Abstract
Increasing evidence suggests that the impaired neuroprotection of vesicular monoamine transporter 2 (VMAT2) contributes to the pathogenesis of Parkinson's disease. That has been linked to aberrant subcellular retrograde trafficking as strongly indicated by recent genomic studies on familial Parkinson's diseases. However, whether VMAT2 function is regulated by retrograde trafficking is unknown. By using biochemistry and cell biology approaches, we have shown that VMAT2 was stringently localized to the trans-Golgi network and underwent retrograde trafficking in non-neuronal cells. The transporter also interacted with the key component of retromer, Vps35, biochemically and subcellularly. Using specific siRNA, we further showed that Vps35 depletion altered subcellular localization of VMAT2. Moreover, siRNA-mediated Vps35 knockdown also decreased the stability of VMAT2 as demonstrated by the reduced half-life. Thus, our work suggested that altered vesicular trafficking of VMAT2 may play a vital role in neuroprotection of the transporter as well as in the pathogenesis of Parkinson's disease.
Highlights
Parkinson's disease (PD) is a progressive neurodegenerative disease which commonly occurs in the elderly population
Transient transfected cells were lysed in lysis buffer containing 0.5% NP-40 and HA-tagged vesicular monoamine transporter 2 (VMAT2) was pull down as the bait protein, followed by immunoblotting to determine whether Vps35 can be detected as a binding partner
When another retromer component, SNX1, was depleted via the specific siRNA-mediated knockdown, the interaction between VMAT2 and Vps35 overexpressed in the transient transfected COS7 cells was not significantly altered (Fig. 1B), indicating that SNX1 was not required for this functional interaction
Summary
Parkinson's disease (PD) is a progressive neurodegenerative disease which commonly occurs in the elderly population. Its pathological changes are mainly embodied in the dopaminergic neuronal loss in the substantia nigra of midbrain. Previous studies on PD pathogenesis have been primarily focused on the finding of exogenous neurotoxin and related mechanisms leading to neuronal loss[3,4], whereas the endogenous protective mechanism is poorly investigated. Our laboratory previously found that vesicular monoamine transporters (VMATs, SLC18A family) can protect dopaminergic neurons from the toxicity of neurotoxin MPP+[5,6]. There is increasing evidence supporting such reduced neuroprotection of VMAT2 in PD pathogenesis[7], limited molecular and cellular mechanistic studies have been reported. Works on the mechanism of the vesicular positioning and the membrane trafficking of ΔThese two authors contributed to this work.
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