Sulfated glycosaminoglycans inhibit transglutaminase 2 by stabilizing its closed conformation

Abstract

Transglutaminases (TGs) catalyze the covalent crosslinking of proteins via isopeptide bonds. The most prominent isoform, TG2, is associated with physiological processes such as extracellular matrix (ECM) stabilization and plays a crucial role in the pathogenesis of e.g. fibrotic diseases, cancer and celiac disease. Therefore, TG2 represents a pharmacological target of increasing relevance. The glycosaminoglycans (GAG) heparin (HE) and heparan sulfate (HS) constitute high-affinity interaction partners of TG2 in the ECM. Chemically modified GAG are promising molecules for pharmacological applications as their composition and chemical functionalization may be used to tackle the function of ECM molecular systems, which has been recently described for hyaluronan (HA) and chondroitin sulfate (CS). Herein, we investigate the recognition of GAG derivatives by TG2 using an enzyme-crosslinking activity assay in combination with in silico molecular modeling and docking techniques. The study reveals that GAG represent potent inhibitors of TG2 crosslinking activity and offers atom-detailed mechanistic insights.

Tissue Transglutaminase 2 has higher affinity for relaxed than for stretched fibronectin fibers

“…More research is required to establish the physiological role of this homodimer and its binding mode to fibrillar FN. Therefore, our results indicate that, like for Syndecan-4 [94] or α5β1 integrins, the FN-binding epitope on TG2 is conformational. Interestingly, studies have identified anti-TG2 autoantibodies that induce a shift in a pool of effector-free TG2 either toward the "closed" or "open" conformation, depending on the epitope on TG2 they bind to [41,106].…”

“…8). TG2 is inactive when TG2's N-terminal and C-terminal domains are in spatial proximity due to GDP/GTP binding and/or when TG2 interacts with syndecan-4 [94]. We propose here that TG2 and FN can form additional interactions due to the C-terminal β-barrels making synergistic contacts with FNI 8-9 , while TG2's N-terminal domain interacts with FNI 7 (Fig.…”

“…On the cell surface, where TG2 acts as an adhesion co-receptor for FN [21], it primarily associates with integrins and the heparan sulfate proteoglycan syndecan-4, forming ternary and/or quaternary adhesive complexes with FN [19,20,93]. Recent advances in understanding of TG2-syndecan-4 interactions suggest that this interaction stabilizes TG2 in a closed conformation, due to a composite binding site consisting of two clusters that form a single high affinity heparin-binding site when brought in proximity in a closed conformation [94,95]. Our data now suggest an additional mechanism that might stabilize this heterocomplex with FN and Syndecan-4, as the synergistic interactions of TG2 N-and C-terminal domains with FN are expected to stabilize TG2's closed conformation despite high (millimolar) extracellular Ca 2+ concentrations.…”

The Role of Transglutaminase 2 in Cancer: An Update

“…MMPs promote new matrix synthesis by fibroblasts, which then secrete TG2 and LOXs to adjust its consistency. A metalloprotease's physiological role is to degrade ECM proteins, thus opposing TG2 crosslinking and stabilization [54,55]. in structural conformation (further influenced by Ca2 + and GTP concentrations).…”