Tetraspanin (TSP-17) protects dopaminergic neurons against 6-OHDA-induced neurodegeneration in C. elegans.

Neda Masoudi,Anton Gartner,Sarah-Lena Offenburger,Pablo Ibanez-Cruceyra,Alexander Holmes,Kim A Caldwell

doi:10.1371/journal.pgen.1004767

Abstract

Parkinson's disease (PD), the second most prevalent neurodegenerative disease after Alzheimer's disease, is linked to the gradual loss of dopaminergic neurons in the substantia nigra. Disease loci causing hereditary forms of PD are known, but most cases are attributable to a combination of genetic and environmental risk factors. Increased incidence of PD is associated with rural living and pesticide exposure, and dopaminergic neurodegeneration can be triggered by neurotoxins such as 6-hydroxydopamine (6-OHDA). In C. elegans, this drug is taken up by the presynaptic dopamine reuptake transporter (DAT-1) and causes selective death of the eight dopaminergic neurons of the adult hermaphrodite. Using a forward genetic approach to find genes that protect against 6-OHDA-mediated neurodegeneration, we identified tsp-17, which encodes a member of the tetraspanin family of membrane proteins. We show that TSP-17 is expressed in dopaminergic neurons and provide genetic, pharmacological and biochemical evidence that it inhibits DAT-1, thus leading to increased 6-OHDA uptake in tsp-17 loss-of-function mutants. TSP-17 also protects against toxicity conferred by excessive intracellular dopamine. We provide genetic and biochemical evidence that TSP-17 acts partly via the DOP-2 dopamine receptor to negatively regulate DAT-1. tsp-17 mutants also have subtle behavioral phenotypes, some of which are conferred by aberrant dopamine signaling. Incubating mutant worms in liquid medium leads to swimming-induced paralysis. In the L1 larval stage, this phenotype is linked to lethality and cannot be rescued by a dop-3 null mutant. In contrast, mild paralysis occurring in the L4 larval stage is suppressed by dop-3, suggesting defects in dopaminergic signaling. In summary, we show that TSP-17 protects against neurodegeneration and has a role in modulating behaviors linked to dopamine signaling.

Highlights

Parkinson’s Disease (PD) is the second most common neurodegenerative disease, after Alzheimer’s disease, and affects,2% of the population aged over 65 years
We found that TSP-17, a member of the tetraspanin family of membrane proteins, protects dopaminergic neurons from 6-OHDAinduced degeneration
By adapting procedures initially established by Nass et al [3] and using the same pdat-1::GFP reporter that highlights dopaminergic neurons, we screened,2500 F2 ethyl methanesulfonate (EMS)-mutagenized worms at the L1 developmental stage by incubating with 10 mM 6-OHDA for 1 h

Summary

Introduction

Parkinson’s Disease (PD) is the second most common neurodegenerative disease, after Alzheimer’s disease, and affects ,2% of the population aged over 65 years. 15 disease loci are known, most of which are conserved in C. elegans [6,7]. The vast majority of PD cases are ‘sporadic’ with no clear family history. Epidemiological studies have shown risk factors for ‘sporadic’ PD to include a long-term history of rural living, farming, well-water drinking and pesticide exposure. Similar to sporadic PD cases, PD-like symptoms resulting from MPTP exposure could be alleviated by administration of the dopamine precursor L-3,4-dihydrooxyphenylalanine (L-DOPA) [8]. Exposure to pesticides such as paraquat and rotenone has been implicated in PD development [9]. The disease is thought to be triggered by a combination of environmental factors and genetic susceptibility [5]

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