Dataset Information

The gamma chain subunit of Fc receptors is required for alpha-synuclein-induced pro-inflammatory signaling in microglia.

ABSTRACT:

Background

The protein alpha-synuclein (?-SYN), which is found in the Lewy bodies of dopamine-producing (DA) neurons in the substantia nigra (SN), has an important role in the pathogenesis of Parkinson's disease (PD). Previous studies have shown that neuroinflammation plays a key role in PD pathogenesis. In an AAV-synuclein mouse model of PD, we have found that over-abundance of ?-SYN triggers the expression of NF-?B p65, and leads to microglial activation and DA neurodegeneration. We also have observed that Fc? receptors (Fc?R), proteins present on the surface of microglia that bind immunoglobulin G (IgG) and other ligands, are key modulators of ?-SYN-induced neurodegeneration.

Methods

In order to study the role of Fc?Rs in the interactions of ?-SYN and microglia, we treated the primary microglial cultures from wild-type (WT) and Fc?R-/- mice with aggregated human ?-SYN in vitro.

Results

Using immunocytochemistry, we found that ?-SYN was taken up by both WT and Fc?R-/- microglia, however, their patterns of internalization were different, with aggregation in autophagosomes in WT cells and more diffuse localization in Fc?R-/- microglia. In WT microglia, ?-SYN induced the nuclear accumulation of NF-?B p65 protein and downstream chemokine expression while in Fc?R-/- mouse microglia, ?-SYN failed to trigger the enhancement of nuclear NF-?B p65, and the pro-inflammatory signaling was reduced.

Conclusions

Our results suggest that ?-SYN can interact directly with microglia and can be internalized and trafficked to autophagosomes. Fc?Rs mediate this interaction, and in the absence of the gamma chain, there is altered intracellular trafficking and attenuation of pro-inflammatory NF-?B signaling. Therefore, blocking either Fc?R signaling or downstream NF-?B activation may be viable therapeutic strategies in PD.

SUBMITTER: Cao S

PROVIDER: S-EPMC3526448 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The gamma chain subunit of Fc receptors is required for alpha-synuclein-induced pro-inflammatory signaling in microglia.

Cao Shuwen S Standaert David G DG Harms Ashley S AS

Journal of neuroinflammation 20121127

<h4>Background</h4>The protein alpha-synuclein (α-SYN), which is found in the Lewy bodies of dopamine-producing (DA) neurons in the substantia nigra (SN), has an important role in the pathogenesis of Parkinson's disease (PD). Previous studies have shown that neuroinflammation plays a key role in PD pathogenesis. In an AAV-synuclein mouse model of PD, we have found that over-abundance of α-SYN triggers the expression of NF-κB p65, and leads to microglial activation and DA neurodegeneration. We al ...[more]

PMID: 23186369

Similar Datasets

Project description:Antibody-dependent cellular cytotoxicity (ADCC) is an important effector function determining the clinical efficacy of therapeutic antibodies. Core fucose removal from N-glycans on the Fc portion of immunoglobulin G (IgG) improves the binding affinity for Fc? receptor IIIa (Fc?RIIIa) and dramatically enhances ADCC. Our previous structural analyses revealed that Tyr-296 of IgG1-Fc plays a critical role in the interaction with Fc?RIIIa, particularly in the enhanced Fc?RIIIa binding of nonfucosylated IgG1. However, the importance of the Tyr-296 residue in the antibody in the interaction with various Fc? receptors has not yet been elucidated. To further clarify the biological importance of this residue, we established comprehensive Tyr-296 mutants as fucosylated and nonfucosylated anti-CD20 IgG1s rituximab variants and examined their binding to recombinant soluble human Fc? receptors: shFc?RI, shFc?RIIa, shFc?RIIIa, and shFc?RIIIb. Some of the mutations affected the binding of antibody to not only shFc?RIIIa but also shFc?RIIa and shFc?RIIIb, suggesting that the Tyr-296 residue in the antibody was also involved in interactions with Fc?RIIa and Fc?RIIIb. For Fc?RIIIa binding, almost all Tyr-296 variants showed lower binding affinities than the wild-type antibody, irrespective of their core fucosylation, particularly in Y296K and Y296P. Notably, only the Y296W mutant showed improved binding to Fc?RIIIa. The 3.00 Å-resolution crystal structure of the nonfucosylated Y296W mutant in complex with shFc?RIIIa harboring two N-glycans revealed that the Tyr-to-Trp substitution increased the number of potential contact atoms in the complex, thus improving the binding of the antibody to shFc?RIIIa. The nonfucosylated Y296W mutant retained high ADCC activity, relative to the nonfucosylated wild-type IgG1, and showed greater binding affinity for Fc?RIIa. Our data may improve our understanding of the biological importance of human IgG1-Fc Tyr-296 in interactions with various Fc? receptors, and have applications in the modulation of the IgG1-Fc function of therapeutic antibodies.

Project description:Anti-factor VIII (fVIII) alloantibodies, which can develop in patients with hemophilia A, limit the therapeutic options and increase morbidity and mortality of these patients. However, the factors that influence anti-fVIII antibody development remain incompletely understood. Recent studies suggest that Fc gamma receptors (FcγRs) may facilitate recognition and uptake of fVIII by recently developed or pre-existing naturally occurring anti-fVIII antibodies, providing a mechanism whereby the immune system may recognize fVIII following infusion. However, the role of FcγRs in anti-fVIII antibody formation remains unknown. In order to define the influence of FcγRs on the development of anti-fVIII antibodies, fVIII was injected into WT or FcγR knockout recipients, followed by evaluation of anti-fVIII antibodies. Anti-fVIII antibodies were readily observed following fVIII injection into FcγR knockouts, with similar anti-fVIII antibody levels occurring in FcγR knockouts as detected in WT mice injected in parallel. As antibodies can also fix complement, providing a potential mechanism whereby anti-fVIII antibodies may influence anti-fVIII antibody formation independent of FcγRs, fVIII was also injected into complement component 3 (C3) knockout recipients in parallel. Similar to FcγR knockouts, C3 knockout recipients developed a robust response to fVIII, which was likewise similar to that observed in WT recipients. As FcγRs or C3 may compensate for each other in recipients only deficient in FcγRs or C3 alone, we generated mice deficient in both FcγRs and C3 to test for potential antibody effector redundancy in anti-fVIII antibody formation. Infusion of fVIII into FcγRs and C3 (FcγR × C3) double knockouts likewise induced anti-fVIII antibodies. However, unlike individual knockouts, anti-fVIII antibodies in FcγRs × C3 knockouts were initially lower than WT recipients, although anti-fVIII antibodies increased to WT levels following additional fVIII exposure. In contrast, infusion of RBCs expressing distinct alloantigens into FcγRs, C3 or FcγR × C3 knockout recipients either failed to change anti-RBC levels when compared to WT recipients or actually increased antibody responses, depending on the target antigen. Taken together, these results suggest FcγRs and C3 can differentially impact antibody formation following exposure to distinct alloantigens and that FcγRs and C3 work in concert to facilitate early anti-fVIII antibody formation.

Dataset Information

The gamma chain subunit of Fc receptors is required for alpha-synuclein-induced pro-inflammatory signaling in microglia.

Background

Methods

Results

Conclusions

Publications

The gamma chain subunit of Fc receptors is required for alpha-synuclein-induced pro-inflammatory signaling in microglia.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure