Receptor and Molecular Mechanism of AGGF1 Signaling in Endothelial Cell Functions and Angiogenesis

Abstract

Objective: Angiogenic factor AGGF1 (angiogenic factor and G-patch and FHA [Forkhead-associated] domain 1) promotes angiogenesis as potently as VEGFA (vascular endothelial growth factor A) and regulates endothelial cell (EC) proliferation, migration, specification of multipotent hemangioblasts and venous ECs, hematopoiesis, and vascular development and causes vascular disease Klippel-Trenaunay syndrome when mutated. However, the receptor for AGGF1 and the underlying molecular mechanisms remain to be defined. Approach and Results: Using functional blocking studies with neutralizing antibodies, we identified α5β1 as the receptor for AGGF1 on ECs. AGGF1 interacts with α5β1 and activates FAK (focal adhesion kinase), Src, and AKT. Functional analysis of 12 serial N-terminal deletions and 13 C-terminal deletions by every 50 amino acids mapped the angiogenic domain of AGGF1 to a domain between amino acids 604-613 (FQRDDAPAS). The angiogenic domain is required for EC adhesion and migration, capillary tube formation, and AKT activation. The deletion of the angiogenic domain eliminated the effects of AGGF1 on therapeutic angiogenesis and increased blood flow in a mouse model for peripheral artery disease. A 40-mer or 15-mer peptide containing the angiogenic domain blocks AGGF1 function, however, a 15-mer peptide containing a single amino acid mutation from −RDD- to −RGD- (a classical RGD integrin-binding motif) failed to block AGGF1 function. Conclusions: We have identified integrin α5β1 as an EC receptor for AGGF1 and a novel AGGF1-mediated signaling pathway of α5β1-FAK-Src-AKT for angiogenesis. Our results identify an FQRDDAPAS angiogenic domain of AGGF1 crucial for its interaction with α5β1 and signaling.

Angiogenic factor AGGF1 blocks neointimal formation after vascular injury via interaction with integrin α7 on vascular smooth muscle cells

“…We recently found that AGGF1 regulated endothelial cell (EC) functions and angiogenesis by interacting with its receptor integrin α5 on endothelial cell surface ( 16 ). As integrin α5 is also expressed in VSMCs, we investigated whether integrin α5 mediated the adhesion of AGGF1 to VSMCs.…”

“…In an accompanying study, we showed that cell adhesion to AGGF1 was not disrupted by neutralizing antibodies against integrins α1, α2, α3, α4, α6, αv, and β3; therefore, these integrins are unlikely to affect the function of AGGF1 in VSMCs. However, we found that integrin α5β1 acted as a receptor for AGGF1 in endothelial cells, activated FAK-Src-AKT signaling, and modulated the signaling and functions of AGGF1 in endothelial cells and therapeutic angiogenesis in a model for peripheral artery disease (PAD) ( 16 ). The question is whether integrin α5β1 also acts as a receptor for AGGF1 in VSMCs.…”

Therapeutic angiogenesis-based strategy for peripheral artery disease

“…Yao et al revealed that AGGF1 activated the antioxidative processes in EPCs to inhibit reactive oxygen species generation, thus promoting EPCs function in diabetic HLI model mice 115 . Moreover, Wang et al reported integrin α5β1 as a receptor for AGGF1 in ECs could promote ECs adhesion, migration, capillary tube formation, and therapeutic angiogenesis in the HLI mouse model 116 .…”

DNA methylation signatures on vascular differentiation genes are aberrant in vessels of human cerebral arteriovenous malformation nidus

“…To substantiate the DNA hypermethylation, we used DNA isolated from AVM nidus and control tissue (3rd sample) and performed the promoter DNA methylation analysis for the CpG islands of selected genes. We performed bisulfite conversion and sequencing of the selected gene promoters, which are known to involve in vascular development [16,17,25,31,38]. We selected four genes such as ZNF24 (also known (Kox17), AGGF1 (Angiogenic factor with G patch and FHA domains 1), ANKRD65 (Ankyrin repeat domain 65), and FAAH (Fatty acid amid hydrolase) for further validation of DNA hypermethylation on the promoter of these genes [16,17,25,31,38].…”