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Paraneoplastic CDR2 and CDR2L antibodies affect Purkinje cell calcium homeostasis.

ABSTRACT: Paraneoplastic cerebellar degeneration (PCD) is characterized by loss of Purkinje cells (PCs) associated with progressive pancerebellar dysfunction in the presence of onconeural Yo antibodies. These antibodies recognize the cerebellar degeneration-related antigens CDR2 and CDR2L. Response to PCD therapy is disappointing due to limited understanding of the neuropathological mechanisms. Here, we report the pathological role of CDR antibodies on the calcium homeostasis in PCs. We developed an antibody-mediated PCD model based on co-incubation of cerebellar organotypic slice culture with human patient serum or rabbit CDR2 and CDR2L antibodies. The CDR antibody-induced pathology was investigated by high-resolution multiphoton imaging and biochemical analysis. Both human and rabbit CDR antibodies were rapidly internalized by PCs and led to reduced immunoreactivity of calbindin D28K (CB) and L7/Pcp-2 as well as reduced dendritic arborizations in the remaining PCs. Washout of the CDR antibodies partially recovered CB immunoreactivity, suggesting a transient structural change in CB calcium-binding site. We discovered that CDR2 and CB co-immunoprecipitate. Furthermore, the expression levels of voltage-gated calcium channel Cav2.1, protein kinase C gamma and calcium-dependent protease, calpain-2, were increased after CDR antibody internalization. Inhibition of these signaling pathways prevented or attenuated CDR antibody-induced CB and L7/Pcp-2 immunoreactivity loss, morphological changes and increased protein expression. These results signify that CDR antibody internalization causes dysregulation of cell calcium homeostasis. Hence, drugs that modulate these events may represent novel neuroprotective therapies that limit the damaging effects of CDR antibodies and prevent PC neurodegeneration.

SUBMITTER: Schubert M

PROVIDER: S-EPMC4231287 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background and objectiveParaneoplastic neurological syndromes (PNS) are a group of rare syndromes associated with immunopathological process and tumors. Paraneoplastic autoantibodies are important for the diagnosis of PNS and for searching for underlying tumors. With the development of detection methods and discovery of new autoantibodies, the 2004 guidelines on PNS have recently been updated by a worldwide PNS-Care expert group. For clinicians, proper testing methods and testing results explanation are important for the diagnosis and treatment of PNS. This review aims to review the detection of paraneoplastic autoantibodies and the significance of testing results.MethodsWe summarize the studies on detection methods, association of autoantibodies and PNS or tumors, particularly the guidelines of PNS.Key content and findingsAntibodies are divided into 3 groups in the context of PNS according to the frequency of cancer association regardless of their eventual pathogenic effect. Instead of well-characterized antibodies and partially-characterized antibodies, high-risk antibodies, intermediate risk antibodies and lower risk antibodies were applied. According to the location of recognized antigens, these autoantibodies are divided as anti-intracellular antigen antibodies and neuronal surface antibodies (NSAbs). Tissue-based assays is recommended as screening method for paraneoplastic antibodies. Moreover, this method is helpful to discover new autoantibodies. A combination of a screening method [tissue-based assays (TBA)] and a confirmatory test [immunoblot and cell-based assay (CBA)] can improve sensitivity and specificity of the tests. Many PNSs are associated with specific antineuronal antibodies, but there is considerable diversity. Some autoantibodies are markers of specific neurological syndromes. Paraneoplastic antibodies are often specific for the PNS-associated tumor rather than for a particular neurological syndrome.ConclusionsDiagnosis of PNS depends on integrated analysis of clinical manifestations and auxiliary examinations. During diagnosis, selection of candidate antibodies for testing is challenging due to the varying clinical phenotypes and tumors associated with a given antibody. Broad antibody panels are more likely to capture causative antibodies and should be considered. According to different subtypes of autoantibodies, specific tumors or PNS should be considered. However, antibody titers, including cerebrospinal fluid (CSF) titers, should not be the primary driver of treatment decisions.

Project description:ImportanceLittle is known of glutamic acid decarboxylase antibodies (GAD-abs) in the paraneoplastic context. Clinical recognition of such cases will lead to prompt tumor diagnosis and appropriate treatment.ObjectiveTo report the clinical and immunological features of patients with paraneoplastic neurological syndromes (PNS) and GAD-abs.Design, setting, and participantsRetrospective case series study and immunological investigations conducted in February 2014 in a center for autoimmune neurological disorders. Fifteen cases with GAD65-abs evaluated between 1995 and 2013 who fulfilled criteria of definite or possible PNS without concomitant onconeural antibodies were included in this study.Main outcomes and measuresAnalysis of the clinical records of 15 patients and review of 19 previously reported cases. Indirect immunofluorescence with rat hippocampal neuronal cultures and cell-based assays with known neuronal cell-surface antigens were used. One hundred six patients with GAD65-abs and no cancer served as control individuals.ResultsEight of the 15 patients with cancer presented as classic paraneoplastic syndromes (5 limbic encephalitis, 1 paraneoplastic encephalomyelitis, 1 paraneoplastic cerebellar degeneration, and 1 opsoclonus-myoclonus syndrome). When compared with the 106 non-PNS cases, those with PNS were older (median age, 60 years vs 48 years; P = .03), more frequently male (60% vs 13%; P < .001), and had more often coexisting neuronal cell-surface antibodies, mainly against γ-aminobutyric acid receptors (53% vs 11%; P < .001). The tumors more frequently involved were lung (n = 6) and thymic neoplasms (n = 4). The risk for an underlying tumor was higher if the presentation was a classic PNS, if it was different from stiff-person syndrome or cerebellar ataxia (odds ratio, 10.5; 95% CI, 3.2-34.5), or if the patient had coexisting neuronal cell-surface antibodies (odds ratio, 6.8; 95% CI, 1.1-40.5). Compared with the current series, the 19 previously reported cases had more frequent stiff-person syndrome (74% vs 13%; P = .001) and better responses to treatment (79% vs 27%; P = .005). Predictors of improvement in the 34 patients (current and previously reported) included presentation with stiff-person syndrome and the presence of a thymic tumor.Conclusions and relevancePatients with GAD-abs must be screened for an underlying cancer if they have clinical presentations different from those typically associated with this autoimmunity or develop classic PNS. The risk for cancer increases with age, male sex, and the presence of coexisting neuronal cell-surface antibodies.

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Paraneoplastic CDR2 and CDR2L antibodies affect Purkinje cell calcium homeostasis.

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