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A Novel Homozygous Mutation Destabilizes IKK? and Leads to Human Combined Immunodeficiency.

ABSTRACT: Mutations in the IKBKB gene cause severe immunodeficiency, characterized clinically by persistent respiratory or gastrointestinal infections. Targeted gene panel sequencing revealed a novel homozygous missense mutation in the IKBKB gene of a patient with immune dysregulation and combined T and B cell functional defects. PBMCs from the patient, Ikbkb Y397H mice, and transfected cells were used to elucidate how the Y395H mutation triggers IKK? deficiency and impairs immune function. Here, we found that cells from both the patient and Ikbkb Y397H mice lacked or showed decreased levels of IKK? protein, along with impaired lymphocyte function. IKK? and IKK? protein expression by human PBMCs harboring the Y395H mutation was normal, but degradation of IKK? protein was accelerated. Binding of human NF-?B to DNA in patient PBMCs fell upon stimulation with TNF-? or LPS. Additionally, a structural model of Y395H revealed loss of the hydrogen bond with D389. These data suggest that IKBKB deficiency induces abnormal IKK? protein degradation, leading to impaired NF-?B signaling and immune function. We postulate that the Y395H variant in the IKK? protein lost the hydrogen bond with D389, thereby affecting interaction between Y395 and D389 and increasing protein instability.

SUBMITTER: Qin T

PROVIDER: S-EPMC7917045 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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A Novel Homozygous Mutation Destabilizes IKKβ and Leads to Human Combined Immunodeficiency.

Qin Tao T Jia Yanjun Y Liu Yuhang Y Dai Rongxin R Zhou Lina L Okada Satoshi S Tsumura Miyuki M Ohnishi Hidenori H Kato Zenichiro Z Kanegane Hirokazu H Sun Xiulian X Zhao Xiaodong X

Frontiers in immunology 20210215

Mutations in the IKBKB gene cause severe immunodeficiency, characterized clinically by persistent respiratory or gastrointestinal infections. Targeted gene panel sequencing revealed a novel homozygous missense mutation in the IKBKB gene of a patient with immune dysregulation and combined T and B cell functional defects. PBMCs from the patient, Ikbkb Y397H mice, and transfected cells were used to elucidate how the Y395H mutation triggers IKKβ deficiency and impairs immune fun ...[more]

PMID: 33658989

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Project description:Primary immunodeficiency disorders (PIDs) render patients vulnerable to infection with a wide range of microorganisms and thus provide good in vivo models for the assessment of immune responses during infectious challenges. Priming of the immune system, especially in infancy, depends on different environmental exposures and medical practices. This may determine the timing and phenotype of clinical appearance of immune deficits as exemplified with early exposure to Bacillus Calmette-Guérin (BCG) vaccination and dissemination in combined immunodeficiencies. Varied phenotype expression poses a challenge to identification of the putative immune deficit. Without the availability of genomic diagnosis and data analysis resources and with limited capacity for functional definition of immune pathways, it is difficult to establish a definitive diagnosis and to decide on appropriate treatment. This study describes the use of exome sequencing to identify a homozygous recessive variant in MAP3K14, NIKVal345Met, in a patient with combined immunodeficiency, disseminated BCG-osis, and paradoxically elevated lymphocytes. Laboratory testing confirmed hypogammaglobulinemia with normal CD19, but failed to confirm a definitive diagnosis for targeted treatment decisions. NIKVal345Met is predicted to be deleterious and pathogenic by two in silico prediction tools and is situated in a gene crucial for effective functioning of the non-canonical nuclear factor-kappa B signaling pathway. Functional analysis of NIKVal345Met- versus NIKWT-transfected human embryonic kidney-293T cells showed that this mutation significantly affects the kinase activity of NIK leading to decreased levels of phosphorylated IkappaB kinase-alpha (IKK?), the target of NIK. BCG-stimulated RAW264.7 cells transfected with NIKVal345Met?also presented with reduced levels of phosphorylated IKK?, significantly increased p100 levels and significantly decreased p52 levels compared to cells transfected with NIKWT. Ideally, these experiments would have been conducted in patient-derived immune cells, but we were unable to source these cells from the patient. The functional analysis described in this paper supports previous illustrations of the importance of NIK in human immune responses and demonstrates the involvement of function-altering mutations in MAP3K14 in PIDs. The genomic approach used for this patient demonstrates its value in the diagnosis of an unusual PID and as a tool for detecting rarer mutations to help guide treatment approaches.

Dataset Information

A Novel Homozygous Mutation Destabilizes IKK? and Leads to Human Combined Immunodeficiency.

Publications

A Novel Homozygous Mutation Destabilizes IKKβ and Leads to Human Combined Immunodeficiency.

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