mutation; D017346:Protein Serine-Threonine Kinases; D014404:Tubulin / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; C456608:Grip-1 protein, C elegans; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D014404:Tubulin; C512642:par-6 protein, C elegans; C097238:PAR-3 protein, C elegans; D017346:Protein Serine-Threonine Kinases