Nicotine‐Mediated Rescue of α‐Synuclein Toxicity Requires Synaptic Vesicle Glycoprotein 2 in Drosophila

Abstract

Background Parkinson's disease (PD) is characterized by α‐synuclein aggregation and loss of dopamine neurons. Risk of PD arises due to a combination of genetic and environmental factors, which may interact, termed gene–environment (G×E) interactions. An inverse association between smoking and the risk of PD is well established, and a previous genome‐wide G×E interaction study identified genetic variation in the synaptic‐vesicle glycoprotein 2C (SV2C) locus as an important mediator of the degree to which smoking is inversely associated with PD. Objective We sought to determine the mechanism of the smoking–SV2C interaction in a Drosophila model of PD. Methods Flies expressing human α‐synuclein in all neurons develop the hallmarks of PD, including motor dysfunction, loss of dopaminergic (DA) neurons, and formation of α‐synuclein inclusions. We assessed the effects of increasing doses of nicotine on these parameters of neurodegeneration, in the presence or absence of knockdown of two Drosophila orthologues of SV2, hereafter referred to as SV2L1 and SV2L2. Results The α‐synuclein–expressing flies treated with nicotine had improved locomotion, DA neuron counts, and α‐synuclein aggregation. However, in α‐synuclein–expressing flies in which SV2L1 and SV2L2 were knocked down, nicotine failed to rescue neurodegeneration. Conclusions This work confirms a G×E interaction between nicotine and SV2, defines a role for this interaction in α‐synuclein proteostasis, and suggests that future clinical trials on nicotine should consider genetic variation in SV2C. Furthermore, this provides proof of concept that our model can be used for the mechanistic study of G×E, paving the way for the investigation of additional G×E interactions or the identification of novel G×E. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Synaptic deregulation of cholinergic projection neurons causes olfactory dysfunction across 5 fly Parkinsonism models

“…However, dopaminergic neurons have a high density of nicotinic acetylcholine receptors, and evidence suggests that stimulating these receptors enhances DAN survival (Brimblecombe et al, 2018). This is supported by epidemiological data indicating that nicotine exposure from chronic smoking protects against PD (Janssens et al, 2022;Wang et al, 2019), and various studies, including our own unpublished data, showing that direct nicotine supplementation mitigates DAN dysfunction in mouse and fly PD models (Chambers et al, 2013;Fares et al, 2023;Olsen et al, 2023). These findings imply that factors affecting the function of cholinergic neurons might, by absence of insufficient innervation, lead to DAN problems and degeneration, warranting further exploration of the underlying molecular mechanisms.…”

Integrative analysis reveals a conserved role for the amyloid precursor protein in proteostasis during aging

“…Flies expressing GFP-mCherry-Atg8a were dissected in Schneider’s medium and imaged immediately using confocal microscopy as described. 34,81…”

“…Flies expressing GFP-mCherry-Atg8a were dissected in Schneider's medium and imaged immediately using confocal microscopy as described. 34,81 Brains from 18-month-old mice were postfixed in 4% paraformaldehyde, infiltrated with 30% sucrose and sectioned at 40 µm. Free-floating vibratome sections were permeabilized using PBS with 0.1% Triton X-100, blocked with PBS with 0.1% Triton X-100 and 3% BSA for 1 hour at room temperature, and incubated in primary antibody overnight at 4˚C.…”

“…Quantification of ratio between GFP and mCherry in Drosophila brain was performed using ImageJ as described. 34,81 For immunofluorescence of mouse and human neurons the mean fluorescence intensity was quantified using ImageJ. At least 45 neurons were analyzed per genotype in mouse sections.…”

Identification of Glycerol 3-phosphate acyltransferase as a potent modifier of α-Synuclein-induced toxicity

“…Given that GPAT catalyzes crucial early steps in glycerolipid synthesis, we investigated whether GPAT in uences the formation of α-syn oligomers/aggregates. In contrast to many α-syn-based PD models employing mammalian cells, α-syn expressed in the Drosophila brains is predominantly detected as monomers in both soluble and insoluble fractions 42,57 . However, oligomeric species of α-syn can be revealed through removing Triton X-100 and DTT from buffers while using cross-linkers like Dimethyl dithiobispropionimidate (DTBP) 58 .…”