SVEP1 influences monocyte to macrophage differentiation via integrin a4 beta 1/a9 beta 1 and Rho/Rac signalling

Background: The large extracellular matrix protein SVEP1 mediates cell adhesion via integrin a9 ss 1. Recent studies have identified an association between a missense variant in SVEP1 and increased risk of coronary artery disease (CAD) in humans and in mice Svep1 deficiency alters the development of atherosclerotic plaques. However how SVEP1 functionally contributes to CAD pathogenesis is not fully understood. Monocyte recruitment and differentiation to macrophages is a key step in the development of atherosclerosis. Here, we investigated the requirement for SVEP1 in this process. Methods: SVEP1 expression was measured during monocyte-macrophage differentiation in primary monocytes and THP-1 human monocytic cells. SVEP1 knockout THP-1 cell lines and the dual integrin alpha 4 ss 1/alpha 9 ss 1 inhibitor, BOP, were utilised to investigate the effect of these proteins in THP-1 cell adhesion, migration and cell spreading assays. Subsequent activation of downstream integrin signalling intermediaries was quantified by western blotting. Results: SVEP1 gene expression increases in monocyte to macrophage differentiation in human primary monocytes and THP-1 cells. Using two SVEP1 knockout THP-1 cells we observed reduction in monocyte adhesion, migration, and cell spreading compared to control cells. Similar results were found with integrin alpha a4 ss 1/alpha 9 ss 1 inhibition. We demonstrate reduced activity of Rho and Rac1 in SVEP1 knockout THP-1 cells. Conclusions: SVEP1 regulates monocyte recruitment and differentiation phenotypes through an integrin alpha 4 ss 1/ alpha 9 ss 1 dependent mechanism. General significance: These results describe a novel role for SVEP1 in monocyte behaviour relevant to CAD pathophysiology.

Automated summary

The large extracellular matrix protein SVEP1 plays a crucial role in cell adhesion through integrin α9β1. This study reveals the significant involvement of SVEP1 in the pathogenesis of coronary artery disease (CAD). It shows that SVEP1 plays a critical role in monocyte recruitment and differentiation into macrophages.