The Role of Adaptor Protein Disabled-2 in Maintaining Endothelial Cell Function in Atherosclerosis

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PROJECT SUMMARY/ABSTRACT Cardiovascular diseases are often associated with impaired responses from the endothelium, which results from endothelial cell dysfunction. Endothelial cell dysfunction causes endothelial activation and sub-endothelial retention of modified low-density lipoprotein (LDL) particles, leading to the recruitment of immune and inflammatory cells to the intima, which initiate atheromatous plaque build-up. Of major importance, transitioning from a stable to vulnerable atheroma fuels myocardial infarction and stroke, posing enormous health challenges with the highest morbidity and mortality in the United States. New research is urgently needed to uncover critical pathophysiological mechanisms and identify molecules that limit endothelial dysfunction. This has led us to determine a novel and indispensable role for an endocytic adaptor protein called Disabled homolog 2 (Dab2), which participates in clathrin-mediated endocytosis in addition to moonlighting as a tumor suppressor. Curiously, little to no prior work has been done to identify its role in endothelial cells. Our pilot assessment has revealed that Dab2 levels are strikingly decreased in the atherosclerotic endothelium of mouse and human fatty streaks—suggesting a protective role in atherogenesis. As the atheroprotective effects of Dab2 are poorly understood in the context of endothelial cells, we created endothelial-specific inducible Dab2 knockout mice (EC-iDab2KO) and bred them to an ApoE-null background (EC-Dab2iKO/ApoE-/-). Western diet-fed EC-iDab2KO/ApoE-/- mice exhibit heightened arterial inflammation and more severe plaque formation; yet, the molecular mechanisms and signaling pathways that direct Dab2 to combat arterial inflammation are completely unknown. Our initial investigation indicates that Dab2 expression is upregulated in response to atheroprotective flow, and Dab2 deficiency in human aortic endothelial cells suppresses endothelial nitric oxide synthase (eNOS) activation. To ensure the clinical relevance of our work, we are employing an innovative nanotechnology to deliver Dab2 mRNA to the atherogenic endothelium using an engineered nanoparticle to restore Dab2 function. This technology increases Dab2 expression in the atheroma, which restrains plaque progression in ApoE-/- mice. The goal of this proposal is to define the signaling mechanisms underpinning the essential role of Dab2 in protecting the atherogenic endothelium. To this end, we seek to determine molecular mechanisms by which Dab2 curbs arterial inflammation and activates eNOS in endothelial cells. Our possession of innovative targeting reagents and novel animal models will greatly facilitate our paradigm-shifting endeavor. If fruitful, the exciting work proposed in our application will provide a foundation for the development of new treatments to benefit patients at-risk for heart attacks and strokes.