A close functional and molecular integration between metabolic and immune systems is crucial for systemic homeostasis and its’ deregulation is causally linked to obesity and associated diseases including insulin resistance, diabetes and atherosclerosis and known as cardiometabolic syndrome (CMS). Metabolic overload initiates a chronic inflammatory and stress response known as metaflammation and promotes the complications of CMS. The precise molecular mechanisms linking metabolic stress to immune activation and stress responses, however, remain elusive.Earlier studies demonstrated metabolic overload stresses the endoplasmic reticulum (ER) and activates the unfolded protein response (UPR). ER is a critical intracellular metabolic hub orchestrating protein, lipid and calcium metabolism. These vital functions of ER are maintained by a conserved, adaptive stress response or UPR that emanates from its membranes. ER stress has emerged as a central paradigm in the pathogenesis of CMS and its reduction prevents atherosclerosis and promotes insulin sensitivity. However, a clear understanding of how metabolic stress is sensed and communicated by the ER is fundamental in designing specific and targeted therapy to ER stress in CMS. This application will investigate the ER stress response that can sense excess lipids and couple to inflammatory and stress responses, and whether its unique operation under metabolic stress can be suitable for therapeutic exploitation in CMS. This proposal tackles the unique modes of operation of two important players in the ER stress response that are coupled by metabolic stress, inositol-requiring enzyme-1 (IRE-1) and double-stranded RNA-activated kinase (PKR), by taking advantage of chemical-genetics to specifically modify their activities. When completed the proposed studies will have shed light on a little explored but central question in the field of immunometabolism regarding how nutrients engage inflammatory and stress pathways.