BNIP-2 Activation of Cellular Contractility Inactivates YAP for H9c2 Cardiomyoblast Differentiation

Rho GTPases and Hippo kinases are key regulators of cardiomyoblast differentiation. However, how these signaling axes are coordinated spatiotemporally remains unclear. Here, the central and multifaceted roles of the BCH domain containing protein, BNIP-2, in orchestrating the expression of two key cardiac genes (cardiac troponin T [cTnT] and cardiac myosin light chain [Myl2]) in H9c2 and human embryonic stem cell-derived cardiomyocytes are delineated. This study shows that BNIP-2 mRNA and protein expression increase with the onset of cTnT and Myl2 and promote the alignment of H9c2 cardiomyocytes. Mechanistically, BNIP-2 is required for the inactivation of YAP through YAP phosphorylation and its cytosolic retention. Turbo-ID proximity labeling corroborated by super-resolution analyses and biochemical pulldown data reveals a scaffolding role of BNIP-2 for LATS1 to phosphorylate and inactivate YAP in a process that requires BNIP-2 activation of cellular contractility. The findings identify BNIP-2 as a pivotal signaling scaffold that spatiotemporally integrates RhoA/Myosin II and LATS1/YAP mechanotransduction signaling to drive cardiomyoblast differentiation, by switching the genetic programming from YAP-dependent growth to YAP-silenced differentiation. These findings offer insights into the importance of scaffolding proteins in bridging the gap between mechanical and biochemical signals in cell growth and differentiation and the prospects in translational applications.