Systemic protein aggregation in stress and aging restructures cytoplasmic architecture
A common maxim of protein biochemistry states, “structure is function.” This is generally just as true for an individual polypeptide chains as for multi-protein complexes. The advent of yeast tagged-protein libraries has allowed systematic screening of a protein’s local interaction partners as well as a roughly mapping its cellular location. Recently our group and others discovered hundreds proteins forming new structures in stationary phase yeast cells using the yeast GFP-tag library. That equates to well over a quarter of normally diffuse cytoplasmic proteins assembled into discrete structures that appear as foci or fibers, all of unknown function. This study provides evidence that many of these foci are formed by protein aggregation- that contrary the maxim, structure can be dysfunction. Furthermore, this study uses yeast to demonstrate the generality of cytoplasmic protein aggregation in response to a variety of stresses, provides evidence that increasing aggregation of particular cytoplasmic proteins correlates with aging even across organisms, and proposes a theoretical framework for how cellular energy levels affect protein aggregation propensity.