An Exclusive NEMO B Mutation Leads to NF-κB-linked Recurrent Pneumonia by Disrupting the NEMO/IKK Complex

Abstract Purpose A number of NEMO mutations in the shared sequences of NEMO isoform A and B have been associated with NF-κB-linked diseases. Here, we first report an exclusive NEMO B mutation as the genetic etiology of a male case with recurrent bacterial pneumonia and explore the underlying mechanism. Methods The genomic protein-coding regions of genes were analyzed using the whole exome sequencing (WES) technique, and the rare gene variant was confirmed by Sanger sequence analysis; activation of NF-kB signaling pathway was assessed by co-immunoprecipitation, western blotting, and single-cell RNA-seq analysis; glycolytic changes of peripheral immune cells were evaluated by extracellular acidification rate assay; protein-protein binding affinity and stability were estimated by structure modeling and molecular docking analysis. Results A c.20T > C mutation in exon 1 of the IKBKG germline sequence (NM_001099856.2) resulted in a Val7Ala replacement in the exclusive N-terminal sequence of NEMO B. This mutation significantly decreased the binding affinity and stability of NEMO B with IKKα/β, leading to the failure to form functional NEMO/IKK complex and the subsequent inhibition of RelA phosphorylation and nuclear translocation to initiate pro-inflammatory TNF-α and IL-1β gene transcription and metabolic support by glycolysis in response to the TLR4 agonist LPS. Single-cell sequencing analysis revealed abnormalities in monocyte and T-lymphocyte function and B-cell hyperplasia. Conclusions The exclusive N-terminal sequence of NEMO B is essential for a functional NEMO/IKKa/IKKb complex to activate NF-κB-dependent antibacterial immunity.