Patronin regulates the microtubule network by protecting microtubule minus ends.
Tubulin assembles into microtubule polymers that have distinct plus and minus ends. Most microtubule plus ends in living cells are dynamic; the transitions between growth and shrinkage are regulated by assembly-promoting and destabilizing proteins. In contrast, minus ends are generally not dynamic, suggesting their stabilization by some unknown protein. Here, we have identified Patronin (also known as ssp4) as a protein that stabilizes microtubule minus ends in Drosophila S2 cells. In the absence of Patronin, minus ends lose subunits through the actions of the Kinesin-13 microtubule depolymerase, leading to a sparse interphase microtubule array and short, disorganized mitotic spindles. In vitro, the selective binding of purified Patronin to microtubule minus ends is sufficient to protect them against Kinesin-13-induced depolymerization. We propose that Patronin caps and stabilizes microtubule minus ends, an activity that serves a critical role in the organization of the microtubule cytoskeleton.
The Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158-2200, USA.
Sarah S
SS
Goodwin
Ronald D
RD
Vale
D000818:Animals; D003599:Cytoskeleton / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism*; D007399:Interphase; D016547:Kinesins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis
D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; C553301:patronin protein, Drosophila; C481339:KLP10A protein, Drosophila; D016547:Kinesins