Ubiquitination increases parkin activity to promote autophagic α-synuclein clearance

Nilotinib Effects in Parkinson's disease and Dementia with Lewy bodies

BACKGROUND

We evaluated the effects of low doses of the tyrosine kinase Abelson (Abl) inhibitor Nilotinib, on safety and pharmacokinetics in Parkinson's disease dementia or dementia with Lewy bodies.

OBJECTIVES

The primary outcomes of this study were safety and tolerability; pharmacokinetics and target engagement were secondary, while clinical outcomes were exploratory.

METHODS

Twelve subjects were randomized into 150 mg (n = 5) or 300 mg (n = 7) groups and received Nilotinib orally every day for 24 weeks.

RESULTS

This study shows that 150 mg and 300 mg doses of Nilotinib appear to be safe and tolerated in subjects with advanced Parkinson's disease. Nilotinib is detectable in the cerebrospinal fluid (CSF) and seems to engage the target Abl. Motor and cognitive outcomes suggest a possible beneficial effect on clinical outcomes. The CSF levels of homovanillic acid are significantly increased between baseline and 24 weeks of treatment. Exploratory CSF biomarkers were measured.

CONCLUSIONS

This small proof-of-concept study lacks a placebo group and participants were not homogenous, resulting in baseline differences between and within groups. This limits the interpretations of the biomarker and clinical data, and any conclusions should be drawn cautiously. Nonetheless, the collective observations suggest that it is warranted to evaluate the safety and efficacy of Nilotinib in larger randomized, double-blind, placebo-controlled trials.

Parkin Modulates Endosomal Organization and Function of the Endo-Lysosomal Pathway

Mutations in PARK2 (parkin), which encodes Parkin protein, an E3 ubiquitin ligase, are associated with autosomal recessive early-onset Parkinson's disease (PD). While several studies implicated Parkin in the regulation of mitophagy and proteasomal degradation, the precise mechanism leading to neurodegeneration upon Parkin loss of function remains incompletely understood. In this study, we found that Parkin modulates the endocytic pathway through the regulation of endosomal structure and function. We showed that loss of Parkin function led to decreased endosomal tubulation and membrane association of vesicle protein sorting 35 (VPS35) and sorting nexin 1 (SNX1), as well as decreased mannose 6 phosphate receptor (M6PR), suggesting the impairment of retromer pathway in Parkin-deficient cells. We also found increased formation of intraluminal vesicles coupled with enhanced release of exosomes in the presence of mutant Parkin. To elucidate the molecular mechanism of these alterations in the endocytic pathway in Parkin-deficient cells, we found that Parkin regulates the levels and activity of Rab7 by promoting its ubiquitination on lysine 38 residue. Both endogenous Rab7 in Parkin-deficient cells and overexpressed K38 R-Rab7 mutant displayed decreased effector binding and membrane association. Furthermore, overexpression of K38R-Rab7 in HEK293 cells phenocopied the increased secretion of exosomes observed in Parkin-deficient cells, suggesting that Rab7 deregulation may be at least partially responsible for the endocytic phenotype observed in Parkin-deficient cells. These findings establish a role for Parkin in regulating the endo-lysosomal pathway and retromer function and raise the possibility that alterations in these pathways contribute to the development of pathology in Parkin-linked Parkinson's disease.

Carnosic acid protects SH-SY5Y cells against 6-hydroxydopamine-induced cell death through upregulation of parkin pathway

Parkin is a Parkinson's disease (PD)-linked gene that plays an important role in the ubiquitin-proteasome system (UPS). This study explored whether carnosic acid (CA) from rosemary protects against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity via upregulation of parkin in vivo and in vitro. We found that the reduction in proteasomal activity by 6-OHDA was attenuated in SH-SY5Y cells pretreated with 1 μM CA. Immunoblots showed that CA reversed the induction of ubiquitinated protein and the reduction of PTEN-induced putative kinase 1 (PINK1) and parkin protein in 6-OHDA-treated SH-SY5Y cells and rats. Moreover, in a transgenic OW13 Caenorhabditis elegans model of PD that expresses human α-synuclein in muscle cells, CA reduced α-synuclein accumulation in a dose-dependent manner. In cells pretreated with the proteasome inhibitor MG132, CA no longer reversed the 6-OHDA-mediated induction of cleavage of caspase 3 and poly(ADP)-ribose polymerase and no longer reversed the suppression of proteasome activity. When parkin expression was silenced by use of small interfering RNA, the ability of CA to inhibit apoptosis and induce proteasomal activity was significantly reduced. The reduction in 6-OHDA-induced neurotoxicity by CA was associated with the induction of parkin, which in turn upregulated the UPS and then decreased cell death.

Carnosic Acid Attenuates 6-Hydroxydopamine-Induced Neurotoxicity in SH-SY5Y Cells by Inducing Autophagy Through an Enhanced Interaction of Parkin and Beclin1

Enhanced removal of abnormal protein aggregates or injured organelles through autophagy is related to neuroprotection in Parkinson's disease. In this study, we explored whether the induction of autophagy is associated with the neuroprotection of rosemary carnosic acid (CA) against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in SH-SY5Y cells. The results indicated that cells treated with CA had increased protein levels of parkin and autophagy-related markers, including phosphatidylinositol 3-kinase p100, Beclin1, autophagy-related gene 7, and microtubule-associated protein 1 light chain 3-II, as well as enhanced formation of autophagic vacuoles. Treatment of cells with 6-OHDA decreased the levels of parkin and the autophagy markers, but CA pretreatment reversed these effects. However, wortmannin (an autophagosome formation blocker) pretreatment attenuated the effect of CA. After CA pretreatment, the induction of cleaved caspase 3, cleaved poly-ADP ribose polymerase, and nuclear condensation by 6-OHDA were alleviated. Both wortmannin and bafilomycin A1 (an autophagosome-lysosome fusion blocker) inhibited the anti-apoptosis effects of CA. Additionally, we performed immunoprecipitation with anti-parkin antibody and found that the interaction of parkin and Beclin1 protein was reduced by 6-OHDA but that this effect was reversed in cells pretreated with CA. Moreover, transfection of parkin siRNA in cells inhibited the ability of CA to alleviate 6-OHDA-decreased autophagy-related markers and nuclear condensation. In conclusion, CA protects against 6-OHDA-induced apoptosis by inducing autophagy through the interaction of parkin and Beclin1. These results provide a future strategy for use of CA in the prevention of Parkinson's disease.

Multiple viral introductions: molecular characterization of influenza B virus in Wenzhou, Zhejiang, China, from 2011 to 2014 based on hemagglutinin and neuraminidase genes

Influenza B virus is a major causative agent of respiratory disease in humans. Our study of an outbreak of influenza B virus in Wenzhou from 2011 to 2014 revealed that 163 (5.58 %) of 2921 samples were influenza B positive. Sequencing of the hemagglutinin and neuraminidase genes showed substitutions at the amino acid level. Phylogenetic analysis revealed co-circulation of the B/Victoria and B/Yamagata lineages in the Wenzhou area from 2011 to 2014. Multiple viral introductions from both Chinese and international sources played important roles in endemic co-circulation and transmission in coastal southeastern China.

UPS Activation in the Battle Against Aging and Aggregation-Related Diseases: An Extended Review

Aging is a biological process accompanied by gradual increase of damage in all cellular macromolecules, i.e., nucleic acids, lipids, and proteins. When the proteostasis network (chaperones and proteolytic systems) cannot reverse the damage load due to its excess as compared to cellular repair/regeneration capacity, failure of homeostasis is established. This failure is a major hallmark of aging and/or aggregation-related diseases. Dysfunction of the major cellular proteolytic machineries, namely the proteasome and the lysosome, has been reported during the progression of aging and aggregation-prone diseases. Therefore, activation of these pathways is considered as a possible preventive or therapeutic approach against the progression of these processes. This chapter focuses on UPS activation studies in cellular and organismal models and the effects of such activation on aging, longevity and disease prevention or reversal.

Genes associated with Parkinson's disease: regulation of autophagy and beyond

Substantial progress has been made in the genetic basis of Parkinson's disease (PD). In particular, by identifying genes that segregate with inherited PD or show robust association with sporadic disease, and by showing the same genes are found on both lists, we have generated an outline of the cause of this condition. Here, we will discuss what those genes tell us about the underlying biology of PD. We specifically discuss the relationships between protein products of PD genes and show that common links include regulation of the autophagy-lysosome system, an important way by which cells recycle proteins and organelles. We also discuss whether all PD genes should be considered to be in the same pathway and propose that in some cases the relationships are closer, whereas in other cases the interactions are more distant and might be considered separate. Beilina and Cookson review the links between genes for Parkinson's disease (red) and the autophagy-lysosomal system. They propose the hypothesis that many of the known PD genes can be assigned to pathways that affect (I) turnover of mitochondria via mitophagy (II) turnover of several vesicular structures via macroautophagy or chaperone-mediated autophagy or (III) general lysosome function. This article is part of a special issue on Parkinson disease.

Proteasome activation: An innovative promising approach for delaying aging and retarding age-related diseases

Aging is a natural process accompanied by a progressive accumulation of damage in all constituent macromolecules (nucleic acids, lipids and proteins). Accumulation of damage in proteins leads to failure of proteostasis (or vice versa) due to increased levels of unfolded, misfolded or aggregated proteins and, in turn, to aging and/or age-related diseases. The major cellular proteolytic machineries, namely the proteasome and the lysosome, have been shown to dysfunction during aging and age-related diseases. Regarding the proteasome, it is well established that it can be activated either through genetic manipulation or through treatment with natural or chemical compounds that eventually result to extension of lifespan or deceleration of the progression of age-related diseases. This review article focuses on proteasome activation studies in several species and cellular models and their effects on aging and longevity. Moreover, it summarizes findings regarding proteasome activation in the major age-related diseases as well as in progeroid syndromes.

Nilotinib and bosutinib modulate pre-plaque alterations of blood immune markers and neuro-inflammation in Alzheimer's disease models

Alzheimer's disease (AD) brains exhibit plaques and tangles in association with inflammation. The non-receptor tyrosine kinase Abl is linked to neuro-inflammation in AD. Abl inhibition by nilotinib or bosutinib facilitates amyloid clearance and may decrease inflammation. Transgenic mice that express Dutch, Iowa and Swedish APP mutations (TgAPP) and display progressive Aβ plaque deposition were treated with tyrosine kinase inhibitors (TKIs) to determine pre-plaque effects on systemic and CNS inflammation using milliplex® ELISA. Plaque Aβ was detected at 4months in TgAPP and pre-plaque intracellular Aβ accumulation (2.5months) was associated with changes of cytokines and chemokines prior to detection of glial changes. Plaque formation correlated with increased levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-1α, IL-1β) and markers of immunosuppressive and adaptive immunity, including, IL-4, IL-10, IL-2, IL-3, Vascular Endothelial Growth Factor (VEGF) and IFN-γ. An inverse relationship of chemokines was observed as CCL2 and CCL5 were lower than WT mice at 2months and significantly increased after plaque appearance, while soluble CX3CL1 decreased. A change in glial profile was only robustly detected at 6months in Tg-APP mice and TKIs reduced astrocyte and dendritic cell number with no effects on microglia, suggesting alteration of brain immunity. Nilotinib decreased blood and brain cytokines and chemokines and increased CX3CL1. Bosutinib increased brain and blood IL-10 and CX3CL1, suggesting a protective role for soluble CX3CL1. Taken together these data suggest that TKIs regulate systemic and CNS immunity and may be useful treatments in early AD through dual effects on amyloid clearance and immune modulation.

Pathologic and therapeutic implications for the cell biology of parkin

Mutations in the E3 ligase parkin are the most common cause of autosomal recessive Parkinson's disease (PD), but it is believed that parkin dysfunction may also contribute to idiopathic PD. Since its discovery, parkin has been implicated in supporting multiple neuroprotective pathways, many revolving around the maintenance of mitochondrial health quality control and governance of cell survival. Recent advances across the structure, biochemistry, and cell biology of parkin have provided great insights into the etiology of parkin-linked and idiopathic PD and may ultimately generate novel therapeutic strategies to slow or halt disease progression. This review describes the various pathways in which parkin acts and the mechanisms by which parkin may be targeted for therapeutic intervention. This article is part of a Special Issue entitled 'Neuronal Protein'.

Regulation of the Tumor-Suppressor Function of the Class III Phosphatidylinositol 3-Kinase Complex by Ubiquitin and SUMO

The occurrence of cancer is often associated with a dysfunction in one of the three central membrane-involution processes—autophagy, endocytosis or cytokinesis. Interestingly, all three pathways are controlled by the same central signaling module: the class III phosphatidylinositol 3-kinase (PI3K-III) complex and its catalytic product, the phosphorylated lipid phosphatidylinositol 3-phosphate (PtdIns3P). The activity of the catalytic subunit of the PI3K-III complex, the lipid-kinase VPS34, requires the presence of the membrane-targeting factor VPS15 as well as the adaptor protein Beclin 1. Furthermore, a growing list of regulatory proteins associates with VPS34 via Beclin 1. These accessory factors define distinct subunit compositions and thereby guide the PI3K-III complex to its different cellular and physiological roles. Here we discuss the regulation of the PI3K-III complex components by ubiquitination and SUMOylation. Especially Beclin 1 has emerged as a highly regulated protein, which can be modified with Lys11-, Lys48- or Lys63-linked polyubiquitin chains catalyzed by distinct E3 ligases from the RING-, HECT-, RBR- or Cullin-type. We also point out other cross-links of these ligases with autophagy in order to discuss how these data might be merged into a general concept.

Models of α-synuclein aggregation in Parkinson's disease

Parkinson's disease (PD) is not only characterized by motor disturbances but also, by cognitive, sensory, psychiatric and autonomic dysfunction. It has been proposed that some of these symptoms might be related to the widespread pathology of α-synuclein (α-syn) aggregation in different nuclei of the central and peripheral nervous system. However, the pathogenic formation of α-syn aggregates in different brain areas of PD patients is poorly understood. Most experimental models of PD are valuable to assess specific aspects of its pathogenesis, such as toxin-induced dopaminergic neurodegeneration. However, new models are required that reflect the widespread and progressive formation of α-syn aggregates in different brain areas. Such α-syn aggregation is induced in only a few animal models, for example perikaryon inclusions are found in rats administered rotenone, aggregates with a neuritic morphology develop in mice overexpressing either mutated or wild-type α-syn, and in Smad3 deficient mice, aggregates form extensively in the perikaryon and neurites of specific brain nuclei. In this review we focus on α-syn aggregation in the human disorder, its genetics and the availability of experimental models. Indeed, evidences show that dopamine (DA) metabolism may be related to α-syn and its conformational plasticity, suggesting an interesting link between the two pathological hallmarks of PD: dopaminergic neurodegeneration and Lewy body (LB) formation.

Ubiquitin pathways in neurodegenerative disease

Control of proper protein synthesis, function, and turnover is essential for the health of all cells. In neurons these demands take on the additional importance of supporting and regulating the highly dynamic connections between neurons that are necessary for cognitive function, learning, and memory. Regulating multiple unique synaptic protein environments within a single neuron while maintaining cell health requires the highly regulated processes of ubiquitination and degradation of ubiquitinated proteins through the proteasome. In this review, we examine the effects of dysregulated ubiquitination and protein clearance on the handling of disease-associated proteins and neuronal health in the most common neurodegenerative diseases.

Parkin-mediated reduction of nuclear and soluble TDP-43 reverses behavioral decline in symptomatic mice

The transactivation DNA-binding protein (TDP)-43 binds to thousands of mRNAs, but the functional outcomes of this binding remain largely unknown. TDP-43 binds to Park2 mRNA, which expresses the E3 ubiquitin ligase parkin. We previously demonstrated that parkin ubiquitinates TDP-43 and facilitates its translocation from the nucleus to the cytoplasm. Here we used brain penetrant tyrosine kinase inhibitors (TKIs), including nilotinib and bosutinib and showed that they reduce the level of nuclear TDP-43, abrogate its effects on neuronal loss, and reverse cognitive and motor decline. Nilotinib decreased soluble and insoluble TDP-43, while bosutinib did not affect the insoluble level. Parkin knockout mice exhibited high levels of endogenous TDP-43, while nilotinib and bosutinib did not alter TDP-43, underscoring an indispensable role for parkin in TDP-43 sub-cellular localization. These data demonstrate a novel functional relationship between parkin and TDP-43 and provide evidence that TKIs are potential therapeutic candidates for TDP-43 pathologies.

Tyrosine Kinase Inhibition Regulates Early Systemic Immune Changes and Modulates the Neuroimmune Response in α-Synucleinopathy

Objectives

Neuro-inflammation is common in α-Synucleinopathies and Tauopathies; and evidence suggests a link between the tyrosine kinase Abl and neurodegeneration. Abl upregulates α-Synuclein and promotes Tau hyper-phosphorylation (p-Tau), while Abl inhibitors facilitate autophagic clearance.

Methods

A model of α-Synucleinopathy harboring human mutant A53T α-Synuclein and exhibits concomitant increase in murine p-Tau was used to determine the immunological response to Abl inhibition.

Results

Age-dependent alterations of brain immunity, including loss of IL-10 and decreased levels of IL-2 and IL-3 were observed in old A53T mice. Brain CCL2 and CCL5 were decreased, but CX3CL1 remained constantly elevated. Young A53T mice exhibited differential systemic and central immune profiles in parallel with increased blood markers of adaptive immunity, suggesting an early systemic immune response. Tyrosine kinase inhibitors (TKIs), including nilotinib and bosutinib reduced brain and peripheral α-Synuclein and p-Tau and modulated blood immunological responses. TKIs did not affect brain IL-10, but they changed the levels of all measured blood immune markers, except CX3CL1. TKIs altered microglia morphology and reduced the number of astrocyte and dendritic cells, suggesting beneficial regulation of microglia.

Conclusions

These data indicate that tyrosine kinase inhibition affects neuro-inflammation via early changes of the peripheral immune profile, leading to modulation of the neuro-immune response to α-Synuclein and p-Tau.