Structure of Amyloid Proteins in vivo
For an organism to survive, its proteins must adopt complex conformations in a challenging environment where macromolecular crowding can derail even robust biological pathways. This situation becomes perilous when considering proteins that must attain a particular conformation, but whose energetic folding landscapes are rather flat or have several local minima. In these cases, the environment can clearly influence the conformation by favoring one pathway over another. Such decisions can have dire biological consequences, as is the case for neurodegenerative diseases like Alzheimer’s, Parkinson’s and Huntingtin’s where loss of neuronal function is linked with the presence of large aggregates of mis-folded proteins. Strikingly, the aggregating proteins often have identical sequences in both healthy and afflicted individuals, suggesting that differences in cellular environment are responsible for the mis-folding. Despite the importance of the environment for protein folding, structural investigations of biomolecules are typically confined to in vitro systems, which cannot capture important structural features imposed by biological environments.
We recently demonstrated that structural investigation of proteins at their normal concentrations in biologically complex environments is possible by using state-of-the-art sensitivity-enhanced (DNP) solid-state nuclear magnetic resonance (NMR) techniques. We demonstrated that the native context can and does have a dramatic influence on protein structure. Having established that DNP NMR provides the necessary sensitivity and specificity, the challenge is now to develop approaches appropriate for DNP NMR to study protein structures in whole living cells. In doing so, we are poised to overcome previous obstacles to our understanding about protein folding and toxicity. Such approaches will enable us to determine how disease related proteins misfold in the complex physiological environments of both healthy and sick cells. Ultimately we seek not only to understand how cellular environments influence protein conformation, but also to use these insights to identify means of manipulating the system for therapeutic benefit.