Showing papers by "Valina L. Dawson published in 2009"
TL;DR: It is evident that further understanding of parthanatos opens up new avenues for therapy in ameliorating diseases related to PARP-1 overactivation, as evidence shows that poly-ADP ribose (PAR) polymer itself can act as a cell death effector downstream of PARp-1.
Abstract: Poly-ADP-ribose polymerase-1 (PARP-1)'s roles in the cell span from maintaining life to inducing death. The processes PARP-1 is involved in include DNA repair, DNA transcription, mitosis, and cell death. Of PARP-1's different cellular functions, its role in cell death is of particular interest to designing therapies for diseases. Genetic deletion of PARP-1 revealed that PARP-1 overactivation underlies cell death in models of stroke, diabetes, inflammation and neurodegeneration. Since interfering with PARP-1 mediated cell death will be clinically beneficial, great effort has been invested into understanding mechanisms downstream of PARP-1 overactivation. Recent evidence shows that poly-ADP ribose (PAR) polymer itself can act as a cell death effector downstream of PARP-1. We coined the term parthanatos after Thanatos, the personification of death in Greek mythology, to refer to PAR-mediated cell death. In this review, we will present evidence and questions raised by these recent findings, and summarize the proposed mechanisms by which PARP-1 overactivation kills. It is evident that further understanding of parthanatos opens up new avenues for therapy in ameliorating diseases related to PARP-1 overactivation.
345 citations
TL;DR: Targeting PAR-mediated AIF release could be a potential approach for the therapy of neurologic disorders after identifying the key event initiating the deadly crosstalk between the nucleus and the mitochondria in parthanatos.
337 citations
TL;DR: Investigations have begun to reveal the influence of miRNAs on both neuronal survival and the accumulation of toxic proteins that are associated with neurodegeneration, and are providing clues as to how these toxic proteins can influence miRNA expression.
Abstract: Multiple roles for microRNA-mediated regulation of mRNA translation in the nervous system have emerged in recent years. Dawson and colleagues discuss the mechanisms by which microRNAs might influence neurodegenerative disease pathogenesis and outline key questions for future research.
263 citations
TL;DR: Transgenic flies harboring G2019S, Y1699C, or G2385R LRRK2 variant, but not the wild-type protein, exhibit late-onset loss of dopaminergic neurons in selected clusters that is accompanied by locomotion deficits, and coexpression of human parkin in L RRK2 G 2019S-expressing flies provides significant protection against DA neurodegeneration that occurs with age or in response to rotenone.
Abstract: Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are currently recognized as the most common genetic cause of parkinsonism. Among the large number of LRRK2 mutations identified to date, the G2019S variant is the most common. In Asia, however, another LRRK2 variant, G2385R, appears to occur more frequently. To better understand the contribution of different LRRK2 variants toward disease pathogenesis, we generated transgenic Drosophila over-expressing various human LRRK2 alleles, including wild type, G2019S, Y1699C, and G2385R LRRK2. We found that transgenic flies harboring G2019S, Y1699C, or G2385R LRRK2 variant, but not the wild-type protein, exhibit late-onset loss of dopaminergic (DA) neurons in selected clusters that is accompanied by locomotion deficits. Furthermore, LRRK2 mutant flies also display reduced lifespan and increased sensitivity to rotenone, a mitochondrial complex I inhibitor. Importantly, coexpression of human parkin in LRRK2 G2019S-expressing flies provides significant protection against DA neurodegeneration that occurs with age or in response to rotenone. Together, our results suggest a potential link between LRRK2, parkin, and mitochondria in the pathogenesis of LRRK2-related parkinsonism.
215 citations
TL;DR: It is shown that the carboxyl terminus of HSP70-interacting protein (CHIP) binds, ubiquitinates, and promotes the ubiquitin proteasomal degradation of LRRK2, and that increasing CHIP E3 ligase activity and blocking HSP90 chaperone activity can prevent the deleterious effects of L RRK2.
Abstract: Mutation in leucine-rich repeat kinase-2 (LRRK2) is the most common cause of late-onset Parkinson's disease (PD). Although most cases of PD are sporadic, some are inherited, including those caused by LRRK2 mutations. Because these mutations may be associated with a toxic gain of function, controlling the expression of LRRK2 may decrease its cytotoxicity. Here we show that the carboxyl terminus of HSP70-interacting protein (CHIP) binds, ubiquitinates, and promotes the ubiquitin proteasomal degradation of LRRK2. Overexpression of CHIP protects against and knockdown of CHIP exacerbates toxicity mediated by mutant LRRK2. Moreover, HSP90 forms a complex with LRRK2, and inhibition of HSP90 chaperone activity by 17AAG leads to proteasomal degradation of LRRK2, resulting in increased cell viability. Thus, increasing CHIP E3 ligase activity and blocking HSP90 chaperone activity can prevent the deleterious effects of LRRK2. These findings point to potential treatment options for LRRK2-associated PD.
191 citations
TL;DR: The results confirm that nitrosative stress contributes to PD pathogenesis through the impairment of prosurvival proteins such as parkin and XIAP through different mechanisms, indicating that abnormal S-nitrosylation plays an important role in the process of neurodegeneration.
Abstract: Inhibitors of apoptosis (IAPs) are a family of highly-conserved proteins that regulate cell survival through binding to caspases, the final executioners of apoptosis. X-linked IAP (XIAP) is the most widely expressed IAP and plays an important function in regulating cell survival. XIAP contains 3 baculoviral IAP repeats (BIRs) followed by a RING finger domain at the C terminal. The BIR domains of XIAP possess anticaspase activities, whereas the RING finger domain enables XIAP to function as an E3 ubiquitin ligase in the ubiquitin and proteasomal system. Our previous study showed that parkin, a protein that is important for the survival of dopaminergic neurons in Parkinson's disease (PD), is S-nitrosylated both in vitro and in vivo in PD patients. S-nitrosylation of parkin compromises its ubiquitin E3 ligase activity and its protective function, which suggests that nitrosative stress is an important factor in regulating neuronal survival during the pathogenesis of PD. In this study we show that XIAP is S-nitrosylated in vitro and in vivo in an animal model of PD and in PD patients. Nitric oxide modifies mainly cysteine residues within the BIR domains. In contrast to parkin, S-nitrosylation of XIAP does not affect its E3 ligase activity, but instead directly compromises its anticaspase-3 and antiapoptotic function. Our results confirm that nitrosative stress contributes to PD pathogenesis through the impairment of prosurvival proteins such as parkin and XIAP through different mechanisms, indicating that abnormal S-nitrosylation plays an important role in the process of neurodegeneration.
143 citations
TL;DR: It is suggested that LRRK2 plays little if any role in the development and survival of DA neurons under physiologic conditions, and PD due to L RRK2 mutations are likely not due to a loss of function.
Abstract: Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common known cause of Parkinson's disease (PD). Whether loss of LRRK2 function accounts for neurodegeneration of dopamine neurons in PD is not known, nor is it known whether LRRK2 kinase activity modulates the susceptibility of dopamine (DA) neurons to the selective dopaminergic toxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). To better understand the role of LRRK2 in DA neuronal survival and its role in the susceptibility of DA neurons to MPTP, we generated LRRK2 knock-out (KO) mice lacking the kinase domain of LRRK2. Here, we show that LRRK2 KO mice are viable and have no major abnormalities and live to adulthood. The dopaminergic system is normal in LRRK2 KO mice as assessed via HPLC for DA and its metabolites and via stereologic assessment of DA neuron number in young and aged mice. Importantly, there is no significant difference in the susceptibility of LRRK2 KO and wild-type mice to MPTP. These results suggest that LRRK2 plays little if any role in the development and survival of DA neurons under physiologic conditions. Thus, PD due to LRRK2 mutations are likely not due to a loss of function. Moreover, LRRK2 is not required for the susceptibility of DA neurons to MPTP.
133 citations
TL;DR: Many of the advances in the last decade regarding the identification of new targets for the treatment of PD based on understanding the molecular mechanisms of how mutations in genes linked to PD cause neurodegeneration are reviewed.
Abstract: Currently, there is no proven neuroprotective or neurorestorative therapy for Parkinson's disease (PD). Several advances in the genetics of PD have created an opportunity to develop mechanistic-based therapies that hold particular promise for identifying agents that slow and even halt the progression of PD, as well as restore function. Here we review many of the advances in the last decade regarding the identification of new targets for the treatment of PD based on understanding the molecular mechanisms of how mutations in genes linked to PD cause neurodegeneration.
132 citations
TL;DR: It is shown that calpain activation is not required for AIF release during parthanatos, suggesting that other mechanisms rather than calpain are involved in mitochondrial AIFRelease in parthanato.
Abstract: Apoptosis-inducing factor (AIF) is critical for poly(ADP-ribose) polymerase-1 (PARP-1)-dependent cell death (parthanatos). The molecular mechanism of mitochondrial AIF release to the nucleus remains obscure, although a possible role of calpain I has been suggested. Here we show that calpain is not required for mitochondrial AIF release in parthanatos. Although calpain I cleaved recombinant AIF in a cell-free system in intact cells under conditions where endogenous calpain was activated by either NMDA or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) administration, AIF was not cleaved, and it was released from mitochondria to the nucleus in its 62-kDa uncleaved form. Moreover, NMDA administration under conditions that failed to activate calpain still robustly induced AIF nuclear translocation. Inhibition of calpain with calpastatin or genetic knockout of the regulatory subunit of calpain failed to prevent NMDA- or MNNG-induced AIF nuclear translocation and subsequent cell death, respectively, which was markedly prevented by the PARP-1 inhibitor, 3,4-dihydro-5-[4-(1-piperidinyl)butoxyl]-1(2H)-iso-quinolinone. Our study clearly shows that calpain activation is not required for AIF release during parthanatos, suggesting that other mechanisms rather than calpain are involved in mitochondrial AIF release in parthanatos.
96 citations
TL;DR: The expression of αSyn119 in the mouse nigrostriatal dopaminergic pathway may provide a useful model of striatal dopamine depletion and could potentially provide a presymptomatic model of PD, and support the pathophysiological relevance of C-terminally truncated α-synuclein species in vivo.
Abstract: Missense mutations and multiplications of the α-synuclein gene cause autosomal dominant familial Parkinson's disease (PD). α-Synuclein protein is also a major component of Lewy bodies, the hallmark pathological inclusions of PD. Therefore, α-synuclein plays an important role in the pathogenesis of familial and sporadic PD. To model α-synuclein-linked disease in vivo, transgenic mouse models have been developed that express wild-type or mutant human α-synuclein from a variety of neuronal-selective heterologous promoter elements. These models exhibit a variety of behavioral and neuropathological features resembling some aspects of PD. However, an important deficiency of these models is the observed lack of robust or progressive nigrostriatal dopaminergic neuronal degeneration that is characteristic of PD. We have developed conditional α-synuclein transgenic mice that can express A53T, E46K or C-terminally truncated (1–119) human α-synuclein pathological variants from the endogenous murine ROSA26 promoter in a Cre recombinase-dependent manner. Using these mice, we have evaluated the expression of these α-synuclein variants on the integrity and viability of nigral dopaminergic neurons with age. Expression of A53T α-synuclein or truncated αSyn119 selectively in nigrostriatal pathway dopaminergic neurons for up to 12 months fails to precipitate dopaminergic neuronal loss in these mice. However, αSyn119 expression in nigral dopaminergic neurons for up to 12 months causes a marked reduction in the levels of striatal dopamine and its metabolites together with other subtle neurochemical alterations. We have developed and evaluated novel conditional α-synuclein transgenic mice with transgene expression directed selectively to nigrostriatal dopaminergic neurons as a potential new mouse model of PD. Our data support the pathophysiological relevance of C-terminally truncated α-synuclein species in vivo. The expression of αSyn119 in the mouse nigrostriatal dopaminergic pathway may provide a useful model of striatal dopamine depletion and could potentially provide a presymptomatic model of PD perhaps representative of the earliest derangements in dopaminergic neuronal function observed prior to neuronal loss. These conditional α-synuclein transgenic mice provide novel tools for evaluating and dissecting the age-related effects of α-synuclein pathological variants on the function of the nigrostriatal dopaminergic pathway or other specific neuronal populations.
82 citations
TL;DR: A second pool of AIF is shown for the first time in brain mitochondria and it is demonstrated that this pool does not require cleavage and that it contributes to the rapid release of A IF.
Abstract: Poly(ADP-ribose) polymerase-1-dependent cell death (known as parthanatos) plays a pivotal role in many clinically important events including ischaemia/reperfusion injury and glutamate excitotoxicity. A recent study by us has shown that uncleaved AIF (apoptosis-inducing factor), but not calpain-hydrolysed truncated-AIF, was rapidly released from the mitochondria during parthanatos, implicating a second pool of AIF that might be present in brain mitochondria contributing to the rapid release. In the present study, a novel AIF pool is revealed in brain mitochondria by multiple biochemical analyses. Approx. 30% of AIF loosely associates with the outer mitochondrial membrane on the cytosolic side, in addition to its main localization in the mitochondrial intermembrane space attached to the inner membrane. Immunogold electron microscopic analysis of mouse brain further supports AIF association with the outer, as well as the inner, mitochondrial membrane in vivo. In line with these observations, approx. 20% of uncleaved AIF rapidly translocates to the nucleus and functionally causes neuronal death upon NMDA (N-methyl-d-aspartate) treatment. In the present study we show for the first time a second pool of AIF in brain mitochondria and demonstrate that this pool does not require cleavage and that it contributes to the rapid release of AIF. Moreover, these results suggest that this outer mitochondrial pool of AIF is sufficient to cause cell death during parthanatos. Interfering with the release of this outer mitochondrial pool of AIF during cell injury paradigms that use parthanatos hold particular promise for novel therapies to treat neurological disorders.
TL;DR: It is suggested that LRRK2 normally localizes to the endosomal-lysosomal compartment within morphologically altered neurons in neurodegenerative diseases, particularly in the brains of patients with LB diseases.
Abstract: Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most common causes of both familial and sporadic forms of Parkinson disease and are also associated with diverse pathological alterations. The mechanisms whereby LRRK2 mutations cause these pathological phenotypes are unknown. We used immunohistochemistry with 3 distinct anti-LRRK2 antibodies to characterize the expression of LRRK2 in the brains of 21 subjects with various neurodegenerative disorders and 7 controls. The immunoreactivity of LRRK2 was localized in a subset of brainstem-type Lewy bodies (LBs) but not in cortical-type LBs, tau-positive inclusions, or TAR-DNA-binding protein-43-positive inclusions. The immunoreactivity of LRRK2 frequently appeared as enlarged granules or vacuoles within neurons of affected brain regions, including the substantia nigra, amygdala, and entorhinal cortex in patients with Parkinson disease or dementia with LBs. The volumes of LRRK2-positive granular structures in neurons of the entorhinal cortex were significantly increased in dementia with LBs brains compared with age-matched control brains (p < 0.05). Double immunolabeling demonstrated that these LRRK2-positive granular structures frequently colocalized with the late-endosomal marker Rab7B and occasionally with the lysosomal marker, the lysosomal-associated membrane protein 2. These results suggest that LRRK2 normally localizes to the endosomal-lysosomal compartment within morphologically altered neurons in neurodegenerative diseases, particularly in the brains of patients with LB diseases.
TL;DR: It is found that not only nuclear, but also mitochondrial, DNA is a target for the MPTP insult and this results suggest that the loss of genomic integrity can be triggered by the concerted actions of nNOS and Cox-2 and provide further support to the view that DNA damage may contribute to the neurodegenerative process in Parkinson disease.
01 Jan 2009
TL;DR: In this article, a large-scale proteome analysis of poly(ADP-ribose) binding proteins was performed to establish a comprehensive repertoire of pADPr-associated proteins.
Abstract: Poly(ADP-ribose) (pADPr) is a polymer assembled from the enzymatic polymerization of the ADP-ribosyl moiety of NAD by poly(ADP-ribose) polymerases (PARPs). The dynamic turnover of pADPr within the cell is essential for a number of cellular processes including progression through the cell cycle, DNA repair and the maintenance of genomic integrity, and apoptosis. In spite of the considerable advances in the knowledge of the physiological conditions modulated by poly(ADP-ribosyl)ation reactions, and notwithstanding the fact that pADPr can play a role of mediator in a wide spectrum of biological processes, few pADPr binding proteins have been identified so far. In this study, refined in silico prediction of pADPr binding proteins and large-scale mass spectrometry-based proteome analysis of pADPr binding proteins were used to establish a comprehensive repertoire of pADPr-associated proteins. Visualization and modeling of these pADPr-associated proteins in networks not only reflect the widespread involvement of poly(ADP-ribosyl)ation in several pathways but also identify protein targets that could shed new light on the regulatory functions of pADPr in normal physiological conditions as well as after exposure to genotoxic stimuli.
TL;DR: This SnapShot summarizes the roles that proteins encoded by PD-associated genes play in both common and divergent mechanisms of PD pathogenesis.
Journal Article•
01 Jan 2009
TL;DR: NO has been linked to the development and progression of neural injury in stroke, Parkinson's disease, and Alzheimer’s disease and is involved in a wide range of physiological and pathophysiological actions.
Abstract: Nitric oxide (NO) is an unprecedented biological messenger molecule. NO is synthesized by the enzymes NO synthases, that catalyze the essential amino acid l-arginine into NO and l-citrulline. In the central nervous system, NO is an unusual neuronal messenger molecule; due to its small size and ability to move through lipids, NO reaches its targets through diffusion. NO forms covalent and noncovalent linkages with protein and nonprotein targets and is involved in a wide range of physiological and pathophysiological actions. NO has been linked to the development and progression of neural injury in stroke, Parkinson’s disease, and Alzheimer’s disease.