In eukaryotic cells, the recycling of damaged or misformed proteins is governed by a small regulatory protein called ubiquitin in a process called "ubiquitination". By attaching itself to a protein, a ubiquitin molecule can tag the protein for destruction by proteasomes, large protein complexes that degrade and recycle unneeded proteins in the cell. This recycling of proteins by proteasomes is crucial to the maintenance of cellular homeostasis.
With their research, the BSI research group sought to shed light on one area where proteasome-based recycling falls short: protein complexes or aggregates, which proteasomes have trouble degrading. The group shows that this weakness is made up for by the phosphorylation of a protein called p62 at the serine 403 (S403) loci of its ubiquitin-associated (UBA) domain, which triggers a catabolic process called selective autophagy that degrades protein aggregates. It does this by forming a "sequestosome", a structure which sequesters polyubiquitinated protein aggregates in preparation for autophagy. (Figure 1)
Source: Eurekalert
