Transfection‐enforced Bcl‐2 overexpression and an anti‐Parkinson drug, rasagiline, prevent nuclear accumulation of glyceraldehyde‐3‐phosphate dehydrogenase induced by an endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol

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Abstract
An endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol, was found to induce apoptosis in human dopaminergic SH‐SY5Y cells by step‐wise activation of apoptotic cascade; collapse in mitochondrial membrane potential, ΔΨm, activation of caspases, and fragmentation of DNA. Recently, accumulation of gylceraldehyde‐3‐phosphate dehydrogenase (GAPDH) in nuclei was proposed to play an important role in apoptosis. In this paper, involvement of GAPDH in apoptosis induced by N‐methyl(R)salsolinol was studied. The isoquinoline reduced ΔΨm within 3 h, as detected by a fluorescence indicator, JC‐1, then after 16 h incubation, GAPDH accumulated in nuclei by detection with immunostaining. To clarify the role of GAPDH in apoptotic process, a stable cell line of Bcl‐2 overexpressed SH‐SY5Y cells was established. Overexpression of Bcl‐2 prevented the decline in ΔΨm and also apoptotic DNA damage induced by N‐methyl(R)salsolinol. In Bcl‐2 transfected cells, nuclear translocation of GAPDH was also completely suppressed. In addition, a novel antiparkinsonian drug, rasagiline, prevented nuclear accumulation of GAPDH induced by N‐methyl(R)salsolinol in control cells. These results suggest that GAPDH may accumulate in nuclei as a consequence of signal transduction, which is antagonized by anti‐apoptotic Bcl‐2 protein family and rasagiline. The results are discussed in concern to intracellular mechanism underlying anti‐apoptotic function of rasagiline analogues.