Annexin A2 and Ahnak control cortical NuMA-dynein localization and mitotic spindle orientation

Proper mitotic spindle orientation depends on the correct anchorage of astral microtubules to the cortex. It relies on the remodeling of the cell cortex, a process not fully understood. Annexin A2 (Anx2; also known as ANXA2) is a protein known to be involved in cortical domain remodeling. Here, we report that in HeLa cell early mitosis, Anx2 recruits the scaffold protein Ahnak at the cell cortex facing spindle poles, and the distribution of both proteins is controlled by cell adhesion. Depletion of either protein or impaired cortical Ahnak localization result in delayed anaphase onset and unstable spindle anchoring, which leads to altered spindle orientation. We find that Ahnak is present in a complex with dynein-dynactin. Furthermore, Ahnak and Anx2 are required for correct dynein and NuMA (also known as NUMA1) cortical localization and dynamics. We propose that the Ahnak-Anx2 complex influences the cortical organization of the astral microtubule-anchoring complex, and thereby mitotic spindle positioning in human cells. This article has an associated First Person interview with the first author of the paper.