Apical polarity and actomyosin dynamics regulate Hippo signaling by controlling Kibra subcellular localization

Cell polarity and actomyosin networks are key features that organize cells of epithelial tissues and are known to regulate tissue growth. However, the mechanisms by which polarity cues and actomyosin cytoskeleton influence intracellular signaling cascades that control growth remain poorly understood. The Hippo pathway is an evolutionarily conserved regulator of tissue growth and is known to integrate inputs from both polarity and actomyosin components. An upstream activator of the Hippo pathway, Kibra, localizes into distinct pools at the junctional and medial regions of the apical cortex in epithelial cells, and medial accumulation was shown to promote Kibra activity. Here, we demonstrate that cortical Kibra distribution is controlled by a tug of war between apical polarity and actomyosin dynamics. We show that while the apical polarity network, in part via aPKC, tethers Kibra at the junctional cortex to silence its activity, medial actomyosin flows promote Kibra-mediated Hippo complex formation at the medial cortex, thereby activating the Hippo pathway. This study provides a mechanistic understanding of the relationship between the Hippo pathway, polarity, and actomyosin cytoskeleton and offers novel insights into how fundamental features of epithelial tissue architecture can serve as inputs into signaling cascades that control tissue growth, patterning, and morphogenesis.