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. 2014 Feb 15;127(Pt 4):727-39.
doi: 10.1242/jcs.126482. Epub 2013 Dec 11.

POPX2 Phosphatase Regulates the KIF3 Kinesin Motor Complex

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POPX2 Phosphatase Regulates the KIF3 Kinesin Motor Complex

Hui-Qun Phang et al. J Cell Sci. .
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The kinesin motors are important in the regulation of cellular functions such as protein trafficking, spindle organization and centrosome separation. In this study, we have identified POPX2, a serine-threonine phosphatase, as an interacting partner of the KAP3 subunit of the kinesin-2 motor. The kinesin-2 motor is a heterotrimeric complex composed of KIF3A, KIF3B motor subunits and KAP3, the non-motor subunit, which binds the cargo. Here we report that the phosphatase POPX2 is a negative regulator of the trafficking of N-cadherin and other cargoes; consequently, it markedly influences cell-cell adhesion. POPX2 affects trafficking by determining the phosphorylation status of KIF3A at serine 690. This is consistent with the observation that the KIF3A-S690A mutant is defective in cargo trafficking. Our studies also implicate CaMKII as the kinase that phosphorylates KIF3A at serine 690. These results strongly suggest that POPX2 and CaMKII are a phosphatase-kinase pair that regulates kinesin-mediated transport and cell-cell adhesion.

Keywords: Calcium-calmodulin kinase; Kinesin-2 motor; N-cadherin; POPX2 phosphatase.

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