Modulation of Contraction-Induced Changes in Muscle mTOR Signaling by Alcohol

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DESCRIPTION (provided by applicant): Binge drinking and chronic alcohol abuse (i.e. alcoholism) represent important public health issues as these are associated with high risk behaviors, multiple organ system dysfunction, impaired recovery from illness and even premature death. Habitual alcohol abuse leads to skeletal muscle myopathy characterized by muscle loss, weakness, and decreased physical function. These symptoms are associated with molecular changes including a depressed rate of mTOR-dependent protein synthesis in skeletal muscle. Few treatment strategies exist to aid in the recovery from this disease both in the continued presence of alcohol and under circumstances where abstinence is achieved. However, skeletal muscle contraction activates mTOR kinase activity and increases protein synthesis. Importantly, when an intermittent contractile stimulus is sustained over several weeks it induces significant muscle growth and a coordinate increase in muscle function. Therefore, stimulated muscle contraction, either voluntarily or via transcutaneous electrical stimulation, may represent a potential therapeutic modality for individuals with alcoholic muscle disease who have limited mobility and functional capacity. Our long term goal is to determine the effects of alcohol on skeletal muscle protein synthesis and mTOR activity that has been increased by stimulated muscle contraction, and to identify potential signaling changes and new proteins that mediate the observed response. Progression towards this goal will be achieved through the following specific aims: (1) Determine whether acute alcohol intoxication reverses the pre-existing increase in mTOR activity, protein synthesis and muscle hypertrophy induced by acute or chronic muscle contraction; (2) Establish the therapeutic relevance of acute and chronic muscle contraction in a model of chronic alcoholic myopathy with regards to changes in muscle mTOR activity, protein synthesis and muscle hypertrophy; (3) Define the role of endosomal/lysosomal targeting of TSC2 and mTOR following acute and chronic alcohol, and muscle contraction relevant to previously observed changes in hypertrophy, contractility and mTOR signaling; and (4) Identify skeletal muscle proteins whose synthetic rate is altered by alcohol and/or muscle contraction using puromycin-associated nascent chain proteomics (PUNCH- P). These aims represent a set of novel and comprehensive experiments utilizing several innovative in vivo and ex vivo techniques including rodent models of acute and chronic alcohol abuse, isolated muscle strength and fatigability testing, visualization of the molecular trafficking of mTOR and TSC2, as well as mass spectrometry to identify newly made proteins following alcohol and muscle contraction. Data garnered from these experiments will provide clinically relevant knowledge to significantly advance treatment strategies and contribute to the mechanistic understanding of the etiology of acute and chronic alcoholic muscle disease.