title: Nox NADPH oxidases and the endoplasmic reticulum.
abstract: CONCLUSIONS
  Understanding isoform- and context-specific subcellular Nox reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase compartmentalization allows relevant functional inferences. This review addresses the interplay between Nox NADPH oxidases and the endoplasmic reticulum (ER), an increasingly evident player in redox pathophysiology given its role in redox protein folding and stress responses.
  
  
  BACKGROUND
  Catalytic/regulatory transmembrane subunits are synthesized in the ER and their processing includes folding, N-glycosylation, heme insertion, p22phox heterodimerization, as shown for phagocyte Nox2. Dual oxidase (Duox) maturation also involves the regulation by ER-resident Duoxa2. The ER is the activation site for some isoforms, typically Nox4, but potentially other isoforms. Such location influences redox/Nox-mediated calcium signaling regulation via ER targets, such as sarcoendoplasmic reticulum calcium ATPase (SERCA). Growing evidence suggests that Noxes are integral signaling elements of the unfolded protein response during ER stress, with Nox4 playing a dual prosurvival/proapoptotic role in this setting, whereas Nox2 enhances proapoptotic signaling. ER chaperones such as protein disulfide isomerase (PDI) closely interact with Noxes. PDI supports growth factor-dependent Nox1 activation and mRNA expression, as well as migration in smooth muscle cells, and PDI overexpression induces acute spontaneous Nox activation.
  
  
  RESULTS
  Mechanisms of PDI effects include possible support of complex formation and RhoGTPase activation. In phagocytes, PDI supports phagocytosis, Nox activation, and redox-dependent interactions with p47phox. Together, the results implicate PDI as possible Nox organizer.
  
  
  CONCLUSIONS
  We propose that convergence between Noxes and ER may have evolutive roots given ER-related functional contexts, which paved Nox evolution, namely calcium signaling and pathogen killing. Overall, the interplay between Noxes and the ER may provide relevant insights in Nox-related (patho)physiology.
authors.affiliation: Vascular Biology Laboratory, Heart Institute (InCor), University of São Paulo School of Medicine , São Paulo, Brazil .
authors.forename: Francisco R M
authors.initials: FR
authors.lastname: Laurindo
authors.forename: Thaís L S
authors.initials: TL
authors.lastname: Araujo
authors.forename: Thalita B
authors.initials: TB
authors.lastname: Abrahão
mesh_terms: D000818:Animals; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D006801:Humans; D019255:NADPH Oxidases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000235:genetics*; D017510:Protein Folding; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D017382:Reactive Oxygen Species; D019255:NADPH Oxidases