Effects of selegiline on neuronal autophagy involving α-synuclein secretion.

Cell-to-cell transmission of α-synuclein (α-syn) pathology underlies the spread of neurodegeneration in Parkinson's disease. α-Syn secretion is an important factor in the transmission of α-syn pathology. However, it is unclear how α-syn secretion is therapeutically modulated. Here, we investigated effects of monoamine oxidase (MAO)-B inhibitor selegiline on α-syn secretion. Treatment with selegiline promoted α-syn secretion in mouse primary cortical neuron cultures, and this increase was kept under glial cell-eliminated condition by Ara-C. Selegiline-induced α-syn secretion was blocked by cytosolic Ca2+ chelator BAPTA-AM in primary neurons. Selegiline-induced α-syn secretion was retained in MAOA siRNA knockdown, whereas it was abrogated by ATG5 knockdown in SH-SY5Y cells. Selegiline increased LC3-II generation with a reduction in intracellular p62/SQSTM1 levels in primary neurons. The increase in LC3-II generation was blocked by co-treatment with BAPTA-AM in primary neurons. Additionally, fractionation experiments showed that selegiline-induced α-syn secretion occurred in non-extracellular vesicle fractions of primary neurons and SH-SY5Y cells. Collectively, these findings show that selegiline promotes neuronal autophagy involving secretion of non-exosomal α-syn via a change of cytosolic Ca2+ levels.

Neuronal activity promotes secretory autophagy for the extracellular release of α-synuclein.

Extracellular secretion is an essential mechanism for α-synuclein (α-syn) proteostasis. Although it has been reported that neuronal activity affects α-syn secretion, the underlying mechanisms remain unclear. Here, we investigated the autophagic processes that regulate the physiological release of α-syn in mouse primary cortical neurons and SH-SY5Y cells. Stimulating neuronal activity with glutamate or depolarization with high KCl enhanced α-syn secretion. This glutamate-induced α-syn secretion was blocked by a mixture of NMDA receptor antagonist AP5 and AMPA receptor antagonist NBQX, as well as by cytosolic Ca2+ chelator BAPTA-AM. Additionally, mTOR inhibitor rapamycin increased α-syn and p62/SQSTM1 (p62) secretion, and this effect of rapamycin was reduced in primary cortical neurons deficient in the autophagy regulator beclin 1 (derived from BECN1+/- mice). Glutamate-induced α-syn and p62 secretion was suppressed by the knockdown of ATG5, which is required for autophagosome formation. Glutamate increased LC3-II generation and decreased intracellular p62 levels, and the increase in LC3-II levels was blocked by BAPTA-AM. Moreover, glutamate promoted co-localization of α-syn with LC3-positive puncta, but not with LAMP1-positive structures in the neuronal somas. Glutamate-induced α-syn and p62 secretion were also reduced by the knockdown of RAB8A, which is required for autophagosome fusion with the plasma membrane. Collectively, these findings suggest that stimulating neuronal activity mediates autophagic α-syn secretion in a cytosolic Ca2+-dependent manner, and autophagosomes may participate in autophagic secretion by functioning as α-syn carriers.

[A case of anti-myelin oligodendrocyte glycoprotein antibody-positive multiphasic disseminated encephalomyelitis showing significant recovery after immunoadsorption plasmapheresis].

The patient is an 18-year-old female. She had a history of acute disseminated encephalomyelitis at the age of 6 and 7. She visited our hospital due to acute disturbance of consciousness, quadriplegia, and numbness of left upper and lower extremities. Brain MRI showed multiple DWI/FLAIR high-signal lesions in the bilateral cerebral hemispheres, cerebellum, and brainstem. Qualitative test indicated that serum anti-MOG antibodies was positive, and she was diagnosed with anti-MOG antibody-positive polyphasic disseminated encephalomyelitis. Intravenous mPSL pulse therapy was performed twice, but the symptoms worsened. As a second line treatment, plasma exchange was started. However, she developed transfusion related acute lung injury. Alternatively, she was treated with immunoadsorption plasmapheresis. Her symptoms were significantly improved. This case seems to be valuable because there are few reports showing effectiveness of immunoadsorption therapy on anti-MOG antibody-related diseases, especially for polyphasic disseminated encephalomyelitis.

Whole-exome sequencing and human leukocyte antigen analysis in familial myasthenia gravis with thymoma: Case report and literature review.

Myasthenia gravis (MG) is an autoimmune disease characterized by impaired neurotransmission at the neuromuscular junction. MG is generally non-inherited but is rarely inherited. Here, we report two patients with MG in the same pedigree: a 62-year-old Japanese man and his 46-year-old daughter who were positive for anti-acetylcholine receptor antibodies and had thymoma. We performed whole-exome sequencing (WES) and human leukocyte antigen (HLA) analyses to investigate the genetic contribution to familial onset. WES analysis of both patients showed no known variations in candidate genes for familial MG, and HLA analysis failed to detect HLA haplotypes seen in early-onset and late-onset MG. These findings suggest the presence of an unknown genetic background. Previous genetic studies on familial MG have identified ENOX1 and IFNGR1 as candidate genes in patients without thymoma, whereas no studies have identified candidate genes in patients with thymoma. To explore causative genes, it may be necessary to consider whether the genetic background differs between patients with and without thymoma in familial autoimmune MG.

Monoamine Oxidase-B Inhibition Facilitates α-Synuclein Secretion In Vitro and Delays Its Aggregation in rAAV-Based Rat Models of Parkinson's Disease.

Cell-to-cell transmission of α-synuclein (α-syn) pathology is considered to underlie the spread of neurodegeneration in Parkinson's disease (PD). Previous studies have demonstrated that α-syn is secreted under physiological conditions in neuronal cell lines and primary neurons. However, the molecular mechanisms that regulate extracellular α-syn secretion remain unclear. In this study, we found that inhibition of monoamine oxidase-B (MAO-B) enzymatic activity facilitated α-syn secretion in human neuroblastoma SH-SY5Y cells. Both inhibition of MAO-B by selegiline or rasagiline and siRNA-mediated knock-down of MAO-B facilitated α-syn secretion. However, TVP-1022, the S-isomer of rasagiline that is 1000 times less active, failed to facilitate α-syn secretion. Additionally, the MAO-B inhibition-induced increase in α-syn secretion was unaffected by brefeldin A, which inhibits endoplasmic reticulum (ER)/Golgi transport, but was blocked by probenecid and glyburide, which inhibit ATP-binding cassette (ABC) transporter function. MAO-B inhibition preferentially facilitated the secretion of detergent-insoluble α-syn protein and decreased its intracellular accumulation under chloroquine-induced lysosomal dysfunction. Moreover, in a rat model (male Sprague Dawley rats) generated by injecting recombinant adeno-associated virus (rAAV)-A53T α-syn, subcutaneous administration of selegiline delayed the striatal formation of Ser129-phosphorylated α-syn aggregates, and mitigated loss of nigrostriatal dopaminergic neurons. Selegiline also delayed α-syn aggregation and dopaminergic neuronal loss in a cell-to-cell transmission rat model (male Sprague Dawley rats) generated by injecting rAAV-wild-type α-syn and externally inoculating α-syn fibrils into the striatum. These findings suggest that MAO-B inhibition modulates the intracellular clearance of detergent-insoluble α-syn via the ABC transporter-mediated non-classical secretion pathway, and temporarily suppresses the formation and transmission of α-syn aggregates.SIGNIFICANCE STATEMENT The identification of a neuroprotective agent that slows or stops the progression of motor impairments is required to treat Parkinson's disease (PD). The process of α-synuclein (α-syn) aggregation is thought to underlie neurodegeneration in PD. Here, we demonstrated that pharmacological inhibition or knock-down of monoamine oxidase-B (MAO-B) in SH-SY5Y cells facilitated α-syn secretion via a non-classical pathway involving an ATP-binding cassette (ABC) transporter. MAO-B inhibition preferentially facilitated secretion of detergent-insoluble α-syn protein and reduced its intracellular accumulation under chloroquine-induced lysosomal dysfunction. Additionally, MAO-B inhibition by selegiline protected A53T α-syn-induced nigrostriatal dopaminergic neuronal loss and suppressed the formation and cell-to-cell transmission of α-syn aggregates in rat models. We therefore propose a new function of MAO-B inhibition that modulates α-syn secretion and aggregation.

Assessment of clinical factors affecting outcome of myasthenia gravis.

INTRODUCTION/AIMS: In myasthenia gravis (MG) therapy, achieving Myasthenia Gravis Foundation of America minimal manifestation (MM) or better status is proposed as a desirable target. However, this level of control is often not achieved and clinical factors affecting prognosis remain unclear. METHODS: Participants were 104 consecutive patients with MG who visited Osaka Medical College Hospital. We retrospectively assessed the association of clinical and laboratory features at baseline with prognosis. Eighty patients who achieved MM or better status were classified as the good outcome group and the remaining 24 patients were classified as the poor outcome group. RESULTS: The rate of dysphagia at baseline was significantly higher in the poor outcome group than in the good outcome group (P = .002). The levels of serum total protein and albumin at baseline were both significantly lower in the poor outcome group than in the good outcome group (P = .036 and P = .014, respectively). In addition, Controlling Nutritional Status scores at baseline were significantly higher in the poor outcome group than in the good outcome group (P = .043). Multivariate analysis using a Cox proportional hazards model showed that dysphagia (hazard ratio [HR], 6.92; 95% confidence interval [CI], 1.49-40.31) and hypoalbuminemia (HR, 2.57; 95% CI, 1.04-6.57) at baseline were risk factors that predicted prognosis. DISCUSSION: These findings suggest that dysphagia and hypoalbuminemia at baseline are associated with outcomes and are predictive risk factors for poorer outcomes in patients with MG.

Exploration of pathomechanism using comprehensive analysis of serum cytokines in polymyositis/dermatomyositis-interstitial lung disease.

OBJECTIVES: To elucidate the serum cytokine profile and address the pathomechanism of interstitial lung disease (ILD) complicated with PM/DM. METHODS: Forty patients with PM/DM-ILD were enrolled, and principal components analysis and cluster analysis were performed to classify patients into subgroups. Additionally, we compared cytokine profiles between the survivors and dead patients and between anti-melanoma differentiation-associated gene 5 antibody- and anti-aminoacyl tRNA synthetase antibody-positive ILD patients. We also examined the association of various cytokines with disease activity indicators and prognosis of ILD. RESULTS: The principal components analysis data allowed classification of the cytokine profile into three groups: group 1, neutrophilic and M1-macrophage-driven cytokines; group 2, type 1 Th cell-driven and M2-macrophage-induced cytokines; and group 3, M2-macrophage-driven cytokines. Cluster analysis showed the presence of PM/DM-ILD patient groups with high or low levels of total cytokines. Ninety percent of patients who died of ILD were included in clusters with high cytokine levels. Serum cytokine levels of all groups were significantly higher in the anti-melanoma differentiation-associated gene 5 antibody-positive patients than in the anti-aminoacyl tRNA synthetase antibody-positive patients. Groups 1 and 2 significantly correlated with known factors for poor prognosis, such as serum ferritin levels and alveolar-arterial oxygen difference. Serum cytokine levels of patients in group 1 were significantly higher initially and at 2 and 4 weeks in those who died. CONCLUSION: These findings suggested that the activation of monocytes, macrophages and type 1 Th cells, and neutrophils play roles in the pathomechanism of PM/DM-ILD, and group 1 cytokines could be useful biomarkers for predicting prognosis of PM/DM-ILD.

[An autopsy case of nivolumab-induced myasthenia gravis and myositis].

An 84-year-old woman developed blepharoptosis, diplopia, weakness of extremities, and dysphagia with elevation of serum CK levels after treatment with nivolumab against renal cell carcinoma. 3 Hz repetitive stimulation showed waning in the trapezius muscle, leading to the diagnosis of myasthenia gravis. Laboratory examination showed that anti-acetylcholine receptor antibody was negative. We performed IVIg and steroid therapy. However, her symptoms did not improve, and she died of respiratory failure, although serum CK levels ameliorated to the normal range. The results of autopsy showed atrophy of muscle fibers and massive infiltration of inflammatory cells in the endomysium of the iliopsoas muscle and diaphragm, indicating occurrence of myositis. Immunohistochemical analysis showed that CD8-positive T cells mainly infiltrates in the endomysium with a small number of CD4-potive T cells. Here, we report an autopsy case of nivolumab-induced myasthenia gravis and myositis.

Efficacy and safety of oral high-trough level tacrolimus in acute/subacute interstitial pneumonia with dermatomyositis.

OBJECTIVES: We assessed the efficacy and safety of combination therapy with glucocorticoids and high-trough level tacrolimus (TAC) for the treatment of acute/subacute interstitial pneumonia (A/SIP) in patients with dermatomyositis (DM). METHODS: Eleven DM-A/SIP patients were enrolled. The combination therapy with glucocorticoids and TAC was started as early as possible after DM-A/SIP was diagnosed. We monitored the trough concentration of TAC. In the initial 3 months, we maintained the trough concentration of TAC at relatively high levels within a range of 15-20 ng/mL. Then, we decreased the TAC doses stepwise to keep the trough concentration at 10-15 ng/mL in the next 3 months and 5-10 ng/mL as a maintenance dose. RESULTS: Seven patients had clinically amyopathic DM. Six patients were positive for anti-aminoacyl-tRNA synthetase antibody and two were positive for anti-melanoma differentiation-associated gene 5 antibody. Ten patients survived for the period of the 24-week follow up. One patient died under a tentative diagnosis of viral encephalitis at 4 months after the treatment. In the 10 surviving patients, interstitial pneumonia improved in eight patients and was not worse in two patients. Clinical examinations, including the Krebs von den Lungen-6 levels, % forced vital capacity, and chest computed tomography score, were significantly improved by this combination therapy. Although grade 1 and 2 renal damage occurred in 4 and 2 patients, respectively. CONCLUSIONS: The present findings suggest that early therapeutic intervention by a combination with glucocorticoids and initial high-trough level TAC is effective for DM-A/SIP although consideration of the risks of infection and renal damage is required.

Eosinophilic granulomatosis with polyangiitis complicated by subarachnoid hemorrhage and coronary vasculitis: a case report and review of the literature.

Eosinophilic granulomatosis with polyangiitis (EGPA) is characterized by necrotizing vasculitis of small-sized vessels with extravascular granulomas and eosinophilic infiltration. The case of a 48-year-old Japanese woman with EGPA, who presented concurrently with subarachnoid hemorrhage (SAH) and coronary vasculitis, is reported. She initially presented with bronchial asthma, and then 8 months later she developed various symptoms caused by systemic eosinophilic vasculitis and was admitted to our hospital. Three days after admission, she started oral corticosteroid therapy, and her 2009 Five-Factor Score (FFS) was 0. However, she developed an SAH, followed by coronary vasculitis 1 day later. With extensive treatment with a combination of betamethasone, cyclophosphamide, intravenous immunoglobulin, and rituximab, her systemic vasculitis improved dramatically. This seems to be the first case of EGPA with SAH and coronary vasculitis. In previous reports of EGPA with SAH, 4 of 11 cases developed SAH as an exacerbation of systemic vasculitis during remission induction therapy. The present patient also had SAH during remission induction therapy. However, the period between bronchial asthma and SAH was only 8 months. This is the shortest among case reports of EGPA with SAH. In addition, the present patient rapidly developed coronary vasculitis. These findings suggest that EGPA causes SAH and coronary vasculitis as early complications of systemic vasculitis. In EGPA, it is necessary to pay careful attention to rapid changes of disease activity, even when the FFS indicates a good prognosis.

Mechanisms underlying extensive Ser129-phosphorylation in α-synuclein aggregates.

Parkinson's disease (PD) is characterized neuropathologically by intracellular aggregates of fibrillar α-synuclein, termed Lewy bodies (LBs). Approximately 90% of α-synuclein deposited as LBs is phosphorylated at Ser129 in brains with PD. In contrast, only 4% of total α-synuclein is phosphorylated at Ser129 in brains with normal individuals. It is unclear why extensive phosphorylation occurs in the pathological process of PD. To address this issue, we investigated a mechanism and role of Ser129-phosphorylation in regulating accumulation of α-synuclein. In CHO cells, the levels of Ser129-phosphorylated soluble α-synuclein were maintained constantly to those of total α-synuclein in intracellular and extracellular spaces. In SH-SY5Y cells and rat primary cortical neurons, mitochondrial impairment by rotenone or MPP+ enhanced Ser129-phosphorylation through increased influx of extracellular Ca2+. This elevation was suppressively controlled by targeting Ser129-phosphorylated α-synuclein to the proteasome pathway. Rotenone-induced insoluble α-synuclein was also targeted by Ser129-phosphoryation to the proteasome pathway. Experiments with epoxomicin and chloroquine showed that proteasomal targeting of insoluble Ser129-phosphorylated α-synuclein was enhanced under lysosome inhibition and it reduced accumulation of insoluble total α-synuclein. However, in a rat AAV-mediated α-synuclein overexpression model, there was no difference in the number of total α-synuclein aggregates between A53T mutant and A53T plus S129A double mutant α-synuclein, although Ser129-phosphorylated α-synuclein-positive aggregates were increased in rats expressing A53T α-synuclein. These findings suggest that Ser129-phosphorylation occurs against stress conditions, which increases influx of extracellular Ca2+, and it prevents accumulation of insoluble α-synuclein by evoking proteasomal clearance complementary to lysosomal one. However, Ser129-phosphorylation may provide an ineffective signal for degradation-resistant aggregates, causing extensive phosphorylation in aggregates.

Inflammatory Pseudotumor of the Brain Parenchyma with IgG4 Hypergammaglobulinemia.

A 58-year-old woman with a 1-month history of right hand clumsiness and speaking difficulty was admitted to our hospital. A neurological examination revealed sensory aphasia and right hemiparesis. Her laboratory tests showed elevated serum levels of IgG and IgG4, pancytopenia, and liver dysfunction. The results of the imaging studies of her abdomen were compatible with sclerosing cholangitis. Brain MRI showed extensive signal abnormalities in the left hemisphere on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images, extending from left internal capsule to the cerebral peduncle with an irregularly enhancing lesion in the left parietal lobe. A brain biopsy revealed lymphocyte and plasma cell infiltration and reactive gliosis. Most of the plasma cells were IgG positive; however, IgG4-positive plasma cells were sparsely observed. After the initiation of betamethasone treatment, her symptoms and the brain MRI abnormalities showed significant improvement. The brain biopsy results did not meet the current criteria of IgG4-related disease. This is the first reported case of a tumefactive lesion of the brain parenchyma with serum IgG4 elevation, which was responsive to steroid treatment. The accumulation of a greater number of reports on the pathological investigation of cases of possible IgG4-related disease may help to elucidate the exact role of IgG4 in IgG4-related disorders.

Sensitive western blotting for detection of endogenous Ser129-phosphorylated α-synuclein in intracellular and extracellular spaces.

α-Synuclein deposited in Lewy bodies, a pathological hallmark of Parkinson's disease (PD), is highly phosphorylated at serine 129 (Ser129). In contrast, there is very little Ser129-phosphorylated α-synuclein in the normal brains. This difference suggests that Ser129-phosphorylation is involved in neurodegenerative processes of PD. However, the role of this modification remains unclear. One limiting factor for relevant biochemical analyses is that it is difficult to detect endogenous Ser129-phosphorylated α-synuclein by western blotting, because α-synuclein monomers detached from the transferred membrane during incubation. Here, we reported that combination fixation of the transferred membrane with 4% paraformaldehyde and 0.01 ~ 0.1% glutaraldehyde produced an approximately 10-fold increase in the sensitivity for Ser129-phosphorylated α-synuclein monomers, allowing detection of endogenous proteins even in conditioned medium, human cerebrospinal fluid, and extracts from cell lines and human brain. This method may enable more detailed biochemical analyses for α-synuclein transmission between intra and extracellular spaces under physiological and pathological conditions.

Zonisamide attenuates α-synuclein neurotoxicity by an aggregation-independent mechanism in a rat model of familial Parkinson's disease.

The anti-epileptic agent zonisamide (ZNS) has been shown to exert protective effects in neurotoxin-based mouse models of Parkinson disease. However, it is unknown whether ZNS can attenuate toxicity of familial Parkinson's disease-causing gene products. In this study, we investigated the effects of ZNS on neurodegeneration induced by expression of A53T α-synuclein in the rat substantia nigra using a recombinant adeno-associated virus vector. Expression of A53T α-synuclein yielded severe loss of nigral dopamine neurons and striatal dopamine nerve terminals from 2 weeks to 4 weeks after viral injection. Oral administration of ZNS (40 mg/kg/day) significantly delayed the pace of degeneration at 4 weeks after viral injection as compared with the vehicle group. This effect lasted until 8 weeks after viral injection, the final point of observation. ZNS treatment had no impact on the survival of nigrostriatal dopamine neurons in rats expressing green fluorescent protein. Quantification of striatal Ser129-phosphorylated α-synuclein-positive aggregates showed that these aggregates rapidly formed from 2 weeks to 4 weeks after viral injection. This increase was closely correlated with loss of nigrostriatal dopamine neurons. However, ZNS treatment failed to alter the number of all striatal Ser129-phosphorylated α-synuclein-positive aggregates, including small dot-like and large round structures. The number of these aggregates was almost constant at 4 weeks and 8 weeks after viral injection, although ZNS persistently prevented loss of nigrostriatal dopamine neurons during this period. Also, ZNS treatment did not affect the number of striatal aggregates larger than 10 µm in diameter. These data show that ZNS attenuates α-synuclein-induced toxicity in a manner that is independent of the formation and maturation of α-synuclein aggregates in an in vivo model of familial Parkinson's disease, suggesting that ZNS may protect nigrostriatal dopamine neurons by modulating cellular damage or a cell death pathway commonly caused by neurotoxins and α-synuclein.

An elderly Japanese patient with adult-onset type II citrullinemia with a novel D493G mutation in the SLC25A13 gene.

Mutations in the SLC25A13 gene lead to neonatal intrahepatic cholestasis caused by citrin deficiency and/or adult-onset type II citrullinemia (CTLN2). A 62-year-old man presented with recurrent episodes of neuropsychiatric manifestations. On admission, he had disorientation and flapping tremor. Laboratory data showed hyperferritinemia in addition to postprandial hyperammonemia and citrullinemia. A liver biopsy specimen revealed moderate hemosiderin deposits and hepatocytes with macrovesicular fat droplets. Genetic analysis of the SLC25A13 gene identified the previously reported p.S225X mutation and a novel p.D493G mutation. Hyperferritinemia might also be a characteristic finding of CTLN2-related fatty changes of the liver.

A Japanese adult case of megalencephalic leukoencephalopathy with subcortical cysts with a good long-term prognosis.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a recently recognized neurological disease, and mutations in the MLC1 gene have been identified as the cause of the disorder. A 54-year-old Japanese woman with macrocephaly presented with progressive mental decline, gait disturbance due to spasticity and ataxia, and choreoathetotic movement in the left upper extremity. Brain magnetic resonance imaging (MRI) revealed characteristic subcortical cysts in addition to diffuse white matter involvement. Genetic analysis of the MLC1 gene identified an S93L mutation in a homozygous state. This case is particularly valuable because of the lack of knowledge on the long-term prognosis of MLC.

Authentically phosphorylated α-synuclein at Ser129 accelerates neurodegeneration in a rat model of familial Parkinson's disease.

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra (SN) and the appearance of fibrillar aggregates of insoluble α-synuclein (α-syn) called Lewy bodies (LBs). Approximately 90% of α-syn deposited in LBs is phosphorylated at serine 129 (Ser129). In contrast, only 4% of total α-syn is phosphorylated in normal brain, suggesting that accumulation of Ser129-phosphorylated α-syn is involved in the pathogenesis of PD. However, the role of Ser129 phosphorylation in α-syn neurotoxicity remains unclear. In this study, we coexpressed familial PD-linked A53T α-syn and G-protein-coupled receptor kinase 6 (GRK6) in the rat SN pars compacta using recombinant adeno-associated virus 2. Coexpression of these proteins yielded abundant Ser129-phosphorylated α-syn and significantly exacerbated degeneration of dopaminergic neurons when compared with coexpression of A53T α-syn and GFP. Immunohistochemical analysis revealed that Ser129-phosphorylated α-syn was preferentially distributed to swollen neurites. However, biochemical analysis showed that the increased expression of Ser129-phosphorylated α-syn did not promote accumulation of detergent-insoluble α-syn. Coexpression of catalytically inactive K215R mutant GRK6 failed to accelerate A53T α-syn-induced degeneration. Furthermore, introducing a phosphorylation-incompetent mutation, S129A, into A53T α-syn did not alter the pace of degeneration, even when GRK6 was coexpressed. Our study demonstrates that authentically Ser129-phosphorylated α-syn accelerates A53T α-syn neurotoxicity without the formation of detergent-insoluble α-syn, and suggests that the degenerative process could be constrained by inhibiting the kinase that phosphorylates α-syn at Ser129.

Phosphorylated alpha-synuclein at Ser-129 is targeted to the proteasome pathway in a ubiquitin-independent manner.

α-Synuclein (a-Syn) is a major component of fibrillar aggregates in Lewy bodies (LBs), a characteristic hallmark of Parkinson disease. Almost 90% of a-Syn deposited in LBs is phosphorylated at Ser-129. However, the role of Ser-129-phosphorylated a-Syn in the biogenesis of LBs remains unclear. Here, we investigated the metabolism of Ser-129-phosphorylated a-Syn. In SH-SY5Y cells, inhibition of protein phosphatase 2A/1 by okadaic acid, and inhibition of the proteasome pathway by MG132 or lactacystin accumulated Ser-129-phosphorylated a-Syn. However, these inhibitions did not alter the amounts of total a-Syn within the observation time. Inhibition of the autophagy-lysosome pathway by 3-methyladenine or chloroquine accumulated Ser-129-phosphorylated a-Syn in parallel to total a-Syn during longer incubations. Experiments using cycloheximide showed that Ser-129-phosphorylated a-Syn diminished rapidly (t(½) = 54.9 ± 6.4 min), in contrast to the stably expressed total a-Syn. The short half-life of Ser-129-phosphorylated a-Syn was blocked by MG132 to a greater extent than okadaic acid. In rat primary cortical neurons, either MG132, lactacystin, or okadaic acid accumulated Ser-129-phosphorylated a-Syn. Additionally, we did not find that phosphorylated a-Syn was ubiquitinated in the presence of proteasome inhibitors. These data show that Ser-129-phosphorylated a-Syn is targeted to the proteasome pathway in a ubiquitin-independent manner, in addition to undergoing dephosphorylation. The proteasome pathway may play a role in the biogenesis of Ser-129-phosphorylated a-Syn-rich LBs.

Mature glycosylation and trafficking of nicastrin modulate its binding to presenilins.

Nicastrin is an integral component of the high molecular weight presenilin complexes that control proteolytic processing of the amyloid precursor protein and Notch. We report here that nicastrin is most probably a type 1 transmembrane glycoprotein that is expressed at moderate levels in the brain and in cultured neurons. Immunofluorescence studies demonstrate that nicastrin is localized in the endoplasmic reticulum, Golgi, and a discrete population of vesicles. Glycosidase analyses reveal that endogenous nicastrin undergoes a conventional, trafficking-dependent maturation process. However, when highly expressed in transfected cells, there is a disproportionate accumulation of the endo-beta-N-acetylglucosaminidase H-sensitive, immature form, with no significant increase in the levels of the fully mature species. Immunoprecipitation revealed that presenilin-1 interacts preferentially with mature nicastrin, suggesting that correct trafficking and co-localization of the presenilin complex components are essential for activity. These findings demonstrate that trafficking and post-translational modifications of nicastrin are tightly regulated processes that accompany the assembly of the active presenilin complexes that execute gamma-secretase cleavage. These results also underscore the caveat that simple overexpression of nicastrin in transfected cells may result in the accumulation of large amounts of the immature protein, which is apparently unable to assemble into the active complexes capable of processing amyloid precursor protein and Notch.