Palladin is a novel microtubule-associated protein responsible for spindle orientation

Mitotic spindles, which consist of microtubules (MTs) and associated proteins, play critical roles in controlling cell division and maintaining tissue homeostasis. The orientation of the mitotic spindle is closely related with the duration of mitosis. However, the molecular mechanism in regulating the orientation of the mitotic spindles is largely undefined. In this study, we found that Palladin is a novel MT-associated protein and regulator of spindle orientation, which maintains proper spindle orientation by stabilizing astral MTs. Palladin depletion distorted spindle orientation, prolonged the metaphase, and impaired proliferation of HeLa cells. Results showed that Palladin depletion-induced spindle misorientation and astral MT instability could be rescued by constitutively active AKT1 or dominant negative GSK3 beta. Our findings revealed that Palladin regulates spindle orientation and mitotic progression mainly through the AKT1-GSK3 beta pathway.