Matrix GLA Protein Stimulates VEGF Expression through Increased Transforming Growth Factor-β1 Activity in Endothelial Cells

Kristina Boström,Amina F Zebboudj,Yucheng Yao,Than S Lin,Alejandra Torres

doi:10.1074/jbc.m406868200

Kristina Boström, Amina F Zebboudj + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m406868200

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Abstract

Matrix GLA protein (MGP) is expressed in endothelial cells (EC), and MGP deficiency results in developmental defects suggesting involvement in EC function. To determine the role of MGP in EC, we cultured bovine aortic EC with increasing concentrations of human MGP (hMGP) for 24 h. The results showed increased proliferation, migration, tube formation, and increased release of vascular endothelial growth factor-A (VEGF-A) and basic fibroblast growth factor (bFGF). HMGP, added endogenously or transiently expressed, increased VEGF gene expression dose-dependently as determined by real-time PCR. To determine the mechanism by which hMGP increased VEGF expression, we studied the effect of MGP on the activity of transforming growth factor (TGF)-beta1 compared with that of bone morphogenetic protein (BMP)-2 using transfection assays with TGF-beta- and BMP-response element reporter genes. Our results showed a strong enhancement of TGF-beta1 activity by hMGP, which was paralleled by increased VEGF expression. BMP-2 activity, on the other hand, was inhibited by hMGP. Neutralizing antibodies to TGF-beta blocked the effect of MGP on VEGF expression. The enhanced TGF-beta1 activity specifically activated the Smad1/5 pathway indicating that the TGF-beta receptor activin-like kinase 1 (ALK1) had been stimulated. It occurred without changes in expression of TGF-beta1 or ALK1 and was mimicked by transfection of constitutively active ALK1, which increased VEGF expression. Expression of VEGF and MGP was induced by TGF-beta1, but the induction of MGP preceded that of VEGF, consistent with a promoting effect on VEGF expression. Together, the results suggest that MGP plays a role in EC function, altering the response to TGF-beta superfamily growth factors.

Highlights

Expression of matrix GLA protein (MGP)1 has been reported in vascular endothelium of species as different as human and teleost fish [1, 2], suggesting that Matrix GLA protein (MGP) has a role in endothelial cell (EC) function
MGP expression has been reported in vascular endothelium in species as different as human and teleost fish [1, 2], suggesting that MGP has a role in endothelial cells (EC) function
Several features in MGP deficiency [3,4,5,6,7,8] suggest involvement of vascular endothelium, including peripheral pulmonary stenosis, that may result from a failure in angiogenesis or vessel fusion [9, 10], arterial calcification that may relate to endothelial dysfunction during vascular maturation [11], and loss of architecture and hypertrophic chondrocytes in the bone growth plate that may relate to disturbed vascularization [12]

Summary

Introduction

Expression of matrix GLA protein (MGP) has been reported in vascular endothelium of species as different as human and teleost fish [1, 2], suggesting that MGP has a role in endothelial cell (EC) function. Increased MGP expression has been reported in tube-forming EC as determined by subtractive hybridization [13], and in myometrial EC treated with vascular endothelial growth factor (VEGF) as determined by microarray analysis [14]. Our results indicate that MGP promotes release of VEGF-A and basic fibroblast growth factor (bFGF), both involved in angiogenesis. The results suggest that MGP plays a role in EC function by altering the response to TGF-␤ growth factors, which in part may explain the vascular abnormalities seen in MGP deficiency

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