MAPT and Cognitive impairment: Indeed, the deubiquitinating and protein degradation role of UCH-L1, the most abundant (up to 5%) among CNS proteins,16 has been shown to complement the axon microtubule stabilization function of tau as inhibition of UCH-L1 can decrease the microtubule-binding ability of tau and promote the accumulation of abnormal aggregates of hyperphosphorylated tau,31 a critical mediator implicated in cognitive impairment in neurodegenerative disorders.32