Protein Assembly Modulation: A New Approach to Amyotrophic Lateral Sclerosis (ALS) Therapeutics

Amyotrophic Lateral Sclerosis (ALS) is a devastating and progressive neurodegenerative disease with a complex, multifactorial pathophysiology, culminating in death of motor neurons. We introduce a new mechanism of ALS pathogenesis via study of a novel drug-like small molecule series that targets a subset of protein disulfide isomerase (PDI) within a previously largely unappreciated transient and energy-dependent multi-protein complex enriched for proteins of the ALS interactome. This drug, found by a novel phenotypic screen, has activity in cellular models for both familial and sporadic ALS, as well as in transgenic worms, flies, and mice bearing a diversity of human genes with ALS-associated mutations. The hit compound was initially identified as a modulator of human immunodeficiency virus (HIV) capsid assembly in cell-free protein synthesis and assembly (CFPSA) systems, with demonstrated antiviral activity against infectious HIV in cell culture. Its advancement for ALS-therapeutics, subsequent separation of activity against HIV and ALS into separate chemical subseries through structure-activity-relationship (SAR) optimization, and identification of the drug target by affinity chromatography as shown here, may provide insights into the molecular mechanisms governing pathophysiology of disordered homeostasis relevant to ALS.