Technology for Discovery of Antifibrotic Drugs: Phenotypic Screening for LARP6 Inhibitors Using Inverted Yeast Three Hybrid System.

Fibrosis is defined by excessive production of type I collagen in various organs. Excessive type I collagen production in fibrosis is stimulated by binding of RNA protein LARP6 to the structural element of collagen mRNAs, the 5' stem loop (5'SL). The LARP6-dependent regulation is specific for type I collagen and critical for fibrosis development. Inhibitors of LARP6 binding have potential to be specific antifibrotic drugs, as evidenced by the discovery of one such inhibitor. To create technology for phenotypic screening of additional compounds we developed an inverted yeast three hybrid system. The system is based on expression of human LARP6 and a short RNA containing the 5'SL of human collagen α1(I) mRNA in Saccharomyces cerevisiae cells. The cells were engineered in such a way that when LARP6 is bound to 5'SL RNA they fail to grow in a specific synthetic medium. Dissociation of LARP6 from 5'SL RNA permits the cell growth, allowing identification of the inhibitors of LARP6 binding. The assay simply involves measuring optical density of cells growing in multiwall plates and is pertinent for high throughput applications. We describe the specificity of the system and its characteristics for high throughput screening. As a proof of principle, the result of one screen using collection of FDA approved drugs is also presented. This screen demonstrates that using this technology discovery of novel LARP6 inhibitors is possible.

Probing the chemical-biological relationship space with the Drug Target Explorer.

Modern phenotypic high-throughput screens (HTS) present several challenges including identifying the target(s) that mediate the effect seen in the screen, characterizing 'hits' with a polypharmacologic target profile, and contextualizing screen data within the large space of drugs and screening models. To address these challenges, we developed the Drug-Target Explorer. This tool allows users to query molecules within a database of experimentally-derived and curated compound-target interactions to identify structurally similar molecules and their targets. It enables network-based visualizations of the compound-target interaction space, and incorporates comparisons to publicly-available in vitro HTS datasets. Furthermore, users can identify molecules using a query target or set of targets. The Drug Target Explorer is a multifunctional platform for exploring chemical space as it relates to biological targets, and may be useful at several steps along the drug development pipeline including target discovery, structure-activity relationship, and lead compound identification studies.

Inhibiting Stearoyl-CoA Desaturase Ameliorates α-Synuclein Cytotoxicity.

The lack of disease-modifying treatments for neurodegenerative disease stems in part from our rudimentary understanding of disease mechanisms and the paucity of targets for therapeutic intervention. Here we used an integrated discovery paradigm to identify a new therapeutic target for diseases caused by α-synuclein (α-syn), a small lipid-binding protein that misfolds and aggregates in Parkinson's disease and other disorders. Using unbiased phenotypic screening, we identified a series of compounds that were cytoprotective against α-syn-mediated toxicity by inhibiting the highly conserved enzyme stearoyl-CoA desaturase (SCD). Critically, reducing the levels of unsaturated membrane lipids by inhibiting SCD reduced α-syn toxicity in human induced pluripotent stem cell (iPSC) neuronal models. Taken together, these findings suggest that inhibition of fatty acid desaturation has potential as a therapeutic approach for the treatment of Parkinson's disease and other synucleinopathies.