scholarly journals ­Bcl-2 homologue debcl enhances α-synuclein-induced phenotypes in Drosophila

2016 ◽  
Author(s):  
Peter G M'Angale ◽  
Brian E Staveley
Keyword(s):  
Parkinson Disease ◽  
Dopaminergic Neurons ◽  
Neuronal Degeneration ◽  
Altered Expression ◽  
Drosophila Model ◽  
Age Dependent ◽  
Climbing Ability ◽  
The Common ◽  
Locomotor Ability

Background Parkinson disease (PD) is a debilitating movement disorder that afflicts 1 to 2% of the population over 50 years of age. The common hallmark for both sporadic and familial forms of PD is mitochondrial dysfunction. Mammals have at least twenty proapoptotic and antiapoptotic Bcl-2 family members, in contrast, only two Bcl-2 family genes have been identified in Drosophila melanogaster, the proapoptotic mitochondrial localized debcl and the antiapoptotic Buffy. The expression of α-synuclein, the first gene identified to contribute to inherited forms of PD, in the dopaminergic neurons (DA) of flies has provided a robust and well-studied Drosophila model of PD complete with the loss of neurons and accompanying motor defects. The altered expression of debcl in the DA neurons and neuron-rich eye and along with the expression of α-synuclein offers an opportunity to highlight the role of debcl in mitochondrial-dependent neuronal degeneration and death. Results The directed overexpression of debcl using the Ddc-Gal4 transgene in the dopaminergic neurons of Drosophila resulted in flies with severely decreased survival and a premature age-dependent loss in climbing ability. The inhibition of debcl resulted in enhanced survival and improved climbing ability whereas the overexpression of debcl in the α-synuclein-induced Drosophila model of PD resulted in more severe phenotypes. In addition, the co-expression of debcl along with Buffy partially counteracts the debcl-induced phenotypes, to improve the lifespan and the associated loss of locomotor ability observed. In complementary experiments, the overexpression of debcl along with the expression of α-synuclein in the eye, enhanced the eye ablation that results from the overexpression of debcl. The co-expression of Buffy along with debcl overexpression results in the rescue of the moderate developmental eye defects. The co-expression of Buffy along with inhibition of debcl partially restores the eye to a roughened eye phenotype. Discussion The overexpression of debcl in DA neurons produces flies with shortened lifespan and impaired locomotor ability, phenotypes that are strongly associated with models of PD in Drosophila. The co-expression of debcl along with α-synuclein enhanced the Parkinson disease-like phenotypes. The co-expression of debcl along with Buffy suppresses these phenotypes. Complementary experiments in the Drosophila eye show similar trends during development. Taken all together these results suggest a role for debcl in neurodegenerative disorders.

scholarly journals ­Bcl-2 homologue debcl enhances α-synuclein-induced phenotypes in Drosophila

2016 ◽  
Author(s):  
Peter G M'Angale ◽  
Brian E Staveley
Keyword(s):  
Parkinson Disease ◽  
Dopaminergic Neurons ◽  
Neuronal Degeneration ◽  
Altered Expression ◽  
Drosophila Model ◽  
Age Dependent ◽  
Climbing Ability ◽  
The Common ◽  
Locomotor Ability

Background Parkinson disease (PD) is a debilitating movement disorder that afflicts 1 to 2% of the population over 50 years of age. The common hallmark for both sporadic and familial forms of PD is mitochondrial dysfunction. Mammals have at least twenty proapoptotic and antiapoptotic Bcl-2 family members, in contrast, only two Bcl-2 family genes have been identified in Drosophila melanogaster, the proapoptotic mitochondrial localized debcl and the antiapoptotic Buffy. The expression of α-synuclein, the first gene identified to contribute to inherited forms of PD, in the dopaminergic neurons (DA) of flies has provided a robust and well-studied Drosophila model of PD complete with the loss of neurons and accompanying motor defects. The altered expression of debcl in the DA neurons and neuron-rich eye and along with the expression of α-synuclein offers an opportunity to highlight the role of debcl in mitochondrial-dependent neuronal degeneration and death. Results The directed overexpression of debcl using the Ddc-Gal4 transgene in the dopaminergic neurons of Drosophila resulted in flies with severely decreased survival and a premature age-dependent loss in climbing ability. The inhibition of debcl resulted in enhanced survival and improved climbing ability whereas the overexpression of debcl in the α-synuclein-induced Drosophila model of PD resulted in more severe phenotypes. In addition, the co-expression of debcl along with Buffy partially counteracts the debcl-induced phenotypes, to improve the lifespan and the associated loss of locomotor ability observed. In complementary experiments, the overexpression of debcl along with the expression of α-synuclein in the eye, enhanced the eye ablation that results from the overexpression of debcl. The co-expression of Buffy along with debcl overexpression results in the rescue of the moderate developmental eye defects. The co-expression of Buffy along with inhibition of debcl partially restores the eye to a roughened eye phenotype. Discussion The overexpression of debcl in DA neurons produces flies with shortened lifespan and impaired locomotor ability, phenotypes that are strongly associated with models of PD in Drosophila. The co-expression of debcl along with α-synuclein enhanced the Parkinson disease-like phenotypes. The co-expression of debcl along with Buffy suppresses these phenotypes. Complementary experiments in the Drosophila eye show similar trends during development. Taken all together these results suggest a role for debcl in neurodegenerative disorders.

scholarly journals Bcl-2homologueDebclenhancesα-synuclein-induced phenotypes inDrosophila

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2461 ◽  
Author(s):  
P. Githure M’Angale ◽  
Brian E. Staveley
Keyword(s):  
Neurodegenerative Disorders ◽  
Dopaminergic Neurons ◽  
Neuronal Degeneration ◽  
Altered Expression ◽  
Drosophila Model ◽  
Age Dependent ◽  
Climbing Ability ◽  
The Common ◽  
Locomotor Ability

BackgroundParkinson disease (PD) is a debilitating movement disorder that afflicts 1–2% of the population over 50 years of age. The common hallmark for both sporadic and familial forms of PD is mitochondrial dysfunction. Mammals have at least twenty proapoptotic and antiapoptoticBcl-2family members, in contrast, only twoBcl-2family genes have been identified inDrosophila melanogaster, the proapoptotic mitochondrial localizedDebcland the antiapoptoticBuffy. The expression of the human transgeneα-synuclein, a gene that is strongly associated with inherited forms of PD, in dopaminergic neurons (DA) of Drosophila, results in loss of neurons and locomotor dysfunction to model PD in flies. The altered expression ofDebclin the DA neurons and neuron-rich eye and along with the expression ofα-synucleinoffers an opportunity to highlight the role ofDebclin mitochondrial-dependent neuronal degeneration and death.ResultsThe directed overexpression ofDebclusing theDdc-Gal4transgene in the DA of Drosophila resulted in flies with severely decreased survival and a premature age-dependent loss in climbing ability. The inhibition ofDebclresulted in enhanced survival and improved climbing ability whereas the overexpression ofDebclin theα-synuclein-induced Drosophila model of PD resulted in more severe phenotypes. In addition, the co-expression ofDebclalong withBuffypartially counteracts theDebcl-induced phenotypes, to improve the lifespan and the associated loss of locomotor ability observed. In complementary experiments, the overexpression ofDebclalong with the expression ofα-synucleinin the eye, enhanced the eye ablation that results from the overexpression ofDebcl. The co-expression ofBuffyalong withDebcloverexpression results in the rescue of the moderate developmental eye defects. The co-expression ofBuffyalong with inhibition ofDebclpartially restores the eye to a roughened eye phenotype.DiscussionThe overexpression ofDebclin DA neurons produces flies with shortened lifespan and impaired locomotor ability, phenotypes that are strongly associated with models of PD in Drosophila. The co-expression ofDebclalong withα-synucleinenhanced the PD-like phenotypes. The co-expression ofDebclalong withBuffysuppresses these phenotypes. Complementary experiments in the Drosophila eye show similar trends during development. Taken all together these results suggest a role forDebclin neurodegenerative disorders.

scholarly journals Bax-inhibitor-1knockdown phenotypes are suppressed byBuffyand exacerbate degeneration in aDrosophilamodel of Parkinson disease

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e2974 ◽  
Author(s):  
P. Githure M’Angale ◽  
Brian E. Staveley
Keyword(s):  
Parkinson Disease ◽  
Dopaminergic Neurons ◽  
Compound Eye ◽  
Neuronal Degeneration ◽  
Transmembrane Protein ◽  
Control Line ◽  
Altered Expression ◽  
Biometric Analysis ◽  
Climbing Ability ◽  
Locomotor Ability

BackgroundBax inhibitor-1 (BI-1) is an evolutionarily conserved cytoprotective transmembrane protein that acts as a suppressor ofBax-induced apoptosis by regulation of endoplasmic reticulum stress-induced cell death. We knocked downBI-1in the sensitivedopa decarboxylase(Ddc) expressing neurons ofDrosophila melanogasterto investigate its neuroprotective functions. We additionally sought to rescue theBI-1-induced phenotypes by co-expression with the pro-survivalBuffyand determined the effect ofBI-1knockdown on the neurodegenerative α-synuclein-induced Parkinson disease (PD) model.MethodsWe used organismal assays to assess longevity of the flies to determine the effect of the altered expression ofBI-1in theDdc-Gal4-expressing neurons by employing two RNAi transgenic fly lines. We measured the locomotor ability of these RNAi lines by computing the climbing indices of the climbing ability and compared them to a control line that expresses thelacZtransgene. Finally, we performed biometric analysis of the developing eye, where we counted the number of ommatidia and calculated the area of ommatidial disruption.ResultsThe knockdown ofBI-1in these neurons was achieved under the direction of theDdc-Gal4transgene and resulted in shortened lifespan and precocious loss of locomotor ability. The co-expression ofBuffy, the Drosophila anti-apoptotic Bcl-2 homologue, withBI-1-RNAiresulted in suppression of the reduced lifespan and impaired climbing ability. Expression of human α-synucleinin Drosophila dopaminergic neurons results in neuronal degeneration, accompanied by the age-dependent loss in climbing ability. We exploited this neurotoxic system to investigate possible BI-1 neuroprotective function. The co-expression of α-synucleinwithBI-1-RNAiresults in a slight decrease in lifespan coupled with an impairment in climbing ability. In supportive experiments, we employed the neuron-rich Drosophila compound eye to investigate subtle phenotypes that result from altered gene expression. The knockdown ofBI-1in the Drosophila developing eye under the direction of theGMR-Gal4transgene results in reduced ommatidia number and increased disruption of the ommatidial array. Similarly, the co-expression ofBI-1-RNAiwithBuffyresults in the suppression of the eye phenotypes. The expression of α-synucleinalong with the knockdown ofBI-1resulted in reduction of ommatidia number and more disruption of the ommatidial array.ConclusionKnockdown ofBI-1in the dopaminergic neurons of Drosophila results in a shortened lifespan and premature loss in climbing ability, phenotypes that appear to be strongly associated with models of PD in Drosophila, and which are suppressed upon overexpression ofBuffyand worsened by co-expression with α-synuclein. This suggests thatBI-1is neuroprotective and its knockdown can be counteracted by the overexpression of the pro-survivalBcl-2homologue.

The HtrA2 Drosophila model of Parkinson’s disease is suppressed by the pro-survival Bcl-2 Buffy

Genome ◽  
2017 ◽  
Vol 60 (1) ◽  
pp. 1-7 ◽  
Author(s):  
P. Githure M’Angale ◽  
Brian E. Staveley
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Drosophila Melanogaster ◽  
High Temperature ◽  
Dopaminergic Neurons ◽  
Inhibitors Of Apoptosis ◽  
Drosophila Model ◽  
Age Dependent ◽  
Climbing Ability ◽  
Locomotor Ability

Mutations in High temperature requirement A2 (HtrA2), also designated PARK13, which lead to the loss of its protease activity, have been associated with Parkinson’s disease (PD). HtrA2 is a mitochondrial protease that translocates to the cytosol upon the initiation of apoptosis where it participates in the abrogation of inhibitors of apoptosis (IAP) inhibition of caspases. Here, we demonstrate that the loss of the HtrA2 function in the dopaminergic neurons of Drosophila melanogaster results in PD-like phenotypes, and we attempt to restore the age-dependent loss in locomotor ability by co-expressing the sole pro-survival Bcl-2 homologue Buffy. The inhibition of HtrA2 in the dopaminergic neurons of Drosophila resulted in shortened lifespan and impaired climbing ability, and the overexpression of Buffy rescued the reduction in lifespan and the age-dependent loss of locomotor ability. In supportive experiments, the inhibition of HtrA2 in the Drosophila eye results in eye defects, marked by reduction in ommatidia number and increased disruption of the ommatidial array; phenotypes that are suppressed by the overexpression of Buffy.

TER94 , the Drosophila Homologue of the ALS-related VCP gene, Influences Lifespan and Leads to a Decline in Motor Function

2020 ◽  
Author(s):  
Emily Priscilla Hurley ◽  
Brian Ernest Staveley
Keyword(s):  
Neurodegenerative Disease ◽  
Motor Neurons ◽  
Dopaminergic Neurons ◽  
Altered Expression ◽  
Locomotor Function ◽  
Aaa Atpase ◽  
Median Lifespan ◽  
Novel Model ◽  
Locomotor Ability ◽  
Over Time

Abstract Background: Valosin-Containing Protein (VCP) is an essential AAA+ ATPase with diverse functions within the cell. Mutations in the VCP gene have been detected in patients with familial amyotrophic lateral sclerosis (ALS). The aim of this study is to create a novel model of human neurodegenerative disease in Drosophila melanogaster by altering the expression of TER94, the Drosophila orthologue of the human VCP gene. TER94 expression was altered in all neurons, the dopaminergic neurons and in the motor neurons, with longevity and locomotor function assessed over time. Altered TER94 expression in combination with the altered expression of known Parkinson Disease (PD) genes was examined to investigate potential interactions.Results: Inhibition of TER94 altered median lifespan in a manner dependent upon the transgene selected for use and the tissue-specific expression directed by the Gal4 transgene selected. Locomotor ability was significantly reduced in all cases of TER94 inhibition tested. The inhibition of TER94 by two TER94-RNAi inhibitory transgenes, in the motor neurons via D42-Gal4 lead to increases in median lifespan, with one inhibitory transgene generating a slightly reduced lifespan. Inhibition of TER94 in the dopaminergic neurons resulted in a severe reduction in lifespan. The co-inhibition of TER94 and parkin in the neurons resulted in a major decline in lifespan by approximately 30%. While the inhibition of TER94 and the co-expression of alpha-synuclein in the neurons resulted in an increase in lifespan by approximately 28%. Conclusions: The inhibition of TER94 in the motor neurons is an interesting model of ALS, due to the small, but reduced lifespan coupled with a strong decline in locomotor function. The inhibition of TER94 in the dopaminergic neurons is a potential model of ALS, due to the reduction of both lifespan and locomotor function over time. The co-inhibition of TER94 and parkin in the neurons provides a promising novel model of neurodegenerative disease, displaying a great reduction in lifespan and in locomotor ability over time.

scholarly journals Bax-inhibitor-1 loss of function phenotypes are suppressed by Buffy in Drosophila

2016 ◽  
Author(s):  
P Githure M'Angale ◽  
Brian E Staveley
Keyword(s):  
Er Stress ◽  
Dopaminergic Neurons ◽  
Compound Eye ◽  
Transmembrane Protein ◽  
Loss Of Function ◽  
Diverse Range ◽  
Biometric Analysis ◽  
Climbing Ability ◽  
Induced Apoptosis ◽  
Locomotor Ability

Background. Bax Inhibitor-1 (BI-1), an integral transmembrane protein, acts as a suppressor of Bax-induced apoptosis through regulation of endoplasmic reticulum (ER) stress-induced cell death. The gene is highly conserved being found in a diverse range of organisms that include yeast, Arabidopsis, Drosophila, mouse and humans. BI-1 is implicated in the regulation of calcium levels, reactive oxygen species, apoptosis, autophagy and ER stress signalling pathways. We inhibited the cytoprotective BI-1 in the dopa decarboxylase (Ddc) expressing neurons and in the developing eye of Drosophila melanogaster to investigate its neuroprotective functions. Methods. We assessed the longevity and locomotor ability of flies in response to altered BI-1 expression in the Ddc-Gal4-expressing neurons where we exploited two RNAi transgenic fly lines. A control that expressed the benign lacZ responding transgene was used to compare against the RNAi transgenic flies. In addition, we compared the effect of the loss of BI-1 expression in the developing eye, through biometric analysis of the number of ommatidia and extent of disruption of the ommatidial arrays. Finally, Buffy and α-synuclein were co-expressed to evaluate the potential for interactions. Results. The inhibition of BI-1 in these neurons resulted in a shortened lifespan and precocious loss of locomotor ability. The co-expression of Buffy, the sole anti-apoptotic Bcl-2 homologue in Drosophila, with BI-1-RNAi resulted in suppression of the reduced lifespan and impaired climbing ability. Expression of human α-synuclein in Drosophila dopaminergic neurons results in age-dependent loss in climbing ability. We exploited this neurotoxic system to investigate possible BI-1 neuroprotective function. The co-expression of α-synuclein with BI-1-RNAi results in decreased survival coupled with an impaired climbing ability. In supportive experiments, we employed the neuron-rich Drosophila compound eye to investigate subtle phenotypes that result from altered gene expression. The inhibition of BI-1 in the Drosophila developing eye under the direction of the GMR-Gal4 transgene results in reduced ommatidia number and increased disruption of the ommatidial array. Similarly, the co-expression of BI-1-RNAi with Buffy results in the suppression of the eye phenotypes. The expression of α-synuclein along with the inhibition of BI-1 results in reduction of ommatidia number and increased disruption of the ommatidial array. Conclusions. Inhibition of BI-1 in the dopaminergic neurons of Drosophila results in a shortened lifespan and premature loss in climbing ability, phenotypes that appear to be strongly associated with models of Parkinson disease in Drosophila. These are suppressed upon overexpression of Buffy and worsened by co-expression with α-synuclein. This suggests that BI-1 acts in neuroprotection and that its inhibition can be counteracted by the overexpression of the pro-survival Bcl-2 homologue, Buffy.

scholarly journals The potential role of neuroinflammation and transcription factors in Parkinson disease

2017 ◽  
Vol 19 (1) ◽  
pp. 71-80 ◽  
Keyword(s):  
Oxidative Stress ◽  
Transcription Factors ◽  
Substantia Nigra ◽  
Parkinson Disease ◽  
Signaling Pathways ◽  
Dopaminergic Neurons ◽  
Neurodegenerative Disorder ◽  
Brain Regions ◽  
Death Domain

Parkinson disease (PD) is a neurodegenerative disorder characterized by dopaminergic neurons affected by inflammatory processes. Post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines, confirming an ongoing neuroinflammation in the affected brain regions. These inflammatory mediators may activate transcription factors—notably nuclear factor κB, Ying-Yang 1 (YY1), fibroblast growth factor 20 (FGF20), and mammalian target of rapamycin (mTOR)—which then regulate downstream signaling pathways that in turn promote death of dopaminergic neurons through death domain-containing receptors. Dopaminergic neurons are vulnerable to oxidative stress and inflammatory attack. An increased level of inducible nitric oxide synthase observed in the substantia nigra and striatum of PD patients suggests that both cytokine—and chemokine-induced toxicity and inflammation lead to oxidative stress that contributes to degeneration of dopaminergic neurons and to disease progression. Lipopolysaccharide activation of microglia in the proximity of dopaminergic neurons in the substantia nigra causes their degeneration, and this appears to be a selective vulnerability of dopaminergic neurons to inflammation. In this review, we will look at the role of various transcription factors and signaling pathways in the development of PD.

Pink1 suppresses α-synuclein-induced phenotypes in a Drosophila model of Parkinson’s disease

Genome ◽  
2008 ◽  
Vol 51 (12) ◽  
pp. 1040-1046 ◽  
Author(s):  
Amy M. Todd ◽  
Brian E. Staveley
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Dopaminergic Neurons ◽  
Autosomal Recessive ◽  
Developmental Defects ◽  
Histological Studies ◽  
Progressive Loss ◽  
Drosophila Model ◽  
Climbing Ability ◽  
Protein Toxicity

Parkinson’s disease (PD) is the most prevalent human neurodegenerative movement disorder and is characterized by a selective and progressive loss of the dopaminergic neurons. Mutations in the genes parkin and PTEN-induced putative kinase 1 (PINK1) result in autosomal recessive forms of PD. It has been suggested that parkin and Pink1 function in the same pathway in Drosophila , with Pink1 acting upstream of parkin. Previous work in our laboratory has shown the ability of parkin to rescue an α-synuclein-induced PD-like phenotype in Drosophila. To investigate the ability of Pink1 to protect against α-synuclein-induced toxicity, we have performed longevity, mobility, and histological studies to determine whether Drosophila Pink1 can rescue the α-synuclein phenotypes. We have found that overexpression of Pink1 results in the rescue of the α-synuclein-induced phenotype of premature loss of climbing ability, suppression of degeneration of the ommatidial array, and the suppression of α-synuclein-induced developmental defects in the Drosophila eye. These results mark the first demonstration of Pink1 counteracting PD phenotypes in a protein toxicity animal model, and they show that Pink1 is able to impart protection against potentially harmful proteins such as α-synuclein that would otherwise result in cellular stress.

scholarly journals Lesion-associated microglia and macrophages react with massive phagocytosis for debris clearance and wound healing after LPS-induced dopaminergic depletion

2021 ◽  
Author(s):  
Paola Heman-Bozadas ◽  
Cristina Romero ◽  
Alba Frías ◽  
Elena Saavedra-López ◽  
Paola Virginia Casanova ◽  
...  
Keyword(s):  
High Resolution ◽  
Dopaminergic Neurons ◽  
Neuronal Degeneration ◽  
Neuronal Loss ◽  
Experimental Models ◽  
Inflammatory Factors ◽  
Phagocytic Capacity ◽  
Bv2 Microglia ◽  
Set Up

Abstract Background Neuroinflammation contributes to neuronal degeneration in Parkinson’s disease (PD). However, how brain inflammatory factors mediate the progression of neurodegeneration is still poorly understood. Experimental models of PD have shed light on the understanding of this phenomenon, but the exploration of inflammation-driven models is necessary to better characterize this aspect of the disorder. The use of lipopolysaccharide (LPS) to induce a neuroinflammation-mediated neuronal loss is useful to induce reliable elimination of dopaminergic neurons. Nevertheless, how this model parallels the PD-like neuroinflammation is uncertain.Methods In the present work, we used the direct LPS stereotactic injection as a model inductor to eliminate dopaminergic neurons of the substantia nigra pars compacta (SNpc) in rats and reevaluated the microanatomy of inflammatory reaction three and seven days after the insult. For this, we analyzed the tissue with high resolution confocal microscopy to assess the neuronal loss, the vulnerability of dopaminergic neurons, as well as the activation of lesion-associated microglia and macrophages (LAMMs) together with the visualization of their phagocytic capacity. In addition, we set up a co-culture of BV2 microglia and PC12 dopaminergic cells to understand the role of LPS-mediated neuroinflammatory toxicity versus phagocytosis.Results High-resolution 3D histological examination revealed that, although LPS induced a reliable elimination of SNpc dopaminergic neurons, it also generated a massive neuroinflammatory response. This inflammation-mediated injury was characterized by a damaged parenchyma occupied by a vast population of LAMMs undertaking wound compaction and scar formation. LAMMs tiled the entire lesion and engaged in long-standing phagocytic activity to resolve the injury. Additionally, modeling LPS inflammation in a cell culture system helped to understand the role of phagocytosis and cytotoxicity in dopaminergic degeneration and indicated that LAMM-mediated toxicity and phagocytosis coexist during LPS-mediated dopaminergic elimination.Conclusions This type of severe inflammatory-mediated injury appears to be different from the ageing-related PD scenario where the architectural structure of the parenchyma is preserved. Thus, the necessity to explore new experimental models to properly mimic the inflammatory compound observed in PD degeneration.

scholarly journals Bax-inhibitor-1 loss of function phenotypes are suppressed by Buffy in Drosophila

2016 ◽  
Author(s):  
P Githure M'Angale ◽  
Brian E Staveley
Keyword(s):  
Er Stress ◽  
Dopaminergic Neurons ◽  
Compound Eye ◽  
Transmembrane Protein ◽  
Loss Of Function ◽  
Diverse Range ◽  
Biometric Analysis ◽  
Climbing Ability ◽  
Induced Apoptosis ◽  
Locomotor Ability

Background. Bax Inhibitor-1 (BI-1), an integral transmembrane protein, acts as a suppressor of Bax-induced apoptosis through regulation of endoplasmic reticulum (ER) stress-induced cell death. The gene is highly conserved being found in a diverse range of organisms that include yeast, Arabidopsis, Drosophila, mouse and humans. BI-1 is implicated in the regulation of calcium levels, reactive oxygen species, apoptosis, autophagy and ER stress signalling pathways. We inhibited the cytoprotective BI-1 in the dopa decarboxylase (Ddc) expressing neurons and in the developing eye of Drosophila melanogaster to investigate its neuroprotective functions. Methods. We assessed the longevity and locomotor ability of flies in response to altered BI-1 expression in the Ddc-Gal4-expressing neurons where we exploited two RNAi transgenic fly lines. A control that expressed the benign lacZ responding transgene was used to compare against the RNAi transgenic flies. In addition, we compared the effect of the loss of BI-1 expression in the developing eye, through biometric analysis of the number of ommatidia and extent of disruption of the ommatidial arrays. Finally, Buffy and α-synuclein were co-expressed to evaluate the potential for interactions. Results. The inhibition of BI-1 in these neurons resulted in a shortened lifespan and precocious loss of locomotor ability. The co-expression of Buffy, the sole anti-apoptotic Bcl-2 homologue in Drosophila, with BI-1-RNAi resulted in suppression of the reduced lifespan and impaired climbing ability. Expression of human α-synuclein in Drosophila dopaminergic neurons results in age-dependent loss in climbing ability. We exploited this neurotoxic system to investigate possible BI-1 neuroprotective function. The co-expression of α-synuclein with BI-1-RNAi results in decreased survival coupled with an impaired climbing ability. In supportive experiments, we employed the neuron-rich Drosophila compound eye to investigate subtle phenotypes that result from altered gene expression. The inhibition of BI-1 in the Drosophila developing eye under the direction of the GMR-Gal4 transgene results in reduced ommatidia number and increased disruption of the ommatidial array. Similarly, the co-expression of BI-1-RNAi with Buffy results in the suppression of the eye phenotypes. The expression of α-synuclein along with the inhibition of BI-1 results in reduction of ommatidia number and increased disruption of the ommatidial array. Conclusions. Inhibition of BI-1 in the dopaminergic neurons of Drosophila results in a shortened lifespan and premature loss in climbing ability, phenotypes that appear to be strongly associated with models of Parkinson disease in Drosophila. These are suppressed upon overexpression of Buffy and worsened by co-expression with α-synuclein. This suggests that BI-1 acts in neuroprotection and that its inhibition can be counteracted by the overexpression of the pro-survival Bcl-2 homologue, Buffy.

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