Neurobiology of Disease (Jun 2004)
Abnormal α-synuclein interactions with rab3a and rabphilin in diffuse Lewy body disease
Abstract
The present study examines α-synuclein interactions with rab3a and rabphilin by antibody arrays, immunoprecipitation and pull-down methods in the entorhinal cortex of control cases and in diffuse Lewy body disease (LBD) cases. α-Synuclein immunoprecipitation revealed α-synuclein binding to rabphilin in control but not in LB cases. Immunoprecipitation with rab3a disclosed rab3a binding to rabphilin in control but not in LB cases. Moreover, rab3a interacted with high molecular weight (66 kDa) α-synuclein only in LB cases, in agreement with parallel studies using antibody arrays. Results were compared with pull-down assays using His6/Flag-tagged rab3, rab5 and rab8, and anti-Flag immunoblotting. Weak bands of 17 kDa, corresponding to α-synuclein, were obtained in LB and, less intensely, in control cases. In addition, α-synuclein-immunoreactive bands of high molecular weight (36 kDa) were seen only in LB cases after pull-down assays with rab3a, rab5 or rab8. These findings corroborate previous observations showing rab3a–rabphilin interactions in control brains, and add substantial information regarding decreased binding of rab3a to rabphilin and increased binding of rab3a to α-synuclein aggregates in LB cases. Since, α-synuclein, rab3a and rabphilin participate in the docking and fusion of synaptic vesicles, it can be suggested that exocytosis of neurotransmitters may be impaired in LB diseases.
