John Engelhardt

Publications (5)24.6 Total impact

• Article: Redox modifier genes and pathways in amyotrophic lateral sclerosis.

  Barrie J Carter, Pervin Anklesaria, Stephanie Choi, John F Engelhardt
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  ABSTRACT: Enhanced redox-stress caused by neuroinflammation, mitochondria, and NADPH oxidases has been hypothesized to play critical roles in disease progression of amyotrophic lateral sclerosis (ALS). However, distinguishing whether the redox-stress observed in ALS is due to a primary defect in cellular reactive oxygen species metabolism/catabolism, or is a secondary consequence of neuroinflammation, has been difficult and the issue remains a matter of debate. Emerging evidence suggests that defects in genes that regulate NADPH oxidases may account for at least some forms of ALS. NADPH oxidases are key signaling complexes that influence cellular responses to growth factors and cytokines. In this context, NADPH oxidase-derived reactive oxygen species exert spatial control over the redox-dependent activation of certain pro-inflammatory receptors. Understanding the biology of how NADPH oxidases control cell signaling may help to clarify how genetic determinants of ALS lead to dysregulated pro-inflammatory signaling. This review provides a framework for understanding endosomal signaling through NADPH oxidases and potential mechanisms whereby gene defects in various forms of ALS may influence this cellular process and lead to motor neuron degeneration. Lastly, this review discusses past and current efforts to treat ALS using antioxidant therapies, as well as the limitations and advantages of each of these approaches.
  Antioxidants & Redox Signaling 02/2009; 11(7):1569-86. · 8.20 Impact Factor
• Article: Signaling components of redox active endosomes: the redoxosomes.

  Fredrick D Oakley, Duane Abbott, Qiang Li, John F Engelhardt
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  ABSTRACT: Subcellular compartmentalization of reactive oxygen species (ROS) plays a critical role in transmitting cell signals in response to environmental stimuli. In this regard, signals at the plasma membrane have been shown to trigger NADPH oxidase-dependent ROS production within the endosomal compartment and this step can be required for redox-dependent signal transduction. Unique features of redox-active signaling endosomes can include NADPH oxidase complex components (Nox1, Noxo1, Noxa1, Nox2, p47phox, p67phox, and/or Rac1), ROS processing enzymes (SOD1 and/or peroxiredoxins), chloride channels capable of mediating superoxide transport and/or membrane gradients required for Nox activity, and novel redox-dependent sensors that control Nox activity. This review will discuss the cytokine and growth factor receptors that likely mediate signaling through redox-active endosomes, and the common mechanisms whereby they act. Additionally, the review will cover ligand-independent environmental injuries, such as hypoxia/reoxygenation injury, that also appear to facilitate cell signaling through NADPH oxidase at the level of the endosome. We suggest that redox-active endosomes encompass a subset of signaling endosomes that we have termed redoxosomes. Redoxosomes are uniquely equipped with redox-processing proteins capable of transmitting ROS signals from the endosome interior to redox-sensitive effectors on the endosomal surface. In this manner, redoxosomes can control redox-dependent effector functions through the spatial and temporal regulation of ROS as second messengers.
  Antioxidants & Redox Signaling 01/2009; 11(6):1313-33. · 8.20 Impact Factor
• Article: Endosomal Nox2 facilitates redox-dependent induction of NF-kappaB by TNF-alpha.

  Qiang Li, Netanya Y Spencer, Fredrick D Oakley, Garry R Buettner, John F Engelhardt
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  ABSTRACT: Growing evidence suggests that NADPH oxidase (Nox)-derived reactive oxygen species (ROS) play important roles in regulating cytokine signaling. We have explored how TNF-alpha induction of Nox-dependent ROS influences NF-kappaB activation. Cellular stimulation by TNF-alpha induced NADPH-dependent superoxide production in the endosomal compartment, and this ROS was required for IKK-mediated activation of NF-kappaB. Inhibiting endocytosis reduced the ability of TNF-alpha to induce both NADPH-dependent endosomal superoxide and NF-kappaB, supporting the notion that redox-dependent signaling of the receptor occurs in the endosome. Molecular analyses demonstrated that endosomal H(2)O(2) was critical for the recruitment of TRAF2 to the TNFR1/TRADD complex after endocytosis. Studies using both Nox2 siRNA and Nox2-knockout primary fibroblasts indicated that Nox2 was critical for TNF-alpha-mediated induction of endosomal superoxide. Redox-active endosomes that form after TNF-alpha or IL-1 beta induction recruit several common proteins (Rac1, Nox2, p67(phox), SOD1), while also retaining specificity for ligand-activated receptor effectors. Our studies suggest that TNF-alpha and IL-1 beta signaling pathways both can use Nox2 to facilitate redox activation of their respective receptors at the endosomal level by promoting the redox-dependent recruitment of TRAFs. These studies help to explain how cellular compartmentalization of redox signals can be used to direct receptor activation from the plasma membrane.
  Antioxidants & Redox Signaling 12/2008; 11(6):1249-63. · 8.20 Impact Factor
• Article: New technologies for genetic manipulation of animal models: Forum introduction

  Ziyi Li, John Engelhardt
  Reproductive Biology and Endocrinology. 01/2003;
• Article: Progress toward generating a ferret model of cystic fibrosis by somatic cell nuclear transfer

  Ziyi Li, John Engelhardt
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  ABSTRACT: Abstract Mammalian cloning by nuclear transfer from somatic cells has created new opportunities to generate animal models of genetic diseases in species other than mice. Although genetic mouse models play a critical role in basic and applied research for numerous diseases, often mouse models do not adequately reproduce the human disease phenotype. Cystic fibrosis (CF) is one such disease. Targeted ablation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in mice does not adequately replicate spontaneous bacterial infections observed in the human CF lung. Hence, several laboratories are pursuing alternative animal models of CF in larger species such as the pig, sheep, rabbits, and ferrets. Our laboratory has focused on developing the ferret as a CF animal model. Over the past few years, we have investigated several experimental parameters required for gene targeting and nuclear transfer (NT) cloning in the ferret using somatic cells. In this review, we will discuss our progress and the hurdles to NT cloning and gene-targeting that accompany efforts to generate animal models of genetic diseases in species such as the ferret.
  Reproductive Biology and Endocrinology. 01/2003;