Grant: Project Grant

Autophagy is a fundamental cellular process in which cytoplasmic proteins and damaged cellular organelles are recycled by forming double membrane vesicles that surround these organells and take them to the lysosome for degradation and recycling. Several reports indicate that autophagy under normal conditions is important for the maintenance of skeletal muscle size and that autophagy is enhanced and promotes muscle wasting under pathological conditions such as fasting, loss of innervation and sepsis sepsis. Despite major progress in our understanding of how autophagosomes (double membrane vesicles) are formed inside skeletal muscles, many of the proteins involved in autophagy remain unclear. We performed preliminary experiments in mouse skeletal muscles to identify novel genes that are involved in autophagy. These experiments revealed the presence of an uncharacterized gene that we named MYTHO (Macroautophagy and YouTH Optimizer). We named as such because our preliminary experiments revealed that this gene is critical for longevity in worms. These experiments also revealed that MYTHO protein is present in skeletal muscles of humans and mice and that deletion of this gene in cultured cells inhibits autophagy. In this proposal, we will conduct several experiments designed to identify the importance of MYTHO in the autophagy of intact skeletal muscles in humans and mice and to identify the mechanisms through which MYTHO regulates autophagosome formation in skeletal muscles. These objectives will be achieved by using molecular biology tools to visualize MYTHO protein inside skeletal muscle fibers and to either increase its expression or reduce it and measure its contribution to the formation of autophagosomes and recycling of proteins and organelles in normal skeletal muscles and in muscles of mice in which autophagy is induced and contributes to muscle wasting. These conditions include acute fasting, denervation and severe sepsis elicited by bacterial products.