UNIVERSITY OF ARIZONA
Protein aggregation resulting from stress, disease or mutation poses a major threat to all cells. Consequently, cells have developed mechanisms of "protein quality control" involving specific proteases and molecular chaperones that prevent or resolve protein aggregation. The proposed research aims to determine the mechanism by which one class of chaperones, the ubiquitous small heat shock proteins (sHSPs), acts in a highly efficient manner to prevent irreversible aggregation of many different protein substrates. sHSPs appear to protect cells from heat, oxidative stress, heavy metals, and ischemic injury, and they are constitutive components of specific tissues in many different organisms. Expression and/or mutation of sHSPs is linked to cancer and to diseases of protein folding. Furthermore, sHSPs have been suggested to have therapeutic potential for amyotrophic lateral sclerosis and multiple sclerosis, and to postively effect longevity in model organisms. Defining the mechanism of sHSP chaperone action, therefore, has wide-ranging implications for understanding cellular stress and disease processes. A key to understanding any function of sHSPs in cells is determining how sHSPs recognize and bind substrates, and this has been a major goal of the parent grant. Using purified recombinant sHSPs and model substrates we have developed a model for sHSP action in protecting denaturing proteins. Exciting results from our recent work have demonstrated that the sHSPs have unique dynamic properties which allow them to present a highly plastic surface for substrate binding. This mode of substrate binding is dramatically different than what is known for other chaperones, and we propose is key to their unique and efficient aggregation-prevention properties. The research to be carried out under this administrative supplement will test a series of specific hypothesis about substrate binding and recognition, utilizing techniques and tools developed in the parent grant.