Modulation of Mitochondria-Endoplasmic Reticulum Contacts (MERCs) by Small Molecules as a New Strategy for Restoring Lipid Metabolism in an Amyotrophic Lateral Sclerosis Model.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease without effective treatment. The progressive motoneuron death in ALS is associated with alterations in lipid metabolism. As its regulation occurs in mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), modulation of mitochondria-ER contacts (MERCs) is emerging as a crucial factor in MAM formation and lipid metabolism control. Using the MERLIN biosensor in a high-throughput screening within the EU-OPENSCREEN ERIC, we discovered small molecules that increase MERCs in HCT116 cells, enhancing their ability to uptake cholesterol. We demonstrated that cholesterol trafficking is decreased in an ALS patient-derived cell model, and this trafficking is restored after treatment with the discovered MERC modulator 24. Electron microscopy revealed that treatment with compound 24 increases MERCs, promotes lipid droplet formation, and restores mitochondrial cristae. Overall, the brain-permeable MERC modulator, compound 24, may serve as a valuable pharmacological tool for studying MAM function and holds potential for in vivo studies in ALS and other MAM dysfunction diseases.