Abstract 529: The Intra-molecular Pathway Of Nck1 In Atherogenic Endothelial Activation

Abstract

Rational: Atherosclerosis, a chronic progressive disease, is the underlying disease process in ischemic heart disease (IHD). Despite our advances, IHD is still the leading cause of disease mortality worldwide. Endothelial Activation due to disturbed blood flow (d-flow) is one of the earliest changes in atherosclerosis. However, the molecular pathway whereby d-flow induces endothelial activation is unclear. Methodology & Results: Herein we identified the signaling protein Nck1 as a key regulator to atherogenic endothelial activation. Nck1 is an adaptor molecule with a multi-domain structure, and in response to d-flow, we found that the Nck1 SH2 (phosophotyrosine binder) and the Nck1 SH3.1 (with a high affinity to bind to proline rich peptides) are critical domains of Nck1 to regulate the prolinflammatory signal activation. In addition, the small molecule inhibitor, AX-024 (50 nM), which occupies the DY pocket of the Nck1 SH3.1, prevents d-flow induced endothelial activation, suggesting downstream mediator that binds to the Nck1 SH3.1 and mediates the activation. In order to determine the Nck1 specific signaling partners, we used affinity purification-mass spectrometry and we identified 6 signaling proteins that significantly interact with Nck1 in response to d-flow. In vivo, our endothelial-specific Nck1 knock out mice show significantly less atherosclerosis lesion burden compared to their littermate controls. Conclusions: A recent GWAS analysis linked Nck1 to IHD, underscoring its importance as a potential therapeutic target. AX-024 is a first-in-class a small molecule inhibitor to Nck1, and is currently being tested in clinical trials. Our data confirms a role for AX-024 in preventing endothelial activation after d-flow exposure and sheds light on a previously uncharacterized function of Nck1 adaptor protein in atherogenic endothelial activation.