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

Masoudi N, Ibanez-Cruceyra P, Offenburger SL, Holmes A, Gartner A - PLoS Genet. (2014)

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Gene Regulation and Expression, University of Dundee, Dow Street, Dundee, United Kingdom.

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 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.

No MeSH data available.


Related in: MedlinePlus

tsp-17 (gt1681) enhances the neurodegeneration phenotype of cat-2-overexpressing lines, and cat-2 overexpression protects against 6-OHDA toxicity.A. cat-2 induced neurodegeneration. Analysis of cat-2-overexpressing stains UA57 baIn4 [pdat-1::gfp pdat-1::cat-2] and TG2402 baIn4[pdat-1::gfp pdat-1::cat-2]; tsp-17(gt1681). Error bars represent standard deviation. Asterisks represent statistical difference between cat-2::gfp adults on days 5 and 7 (**p<0.005). B. cat-2 overexpression suppresses 6-OHDA-induced neurotoxicity. Experiments were done in triplicate and the average is shown. Data presented is from scoring the extent of neurodegeneration 72 h post 6-OHDA intoxication.
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pgen-1004767-g004: tsp-17 (gt1681) enhances the neurodegeneration phenotype of cat-2-overexpressing lines, and cat-2 overexpression protects against 6-OHDA toxicity.A. cat-2 induced neurodegeneration. Analysis of cat-2-overexpressing stains UA57 baIn4 [pdat-1::gfp pdat-1::cat-2] and TG2402 baIn4[pdat-1::gfp pdat-1::cat-2]; tsp-17(gt1681). Error bars represent standard deviation. Asterisks represent statistical difference between cat-2::gfp adults on days 5 and 7 (**p<0.005). B. cat-2 overexpression suppresses 6-OHDA-induced neurotoxicity. Experiments were done in triplicate and the average is shown. Data presented is from scoring the extent of neurodegeneration 72 h post 6-OHDA intoxication.

Mentions: We next wished to address how TSP-17 protects dopaminergic neurons. We hypothesized that TSP-17 might affect dopamine synthesis, or dopamine and 6-OHDA uptake or degradation. Dopamine metabolism is itself a source of oxidative stress and may initiate ROS-mediated injury to dopaminergic neurons. The link between excessive dopamine exposure and toxicity is controversial, but overexpression of CAT-2, the rate-limiting enzyme in dopamine synthesis in C. elegans, is reported to lead to age-dependent degeneration of dopaminergic neurons [46]. We repeated these experiments, and indeed found that neurodegeneration conferred by CAT-2 overexpression in dopaminergic neurons is enhanced in the gt1681 mutant background (Figure 4A). In contrast, we found CAT-2 overexpression to confer a strong resistance toward 6-OHDA-dependent neurodegeneration in both wild-type and gt1618 backgrounds (Figure 4B). We consider it likely that 6-OHDA resistance conferred by CAT-2 overexpression can be explained by reduced 6-OHDA uptake into dopaminergic neurons in the presence of excessive levels of intracellular dopamine. Our results indicate that tsp-17 protects against 6-OHDA toxicity and toxicity caused by excessive dopamine.


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

Masoudi N, Ibanez-Cruceyra P, Offenburger SL, Holmes A, Gartner A - PLoS Genet. (2014)

tsp-17 (gt1681) enhances the neurodegeneration phenotype of cat-2-overexpressing lines, and cat-2 overexpression protects against 6-OHDA toxicity.A. cat-2 induced neurodegeneration. Analysis of cat-2-overexpressing stains UA57 baIn4 [pdat-1::gfp pdat-1::cat-2] and TG2402 baIn4[pdat-1::gfp pdat-1::cat-2]; tsp-17(gt1681). Error bars represent standard deviation. Asterisks represent statistical difference between cat-2::gfp adults on days 5 and 7 (**p<0.005). B. cat-2 overexpression suppresses 6-OHDA-induced neurotoxicity. Experiments were done in triplicate and the average is shown. Data presented is from scoring the extent of neurodegeneration 72 h post 6-OHDA intoxication.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256090&req=5

pgen-1004767-g004: tsp-17 (gt1681) enhances the neurodegeneration phenotype of cat-2-overexpressing lines, and cat-2 overexpression protects against 6-OHDA toxicity.A. cat-2 induced neurodegeneration. Analysis of cat-2-overexpressing stains UA57 baIn4 [pdat-1::gfp pdat-1::cat-2] and TG2402 baIn4[pdat-1::gfp pdat-1::cat-2]; tsp-17(gt1681). Error bars represent standard deviation. Asterisks represent statistical difference between cat-2::gfp adults on days 5 and 7 (**p<0.005). B. cat-2 overexpression suppresses 6-OHDA-induced neurotoxicity. Experiments were done in triplicate and the average is shown. Data presented is from scoring the extent of neurodegeneration 72 h post 6-OHDA intoxication.
Mentions: We next wished to address how TSP-17 protects dopaminergic neurons. We hypothesized that TSP-17 might affect dopamine synthesis, or dopamine and 6-OHDA uptake or degradation. Dopamine metabolism is itself a source of oxidative stress and may initiate ROS-mediated injury to dopaminergic neurons. The link between excessive dopamine exposure and toxicity is controversial, but overexpression of CAT-2, the rate-limiting enzyme in dopamine synthesis in C. elegans, is reported to lead to age-dependent degeneration of dopaminergic neurons [46]. We repeated these experiments, and indeed found that neurodegeneration conferred by CAT-2 overexpression in dopaminergic neurons is enhanced in the gt1681 mutant background (Figure 4A). In contrast, we found CAT-2 overexpression to confer a strong resistance toward 6-OHDA-dependent neurodegeneration in both wild-type and gt1618 backgrounds (Figure 4B). We consider it likely that 6-OHDA resistance conferred by CAT-2 overexpression can be explained by reduced 6-OHDA uptake into dopaminergic neurons in the presence of excessive levels of intracellular dopamine. Our results indicate that tsp-17 protects against 6-OHDA toxicity and toxicity caused by excessive dopamine.

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Centre for Gene Regulation and Expression, University of Dundee, Dow Street, Dundee, United Kingdom.

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 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.

No MeSH data available.


Related in: MedlinePlus