Altered gravity exposure triggers autophagy-dependent morphological alterations of C2C12 murine muscle cells

Abstract

During space missions, muscles are heavily weakened and start to deteriorate, as microgravity makes any kind of exercise physically undemanding. This kind of loss in muscle mass, called space induced muscle atrophy, is of growing interest since it is one of the limiting factors of long-duration space missions. Through researching the changes in muscles which cause this rapid loss, staying in space for a longer period will not be so far away anymore. Autophagy plays an important role during muscle atrophy as it is used to degrade cytosolic components. One autophagy pathway which is crucial for muscle maintenance is the chaperone-assisted selective autophagy (CASA) pathway. For this reason, it is of rising interest to investigate whether CASA plays a role in space induced muscle atrophy. This study shows that CASA is affected during a 24-hour exposure to simulated microgravity, since the protein level as well as the protein turnover change upon simulated microgravity exposure. These results indicate that CASA could possibly be influencing muscle atrophy. In addition, there are first indications that CASA could be involved in a readaptation process, since it could be shown that the protein level changed after the reintroduction to Earth gravity. These new insights contribute to understanding what could cause space induced muscle atrophy. Therefore, it is of growing need to further investigate CASAs role in this disease to find possible countermeasures which could possibly stop muscle atrophy from ever occurring under the absence of gravity.