A centrosomal protein STARD9 promotes microtubule stability and regulates spindle microtubule dynamics

ABSTRACTCentrosomal proteins play important roles in the spindle assembly and the segregation of chromosomes in the eukaryotic cells. STARD9, a recently identified centrosomal protein, was reported to influence the spindle pole assembly. However, the role of STARD9 in maintaining the stability and organization of microtubules are not known. Here, we show that STARD9 regulates the assembly and dynamics of both interphase and mitotic microtubules. The knockdown of STARD9 in HeLa or HCT116 cells with siRNA or shRNA induced a strong depolymerization of the interphase microtubules. The over-expression of the motor domain of STARD9 stabilizes microtubules against cold and nocodazole suggesting that STARD9 stabilizes microtubules in HeLa cells. Using fluorescent recovery after photobleaching, we showed that the knockdown of STARD9 strongly reduced microtubule dynamics in the live spindles of HeLa cells. The reassembly of microtubules in the STARD9-depleted cells was strongly reduced as compared to the microtubul...