α-Synuclein is a major component of Lewy bodies in Parkinson disease (PD) and 
dementia with Lewy bodies (DLB). We recently showed that abnormal α-synuclein 
with resistance to proteinase K (PK) is deposited at presynapses of distinct 
brain anatomic regions from the early stages of PD and DLB. NUB1, a 
synphilin-1-binding protein, also accumulates in Lewy bodies, but it is not 
known whether abnormal α-synuclein is associated with NUB1. Here, we demonstrate 
that, in the brain of patients with PD and DLB, NUB1 accumulates in the 
presynapses in the hippocampus, cerebral neocortex, and substantia nigra in 
which PK-resistant α-synuclein is deposited. Endogenous NUB1 also accumulated 
with PK-resistant α-synuclein in the presynapses of transgenic mice that express 
human α-synuclein with an A53T mutation. Immunoelectron microscopy showed that 
NUB1 is localized to presynaptic nerve terminals where no abnormal filaments are 
seen. Biochemical analyses showed that NUB1 coexists with abnormal α-synuclein 
in the brain of DLB patients. These findings suggest that NUB1 along with 
abnormal α-synuclein is involved in the pathogenesis of Lewy body disease.