Knockdown of dynactin's p150[Glued] subunit abrogates microtubule organization

Dynactin is a multifunctional protein complex composed of at least 11 different subunits. Dynactin functions as a cofactor for cytoplasmic dynein facilitating long-range vesicle movements, microtubule anchoring, endomembrane localization, and mitotic progression. Previous studies have shown that dynactin binds to microtubules at the centrosome maintaining a radial array in interphase. The p150Glued subunit contains two distinct microtubule-binding sequences named CAP-Gly and Basic. While both domains can interact with microtubule, CAP-Gly has a much greater affinity for binding to microtubules, suggesting that the two domains may be active for different dynactin-based functions within the cell. Using siRNA, we found that knockdown of p150Glued was sufficient to alter the maintenance of radial microtubule arrays, cause an increase in centrosome number and mitotic index. In the future we will replace the endogenous protein with versions lacking the CAP-Gly or Basic domains to investigate the contribution of each to microtubule anchoring and cytoskeletal architecture.