LRRK2(I2020T) functional genetic interactors that modify eye degeneration and dopaminergic cell loss in Drosophila.

Progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta is the primary cause for motor symptoms observed in Parkinson's disease (PD). Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most commonly linked contributor to familial PD. LRRK2 is suggested to be involved in a wide variety of cellular processes, but deciphering its role in the pathogenesis of PD has been difficult. Modelling PD in rodents has been a persistent challenge for the field. However, the fruit fly has been exploited to recapitulate PD gene related dopaminergic cell loss. Using the GAL4-UAS system and established models of hLRRK2 induced eye degeneration in Drosophila, we conducted an unbiased suppressor/enhancer screen to uncover genetic modifiers of LRRK2. We have identified 36 candidate interactors that modify LRRK2 induced toxicity in the Drosophila eye. Importantly, we determined that a subset of these interactors also modified hLRRK2(I2020T) induced dopaminergic neuronal loss in the fly brain and uncovered 16 candidates that modify dopaminergic cell loss. Our results suggest LRRK2 may be involved in a wide variety of cellular processes and the results from this screen provide an important genetic resource for further evaluation of LRRK2 function.

Activation of FoxO by LRRK2 induces expression of proapoptotic proteins and alters survival of postmitotic dopaminergic neuron in Drosophila.

Missense mutations in leucine-rich repeat kinase 2 (LRRK2)/Dardarin gene, the product of which encodes a kinase with multiple domains, are known to cause autosomal dominant late onset Parkinson's disease (PD). In the current study, we report that the gene product LRRK2 directly phosphorylates the forkhead box transcription factor FoxO1 and enhances its transcriptional activity. This pathway was found to be conserved in Drosophila, as the Drosophila LRRK2 homolog (dLRRK) enhanced the neuronal toxicity of FoxO. Importantly, FoxO mutants that were resistant to LRRK2/dLRRK-induced phosphorylation suppressed this neurotoxicity. Moreover, we have determined that FoxO targets hid and bim in Drosophila and human, respectively, are responsible for the LRRK2/dLRRK-mediated cell death. These data suggest that the cell death molecules regulated by FoxO are key factors during the neurodegeneration in LRRK2-linked PD.

Leucine-Rich Repeat Kinase 2 interacts with Parkin, DJ-1 and PINK-1 in a Drosophila melanogaster model of Parkinson's disease.

Mutations in the LRRK2 gene are the most common genetic cause of familial Parkinson's disease (PD). However, its physiological and pathological functions are unknown. Therefore, we generated several independent Drosophila lines carrying WT or mutant human LRRK2 (mutations in kinase, COR or LRR domains, resp.). Ectopic expression of WT or mutant LRRK2 in dopaminergic neurons caused their significant loss accompanied by complex age-dependent changes in locomotor activity. Overall, the ubiquitous expression of LRRK2 increased lifespan and fertility of the flies. However, these flies were more sensitive to rotenone. LRRK2 expression in the eye exacerbated retinal degeneration. Importantly, in double transgenic flies, various indices of the eye and dopaminergic survival were modified in a complex fashion by a concomitant expression of PINK1, DJ-1 or Parkin. This evidence suggests a genetic interaction between these PD-relevant genes.

Parkinson's disease-linked LRRK2 is expressed in circulating and tissue immune cells and upregulated following recognition of microbial structures.

Sequence variants at or near the leucine-rich repeat kinase 2 (LRRK2) locus have been associated with susceptibility to three human conditions: Parkinson's disease (PD), Crohn's disease and leprosy. As all three disorders represent complex diseases with evidence of inflammation, we hypothesized a role for LRRK2 in immune cell functions. Here, we report that full-length Lrrk2 is a relatively common constituent of human peripheral blood mononuclear cells (PBMC) including affinity isolated, CD14(+) monocytes, CD19(+) B cells, and CD4(+) as well as CD8(+) T cells. Up to 26% of PBMC from healthy donors and up to 43% of CD14(+) monocytes were stained by anti-Lrrk2 antibodies using cell sorting. PBMC lysates contained full-length (>260 kDa) and higher molecular weight Lrrk2 species. The expression of LRRK2 in circulating leukocytes was confirmed by microscopy of human blood smears and in sections from normal midbrain and distal ileum. Lrrk2 reactivity was also detected in mesenteric lymph nodes and spleen (including in dendritic cells), but was absent in splenic mononuclear cells from lrrk2-null mice, as expected. In cultured bone marrow-derived macrophages from mice we made three observations: (i) a predominance of higher molecular weight lrrk2; (ii) the reduction of autophagy marker LC3-II in (R1441C)lrrk2-mutant cells (<31%); and (iii) a significant up-regulation of lrrk2 mRNA (>fourfold) and protein after exposure to several microbial structures including bacterial lipopolysaccharide and lentiviral particles. We conclude that Lrrk2 is a constituent of many cell types in the immune system. Following the recognition of microbial structures, stimulated macrophages respond with altered lrrk2 gene expression. In the same cells, lrrk2 appears to co-regulate autophagy. A pattern recognition receptor-type function for LRRK2 could explain its locus' association with Crohn's disease and leprosy risk. We speculate that the role of Lrrk2 in immune cells may also be relevant to the susceptibility of developing PD or its progression.

Essential role of cytoplasmic cdk5 and Prx2 in multiple ischemic injury models, in vivo.

Recent evidence suggests that abnormal activation of cyclin-dependent kinase 5 (cdk5) is a critical prodeath signal in stroke. However, the mechanism(s) by which cdk5 promotes death is unclear. Complicating the role of cdk5 are the observations that cdk5 can exist in multiple cellular regions and possess both prosurvival and prodeath characteristics. In particular, the critical role of cytoplasmic or nuclear cdk5 in neuronal jury, in vivo, is unclear. Therefore, we determined where cdk5 was activated in models of ischemia and how manipulation of cdk5 in differing compartments may affect neuronal death. Here, we show a critical function for cytoplasmic cdk5 in both focal and global models of stroke, in vivo. Cdk5 is activated in the cytoplasm and expression of DNcdk5 localized to the cytoplasm is protective. Importantly, we also demonstrate the antioxidant enzyme Prx2 (peroxiredoxin 2) as a critical cytoplasmic target of cdk5. In contrast, the role of cdk5 in the nucleus is context-dependent. Following focal ischemia, nuclear cdk5 is activated and functionally relevant while there is no evidence for such activation following global ischemia. Importantly, myocyte enhancer factor 2D (MEF2D), a previously described nuclear target of cdk5 in vitro, is also phosphorylated by cdk5 following focal ischemia. In addition, MEF2D expression in this paradigm ameliorates death. Together, our results address the critical issue of cdk5 activity compartmentalization, as well as define critical substrates for both cytoplasmic and nuclear cdk5 activity in adult models of stroke.

Vacuolar protein sorting 35 (Vps35) rescues locomotor deficits and shortened lifespan in Drosophila expressing a Parkinson's disease mutant of Leucine-Rich Repeat Kinase 2 (LRRK2).

BACKGROUND: Parkinson's disease (PD) is the most common movement neurodegenerative movement disorder. An incomplete understanding of the molecular pathways involved in its pathogenesis impedes the development of effective disease-modifying treatments. To address this gap, we have previously generated a Drosophila model of PD that overexpresses PD pathogenic mutant form of the second most common causative gene of PD, Leucine-Rich Repeat Kinase 2 (LRRK2). FINDINGS: We employed this model in a genetic modifier screen and identified a gene that encodes for a core subunit of retromer - a complex essential for the sorting and recycling of specific cargo proteins from endosomes to the trans-Golgi network and cell surface. We present evidence that overexpression of the Vps35 or Vps26 component of the cargo-recognition subunit of the retromer complex ameliorates the pathogenic mutant LRRK2 eye phenotype. Furthermore, overexpression of Vps35 or Vps26 significantly protects from the locomotor deficits observed in mutant LRRK2 flies, as assessed by the negative geotaxis assay, and rescues their shortened lifespan. Strikingly, overexpressing Vps35 alone protects from toxicity of rotenone, a neurotoxin commonly used to model parkinsonism, both in terms of lifespan and locomotor activity of the flies, and this protection is sustained and even augmented in the presence of mutant LRRK2. Finally, we demonstrate that knocking down expression of Vps35 in dopaminergic neurons causes a significant locomotor impairment. CONCLUSIONS: From these results we conclude that LRRK2 plays a role in the retromer pathway and that this pathway is involved in PD pathogenesis.

Programmed cell death in Parkinson's disease.

Parkinson's disease is a debilitating disorder characterized by a progressive loss of dopaminergic neurons caused by programmed cell death. The aim of this review is to provide an up-to-date summary of the major programmed cell death pathways as they relate to PD. For a long time, programmed cell death has been synonymous with apoptosis but there now is evidence that other types of programmed cell death exist, such as autophagic cell death or programmed necrosis, and that these types of cell death are relevant to PD. The pathways and signals covered here include namely the death receptors, BCL-2 family, caspases, calpains, cdk5, p53, PARP-1, autophagy, mitophagy, mitochondrial fragmentation, and parthanatos. The review will present evidence from postmortem PD studies, toxin-induced models (especially MPTP/MPP+, 6-hydroxydopamine and rotenone), and from α-synuclein, LRRK2, Parkin, DJ-1, and PINK1 genetic models of PD, both in vitro and in vivo.

The role of Cdk5-mediated apurinic/apyrimidinic endonuclease 1 phosphorylation in neuronal death.

Accumulating evidence suggests that deregulated cyclin-dependent kinase 5 (Cdk5) plays a critical part in neuronal death. However, the pathogenic targets of Cdk5 are not fully defined. Here we demonstrate that the Cdk5 activator p35 interacts directly with apurinic/apyrimidinic endonuclease 1 (Ape1), a protein crucial for base excision repair (BER) following DNA damage. Cdk5 complexes phosphorylate Ape1 at Thr 232 and thereby reduces its apurinic/apyrimidinic (AP) endonuclease activity. Ape1 phosphorylation is dependent on Cdk5 in in vitro and in vivo. The reduced endonuclease activity of phosphorylated Ape1 results in accumulation of DNA damage and contributes to neuronal death. Overexpression of Ape1(WT) and Ape1(T232A), but not the phosphorylation mimic Ape1(T232E), protects neurons against MPP(+)/MPTP. Loss of Ape1 sensitizes neurons to death. Importantly, increased phosphorylated Ape1 was also observed in post-mortem brain tissue from patients with Parkinson's and Alzheimer's diseases, suggesting a potential link between Ape1 phosphorylation and the pathogenesis of neurodegenerative diseases.

Differential effects of endocannabinoids on [(3)H]-GABA uptake in the rat globus pallidus.

In the globus pallidus, cannabinoid CB(1) receptors are localized pre-synaptically on GABAergic neurons. We assessed the influence of the endocannabinoids, anandamide, 2-arachidonoyl-glycerol (2-AG) and noladin ether, on the uptake of [(3)H]-GABA in pallidal slices from rat. Both 2-AG and noladin ether increased [(3)H]-GABA uptake (by 40.8 +/- 8.0% and 38.4 +/- 12.5%). The effect of 2-AG was blocked by the cannabinoid CB(1) receptor antagonist AM 251. In contrast, neither anandamide nor the agonist WIN 55,212-2 had an effect on [(3)H]-GABA uptake. Different roles might be played by different endocannabinoids, both physiologically and in basal ganglia disorders, such as Parkinson's disease.

Decreased endocannabinoid levels in the brain and beneficial effects of agents activating cannabinoid and/or vanilloid receptors in a rat model of multiple sclerosis.

Recent studies have addressed the changes in endocannabinoid ligands and receptors that occur in multiple sclerosis, as a way to explain the efficacy of cannabinoid compounds to alleviate spasticity, pain, tremor, and other signs of this autoimmune disease. Using Lewis rats with experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, we recently found a decrease in cannabinoid CB1 receptors mainly circumscribed to the basal ganglia, which could be related to the motor disturbances characteristic of these rats. In the present study, using the same model, we explored the potential changes in several neurotransmitters in the basal ganglia that might be associated with the motor disturbances described in these rats, but we only found a small increase in glutamate contents in the globus pallidus. We also examined whether the motor disturbances and the changes of CB1 receptors found in the basal ganglia of EAE rats disappear after the treatment with rolipram, an inhibitor of type IV phosphodiesterase able to supress EAE in different species. Rolipram attenuated clinical decline, reduced motor inhibition, and normalized CB1 receptor gene expression in the basal ganglia. As a third objective, we examined whether EAE rats also exhibited changes in endocannabinoid levels as shown for CB1 receptors. Anandamide and 2-arachidonoylglycerol levels decreased in motor related regions (striatum, midbrain) but also in other brain regions, although the pattern of changes for each endocannabinoid was different. Finally, we hypothesized that the elevation of the endocannabinoid activity, following inhibition of endocannabinoid uptake, might be beneficial in EAE rats. AM404, arvanil, and OMDM2 were effective to reduce the magnitude of the neurological impairment in EAE rats, whereas VDM11 did not produce any effect. The beneficial effects of AM404 were reversed by blocking TRPV1 receptors with capsazepine, but not by blocking CB1 receptors with SR141716, thus indicating the involvement of endovanilloid mechanisms in these effects. However, a role for CB1 receptors is supported by additional data showing that CP55,940 delayed EAE progression. In summary, our data suggest that reduction of endocannabinoid signaling is associated with the development of EAE in rats. We have also proved that the reduction of CB1 receptors observed in these rats is corrected following treatment with a compound used in EAE such as rolipram. In addition, the direct or indirect activation of vanilloid or cannabinoid receptors may reduce the neurological impairment experienced by EAE rats, although the efficacy of the different compounds examined seems to be determined by their particular pharmacodynamic and pharmacokinetic characteristics.

Survey on cannabis use in Parkinson's disease: subjective improvement of motor symptoms.

An anonymous questionnaire sent to all patients attending the Prague Movement Disorder Centre revealed that 25% of 339 respondents had taken cannabis and 45.9% of these described some form of benefit.