The Neuroprotective Effect of Cdc42 Inhibition in the G93A Mutant hSOD1 Mouse Model of ALS

Abstract

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease characterized by the selective loss of upper and lower motor neurons, leading to muscle weakness, neuromuscular junction (NMJ) degeneration, paralysis, and eventual death due to respiratory failure. Despite extensive research, effective disease-modifying therapies remain limited, underscoring the need to identify novel molecular targets involved in ALS pathogenesis. Dysregulation of Rho family GTPases has been implicated in neurodegeneration, with Rac and Rho exerting opposing effects on neuronal survival; however, the role of the closely related GTPase Cdc42 remains poorly understood in ALS. In this study, the therapeutic potential of inhibiting Cdc42 was evaluated using ZCL367, a small molecule Cdc42 inhibitor, in the G93Amutant hSOD1 (ℎ𝑆𝑂𝐷1𝐺93𝐴) mouse model of ALS. Treatment was initiated at disease onset and continued until end-stage. Disease progression was assessed through survival analysis, longitudinal behavioral testing of motor strength and coordination using paw grip endurance and rotarod assays, and postmortem histological analysis of NMJs in the gastrocnemius muscle. ZCL367 treatment did not significantly extend survival; however, treated mice exhibited significant preservation of muscle strength, coordination, and endurance compared to untreated and vehicle-treated controls. Additionally, ZCL367-treated mice showed a significant preservation of NMJ size and structural complexity, despite no significant effect on gastrocnemius muscle weight. These findings suggest that Cdc42 inhibition can preserve neuromuscular structure and motor function in ALS, even in the absence of prolonged survival, and identify Cdc42 as a novel contributor to ALS pathogenesis and a promising therapeutic target for slowing functional decline.