RT Journal Article
SR Electronic
T1 Polo-like kinase phosphorylation determines <em>Caenorhabditis</em> <em>elegans</em> centrosome size and density by biasing SPD-5 toward an assembly-competent conformation
JF Biology Open
JO Biology Open
FD Company of Biologists
SP 1431
OP 1440
DO 10.1242/bio.020990
VO 5
IS 10
A1 Wueseke, Oliver
A1 Zwicker, David
A1 Schwager, Anne
A1 Wong, Yao Liang
A1 Oegema, Karen
A1 Jülicher, Frank
A1 Hyman, Anthony A.
A1 Woodruff, Jeffrey B.
YR 2016
UL http://bio.biologists.org/content/5/10/1431.abstract
AB Centrosomes are major microtubule-organizing centers composed of centrioles surrounded by an extensive proteinacious layer called the pericentriolar material (PCM). In Caenorhabditis elegans embryos, the mitotic PCM expands by Polo-like kinase 1 (PLK-1) phosphorylation-accelerated assembly of SPD-5 molecules into supramolecular scaffolds. However, how PLK-1 phosphorylation regulates SPD-5 assembly is not known. We found that a mutant version of SPD-5 that is insensitive to PLK-1 phosphorylation (SPD-54A) could localize to PCM but was unable to rescue the reduction in PCM size and density when wild-type SPD-5 levels were decreased. In vitro, purified SPD-54A self-assembled into functional supramolecular scaffolds over long time scales, suggesting that phosphorylation only controls the rate of SPD-5 scaffold assembly. Furthermore, the SPD-5 scaffold, once assembled, remained intact and supported microtubule nucleation in the absence of PLK-1 activity in vivo. We conclude that PLK-1 is required for rapid assembly of the PCM scaffold but not for scaffold maintenance or function. Based on this idea, we developed a theoretical model that adequately predicted PCM growth rates in different mutant conditions in vivo. We propose that PLK-1 phosphorylation-dependent conversion of SPD-5 into an assembly-competent form underlies PCM formation in vivo and that the rate of this conversion determines final PCM size and density.