Activator of G-protein signaling 8 is involved in VEGF-mediated signal processing during angiogenesis

Abstract

Activator of G-protein signaling 8 (AGS8) is a receptor-independent accessory protein for the Gβγ subunit, which was isolated from the rat heart subjected to repetitive transient ischemia with the substantial development of collaterals. Here, we report the role of AGS8 in vessel formation by endothelial cells. Knockdown of AGS8 by small interfering RNA (siRNA) inhibited VEGF-induced tube formation, as well as VEGF-stimulated cell growth and migration. VEGF stimulated the phosphorylation of the VEGF receptor-2 (VEGFR-2), p42/44 MAPK, and p38 MAPK; however, knockdown of AGS8 inhibited these signaling events. Signal alterations by AGS8 siRNA were associated with a decrease of cell surface VEGFR-2 and an increase of VEGFR-2 in the cytosol. Endocytosis blockers did not influence the decrease of VEGFR-2 by AGS8 siRNA, suggesting the involvement of AGS8 in VEGFR-2 trafficking to the plasma membrane. VEGFR-2 formed a complex with AGS8 in cells, and a peptide designed to disrupt AGS8-Gβγ interaction inhibited VEGF-induced tube formation. These data suggest the potential role for AGS8-Gβγ in VEGF signal processing. AGS8 may play a key role in tissue adaptation by regulating angiogenic events. (179/180)

Activator of G-protein signaling 8 is involved in VEGF-induced choroidal neovascularization

“…Interestingly, intravitreal AGS8 siRNA injections significantly inhibited CNV formation and the vascular budding area of the RPE-choroid complex. These findings complemented the in vitro study, which showed that the molecular mechanism of angiogenesis is mediated by AGS8 15 and demonstrated the regulation of angiogenesis in vivo by accessory proteins for G-protein. Our data also suggest the potential of AGS8 as a therapeutic target to control neovascularization in human diseases.…”

“…The effect of AGS8 knockdown on VEGFR-2 signal is associated with a decrease of cell surface expression of VEGFRs 15,16 . Therefore, we analyzed the cell surface expression of VEGFR-2 in RF/6A cells using FACS analysis with an FITC-conjugated anti-VEGFR-2 antibody.…”

“…Therefore, we further investigated the roles of AGS8 in vascular formation and found that knockdown of AGS8 by small interfering RNA (siRNA) reduced cell surface localization of AGS8 and inhibited VEGF-induced tube formation, cell growth and migration, as well as the phosphorylation status of signaling molecules including VEGFR-2, ERK1/2, and p38/MAPK. Furthermore, AGS8-Gβγ formed a protein complex with VEGFR-2, suggesting a potential role for AGS8-Gβγ in VEGF signal processing during angiogenesis 15 . In addition, we recently demonstrated that AGS8 is also involved in the regulation of VEGFC-induced lymphangiogenesis through VEGFR-3 regulation in lymphatic endothelial cells 16 but is not involved in FGF- or EGF-induced cellular events 15,16 , suggesting that AGS8 is a specific VEGF signaling regulator.…”

“…Furthermore, AGS8-Gβγ formed a protein complex with VEGFR-2, suggesting a potential role for AGS8-Gβγ in VEGF signal processing during angiogenesis 15 . In addition, we recently demonstrated that AGS8 is also involved in the regulation of VEGFC-induced lymphangiogenesis through VEGFR-3 regulation in lymphatic endothelial cells 16 but is not involved in FGF- or EGF-induced cellular events 15,16 , suggesting that AGS8 is a specific VEGF signaling regulator.…”

MicroRNA-378 Promotes Osteogenesis-Angiogenesis Coupling in BMMSCs for Potential Bone Regeneration

“…Wnt signaling pathway positively regulates osteogenesis in BMMSC and ALP and runt-related transcription factor 2 (Runx2), which are the representative factors in the downstream of osteogenesis-angiogenesis [ 5 – 7 ]. Mitogen-activated protein kinase (MAPK) signaling pathway positively regulates angiogenesis by targeting VEGF expression [ 8 – 10 ]. However, exogenous osteogenetic and angiogenic stimulants would cause imbalance of bone formation, leading to excessive bone formation or vascular leakage at the risk of tumorigenesis [ 11 , 12 ].…”