Abstract
Neurodegenerative disorders such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are characterized by impairment of autophagy. Cellular survival is dependent on efficient clearance of phosphorylated α-synuclein, which accumulates as fibrils in the neuronal cytoplasm as Lewy bodies (LBs). The forkhead box O 1 (FOXO1) is a member of the FOXO family that functions in various intracellular processes including regulation of autophagy. Transcriptional activation of FOXO1 has been reported to initiate autophagy by inhibiting the expression of Mechanistic Target of Rapamycin (mTOR), mediated by sestrin 3 (SESN3) and tuberous sclerosis complex 2 (TSC2). Although many autophagy-related proteins are known to be incorporated into LBs, no report has documented the involvement of these autophagy modulators (FOXO1, SESN3 and TSC2) in the pathogenesis of PD and DLB. In the present study, we performed immunostaining and Western blot analysis using the brains of normal controls and patients with PD and DLB in order to clarify the involvement of FOXO1, SESN3 and TSC2 in LBs. Our study demonstrated for the first time the presence of FOXO1, SESN3 and TSC2 in brainstem-type LBs. The expression levels of these proteins in the brain did not differ between the normal controls and patients with PD or DLB. We further utilized mice model to investigate the effect of α-synuclein overexpression on these proteins, and found that TSC2 was significantly increased in α-synuclein transgenic mice relative to wild type mice at 9 weeks of age, but not at 30 weeks of age. Together with expression data showing gradual increase of these molecules with age in wild type mice, these findings suggest that autophagy modulators are incorporated into LBs and that the expression of these proteins can be increased by various factors including aging.