C. elegans PAR proteins function by mobilizing and stabilizing asymmetrically localized protein complexes.
BACKGROUND
The PAR proteins are part of an ancient and widely conserved machinery for polarizing cells during animal development. Here we use a combination of genetics and live imaging methods in the model organism Caenorhabditis elegans to dissect the cellular mechanisms by which PAR proteins polarize cells.


RESULTS
We demonstrate two distinct mechanisms by which PAR proteins polarize the C. elegans zygote. First, we show that several components of the PAR pathway function in intracellular motility, producing a polarized movement of the cell cortex. We present evidence that this cortical motility may drive the movement of cellular components that must become asymmetrically distributed, including both germline-specific ribonucleoprotein complexes and cortical domains containing the PAR proteins themselves. Second, PAR-1 functions to refine the asymmetric localization of germline ribonucleoprotein complexes by selectively stabilizing only those complexes that reach the PAR-1-enriched posterior cell cortex during the period of cortical motility.


CONCLUSIONS
These results identify two cellular mechanisms by which the PAR proteins polarize the C. elegans zygote, and they suggest mechanisms by which PAR proteins may polarize cells in diverse animal systems.
Cheeks
Rebecca J
RJ
Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Canman
Julie C
JC
Gabriel
Willow N
WN
Meyer
Nicole
N
Strome
Susan
S
Goldstein
Bob
B
D048948:14-3-3 Proteins; D000818:Animals; D019521:Body Patterning / Q000235:genetics / Q000502:physiology*; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism* / Q000502:physiology; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D016764:Cell Polarity / Q000235:genetics* / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism* / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000378:metabolism / Q000502:physiology; D005453:Fluorescence; D007734:Kymography; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D048948:14-3-3 Proteins; D029742:Caenorhabditis elegans Proteins; D011506:Proteins; C106207:par-5 protein, C elegans; C512642:par-6 protein, C elegans; D014446:Tyrosine 3-Monooxygenase; C409406:PAR-1 protein, C elegans; C097238:PAR-3 protein, C elegans; D017346:Protein Serine-Threonine Kinases