Centrosome clustering in cancer cells requires microtubule assembly through a RanGTP-dependent TPX2-KIFC1 interaction

Abstract

Aneuploidy, chromosomal instability (CIN), and centrosome amplification are hallmarks of aggressive solid tumors. Cancer cells with supernumerary centrosomes ensure bipolar spindle formation by efficiently clustering them at the spindle poles. TPX2 (targeting protein for Xenopus kinesin-like protein 2), a nuclear and microtubule-associated protein, and its partner, the Aurora-A kinase (AURKA), are key mitotic players frequently co-overexpressed in human cancers. TPX2 overexpression ranks first in the CIN70 signature, and both TPX2 and AURKA are part of the CIN4 chromosomal instability signature, with prognostic value in breast cancer patients. Using proximity biotinylation assays (BioID), we identified the mitotic interactome of TPX2 and AURKA. Ten of their high-confidence proximity interactors are highly correlated with TPX2 and AURKA in cancer. We further validate the interaction of TPX2 and AURKA with one of them, KIFC1, a minus-end-directed kinesin-like motor that has a role in centrosome clustering in cancer cells. We show that TPX2 and KIFC1 cooperate to ensure robust acentrosomal microtubule nucleation and organization. Our data show that this mechanism plays a major role in the clustering of supernumerary centrosomes in cancer cells.