A Novel Superoxide-producing NAD(P)H Oxidase in Kidney

Abstract

During phagocytosis, gp91phox , the catalytic subunit of the phagocyte NADPH oxidase, becomes activated to produce superoxide, a precursor of microbicidal oxidants. Currently increasing evidence suggests that nonphagocytic cells contain similar superoxide-producing oxidases, which are proposed to play crucial roles in various events such as cell proliferation and oxygen sensing for erythropoiesis. Here we describe the cloning of human cDNA that encodes a novel NAD(P)H oxidase, designated NOX4. The NOX4 protein of 578 amino acids exhibits 39% identity to gp91 phox with special conservation in membrane-spanning regions and binding sites for heme, FAD, and NAD(P)H, indicative of its function as a superoxide-producing NAD(P)H oxidase. The membrane fraction of kidney-derived human embryonic kidney (HEK) 293 cells, expressing NOX4, exhibits NADHand NADPH-dependent superoxide-producing activities, both of which are inhibited by diphenylene iodonium, an agent known to block oxygen sensing, and decreased in cells expressing antisense NOX4 mRNA. The human NOX4 gene, comprising 18 exons, is located on chromosome 11q14.2-q21, and its expression is almost exclusively restricted to adult and fetal kidneys. In human renal cortex, high amounts of the NOX4 protein are present in distal tubular cells, which reside near erythropoietin-producing cells. In addition, overexpression of NOX4 in cultured cells leads to increased superoxide production and decreased rate of growth. The present findings thus suggest that the novel NAD(P)H oxidase NOX4 may serve as an oxygen sensor and/or a regulator of cell growth in kidney.

Quinone compounds regulate the level of ROS production by the NADPH oxidase Nox4

“…The specificity of AA-861, duroquinone, and tBuBQ for Nox4 over Nox2, suggests either a direct effect of quinone derivatives in the molecular dynamics of electron transfer mediated by Nox4, or an indirect role on a quinone sensitive functional partner of Nox4. In this work, we suggest a new aspect of Nox4 oxidase activity regulation that takes place not only at a transcriptional level as usually described [13,27,45] but also at a post-translational level as described above with quinone molecules. Quinones are bioreactive molecules that are sensitive to redox mechanism.…”

Inhibition of NADPH oxidase 4 activates apoptosis via the AKT/apoptosis signal-regulating kinase 1 pathway in pancreatic cancer PANC-1 cells

“…Furthermore, expression of Nox4 was also detected in renal cell carcinoma (Shiose et al, 2001) and glioblastoma (Cheng et al, 2001), implying the possible role of Nox4-generated ROS in maintenance of transformation phenotypes. We have recently found that Nox1 is functionally required for maintenance of Ras-induced transformation phenotypes (Mitsushita et al, 2004).…”

Nox enzymes, ROS, and chronic disease: An example of antagonistic pleiotropy

“…Nox4 is expressed in high levels in kidney [99,100], while other Nox1, Nox2 and Nox regulatory subunits are expressed at lower but quantitatively significant levels [101,102], making Nox enzymes attractive candidates for the origin of renal ROS including the relatively high levels of H 2 O 2 seen in urine. In kidney, Nox-dependent ROS is produced in response to agonists that bind to D1-like receptors [103], to Angiotensin II [104,105] and to H + fluxes [106].…”

“…In kidney, Nox-dependent ROS is produced in response to agonists that bind to D1-like receptors [103], to Angiotensin II [104,105] and to H + fluxes [106]. Although physiological roles are not well understood, Nox enzymes have been suggested to function in normal renal physiology in secretion of erythropoietin [100], in renal regulation of blood pressure [103], regulation of mesangial cell protein synthesis [107] and in innate immunity [23]. In addition to their normal roles in renal physiology, Nox-generated ROS are implicated in the pathogenesis of variety of kidney-related diseases:…”