PROJECT SUMMARY Coronary heart disease is the leading cause of death in the US. The atherosclerotic process underlying coronary heart disease is exacerbated by stressors in the vascular environment, including hyperlipidemia, tobacco smoke, and air pollution. These stressors have been known to cause increased inflammation and oxidative stress in the vessel wall, but how these stressors affect the different cell types in the vascular wall has not been well-described. In our preliminary studies, we found that atherogenic stress can induce significant transcriptional and epigenetic changes consistent with proteotoxicity in the atherosclerotic vascular wall. In particular, we found that e-cigarettes activate the unfolded protein response (UPR) in smooth muscle cells (SMCs), and that this response may be dependent on the environment sensing aryl-hydrocarbon receptor (AHR) pathway. The overall objective of this proposal is to characterize the smooth muscle specific misfolded protein aggregates and their functionality. The central hypothesis is that the atherogenic environment can induce tissue-specific protein misfolding and proteotoxic stress in vascular SMCs and that AHR can protect against atherosclerosis by limiting the proteotoxic stress. In Aim 1, we will isolate and identify the misfolded protein aggregates that are associated with atherosclerosis and different disease-causing stimuli. In Aim 2, we will assess the role of AHR in modulating the vascular proteostasis network utilizing primary human coronary artery SMCs in-vitro. Extending the results obtained from PI Dr. Kim’s NHLBI K08 career development award, the proposed work will address a critical knowledge gap in understanding the role of proteotoxic stress in SMCs during atherosclerosis. Ultimately, this work will shed light on novel pathways associated with risk for coronary heart disease. The successful completion of this project will provide the foundation to apply for a larger grant (R01) to address the effect of specific components of the vascular proteostasis network in controlling atherosclerosis.