Endothelial GATA5 positively regulates angiogenesis via cathepsin S-mediated Angpt2/Flk1 and MMP2/9 signaling pathways

Although GATA5 is vital in maintaining the function of endothelial cells, the relationship between GATA5 and angiogenesis, however, remains unclear. Our study aims to determine how endothelial GATA5 mediates angiogenesis. Using the ischemic hindlimb of mice with GATA5 overexpression in the endothelia (EC-Ad mice), we showed that GATA5 overexpression could improve blood perfusion and increase capillary density. Furthermore, we showed that overexpression of GATA5 can increase the protein and mRNA levels of angiopoietin-2 (Angpt2) and fetal liver kinase 1 (Flk1) in the endothelia of EC-Ad mice, while GATA5 knockdown can inhibit the VEGF-165-induced proliferation, tube formation, and migration of human umbilical vein endothelial cells (HUVECs). In addition, we observed a decrease in the Angpt2 and Flk1, and the matrix metalloproteinase (MMP) family proteins: MMP2 and MMP9 while GATA5 was decreased. Meanwhile, our study also demonstrated that the expression of cathepsin S (Cat S) decreases when GATA5 is downregulated. Immunoprecipitation assay indicated that GATA5 could bind to Cat S directly. Furthermore, GATA5 or Cat S overexpression can promote tube formation and migration of HUVECs, restore the Angpt2 and Flk1 expression levels in the GATA5 knockdown HUVECs, and upregulate MMP2 and MMP9 protein levels. In summary, our study demonstrated that endothelial GATA5 could mediate angiogenesis by inducing the expression of Cat S, which mediates the Angpt2/Flk1 and MMP2/9 signaling pathways.