The essential role of tissue transglutaminase in vascular smooth muscle stretch mechanotransduction

The vascular wall is constantly subjected to hemodynamic forces arising from the pulsatile nature of blood pressure and blood flow across diverse vascular beds. Vascular smooth muscle cells (VSMCs) detect these mechanical cues through specialized mechanosensing molecules and cellular structures, which activate coordinated mechanotransduction pathways to maintain vascular homeostasis. Tissue transglutaminase (TG2) is a multifunctional enzyme that, when localized at the cell membrane, interacts with several known mechanosensitive molecules, including fibronectin, integrins, and G protein-coupled receptors. However, whether TG2 functions as a stretch-activated mechanosensor or participates in integrating, harmonizing, and effecting mechanotransduction processes in VSMCs remains unknown. Herein, we demonstrate that mechanical stretch enhances TG2 activity and expression in VSMCs, and that stretch-induced activation of TG2 is modulated by reactive oxygen species. We further demonstrate that stretch-induced actin polymerization and VSMC stiffening occur via a TG2/RhoA/ROCK/LIMK/cofilin/actin signaling axis, and that TG2 activation in isolated mesenteric arteries increases stiffness, an effect abolished by TG2 or LIMK inhibition. Finally, we provide evidence that the effects of stretch on the cytoskeleton mediated by TG2 likely occur through its transamidation activity, as pharmacological activation of TG2 promotes actin polymerization and VSMC stiffening independent of mechanical stretch. Together, these findings identify TG2 as an essential mediator of stretch-induced mechanotransduction that enables VSMCs to adapt their cytoskeleton and mechanical properties in response to mechanical stimuli.