The ubiquitin-proteasome system is one of the ways in which cells remove damaged and unwanted proteins. Proteins are tagged with ubiquitin, which allows them to enter a proteasome and be broken down into component parts for reuse. Increased proteasomal activity has been shown to be beneficial in short-lived laboratory species, with the understanding that this is because cells will maintain a lower level of damaged components, leading to improved function and lesser degrees of downstream damage. As researchers note here, cells upregulate activity of the ubiquitin-proteasome system in response to mild stress, such as that produced by exercise. This is one of the ways in which exercise produces benefits to health and function.
Physical activity benefits health in many ways, including the building and maintenance of healthy muscles, which are important for our ability to move about normally, as well as to fulfill the vital role of regulating metabolism. Maintaining muscular function is essential. Part of our ability to do so depends upon proteins - the building blocks of muscles - being degraded when worn-out and eliminated in a kind of clean up process that allows them to be replaced by freshly synthesized proteins. Now, researchers have demonstrated that a single, intense, roughly 10-minute bicycle ride results in a significant increase in the activity of ubiquitin and a subsequent intensification of the targeting and removal of worn-out proteins in muscles. This paves the way for an eventual build-up of new proteins.
"Ubiquitin itself is a small protein. It attaches itself to the amino acid lysine on worn-out proteins, after which the protein is transported to a proteasome, which is a structure that gobbles up proteins and spits them out as amino acids. These amino acids can then be reused in the synthesis of new proteins. As such, ubiquitin contributes to a very sustainable circulation of the body's proteins. The important role of Ubiquitin for 'cleaning-up' worn-out proteins in connection with muscular activity was not fully appreciated. Now we know that physical activity increases ubiquitin tagging on worn-out proteins. Basically, it explains part of the reason why physical activity is healthy. The beauty is that muscle use, in and of itself, is what initiates the processes that keep muscles 'up to date', healthy, and functional."