Growing evidence has suggested a role for proNGF-p75NTR-sortilin signaling in neurodegeneration and pathogenesis of PD [7], and we have identified the p75 neurotrophin receptor (p75NTR) in the dopamine neurons and kainic acid-induced up-regulation of p75NTR accompanying neuronal degeneration in the substantia nigra [8]. This evidence concerns the gene SORT1 and Parkinson disease.