Lysosomal ionic dysregulation in heart disease

The lysosome is emerging as a key regulatory hub within the cell, crucial for maintaining homeostasis and viability under stress. This acidic, degradative organelle not only supports metabolic adaptation through mitophagy and autophagic clearance but also plays a crucial role in fine-tuning local signaling events via controlled ion release. While thus far lysosomal ionic regulation has proven to be vital for cardiac homeostasis, its alteration in disease states remains largely unexplored. Our recent findings reveal that the calcium/proton-permeable two-pore channel (TPC2) is one of the most significantly altered lysosomal ion channels in cardiac disease, with marked upregulation following acute injury that persists throughout heart failure progression. Replication of this upregulation in vitro and in vivo demonstrates its pathogenic role, with elevated TPC2 activity linked to increased cardiomyocyte death, exacerbated ischemia/reperfusion injury, and progressive cardiac dysfunction. Mechanistic studies suggest that TPC2-mediated cell death is likely driven by lysosomal calcium-induced mitochondrial calcium overload and subsequent permeability transition pore (mPTP) opening. Additionally, proton efflux from hyperactive TPC2 appears to impair lysosomal acidification and autophagic clearance, further diminishing ischemic stress adaptation. Accordingly, the proposed research will test the hypothesis that excessive lysosomal TPC2 ion release significantly contributes to MI pathogenesis by promoting cardiomyocyte death and weakened cellular resilience. We will address this hypothesis in two specific aims: In Aim 1 we will employ in vitro and in vivo genetic manipulations to determine whether sustained increases in TPC2 activity drive ischemic pathological cardiac remodeling and decompensation, and therapeutically test if TPC2-selective inhibition can prevent HF development In Aim 2 we will leverage our range of lysosomal-targeted biosensors, molecular tools, and TPC2 gain- and loss-of-function models to explore how lysosomal calcium and proton efflux independently influence cardiomyocyte resilience and survival, and additionally test whether TPC2-dependent changes in post-MI remodeling preferentially favor one ionic pathway over the other. The outcomes of this research will provide transformative insights into lysosomal ion regulation, stress adaptation, and cell survival, paving the way for novel strategies to combat ischemic heart disease. Project Number: 1R01HL180055-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Jillian Simon | Institution: TEMPLE UNIV OF THE COMMONWEALTH, PHILADELPHIA, PA | Award Amount: $717,558 | Activity Code: R01 | Study Section: Integrative Myocardial Physiology/Pathophysiology B Study Section[MPPB] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL18005501