The Role of Mitochondrial Acid-Sensing Ion Channel 1 in Pulmonary Hypertension

University Of New Mexico Health Scis Ctr, Albuquerque NM

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Abstract

PROJECT SUMMARY The World Health Organization (WHO) defines five broad groups of pulmonary hypertension (PH), including PH resulting from chronic lung diseases and/or conditions causing hypoxia (WHO Group III). Regardless of etiology, central features include increased pulmonary arterial constriction and remodeling. Unfortunately, current therapies lack pulmonary vasculature specificity and do not address the prominent pulmonary arterial remodeling; nonetheless, rates of morbidity and mortality for patients with PH remain high. Our laboratory has identified a pathogenic role of acid-sensing ion channel 1a (ASIC1a) in rodent models of chronic hypoxia (CH)-induced PH. The prominent role of ASIC1a is independent of changes in gene or protein expression. Rather, subcellular localization of ASIC1a in PASMC is altered, wherein plasma membrane-localized ASIC1a (pmASIC1a) is increased and mitochondria-localized ASIC1a (mtASIC1a) is decreased. Following CH, enhanced activation of pmASIC1a causes increased Na+ and Ca2+ influx, which are associated with pulmonary arterial smooth muscle cells (PASMC) dysfunction during PH. However, both the physiological role and the effect of the loss of mtASIC1a on PASMC function are unknown. Our preliminary data shows that the loss of Asic1a results in mitochondrial membrane potential (ΔΨm) hyperpolarization and decreased caspase activation. Lentiviral transduction of PASMC from Asic1a knockout mice with mtASIC1a prevents ΔΨm hyperpolarization. Considering that ΔΨm hyperpolarization is associated with mitochondrial dysfunction and apoptosis resistance, these data suggest an important role of mtASIC1a for PASMC function. Defining the mechanisms of ASIC1a trafficking may provide novel molecular targets to improve PASMC function during PH. Interestingly, we show that the ASIC1a-binding molecular chaperone, sigma-1 receptor (σ1R), is upregulated in intrapulmonary arteries following CH. Moreover, we show that the σ1R antagonist, S1RA, decreases pmASIC1a localization and the σ1R agonist, PRE-084, increases ASIC1a-dependent Ca2+ influx. The proposed studies will test the central hypothesis that σ1R causes altered subcellular localization of ASIC1a following CH that results in aberrant PASMC function associated with PH. The following aims will be investigated to test this hypothesis: 1) Determine the contribution of σ1R to the enhanced localization and activation of pmASIC1a following CH and 2) Define the role of σ1R in mtASIC1a localization and mitochondrial function. The significance of this research lies in defining the role of σ1R in regulating ASIC1a subcellular localization, which controls PASMC function. This study also examines the novel role of ASIC1a to regulate mitochondrial function. These findings address the unmet need for more effective pulmonary hypertension therapies. Moreover, this training plan will positively impact my technical, analytical, and communication skills which will propel me to attain a postdoctoral fellowship studying vascular physiology.