The novel S59P mutation in the TNFRSF1A gene identified in an adult onset TNF receptor associated periodic syndrome (TRAPS) constitutively activates NF-κB pathway

The novel S59P mutation in the TNFRSF1A gene identified in an adult onset TNF receptor associated periodic syndrome (TRAPS) constitutively activates NF-κB pathway

Arthritis Research & Therapy, April 2015

25888769

Eliana Greco, Ada Aita, Paola Galozzi, Alessandra Gava, Paolo Sfriso, Ola H Negm, Patrick Tighe, Francesco Caso, Filippo Navaglia, Emanuela Dazzo, Marzia De Bortoli, Alessandra Rampazzo, Laura Obici, Simona Donadei, Giampaolo Merlini, Mario Plebani, Ian Todd, Daniela Basso, Leonardo Punzi

Mutations in the TNFRSF1A gene, encoding the Tumor Necrosis Factor Receptor 1 (TNF-R1), are associated with the autosomal dominant autoinflammatory disorder, called TNF Receptor Associated Periodic Syndrome (TRAPS). TRAPS is clinically characterized by recurrent episodes of long-lasting fever and systemic inflammation. A novel mutation (c.262 T > C; S59P) in the TNFRSF1A gene at residue 88 of the mature protein was recently identified in our laboratory in an adult TRAPS patient. Aim of this study was to functionally characterize this novel TNFRSF1A mutation evaluating its effects on the TNF-R1-associated signalling pathways, firstly NF-κB, under particular conditions and comparing the results with suitable control mutations. HEK-293 cell line was transfected with pCMV6-AC construct expressing Wild-Type (WT) or c.262 T > C (S59P), c.362G > A (R92Q), c.236C > T (T50M) TNFRSF1A mutants. Peripheral blood mononuclear cells (PBMCs) were instead isolated from two TRAPS patients carrying S59P and R92Q mutations and from five healthy subjects. Both transfected HEK293 and PBMCs were stimulated with Tumor Necrosis Factor (TNF) or Interleukin 1β (IL-1β) to evaluate the expression of TNF-R1, the activation of TNF-R1-associated downstream pathways and the pro-inflammatory cytokines by means of immunofluorescent assay, array-based tecnique, immunoblotting and immunometric assay, respectively. TNF induced cytoplasmic accumulation of TNF-R1 in all mutant cells. Furthermore, all mutants presented a particular set of active TNF-R1 downstream pathways. S59P constitutively activated IL-1β, MAPK and SRC/JAK/STAT3 pathways and inhibited apoptosis. Also NF-κB pathway involvement was demonstrated in vitro by the enhancement of p-IκB-α and p65 nuclear subunit of NF-κB expression in all mutants in presence of TNF or IL-1β stimulation. These in vitro results correlated with patients data from PBMCs. Concerning the pro-inflammatory cytokines secretion, mainly IL-1β induced a significant and persistent enhancement of IL-6 and IL-8 in S59P PBMCs. The novel S59P mutation leads to a defective cellular trafficking and to a constitutive activation of TNF-R1. This mutation also determines a constitutive activation of the IL-1R pathway, inhibition of apoptosis, and an enhanced and persistent NF-κB activation and cytokines secretion in response to IL-1β stimulation.