The expression of hippocalcin, a calcium-sensor protein of the recoverin family, and mixed lineage kinase 2 (MLK2) in Lewy bodies (LBs) was immunohistochemically examined in patients with Parkinson's disease (PD). Hippocalcin and MLK2 were colocalized in the halo of LBs, and neither protein was detected in normal pigmented neurons. Since hippocalcin binds to the C-terminal region of MLK2 [Nagata K., Puls A, Futter C, Aspenstrom P, Schaefer E, Nakata T et al., The MAP kinase kinase kinase MLK2 co-localizes with activated JNK along microtubules and associates with kinesin superfamily motor KIF3. EMBO J 1998;17:149-1588.], it may constitutively activate MLK2. Both hippocalcin and MLK2 may be associated with the pathogenesis of PD.