Nitrosylation of tissue transglutaminase enhances fibroblast migration and regulates MMP activation

In wound healing, the TG2 enzyme plays a dual functional role. TG2 has been shown to regulate extracellular matrix (ECM) stabilization by its transamidase activity while increasing cell migration by acting as a cell adhesion molecule. In this process, nitric oxide (NO) plays a particularly important role by nitrosylation of free cysteine ​​residues on TG2, leading to the irreversible inactivation of the catalytic activity. In this study, transfected fibroblasts expressing TG2 under the control of the tetracycline-off promoter were treated with NO donor S-nitroso-N-acetyl penicillamine (SNAP) to analyze the interplay between NO and TG2 in the regulation of cell migration/invasion as well as TGF-β1-dependent MMP activation. Our results demonstrated that inhibition of TG2 cross-linking activity by SNAP promoted the migration and invasion capacity of fibroblasts by hindering TG2-mediated TGF-β1 activation. While the inhibition of TG2 activity by NO downregulated the biosynthesis and activity of MMP-2 and MMP-9, that of MMP-1a and MMP-13 was shown to be upregulated in a TGF-β1-dependent manner under the same conditions. In the presence of SNAP, interaction of TG2 with its cell surface binding partners Integrin-β1 and Syndecan-4 was reduced, which was paralleled by an increase in TG2 and PDGF association. These findings suggests that migratory phenotype of fibroblasts can be regulated by the interplay between nitric oxide and TG2 activity.