α-catenin mechanosensitivity as a route to cytokinesis failure through sequestration of LZTS2

Epithelial cells can become polyploid upon tissue injury, but mechanosensitive cues that trigger this state are poorly understood. Using α-catenin (α-cat) knock-out Madin Darby Canine Kidney (MDCK) cells reconstituted with wild-type and mutant forms of α-cat as a model system, we find that an established α-cat actin-binding domain unfolding mutant designed to reduce force-sensitive binding to F-actin (α-cat-H0-FABD(+)) can promote cytokinesis failure, particularly along epithelial wound-fronts. Enhanced α-cat coupling to cortical actin is neither sufficient nor mitotic cell-autonomous for cytokinesis failure, but critically requires the mechanosensitive Middle-domain (M1-M2-M3) and neighboring cells. Disease relevant α-cat M-domain missense mutations known to cause a form of retinal pattern dystrophy (α-cat E307K or L436P) are associated with elevated binucleation rates via cytokinesis failure. Similar binucleation rates are seen in cells expressing an α-cat salt-bridge destabilizing mutant (R551A) designed to promote M2-M3 domain unfurling at lower force thresholds. Since binucleation is strongly enhanced by removal of the M1 as opposed to M2-M3 domains, cytokinetic fidelity is most sensitive to α-cat M2-M3 domain opening. To identify α-cat conformation-dependent proximity partners that contribute to cytokinesis, we used a biotin-ligase approach to distinguished proximity partners that show enhanced recruitment upon α-cat M-domain unfurling (R551A). We identified Leucine Zipper Tumor Suppressor 2 (LZTS2), an abscission factor previously implicated in cytokinesis. We confirm that LZTS2 enriches at the midbody, but discover it also localizes to tight and tricellular junctions. LZTS2 knock-down promotes binucleation in both MDCK and Retinal Pigmented Epithelial (RPE) cells. α-cat mutants with persistent M2-M3 domain opening showed elevated junctional enrichment of LZTS2 from the cytosol compared α-cat wild-type cells. These data implicate LZTS2 as a mechanosensitive effector of α-cat that is critical for cytokinetic fidelity. This model rationalizes how persistent mechano-activation of α-cat may drive tension-induced polyploidization of epithelia post-injury and suggests an underlying mechanism for how pathogenic α-cat mutations drive macular dystrophy.