A small molecule pan-inhibitor of Ras-superfamily GTPases with high efficacy towards Rab7

Low molecular weight guanine triphosphate hydrolases (GTPases) are GTP-binding enzymes that play pivotal roles in cell biology. Grouped into three subfamilies which are designated by function, Ras, Rho and Rab GTPases are involved in signal transduction, cytoskeleton modulation, and macromolecule cargo transport and degradation, respectively. Mutation and aberrant gene expression levels have been linked to human diseases including cancer, immunodeficiencies, and neurological disorders. A high through-put screen of the Molecular Libraries Small Molecule Repository (MLSMR) identified a compound, ML282, which potently inhibits GTPases from all three subfamilies. Importantly, this represents the discovery of the first reported compound to inhibit Rab GTPases, especially Rab7, the mutation of which is a causal factor in a heritable neuropathy called Charcot-Marie-Tooth Type 2B disease. ML282 inhibits Rab7 with an average EC50 = 53.2 ± 0.35 nM and with high response, as compared to other GTPases in the panel. The subsequent structure activity relationships (SAR) and secondary assays demonstrate its use as a molecular probe for both biochemical and cellular studies.