Modulating proteostasis: peptidomimetic inhibitors and activators of protein folding.

Protein folding in the cell is a complex process with a fine balance between productive and non-productive folding. To modulate, either up-regulating or down-regulating, the level of one specific protein with multiple approaches is possible, including the modulation of catalysed protein folding, the use of chemical and pharmacological chaperones, alteration of natural protein-protein interactions, the regulation of degradative pathways and manipulation of natural control mechanisms, such as the heat shock response and the unfolded protein response. Errors in proteostasis are linked to a wide range of disease states and many examples exist of the successful manipulation of proteostasis for the partial or complete elimination of the disease phenotype, including for many amyloid based diseases such as Parkinson's and Alzheimer's as well as for 'loss-of-function' diseases such as Fabry's and Gaucher's diseases. This review takes an overview of the different approaches that can be used to alter proteostasis with an emphasis on peptidomimetic inhibitors and activators of protein folding. It covers the modulators available, their mechanisms of action and potential limitations, including the problems of specificity in altering proteostasis.