NOX5 variants are functionally active in endothelial cells

Free Radic Biol Med. 2007 Feb 15;42(4):446-59. doi: 10.1016/j.freeradbiomed.2006.10.054. Epub 2006 Nov 3.


NADPH oxidases have been identified as sources of reactive oxygen species (ROS) in vascular cells. In addition to the initially described enzyme containing gp91phox (NOX2), several homologues to NOX2 have been identified. Whereas NOX1, NOX2, and NOX4 are expressed in endothelial cells, a functional role of NOX5 containing additional N-terminal calcium-binding domains of varying sequences has not been reported in these cells. NOX5 protein was found in the endoplasmic reticulum of human microvascular endothelial cells (HMEC-1) and in the vascular wall. HMEC-1 cells expressed NOX5beta and NOX5delta as well as a variant lacking calcium-binding domains (NOX5S). NOX5beta and NOX5S increased basal ROS levels. Ionomycin exclusively enhanced NOX5beta-mediated ROS production. Although p22phox, when overexpressed, interacted with both NOX5 proteins, it was not essential for NOX5-mediated ROS production. NOX5 proteins stimulated endothelial cell proliferation and the formation of capillary-like structures whereas depletion of NOX5 by siRNA prevented these responses to thrombin. These data show that endothelial cells express different NOX5 variants including NOX5S lacking calcium-binding domains. NOX5 proteins are functional, promoting endothelial ROS production, proliferation, and the formation of capillary-like structures and contribute to the endothelial response to thrombin. These findings suggest that NOX5 variants play a novel role in controlling ROS-dependent processes in the vasculature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cell Line
  • Cell Proliferation
  • DNA Primers
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism*
  • Fluorescent Antibody Technique
  • Humans
  • Immunohistochemistry
  • Immunoprecipitation
  • Membrane Proteins / physiology*
  • NADPH Oxidase 5
  • NADPH Oxidases / physiology*
  • Neovascularization, Physiologic
  • Reactive Oxygen Species / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction


  • DNA Primers
  • Membrane Proteins
  • Reactive Oxygen Species
  • NADPH Oxidase 5
  • NADPH Oxidases
  • NOX5 protein, human