Regulation of dynactin-mediated microtubule anchoring by the p24 subunit

Dynactin is a 1.2 MDa multisubunit complex that is involved in a variety of cellular functions including vesicle motility, microtubule organization, and cell division. The function of most dynactin subunits are at least partially characterized, with the exception of p24. Very few things are known about p24: it has a molecular weight of ~20,800 Da, is mostly α-helical, is only found in dynactin and binds directly to p150Glued. We are using overexpression, shRNA-mediated knockdown, and fluorescent microscopy, to determine a role for p24. When p24 is overexpressed, p150Glued is lost from the centrosome and Arp 1 remains, suggesting disruption of the complex. In addition, microtubule organization is disrupted. When p24 is knocked down, we retain p150Glued at the centrosome, along with Arp 1 and again see microtubule disorganization. These data suggest that p24 may act as an anchor to stabilize p150Glued when it binds to microtubules.