The Mitochondrial Sodium/Calcium Exchanger (NCLX) in Airway Smooth Muscle Remodeling during Asthma

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PROJECT SUMMARY/ABSTRACT Asthma, which has been traditionally characterized as a chronic inflammatory disease of the airways, affects 25.7 million Americans a year. The pathogenesis of this complex disease is now being recognized as not only due to inflammation but also due to structural changes in the airways known as airway remodeling (AR). Specifically, airway smooth muscle (ASM) remodeling has been demonstrated to cause a decline in pulmonary function, contribute to airway hyperresponsiveness (AHR), and worsen asthmatic symptoms. Currently, there is no targeted therapy for AR in asthma. Understanding the molecular mechanisms of AR could lead to significant therapeutic strategies to treat asthma. Studies have demonstrated that mitochondrial metabolism and mass were increased in ASM acutely isolated from remodeled bronchi of asthmatic patients. It was also reported that ASM mitochondrial biogenesis was necessary to maintain the metabolic demands of AR. Calcium (Ca2+) is a crucial signaling molecule that is particularly important for cellular remodeling, especially AR. In addition, Ca2+ signaling regulates mitochondrial biogenesis through Ca2+/Calmodulin Kinase (CaMK). Thus, establishing a mechanistic connection between mitochondrial biogenesis, Ca2+ signaling, and AR could lead to successful strategies for targeting AR in asthma Recently, the newly described mitochondrial sodium (Na+)/Ca2+ exchanger (NCLX) has emerged as a novel modulator of Ca2+ signaling and mitochondrial function and dysregulation of NCLX activity leads to disease. Therefore, I hypothesize that NCLX activity is crucial for AR during asthma through NCLX-mediated shuttling of mitochondrial Ca2+ signals into cytosolic microdomains to regulate mitochondrial biogenesis and metabolism. Here, I propose to understand the mechanism(s) by which NCLX mediates enhancement of ASM mitochondrial biogenesis and AR (Aim 1) and determine the role of NCLX in AR in vivo using smooth muscle-specific NCLX knockout mice and a model of asthma (Aim 2). This proposal will identify novel specific molecular targets for AR and asthma. The research of this F30 proposal serves as an integral part of a comprehensive and individualized training plan to allow Martin Johnson to excel towards his career as a physician-scientist. The Penn State College of Medicine will provide the adequate facilities, resources, and training to complete this training plan. Martin will be mentored by renowned smooth muscle and calcium signaling biologists and physician-scientists to guide him throughout his project. During the duration of this proposed training plan, Martin will contribute stellar first-author papers and present novel mechanistic knowledge at national/international meetings related to ASM remodeling and asthma. As experienced mentors, Drs. Mohamed Trebak and Donald Gill will serve as the sponsor and co- sponsor of Martin’s training plan and provide any necessary assistance to allow Martin to become a successful physician-scientist.