Disrupted autophagy overactivates TBK1 and results in mitotic defects promoting chromosomal instability

Micronuclei are formed during cell division when acentric fragments or lagging chromosomes cannot be incorporated into the primary nucleus. Macroautophagy/autophagy may reduce chromosomal instability (CIN) by clearing isolated, atypical micronuclei. Other studies implicate that the loss of autophagy disrupts DNA repair pathways. However, whether aberrant mitosis contributing to CIN occurs when autophagy is inhibited has yet to be evaluated. We found impaired autophagy initiation contributes to CIN and facilitates the formation of micronuclei and other abnormal nuclear phenotypes either by genetic or pharmacological manipulation in multiple cell lines. We also found that loss of the integral autophagy protein ATG9A resulted in various types of mitotic errors that can contribute to the formation of micronuclei. ATG9A also localizes to centrosomes and midbody during cell division. Autophagy inhibition causes the overactivation and mislocalization of TBK1 (TANK binding kinase 1) into cytoplasmic, punctate structures that colocalize with SQSTM1/p62. This overactivation interferes with its function in cell division as a mitotic kinase and its role at the centrosome. These results indicate that loss of autophagy contributes to genomic instability from multiple angles, one of which being aberrant cell division.