S-Glutathionylation Influences the Property of Fibronectin

Abstract

Fibronectin is a key extracellular matrix (ECM) protein that plays a role in cell growth, migration and differentiation through its engagement of cell surface receptors, known as integrins, in a spatiotemporal manner. Fibronectin is a mechanically sensitive protein displaying force-induced conformational changes that impact its multiple growth factor, integrin, and ECM protein binding domains. Fibronectin is a unique ECM protein in that it contains 4 free cysteine residues that are protected in cryptic sites, but that can be exposed under force. S-glutathionylation is a post-translational modification of cysteines that occurs in oxidative environments like the extracellular space during pathologies like cancer and fibrosis. Here, we show for the first time that fibronectin's cysteines can be glutathionylated when exposed either through chemical unfolding in its soluble form or mechanical unfolding in its fibrillar form (both on the single fiber and matrix level). Moreover, we proved that S-glutathionylation impacts the mechanical properties of fibronectin fibers. Specifically, our results reveal that glutathionylated fibronectin fibers are more extensible and less stiff compared to unmodified fibronectin. This is true for both single fibronectin fibers and fibronectin matrices. Thus S-glutathionylation of mechanically exposed cysteines on fibronectin may act as a mechanism of mechanical memory within fibronectin-rich ECMs, regulating subsequent mechanotransduction. One possible realism of this mechanism could be the enhancement fibronectin's integrin binding mechanoswitch due to fibronectin fibers being more easily stretched under lower force regimes.