Project Grant F31HL186666

T-TUBULE MICRODOMAINS FACILITATE PROTECTIVE MITOPHAGY IN CARDIOMYOCYTES - PROJECT SUMMARY HEART FAILURE WITH PRESERVED EJECTION FRACTION (HFPEF) REPRESENTS ABOUT 50% OF ALL HEART FAILURE INCIDENCE, YET THERE ARE CURRENTLY FEW THERAPEUTIC OPTIONS FOR REDUCING MORTALITY OR REVERSING FAILURE. THE CELLULAR PATHOPHYSIOLOGY OF HFPEF IS POORLY UNDERSTOOD, THOUGH MANY STUDIES HAVE IDENTIFIED THAT MITOCHONDRIAL DYSFUNCTION DRIVEN BY DOWNREGULATION OF CANONICAL MITOPHAGY IS A COMMON PATHOLOGY OF FAILING CARDIOMYOCYTES. PROMISINGLY, SEVERAL STUDIES HAVE SHOWN THAT UPREGULATION OF MITOPHAGY PROTECTS BOTH MITOCHONDRIA AND RESCUES OVERALL HEART FUNCTION. THUS, MECHANISMS REGULATING MITOPHAGY WITHIN CARDIOMYOCYTES OFFER ATTRACTIVE POTENTIAL TARGETS FOR DEVELOPING THERAPIES TO ADDRESS HEART FAILURE PATHOLOGY AT THE CELLULAR LEVEL. PREVIOUS RESEARCH BY OUR LAB HAS IDENTIFIED THAT CARDIOMYOCYTE T-TUBULES CONTAIN CALCIUM-HANDLING MICRODOMAINS FORMED BY THE SCAFFOLDING PROTEIN CARDIAC BRIDGING INTEGRATOR 1 (CBIN1). THESE MICRODOMAINS ARE DISRUPTED IN HEART FAILURE DUE TO REDUCED CBIN1 TRANSCRIPTION, WHILE RESTORATION OF THESE MICRODOMAINS RESCUES CALCIUM HANDLING AND HEART FAILURE IN MURINE AND LARGE ANIMAL MODELS. OUR NEW PRELIMINARY DATA INDICATE THAT ADENO-ASSOCIATED VIRUS 9 TRANSDUCING CBIN1 (AAV9-CBIN1) RESCUES MITOCHONDRIAL DYSFUNCTION IN DIABETIC HEARTS AND THAT CBIN1 MAY PROMOTE PROTECTIVE MITOPHAGY. BASED ON PREVIOUS RESEARCH, CBIN1 MAY BE PLAYING A ROLE IN CANONICAL MITOPHAGY BY FACILITATING RECRUITMENT OF ITS KNOWN BINDING PARTNERS AND KEY MITOPHAGY PLAYERS PARKIN AND CHMP4B. THUS, THE CENTRAL HYPOTHESIS TO BE TESTED BY THIS PROPOSAL IS THAT T-TUBULE CBIN1 FACILITATES MITOPHAGY TO MAINTAIN MITOCHONDRIAL HEALTH IN STRESSED CARDIOMYOCYTES BY PROMOTING PARKIN RECRUITMENT AND ESCRT-DEPENDENT AUTOPHAGOSOME SEALING. TO TEST THE HYPOTHESIS, EXPERIMENTS WILL BE PERFORMED TO DETERMINE WHETHER CBIN1 RECRUITS PARKIN TO DAMAGED MITOCHONDRIA UPON CARDIOMYOCYTE STRESS (AIM 1). TO ACCOMPLISH THIS AIM, BOTH CELLULAR MODELS AND ISOLATED PRIMARY MOUSE CARDIOMYOCYTES WITH REDUCTION AND RESCUE OF CBIN1 LEVELS WILL BE USED TO CARRY OUT MITOPHAGIC FLUX ASSAYS, MITOCHONDRIAL FRACTIONATIONS, AND COLOCALIZATION ASSAYS OF PARKIN WITH CBIN1 AND MITOCHONDRIA. ADDITIONAL EXPERIMENTS LAID OUT IN THIS PROPOSAL WILL TEST WHETHER CBIN1 RECRUITS ESCRT MACHINERY TO FACILITATE THE KEY AUTOPHAGOSOME SEALING STEP IN MITOPHAGY (AIM 2). THE PROPOSAL IS SIGNIFICANT BECAUSE IT WILL CHARACTERIZE HOW T-TUBULE MICRODOMAINS REGULATE MITOCHONDRIAL HEALTH AND THEREBY REVEAL ADDITIONAL THERAPEUTIC TARGETS FOR INCREASING MITOPHAGIC FLUX, BENEFITING MILLIONS OF PATIENTS WITH HFPEF AND OTHER METABOLIC DISEASES. THE HONG LAB AND THE UNIVERSITY OF UTAH PROVIDE AN EXCELLENT MULTIDISCIPLINARY TRAINING ENVIRONMENT IN WHICH THE PROPOSED RESEARCH TRAINING PLAN WILL BE CARRIED OUT. DURING THE PROCESS, THE APPLICANT WILL RECEIVE TRAINING IN ADVANCED EXPERIMENTAL DESIGN, PHARMACOTHERAPY OF CARDIAC DISEASE, NETWORKING WITH INDUSTRY, LEADERSHIP, AND EFFECTIVE SCIENCE COMMUNICATION. THE ENVIRONMENT AND PROPOSED TRAINING PLAN WILL EFFECTIVELY PREPARE THE APPLICANT FOR A CAREER IN PHARMACEUTICAL DEVELOPMENT TARGETING MAJOR HUMAN DISEASE.