Li, Jing; Newhall, Jillian; Ishiyama, Noboru; Gottardi, Cara; Ikura, Mitsuhiko; Leckband, Deborah E.; Tajkhorshid, Emad
Structural Determinants of the Mechanical Stability of alpha-Catenin

alpha-Catenin plays a crucial role in cadherin-mediated adhesion by binding to beta-catenin, F-actin, and vinculin, and its dysfunction is linked to a variety of cancers and developmental disorders. As a mechanotransducer in the cadherin complex at intercellular adhesions, mechanical and force-sensing properties of alpha-catenin are critical to its proper function. Biochemical data suggest that alpha-catenin adopts an autoinhibitory conformation, in the absence of junctional tension, and biophysical studies have shown that alpha-catenin is activated in a tension-dependent manner that in turn results in the recruitment of vinculin to strengthen the cadherin complex/F-actin linkage. However, the molecular switch mechanism from autoinhibited to the activated state remains unknown for alpha-catenin. Here, based on the results of an aggregate of 3 mu s of molecular dynamics simulations, we have identified a dynamic salt-bridge network within the core M region of alpha-catenin that may be the structural determinant of the stability of the autoinhibitory conformation. According to our constant-force steered molecular dynamics simulations, the reorientation of the MII/MIII subdomains under force may constitute an initial step along the transition pathway. The simulations also suggest that the vinculin-binding domain (subdomain MI) is intrinsically much less stable than the other two subdomains in the M region (MII and MIII). Our findings reveal several key insights toward a complete understanding of the multistaged, force-induced conformational transition of alpha-catenin to the activated conformation.


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