SH3BGR Affects Energy Metabolism In Neonatal Rat Cardiomyocytes

Background: The SH3 domain-binding glutamic acid-rich (SH3BGR) gene maps to the genetic fragment associated with Down's syndrome (DS), one of the predominant causes of congenital heart diseases (CHD). We have previously shown that SH3BGR augments cardiomyocyte apoptosis, however, its possible role in cardiomyocyte metabolism is not known yet. Methods: Functional effects of SH3BGR knockdown or overexpression were studied in neonatal rat ventricular cardiomyocytes (NRVCMs) using seahorse metabolic assays, quantitative real-time PCR, immunoblotting, and immunofluorescence microscopy. Results: Since we found significantly altered cardiac levels of SH3BGR in human patients suffering from cardiac hypertrophy, which is reportedly associated with mitochondrial dysfunction, we determined if loss- or gain-of-function of SH3BGR impacts mitochondrial metabolism. We observed significant reduction in oxidative phosphorylation complexes and associated genes. Interestingly, seahorse metabolic activity assays revealed impairment in mitochondrial bioenergetics by both knockdown and overexpression of SH3BGR suggesting the importance of its stead-state levels in cardiomyocyte mitochondrial metabolism. NRVCMs showed inability to meet high energy demand on altered SH3BGR expression indicated by higher proton leak and impeded ATP production. These observations suggest altered mitochondrial respiration, which was further supported by alterations in the expression levels of respective metabolic genes. Combining these results with our previous findings suggests that SH3BGR plays an important role in cardiomyocyte oxidative phosphorylation, cell viability and apoptosis. Conclusion: Our data provide novel insights into potential role of SH3BGR in cardiomyocyte mitochondrial bioenergetics. These findings will help us understand how genetic deletion or SH3BGR mutations are associated with CHD e.g., using CRISPR/CAS mediated genetic manipulations using human patient derived induced pluripotent stem cells.