Biology subjects

Chemin, K.

Publications and source records attributed to Chemin, K..

3 recordsLinked to original sources

bioRxiv2025

Anti-MDA5 monoclonal antibodies from patients with dermatomyositis - B cell characteristics and differential targeting of the helicase domains

ObjectivesAutoantibodies targeting melanoma differentiation associated protein 5 (MDA5) are strongly associated with dermatomyositis (DM) and may contribute to its pathogenesis. Here we aimed to investigate MDA5+ B cells, their phenotype and generate MDA5 monoclonal antibodies to assess their epitope specificity. MethodsMDA5-reactive B cells were captured from peripheral blood of patients with anti-MDA5+ DM (n=3) using an MDA5-fluorescent probe. B cell receptor (BCR) sequences were analysed from single-sorted B cells (n=240). Selected clones were re-expressed as IgG1 monoclonal antibodies (mAbs, n=23). Reactivity was assessed using recombinant MDA5 protein constructs, peptide epitope mapping, ELISA, western blot and a commercial line blot assay. ResultsOf 240 anti-MDA5+ sorted B cells, 23 BCRs were re-expressed as mAbs, two of which showed high reactivity and specificity for MDA5. These antibody sequences originated from one CD19+IgD-CD27-CD38+ and one CD19+IgD-CD27+CD38+ IgG+ B cell with low somatic hypermutation (SHM). Both mAbs had nanomolar apparent affinity and bound to sites within the helicase domains of the MDA5 protein but with distinct epitope recognition. Serology screening confirmed targeting of a linear epitope identified in the mAb studies. ConclusionOur results show that anti-MDA5+ B cells recognize the helicase domains, which are the enzymatically active domains of the protein. These results have implications for understanding the etiopathology of anti-MDA5+ DM and development of new antigen-specific therapies.

immunology↗

bioRxiv2025

AI-Driven Virtual Screening and First-in-Class Conformational Biosensor Enable the Discovery of a GPR183 Inverse Agonist

GPR183 is a chemotactic G protein-coupled receptor implicated in immune cell migration and various diseases. Here, we report the discovery of novel GPR183 inverse agonists using an artificial intelligence-driven virtual screening approach combined with biophysical sensors including a first-in-class conformational biosensor. From an initial screen of 70 compounds and a hit expansion, a selected candidate - compound 78 - demonstrated potent inhibition of GPR183s constitutive and agonist-stimulated Gi activation as well {beta}-arrestin2 recruitment. The binding of the compound to the receptor core was confirmed by studies using a new conformational sensor based on intramolecular BRET, molecular dynamics, and site-directed mutagenesis experiments. Finally, the compound 78 was able to block agonist-induced migration of peripheral blood mononuclear cells ex vivo. This work provides a novel chemical scaffold for GPR183 modulation. It introduces a new tool for dissecting receptor function, paving the way for therapeutic exploration in inflammatory, autoimmune, and neoplastic disorders.

pharmacology and toxicology↗

bioRxiv2017

The association between the HLA-DRB1 shared epitope alleles and the risk of rheumatoid arthritis is influenced by massive gene-gene interactions.

In anti-citrullinated protein antibody positive rheumatoid arthritis (ACPA-positive RA), a particular subset of HLA-DRB1 alleles, called shared epitope alleles (SE), is the highest genetic risk factor. Here, we aimed to investigate whether gene-gene interactions influence this HLA-DRB1 related major disease risk; specifically, we set out to test if non-HLA SNPs, conferring low diseases risk on their own, can modulate the HLA-DRB1 SE effect to develop ACPA-positive RA.\n\nTo address this question, we computed the attributable proportion (AP) due to additive interaction at genome-wide level for two independent ACPA-positive RA cohorts: the Swedish EIRA and the North American NARAC. We found a strong enrichment of significant interactions (AP p-values<0.05) between the HLA-DRB1 SE alleles and a group of SNPs associated with ACPA-positive RA in both cohorts (Kolmogorov-Smirnov [KS] test D=0.35 for EIRA and D=0.25 for NARAC, p<2.2e-16 for both). Interestingly, 201 out of 1,492 SNPs in consistent interaction for both cohorts, were eQTLs in SE alleles context in PBMCs from ACPA-positive RA patients. Finally, we observed that the effect size of HLA-DRB1 SE alleles for disease decreases from 5.2 to 2.5 after discounting the risk alleles of the two top interacting SNPs (rs2476601 and rs10739581, AP FDR corrected p <0.05).\n\nOur data demonstrate that the association between the HLA-DRB1 SE alleles and the risk of ACPA-positive RA is modulated by massive genetic interactions with non-HLA genetic variants.

genetics↗