Coordination of focal adhesion nanostructure and mechano-signaling drives cardiomyocyte differentiation

Focal adhesion (FA) organization and signaling are essential for cell growth and differentiation. However, the molecular mechanism that coordinates the FA signaling with cardiomyocyte differentiation has not been fully understood. Here, we provide empirical evidence that BNIP-2, a BCH-domain-containing protein, is the organizer of FA nanostructure that potentiates FA signaling and cell traction force transmission. Mechanistically, BNIP-2 serves as a scaffold for focal adhesion kinase (FAK), paxillin and vinculin to control their molecular organization and assembly/disassembly within FAs. Constitutively active phosphomimetic mutant FAK Y397D shows enhanced binding to BNIP-2, whereas the depletion of BNIP-2 reduces FAK phosphorylation and interaction between FAK and paxillin. Using H9c2 myoblasts and human embryonic stem cells as model systems, we show that BNIP-2 depletion results in aberrant FA dynamics with impairment of traction force, and changes in signature target genes, hereby impeding cardiomyocyte differentiation. BNIP-2 regulation of FA organization and dynamic is therefore pivotal to the mechanotransduction in cardiomyocyte differentiation, shedding new light to how FA-transduced force modulates cell growth and differentiation.