Abstract MP231: Long Non-coding Rna Camirt Plays A Sentinel Role In Aging-related Heart Failure Via Interaction With Phb2 To Modulate Mitophagy Signaling In The Heart

Abstract

Background: Mitochondrial dysfunction is an important risk factor for heart failure in elderly people. Mitophagy, a physiological process that controls the removal of damaged mitochondria, is compromised in aging or failing hearts. In this study, we examined the physiological role of a cardiac-specific lncRNA Camirt that can potentially modulate mitophagy in the heart. Methods and Results: RNA-seq analysis and RT-PCR reveal a lncRNA is highly expressed in both mouse and human hearts, with undetectable levels in other vital organs. Furthermore, Real time qPCR was used to examine the expression of lncRNA in different animal models and in human hearts, which results showed that the expression of this lncRNA is decreased in aging mouse and human hearts, and failing mouse hearts induced by isoproterenol and doxorubicin. RNA pull-down and RNA-binding protein immunoprecipitation assays identify prohibitin-2 (Phb2), a known mitophagy receptor, as a binding partner for this lncRNA. Thus, we name this novel lncRNA as a cardiac-specific mitophagy-associated RNA transcript (Camirt). Camirt conditional (flox) knockout mice were created via CRISPR /Cas9 technology, and subjected to the longitudinal echocardiographic and survival studies. Mice with cardiac specific deletion of Camirt (Camirt-cKO) display progressive heart failure and die within 12 month after birth. RNA sequencing and gene ontology analysis revealed that genes involved in mitophagy signaling were significantly altered in the Camirt-cKO hearts compared with the littermate wild type mice. Transmission electron microscopy were used to examine the mitochondrial morphology in mouse hearts, and reveal excessive accumulation of mitolysosomes in cardiomyocytes derived from the Camirt-cKO mice. In vitro study with Annexin-V/PI staining showed an increased number of live cells and decreased number of apoptotic cells in cultured neonatal cardiomyocytes with overexpression of Camirt following oxidative stress induced by treatment with H2O2. Increased autophagy (or mitophagy) activity was observed in HL-1 cells with stable overexpression of Camirt and in the presence of chloroquine (an inhibitor for the lysosome degradation). While reduced Camirt expression via shRNA knock-down leads to compromised mitophagy activity in HL-1 cells. Further biochemical studies support the function of Camirt/Phb2 in maintenance of mitochondria function and mitophagy signaling under stress conditions. Conclusion: Overall, our results suggested that Camirt plays a sentinel role in aging-related heart failure via interaction with Phb2 to modulate mitophagy signaling in the heart. Future studies will focus on elucidating the in vivo role and mechanisms of Camirt in modulation of mitophagy under natural aging or stress-induced pathologic conditions using the loss- or gain-of-function of Camirt mouse models.