Necl-5/poliovirus receptor interacts with VEGFR2 and regulates VEGF-induced angiogenesis.

RATIONALE: Vascular endothelial growth factor (VEGF), a major proangiogenic agent, exerts its proangiogenic action by binding to VEGF receptor 2 (VEGFR2), the activity of which is regulated by direct interactions with other cell surface proteins, including integrin α(V)ß(3). However, how the interaction between VEGFR2 and integrin α(V)ß(3) is regulated is not clear. OBJECTIVE: To investigate whether Necl-5/poliovirus receptor, an immunoglobulin-like molecule that is known to bind integrin α(V)ß(3), regulates the interaction between VEGFR2 and integrin α(V)ß(3), and to clarify the role of Necl-5 in the VEGF-induced angiogenesis. METHODS AND RESULTS: Necl-5-knockout mice displayed no obvious defect in vascular development; however, recovery of blood flow after hindlimb ischemia and the VEGF-induced neovascularization in implanted Matrigel plugs were impaired in Necl-5-knockout mice. To clarify the mechanism of the regulation of angiogenesis by Necl-5, we investigated the roles of Necl-5 in the VEGF-induced angiogenic responses in vitro. Knockdown of Necl-5 by siRNAs in human umbilical vein endothelial cells (HUVECs) inhibited the VEGF-induced capillary-like network formation on Matrigel, migration, and proliferation, and conversely, enhanced apoptosis. Coimmunoprecipitation assays showed the interaction of Necl-5 with VEGFR2, and knockdown of Necl-5 prevented the VEGF-induced interaction of integrin α(V)ß(3) with VEGFR2. Knockdown of Necl-5 suppressed the VEGFR2-mediated activation of downstream proangiogenic and survival signals, including Rap1, Akt, and endothelial nitric oxide synthase. CONCLUSIONS: These results demonstrate the critical role of Necl-5 in angiogenesis and suggest that Necl-5 may regulate the VEGF-induced angiogenesis by controlling the interaction of VEGFR2 with integrin α(v)ß(3), and the VEGFR2-mediated Rap1-Akt signaling pathway.

Osteoblast-like differentiation of cultured human coronary artery smooth muscle cells by bone morphogenetic protein endothelial cell precursor-derived regulator (BMPER).

Differentiation of vascular smooth muscle cells (SMCs) into osteoblast-like cells is considered to be a mechanism of vascular calcification. However, regulators of osteoblast-like differentiation of vascular SMCs are not fully elucidated. Here, we investigated the expression of bone morphogenetic protein (BMP)-binding endothelial cell precursor-derived regulator (BMPER), a vertebrate homologue of Drosophila crossveinless-2, in vascular SMCs and the role and mode of action of BMPER in osteoblast-like differentiation of human coronary artery SMCs (HCASMCs). BMPER was expressed in cultured human vascular SMCs, including HCASMCs. Silencing of endogenous BMPER expression by an RNA interference technique inhibited osteoblast-like differentiation of HCASMCs, as evaluated by up-regulation of osteoblast markers such as alkaline phosphatase (ALP) and runt-related transcription factor 2 (Runx2), by down-regulation of a SMC marker α-smooth muscle actin (αSMA), and by mineralization. Treatment with recombinant BMPER enhanced, whereas BMP-2 reduced osteoblast-like differentiation. BMPER antagonized BMP-2-induced phosphorylation of Smad 1/5/8, suggesting that the effect of BMPER was mediated by antagonizing the action of BMP. BMPER increased IκBα phosphorylation and NF-κB activity and specific NF-κB decoy oligonucleotides deteriorated osteoblast-like differentiation of HCASMCs by BMPER. In human coronary artery with atherosclerotic plaque containing calcification, the BMPER-positive signals were observed in the neointimal and medial SMCs in the vicinity of the plaque. These findings indicate that BMPER is a novel regulator of the osteoblast-like differentiation of HCASMCs.

FGD5 mediates proangiogenic action of vascular endothelial growth factor in human vascular endothelial cells.

OBJECTIVE: Vascular endothelial growth factor (VEGF) exerts proangiogenic action and induces activation of a variety of proangiogenic signaling pathways, including the Rho family small G proteins. However, regulators of the Rho family small G proteins in vascular endothelial cells (ECs) are poorly understood. Here we attempted to clarify the expression, subcellular localization, downstream effectors, and proangiogenic role of FGD5, a member of the FGD family of guanine nucleotide exchange factors. METHODS AND RESULTS: FGD5 was shown to be selectively expressed in cultured human vascular ECs. Immunofluorescence microscopy showed that the signal for FGD5 was observed at peripheral membrane ruffles and perinuclear regions in human umbilical vein ECs. Overexpression of FGD5 increased Cdc42 activity, whereas knockdown of FGD5 by small interfering RNAs inhibited the VEGF-induced activation of Cdc42 and extracellular signal-regulated kinase. VEGF-promoted capillary-like network formation, permeability, directional movement, and proliferation of human umbilical vein ECs and the reorientation of the Golgi complex during directional cell movement were attenuated by knockdown of FGD5. CONCLUSIONS: This study provides the first demonstration of expression, subcellular localization, and function of FGD5 in vascular ECs. The results suggest that FGD5 regulates proangiogenic action of VEGF in vascular ECs, including network formation, permeability, directional movement, and proliferation.