DELETERIOUS RELA VARIANTS IN AUTOIMMUNITY
Dr Morgan Downes1, SONIA NAMBADAM1, JOANNE CHOW1, VICKI ATHANASOPOULOS1, ISABELLA BALES1, GEMMA HART1, SIMON JIANG1
1John Curtin School of Medical Research, The Australian National University, Canberra, Australia
Aim: To investigate the molecular and functional impacts of patient-derived genetic variants in RELA.
Background: Phenotypic diversity of autoimmune diseases presents an ongoing diagnostic and drug development challenge for clinicians and scientists. RELA is a member of the NFκB (Nuclear Factor Kappa-light-chain-enhancer of activated B cells) family of transcription factors. Recent discovery of genetic variants in RELA in patients highlight that different pathogenic molecular mechanisms are at play, and likely contribute to the observed diversity in phenotypes and clinical outcomes. We examine the impact of six rare/novel RELA variants in patients with various autoimmune/autoinflammatory phenotypes.
Methods: Wild type (RELA-WT) and mutant RELA proteins were ectopically expressed in HEK293 cells. Western blot, flow cytometry and NFκB/IFNϐ (interferon beta) reporter assays were used to determine RELA expression, phosphorylation, and transcriptional activity, respectively.
Results: Three variants, RELA-I250V, RELA-R295H and RELA-D409N, reduced NFκB transcriptional activity. In contrast to RELA-WT, we observed a reduction in RELA-I250V expression and reduced phosphorylation of RELA-D409N. Despite reduced expression, RELA-I250V induced hyperactivation of the IFNβ promoter. Co-expression of RELA-WT reversed the interferonogenic phenotype of RELA-I250V.
Conclusions: We uncovered three patient-derived variants that reduce the capacity of RELA to activate NFκB-driven genes. The hypomorphic characteristics of RELA-I250V and RELA-D409N are molecularly distinct, derived from changes in protein stability and transactivating phosphorylation events, respectively. Additionally, we expose RELA-I250V as a neomorph, gaining interferonogenic activity – pertinent as the patient has type-I interferon-mediated disease. We reveal distinct molecular mechanisms by which variants in RELA may drive different disease phenotypes. An understanding of these mechanisms will help improve clinical management including diagnosis and optimised treatment strategies for patients.
Presentation Slides PDF – Click here
Biography:
Morgan is an early career postdoctoral researcher in the Personalised Medicine and Autoimmunity Lab at the John Curtin School of Medical Research, Australian National University (ANU) where she investigates patient-derived genetic variants and their impact on immune signalling. She completed her Bachelor of Medical Research (Honours) at the Menzies Research Institute, University of Tasmania. Subsequently, she travelled to Fiji to help establish the Medical Research Laboratory at Fiji National University. In Fiji, she contributed to HIV and dengue fever research to improve the health of indigenous Fijians. Prior to her current role, she was awarded a PhD at ANU for her investigation of NOD2 variants in granulomatous autoinflammatory diseases.