Missense Mutations in the gp91-phox Gene Encoding Cytochromeb558 in Patients With Cytochrome b Positive and Negative X-Linked Chronic Granulomatous Disease

Abstract

Chronic granulomatous disease (CGD) is a disorder of host defense due to genetic defects of the superoxide (O2-) generating NADPH oxidase in phagocytes. A membrane-bound cytochrome b558, a heterodimer consisting of gp91-phox and p22-phox, is a critical component of the oxidase. The X-linked form of the disease is due to defects in the gp91-phox gene. We report here biochemical and genetic analyses of patients with typical and atypical X-linked CGD. Immunoblots showed that neutrophils from one patient had small amounts of p22-phoxand gp91-phox and a low level of O2-forming oxidase activity, in contrast to the complete absence of both subunits in two patients with typical CGD. Using polymerase chain reactions (PCR) on cDNA and genomic DNA, we found novel missense mutations of gp91-phox in the two typical patients and a point mutation in the variant CGD, a characteristic common to two other patients with similar variant CGD reported previously. Spectrophotometric analysis of the neutrophils from the variant patient provided evidence for the presence of heme of cytochromeb558. Recently, we reported another variant CGD with similar amounts of both subunits, but without oxidase activity or the heme spectrum. A predicted mutation at amino acid 101 in gp91-phox was also confirmed in this variant CGD by PCR of the genomic DNA. These results on four patients, including those with two variant CGD, are discussed with respect to the missense mutated sites and the heme binding ligands in gp91-phox.

Molecular and functional characterization of a new X-linked chronic granulomatous disease variant (X91+) case with a double missense mutation in the cytosolic gp91phox C-terminal tail

“…Surprisingly, a deletion of amino acids 488^497 described in an X þ CGD patient, which is indeed localized in this external cytosolic loop, does not a¡ect cytosolic factor assembly to the plasma membrane [35]. An X91 3 has been described by Kaneda et al [42] with a missense mutation in a site very close to our double mutation, changing Glu309 to Lys. In that case, the O 3 2 production was shown to be diminished and related to a low amount of cytochrome b 558 ; no information about FAD content and cytosolic factor translocation was reported.…”

A novel point mutation in the CYBB gene promoter leading to a rare X minus chronic granulomatous disease variant — Impact on the microbicidal activity of neutrophils

“…A number of cases with "variant" forms of the disease, called X91 -CGD have also been described, in which low levels of cytochrome b 558 expression are accompanied by a proportionally decreased NADPH oxidase activity [10]. Mutations associated with this phenotype are usually located in the coding region (exons) of CYBB [11][12][13][14][15][16]. These variants are of interest because…”

Influence of Neutrophil Defects on Burkholderia cepacia Complex Pathogenesis

“…Both cell lines and primary cells have been used in assessment of bacterial virulence in interactions with CGD phagocytes. PMNs and macrophages can be derived from CGD patients, when available, or from CGD animals (Morgenstern et al, 1997 ; Kaneda et al, 1999 ; Zelazny et al, 2009 ). Because these cells are isolated directly from patients or animals with CGD, these cells most closely replicate the CGD defect, but unfortunately are unable to be genetically modified or adequately controlled experimentally.…”