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

Objective: Angiogenic factor AGGF1 (angiogenic factor with 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 alpha 5 beta 1 as the receptor for AGGF1 on ECs. AGGF1 interacts with alpha 5 beta 1 and activates FAK (focal adhesion kinase), Src (proto-oncogene tyrosine-protein kinase), and AKT (protein kinase B). 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 alpha 5 beta 1 as an EC receptor for AGGF1 and a novel AGGF1-mediated signaling pathway of alpha 5 beta 1-FAK-Src-AKT for angiogenesis. Our results identify an FQRDDAPAS angiogenic domain of AGGF1 crucial for its interaction with alpha 5 beta 1 and signaling.

Automated summary

The angiogenic factor AGGF1 promotes angiogenesis and regulates various cellular processes, with integrin alpha 5 beta 1 identified as its receptor. Interaction between AGGF1 and alpha 5 beta 1 activates key signaling molecules involved in angiogenesis. A specific angiogenic domain of AGGF1 plays a crucial role in its function, highlighting potential therapeutic targets for vascular diseases.