Investigating TFEB as a critical node to improve proteostatic maintenance and skeletal muscle function with age

PROJECT SUMMARY/ABSTRACT Skeletal muscle atrophy and dysfunction are a hallmark of aging, sarcopenia, and disuse atrophy that significantly affect individual health span and quality of life. There are currently no effective treatments for age related muscle dysfunction because underlying mechanisms that contribute to muscle pathology are not fully understood. A recently published manuscript from the PI shows that protein synthesis and mTOR activity, a primary regulator of protein synthesis, is high in aged muscle, likely inhibiting TFEB (transcription factor EB) nuclear translocation and subsequent activity. This finding suggests that impaired protein degradation, not protein synthesis, compromises maintenance and recovery of aged muscle. We also showed that there was an accumulation of insoluble ubiquitinated proteins and p62 protein in the insoluble fraction of old muscle. Together, these data suggest that compromised autophagy dependent protein degradation likely impacts skeletal muscle function in aged muscle with sarcopenia and recovery after disuse atrophy. The goal of this project is to determine if TFEB functions as a critical node in muscle maintenance with sarcopenia and recovery with disuse atrophy in aged muscle. TFEB stimulates lysosomal biogenesis and autophagy, which are essential in targeted protein degradation and therefore proteostatic maintenance. The hypothesis of this proposal is that TFEB functions as a critical node to improve maintenance and recovery of skeletal muscle mass and function with aging in two conditions of muscle dysfunction, sarcopenia and disuse atrophy. The following Specific Aims are proposed to test the hypothesis: Aim 1: Determine if increasing TFEB activity improves maintenance of muscle mass and function in aged mice. Aim 2: Determine if mTOR activity regulates TFEB-dependent preservation of proteostatic maintenance and muscle function. Aim 3: Test whether increasing TFEB activity can improve recovery of muscle after disuse atrophy in aged mice. If results support the hypothesis, TFEB may be a novel therapeutic target to protect against sarcopenia and improve recovery with disuse atrophy in aged skeletal muscle. The principal investigator (PI) of this grant is a postdoctoral fellow under the mentorship of Dr. Benjamin Miller at Oklahoma Medical Research Foundation (OMRF). The PI will learn state-of-the-art genetic, molecular, and physiological techniques in mouse and Drosophila melanogaster (fruit flies) to test the effects of TFEB on skeletal muscle proteostasis, in vivo and ex vivo muscle function, protein turnover with stable isotopes, and large proteomics data set bioinformatics analysis. The PI will learn these novel techniques from the mentoring team consisting of Drs. Benjamin Miller, Holly Van Remmen, Fabio Demontis, and Wan Hee Yoon. The mentoring team will monitor the progress of the PI and will also give advice for starting a new laboratory, recruiting members to the PI’s laboratory, and mentoring future scientists as the PI transitions towards research independence.