Article

Lupus-associated causal mutation in neutrophil cytosolic factor 2 (NCF2) brings unique insights to the structure and function of NADPH oxidase

The Lupus Genetic Group, Department of Medicine, University of Southern California, Los Angeles, CA 90089, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 12/2011; 109(2):E59-67. DOI: 10.1073/pnas.1113251108
Source: PubMed

ABSTRACT Systemic lupus erythematosus (SLE), the prototypic systemic autoimmune disease, is a debilitating multisystem autoimmune disorder characterized by chronic inflammation and extensive immune dysregulation in multiple organ systems, resulting in significant morbidity and mortality. Here, we present a multidisciplinary approach resulting in the identification of neutrophil cytosolic factor 2 (NCF2) as an important risk factor for SLE and the detailed characterization of its causal variant. We show that NCF2 is strongly associated with increased SLE risk in two independent populations: childhood-onset SLE and adult-onset SLE. The association between NCF2 and SLE can be attributed to a single nonsynonymous coding mutation in exon 12, the effect of which is the substitution of histidine-389 with glutamine (H389Q) in the PB1 domain of the NCF2 protein, with glutamine being the risk allele. Computational modeling suggests that the NCF2 H389Q mutation reduces the binding efficiency of NCF2 with the guanine nucleotide exchange factor Vav1. The model predicts that NCF2/H389 residue interacts with Vav1 residues E509, N510, E556, and G559 in the ZF domain of Vav1. Furthermore, replacing H389 with Q results in 1.5 kcal/mol weaker binding. To examine the effect of the NCF2 H389Q mutation on NADPH oxidase function, site-specific mutations at the 389 position in NCF2 were tested. Results show that an H389Q mutation causes a twofold decrease in reactive oxygen species production induced by the activation of the Vav-dependent Fcγ receptor-elicited NADPH oxidase activity. Our study completes the chain of evidence from genetic association to specific molecular function.

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    • "In addition to this well-established connection between CGD and autoimmunity, genes encoding oxidase subunits have been associated with autoinflammatory and autoimmune disorders in genome-wide association studies (GWAS). A variation in NCF2, the gene encoding p67phox, has been identified as an important risk factor for SLE (18). NCF4, encoding p40phox, has been associated with rheumatoid arthritis (19) and Crohn’s disease (20, 21). "
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    ABSTRACT: The nicotinamide adenine dinucleotide phosphate (NADPH) oxidase expressed in phagocytes is a multi-subunit enzyme complex that generates superoxide (O2 (.-)). This radical is an important precursor of hydrogen peroxide (H2O2) and other reactive oxygen species needed for microbicidal activity during innate immune responses. Inherited defects in NADPH oxidase give rise to chronic granulomatous disease (CGD), a primary immunodeficiency characterized by recurrent infections and granulomatous inflammation. Interestingly, CGD, CGD carrier status, and oxidase gene polymorphisms have all been associated with autoinflammatory and autoimmune disorders, suggesting a potential role for NADPH oxidase in regulating adaptive immune responses. Here, NADPH oxidase function in antigen processing and presentation is reviewed. NADPH oxidase influences dendritic cell (DC) crosspresentation by major histocompatibility complex class I molecules through regulation of the phagosomal microenvironment, while in B lymphocytes, NADPH oxidase alters epitope selection by major histocompatibility complex class II molecules.
    Frontiers in Immunology 09/2013; 4:295. DOI:10.3389/fimmu.2013.00295
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    • "We also found that B6.Sle2c2 myeloid cells and granulocytes produced more ROS at steady-state than B6 cells. A recent study found a strong association between a coding mutation in the human NCF2 gene with SLE susceptibility, and determined that the disease associated allele was associated with a lower ROS production [24]. This is consistent with decreased levels of Ncf1, a gene encoding for another unit of the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase complex, being associated with collagen-induced arthritis [25] and experimental allergic encephalomyelitis [26]. "
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