Chemical and Biological Approaches Synergize to Ameliorate Protein-Folding Diseases

Abstract

Summary Loss-of-function diseases are often caused by a mutation in a protein traversing the secretory pathway that compromises the normal balance between protein folding, trafficking and degradation. We demonstrate that the innate cellular protein homeostasis, or proteostasis, capacity can be enhanced to fold mutated enzymes that would otherwise misfold and be degraded, using small molecule proteostasis regulators. Two proteostasis regulators are reported that alter the composition of the proteostasis network in the endoplasmic reticulum through the unfolded protein response, increasing the mutant folded protein concentration that can engage the trafficking machinery, restoring function to two non-homologous mutant enzymes associated with distinct lysosomal storage diseases. Co-application of a pharmacologic chaperone and a proteostasis regulator exhibits synergy because of the former’s ability to further increase the concentration of trafficking competent mutant folded enzymes. It may be possible to ameliorate loss-of-function diseases by using proteostasis regulators alone or in combination with a pharmacologic chaperone.

Treatment of Human Fibroblasts Carrying NPC1 Missense Mutations with MG132 Leads to an Improvement of Intracellular Cholesterol Trafficking

“…These are promising results considering that up to date, two different approaches aimed to enhance protein stability and prevent mutant protein degradation, have been successfully assessed in other models of misfolding diseases, such as cystic fibrosis disease and Gaucher: the use of pharmacological chaperons (Alfonso et al 2005) and the use of molecules that enhance the innate cellular protein homeostasis (Wang et al 2006;Mu et al 2008). Although molecules that may function as pharmacological chaperones for NPC1 protein need to be identified and the usefulness of these therapeutic approaches needs to be assessed in NPC cells, our data strongly suggest that, at least some NPC1 patients may benefit from these kind of therapeutic strategies.…”

Firefly luciferase mutants as sensors of proteome stress

“…Since the proteostasis network encompasses a wide range of key proteins involved in different steps in protein biogenesis, maintenance (folding and refolding), trafficking and degradation, both activators and inhibitors have been screened to affect each of these individual steps. A combination of chemical and biological approaches can be used to rebalance the cellular proteostasis capacity under stress conditions and therefore hold a great therapeutic potential to treat several human diseases including protein conformational disorders and cancer (Lindquist and Kelly, 2011;Mu et al, 2008;Powers et al, 2009). …”

“…In a recent study, it was shown that administration of PR such as celastrol or MG132 increase the unfolded protein response (UPR) resulting in the coordinated transcription and translation of chaperones and folding catalysts that promote folding of mutant enzyme in the ER and prevent it from misfolding/aggregation. The co-administration of PC stabilizes the folded state of mutant enzyme and synergizes with PR to effectively rescue the loss-of-function phenotype of the enzyme (Mu et al, 2008). Therefore, it seems possible that a combination therapy of highly specific PR and PC can be useful to treat protein conformational disorders.…”

“…These compounds, called pharmacological chaperones (PC), are highly specific and can rescue proteins from loss-offunction phenotypes (Mu et al, 2008). Therefore, small molecules that resemble natural substrates may act as PC for enzymes.…”

Quantitative approaches to defining normal and aberrant protein homeostasis

“…20 Several studies have involved in vitro studies coupled with computer simulations, [20][21][22][23] and many others have been concerned with the goal of relating processes studied in atomic detail in the test tube to their quantitative effects in living systems. [24][25][26] Moreover, recent findings suggest that further developments in this area could have much more general relevance to understanding the way in which well-established physical and chemical principles can provide new insights into the apparent complexity of biology. 27 The discovery of the common existence of amyloid and amyloid-like states is of unique importance in understanding the nature of biological systems because it reveals that there is an alternative stable and highly ordered state, accessible essentially to all proteins, in addition to the native one; 10,28,29 this observation has profound implications in diverse fields ranging from medicine to materials science.…”