Nox5: Molecular biology and pathophysiology

Abstract

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox), comprise 7 family members (Nox1‐5, duox1/2) and are major producers of reactive oxygen species (ROS) in mammalian cells. ROS are critically involved in cell signalling and function. While all Noxs share structural homology comprising six transmembrane domains with two heme‐binding regions and a NADPH‐binding region on the intracellular C‐terminus, their regulatory systems, mechanisms of activation and tissue distribution differ. This explains the diverse function of Noxs. Of the Noxs, Nox5 is unique in that rodents lack the gene, it is regulated by Ca²⁺, it does not require NADPH oxidase subunits for its activation and it is not glycosylated. Nox5 localises in the perinuclear and ER regions of cells and traffics to the cell membrane upon activation. It is tightly regulated through numerous post‐translational modifications and is activated by vasoactive agents, growth factors and pro‐inflammatory cytokines. The exact pathophysiological significance of Nox5 remains unclear but it seems to be important in the physiological regulation of sperm motility, vascular contraction and lymphocyte differentiation and Nox5 hyperactivation has been implicated in cardiovascular disease, kidney injury and cancer. The field of Nox5 biology is still in its infancy, but with new insights into its biochemistry and cellular regulation, discovery of the Nox5 crystal structure and GWAS studies implicating Nox5 in disease, the time is now ripe to advance Nox5 research. This review provides a comprehensive overview of our current understanding of Nox5, from basic biology to human disease, and highlights the unique characteristics of this enigmatic Nox isoform.

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