Inhibition of Crmp1 Phosphorylation at Ser522 Ameliorates Motor Function and Neuronal Pathology in Amyotrophic Lateral Sclerosis Model Mice

Abstract

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disorder that affects upper and lower motor neurons; however, its pathomechanism has not been fully elucidated. Using a comprehensive phosphoproteomic approach, we have identified elevated phosphorylation of Collapsin response mediator protein 1 (Crmp1) at serine 522 in the lumbar spinal cord of ALS model mice overexpressing a human superoxide dismutase mutant (SOD1 G93A ). We investigated the effects of Crmp1 phosphorylation and depletion in SOD1 G93A mice using Crmp1 S522A (Ser522→Ala) knock-in ( Crmp1 k i /ki ) mice in which the S522 phosphorylation site was abolished and Crmp1 knock-out ( Crmp1 −/− ) mice, respectively. Crmp1 ki / ki / SOD1 G93A mice showed longer latency to fall in a rotarod test while Crmp1 −/− / SOD1 G93A mice showed shorter latency compared with SOD1 G93A mice. Survival was prolonged in Crmp1 ki / ki / SOD1 G93A mice but not in Crmp1 −/− / SOD1 G93A mice. In agreement with these phenotypic findings, residual motor neurons and innervated neuromuscular junctions (NMJs) were comparatively well-preserved in Crmp1 ki / ki / SOD1 G93A mice without affecting microglial and astroglial pathology. Pathway analysis of proteome alterations showed that the sirtuin signaling pathway had opposite effects in Crmp1 ki / ki / SOD1 G93A and Crmp1 −/− / SOD1 G93A mice. Our study indicates that modifying CRMP1 phosphorylation is a potential therapeutic strategy for ALS.

Phosphorylated CRMP1, axon guidance protein, is a component of spheroids and is involved in axonal pathology in amyotrophic lateral sclerosis

“…Sema3A is highly expressed in Schwann cells at the distal ends of motor neuron axons in G93A-SOD1 ALS mice (20). Furthermore, blockade of Sema3A signaling by anti-NRP1 antibody (21) or inhibition of CRMP1 phosphorylation (23) mitigates NMJ damage and restores muscle strength in the G93A-SOD1 mouse model of ALS. These findings are consistent with ALS pathogenesis, which is characterized by progressive distal axonopathy in motor neurons that precedes degeneration of cell bodies (10)(11)(12)(13).…”

“…It has been suggested that CRMP1 is involved in the pathogenesis of neurological diseases such as Huntington's disease ( 34 ) and schizophrenia ( 35 , 36 ). Although its contribution in ALS had not been elucidated except that mass spectrometry data suggests CRMP1 is one of the interacting partners of the Met337Val TDP-43 mutant ( 37 ), we recently have shown that CRMP1 modulates phenotypes of G93A-SOD1 mice ( 23 ).…”

“…In addition, the administration of anti-NRP1 antibody, which blocks Sema3A signaling, improved motor function and survival and reduced denervation of NMJs in G93A-SOD1 mice ( 21 ), and similar ameliorative effects are observed after inhibition of CRMP2 phosphorylation ( 22 ). Furthermore, we recently reported that while Crmp1 knockout leads to deterioration of motor function in G93A-SOD1 mice, phospho-null Crmp1 improves motor function and prevents motor neuron loss and denervation of NMJs ( 23 ).…”