CRMP2 hyperphosphorylation is characteristic of Alzheimer's disease and not a feature common to other neurodegenerative diseases.

Collapsin response mediator protein 2 (CRMP2) is an abundant brain-enriched protein that regulates neurite outgrowth. It is phosphorylated by Cdk5 and GSK3, and these modifications are abnormally high in the brains of Alzheimer's disease (AD) patients. Increased phosphorylation of CRMP2 is also apparent in mouse models of AD that express mutated AßPP and PSEN1, but not AßPP or tau alone, where it is detectable before the appearance of amyloid plaques and neurofibrillary tangles, suggesting it is an early event in AD pathogenesis. Here, we have extended these observations by showing that CRMP2 is not hyperphosphorylated in mice overexpressing mutated PSEN1 alone, or in cultured neurons treated with soluble, oligomeric Aß42 peptide. Similarly, CRMP2 phosphorylation was not increased in a mouse model of severe neurodegeneration (PMSC-1 knockout) or in cultured neurons subjected to neurotoxic concentrations of NMDA or staurosporine. Most interestingly, CRMP2 phosphorylation was not increased in frontal cortex from patients with frontotemporal lobar degeneration associated with mutations in MAPT or with Pick bodies. Together, these observations are consistent with the hypothesis that abnormal phosphorylation of CRMP2 is specific to AD and occurs downstream of excessive processing of AßPP, but that neither excessive Aß42 peptide nor neurotoxicity alone are sufficient to promote hyperphosphorylation.