PAK4 suppresses motor neuron degeneration in hSOD1(G93A)‐linked amyotrophic lateral sclerosis cell and rat models

OBJECTIVES: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons (MN). CREB pathway‐mediated inhibition of apoptosis contributes to neuron protection, and PAK4 activates CREB signalling in diverse cell types. This study aimed to investigate PAK4’s effect and mechanism of action in ALS. METHODS: We analysed RNA levels by qRT‐PCR, protein levels by immunofluorescence and Western blotting, and apoptosis by flow cytometry and TUNEL staining. Cell transfection was performed for in vitro experiment. Mice were injected intraspinally to evaluate PAK4 function in vivo experiment. Rotarod test was performed to measure motor function. RESULTS: The expression and activation of PAK4 significantly decreased in the cell and mouse models of ALS as the disease progressed, which was caused by the negative regulation of miR‐9‐5p. Silencing of PAK4 increased the apoptosis of MN by inhibiting CREB‐mediated neuroprotection, whereas overexpression of PAK4 protected MN from hSOD1(G93A)‐induced degeneration by activating CREB signalling. The neuroprotective effect of PAK4 was markedly inhibited by CREB inhibitor. In ALS models, the PAK4/CREB pathway was inhibited, and cell apoptosis increased. In vivo experiments revealed that PAK4 overexpression in the spinal neurons of hSOD1(G93A) mice suppressed MN degeneration, prolonged survival and promoted the CREB pathway. CONCLUSIONS: PAK4 protects MN from degeneration by activating the anti‐apoptotic effects of CREB signalling, suggesting it may be a therapeutic target in ALS.