A novel extracellular role for tissue transglutaminase in matrix-bound VEGF-mediated angiogenesis

Abstract

The importance of tissue transglutaminase (TG2) in angiogenesis is unclear and contradictory. Here we show that inhibition of extracellular TG2 protein crosslinking or downregulation of TG2 expression leads to inhibition of angiogenesis in cell culture, the aorta ring assay and in vivo models. In a human umbilical vein endothelial cell (HUVEC) co-culture model, inhibition of extracellular TG2 activity can halt the progression of angiogenesis, even when introduced after tubule formation has commenced and after addition of excess vascular endothelial growth factor (VEGF). In both cases, this leads to a significant reduction in tubule branching. Knockdown of TG2 by short hairpin (shRNA) results in inhibition of HUVEC migration and tubule formation, which can be restored by add back of wt TG2, but not by the transamidation-defective but GTP-binding mutant W241A. TG2 inhibition results in inhibition of fibronectin deposition in HUVEC monocultures with a parallel reduction in matrix-bound VEGFA, leading to a reduction in phosphorylated VEGF receptor 2 (VEGFR2) at Tyr1214 and its downstream effectors Akt and ERK1/2, and importantly its association with β1 integrin. We propose a mechanism for the involvement of matrix-bound VEGFA in angiogenesis that is dependent on extracellular TG2-related activity.

Essential Role of Transglutaminase 2 in Vascular Endothelial Growth Factor–Induced Vascular Leakage in the Retina of Diabetic Mice

“…It was recently reported that extracellular TGase2 inhibits VEGF-induced angiogenesis by impeding the interaction of VEGF with heparan sulfate proteoglycans and subsequent VEGF receptor-2 signaling independent of its transamidating activity (39). There are, however, contradictory reports on the involvement of extracellular TGase2 activity in VEGF-mediated angiogenesis (40). Thus it is necessary to elucidate whether extracellular TGase2 participates in VEGF-induced endothelial permeability because TGase2 activation was essential for this pathological process.…”

Reactive Oxygen Species Affect Transglutaminase Activity and Regulate Hematopoiesis in a Crustacean

“…In mammals, extracellular TG2 promotes interactions between cells and the ECM and is important for cell spreading, migration, and differentiation (34). Moreover, the down-regulation of TG2 inhibited angiogenesis in cell culture (36). In addition, osteoblast differentiation is regulated by the presence of collagen type I in the ECM, and TGase is required for collagen secretion and extracellular deposition, which controls osteoblast differentiation (37).…”

Vascular ageing and endothelial cell senescence: Molecular mechanisms of physiology and diseases

“…The importance of TG2 in angiogenesis is unclear and contradictory; mechanisms involving TG2 in angiogenesis are poorly understood. Indeed the enzyme can both stimulate and inhibit angiogenesis (Haroon et al, 1999;Wang et al, 2013), suggesting dependence to different contexts. For instance, in vitro studies performed in HUVEC showed that down-regulation of TG2 expression leads to inhibition of angiogenesis.…”