Bacterial production and direct functional screening of expanded molecular libraries for discovering inhibitors of protein aggregation.

Protein misfolding and aggregation are associated with a many human disorders, including Alzheimer's and Parkinson's diseases. Toward increasing the effectiveness of early-stage drug discovery for these conditions, we report a bacterial platform that enables the biosynthesis of molecular libraries with expanded diversities and their direct functional screening for discovering protein aggregation inhibitors. We illustrate this approach by performing, what is to our knowledge, the largest functional screen of small-size molecular entities described to date. We generated a combinatorial library of ~200 million drug-like, cyclic peptides and rapidly screened it for aggregation inhibitors against the amyloid-ß peptide (Aß42), linked to Alzheimer's disease. Through this procedure, we identified more than 400 macrocyclic compounds that efficiently reduce Aß42 aggregation and toxicity in vitro and in vivo. Finally, we applied a combination of deep sequencing and mutagenesis analyses to demonstrate how this system can rapidly determine structure-activity relationships and define consensus motifs required for bioactivity.

Microbial Genetic Screens for Monitoring Protein Misfolding Associated with Neurodegeneration: Tools for Identifying Disease-Relevant Genes and for Screening Synthetic and Natural Compound Libraries for the Discovery of Potential Therapeutics.

Neurodegenerative Diseases (ND) are a major threat to the aging population and the lack of a single preventive or disease-modifying agent only serves to increase their impact. In the past few years, protein misfolding and the subsequent formation of neurotoxic oligomeric/aggregated protein species have emerged as a unifying theme underlying the pathology of these complex diseases. Recently developed microbial genetic screens and selection systems for monitoring ND-associated protein misfolding have allowed the establishment of highthroughput assays for the identification of cellular factors and processes that are important mediators of NDassociated proteotoxicities. In addition, such systems have facilitated the discovery of synthetic and natural compounds with the ability to rescue the misfolding and the associated pathogenic effects of aggregation-prone proteins associated with NDs. This review outlines such available systems in bacteria and yeast, whose usage will likely accelerate the pre-clinical discovery process for effective drugs against a variety of NDs with high socioeconomic impact.

Publisher Correction: An integrated bacterial system for the discovery of chemical rescuers of disease-associated protein misfolding.

In the version of this Article originally published, in Fig. 1c-e, on the x axes, the lines labelled 'Aß42' and 'Aß42(F19S;L34P)' grouped the data incorrectly; the line labelled Aß42 should have grouped the data for Random 1-2 and Clones 1-10, and the line labelled Aß42(F19S;L34P) should have only grouped the data for Random 1-2 on the right end of the plots and blots. These figures have now been corrected in all versions of the Article.

An integrated bacterial system for the discovery of chemical rescuers of disease-associated protein misfolding.

Protein misfolding and aggregation are common pathological features of several human diseases, including Alzheimer's disease and type 2 diabetes. Here, we report an integrated and generalizable bacterial system for the facile discovery of chemical rescuers of disease-associated protein misfolding. In this system, large combinatorial libraries of macrocyclic molecules are biosynthesized in Escherichia coli cells and simultaneously screened for their ability to rescue pathogenic protein misfolding and aggregation using a flow cytometric assay. We demonstrate the effectiveness of this approach by identifying drug-like, head-to-tail cyclic peptides that modulate the aggregation of the Alzheimer's disease-associated amyloid ß peptide. Biochemical, biophysical and biological assays using isolated amyloid ß peptide, primary neurons and various established Alzheimer's disease nematode models showed that the selected macrocycles potently inhibit the formation of neurotoxic amyloid ß peptide aggregates. We also applied the system to the identification of misfolding rescuers of mutant Cu/Zn superoxide dismutase-an enzyme linked with inherited forms of amyotrophic lateral sclerosis. Overall, the system enables the identification of molecules with therapeutic potential for rescuing the misfolding of disease-associated polypeptides.

Solution structure of CCP modules 10-12 illuminates functional architecture of the complement regulator, factor H.

The 155-kDa plasma glycoprotein factor H (FH), which consists of 20 complement control protein (CCP) modules, protects self-tissue but not foreign organisms from damage by the complement cascade. Protection is achieved by selective engagement of FH, via CCPs 1-4, CCPs 6-8 and CCPs 19-20, with polyanion-rich host surfaces that bear covalently attached, activation-specific, fragments of complement component C3. The role of intervening CCPs 9-18 in this process is obscured by lack of structural knowledge. We have concatenated new high-resolution solution structures of overlapping recombinant CCP pairs, 10-11 and 11-12, to form a three-dimensional structure of CCPs 10-12 and validated it by small-angle X-ray scattering of the recombinant triple-module fragment. Superimposing CCP 12 of this 10-12 structure with CCP 12 from the previously solved CCP 12-13 structure yielded an S-shaped structure for CCPs 10-13 in which modules are tilted by 80-110° with respect to immediate neighbors, but the bend between CCPs 10 and 11 is counter to the arc traced by CCPs 11-13. Including this four-CCP structure in interpretation of scattering data for the longer recombinant segments, CCPs 10-15 and 8-15, implied flexible attachment of CCPs 8 and 9 to CCP 10 but compact and intimate arrangements of CCP 14 with CCPs 12, 13 and 15. Taken together with difficulties in recombinant production of module pairs 13-14 and 14-15, the aberrant structure of CCP 13 and the variability of 13-14 linker sequences among orthologues, a structural dependency of CCP 14 on its neighbors is suggested; this has implications for the FH mechanism.