Moran Benhar

Technion - Israel Institute of Technology, H̱efa, Haifa District, Israel

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Publications (13)152.08 Total impact

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    ABSTRACT: The thioredoxin reductase/thioredoxin system (TrxR/Trx1) plays a major role in protecting cells from oxidative stress. Disruption of the TrxR-Trx1 system keeps Trx1 in the oxidized state leading to cell death through activation of the ASK1-Trx1 apoptotic pathway. The potential mechanism and ability of tri- and tetra oligopeptides derived from the canonical -CxxC- motif of the Trx1-active site to mimic and enhance Trx1 cellular activity, was examined. The Trx mimetics peptides (TXM) protected insulinoma INS832/13 cells from oxidative stress induced by selectively inhibiting TrxR with auranofin (AuF). TXM reversed the AuF-effects preventing apoptosis, and increasing cell-viability. The TXM peptides were effective in inhibiting AuF-induced MAPK, JNK and p38(MAPK) phosphorylation, in correlation with preventing caspase-3 cleavage and thereby PARP-1 dissociation. The ability to form a disulfide-bridge-like conformation was estimated from molecular dynamics simulations. The TXM peptides restored insulin secretion and displayed Trx1 denitrosylase activity. Their potency was 10 to 100 fold higher than redox reagents like NAC, AD4, or ascorbic acid. Unable to reverse ERK1/2 phosphorylation, TXM-CB3 (NAc-Cys-Pro-Cys amide) appeared to function in part, through inhibiting ASK1-Trx dissociation. These highly effective anti-apoptotic effects of Trx1 mimetic peptides exhibited in INS832/13 cells could become valuable in treating adverse oxidative-stress related disorders such as diabetes.
    Biochemical pharmacology 01/2013; · 4.25 Impact Factor
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    ABSTRACT: Protein S-nitrosylation is a reversible protein modification implicated in both physiological and pathophysiological regulation of protein function. In obesity, skeletal muscle insulin resistance is associated with increased S-nitrosylation of insulin-signaling proteins. However, whether adipose tissue is similarly affected in obesity and, if so, what are the causes and functional consequences of increased S-nitrosylation in this tissue are unknown. Total protein S-nitrosylation was increased in intra-abdominal adipose tissue of obese humans and in high fat-fed or leptin-deficient ob/ob mice. Both the insulin receptor β-subunit and Akt were S-nitrosylated, correlating with body weight. Elevated protein and mRNA expression of inducible NO synthase and decreased protein levels of thioredoxin reductase were associated with increased adipose tissue S-nitrosylation. Cultured differentiated pre-adipocyte cell lines exposed to the NO donors S-nitrosoglutathione (GSNO) or S-nitroso-N-acetylpenicillamine exhibited diminished insulin-stimulated phosphorylation of Akt but not of GSK3 nor of insulin-stimulated glucose uptake. Yet the anti-lipolytic action of insulin was markedly impaired in both cultured adipocytes and in mice injected with GSNO prior to administration of insulin. In cells, impaired ability of insulin to diminish phosphorylated PKA substrates in response to isoproterenol suggested impaired insulin-induced activation of PDE3B. Consistently, increased S-nitrosylation of PDE3B was detected in adipose tissue of high fat-fed obese mice. Site-directed mutagenesis revealed that Cys-768 and Cys-1040, two putative sites for S-nitrosylation adjacent to the substrate-binding site of PDE3B, accounted for ∼50% of its GSNO-induced S-nitrosylation. Collectively, PDE3B and the anti-lipolytic action of insulin may constitute novel targets for increased S-nitrosylation of adipose tissue in obesity.
    Journal of Biological Chemistry 09/2011; 286(35):30433-30443. · 4.65 Impact Factor
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    ABSTRACT: Protein S-nitrosylation is a reversible protein modification implicated in both physiological and pathophysiological regulation of protein function. In obesity, skeletal muscle insulin resistance is associated with increased S-nitrosylation of insulin-signaling proteins. However, whether adipose tissue is similarly affected in obesity and, if so, what are the causes and functional consequences of increased S-nitrosylation in this tissue are unknown. Total protein S-nitrosylation was increased in intra-abdominal adipose tissue of obese humans and in high fat-fed or leptin-deficient ob/ob mice. Both the insulin receptor β-subunit and Akt were S-nitrosylated, correlating with body weight. Elevated protein and mRNA expression of inducible NO synthase and decreased protein levels of thioredoxin reductase were associated with increased adipose tissue S-nitrosylation. Cultured differentiated pre-adipocyte cell lines exposed to the NO donors S-nitrosoglutathione (GSNO) or S-nitroso-N-acetylpenicillamine exhibited diminished insulin-stimulated phosphorylation of Akt but not of GSK3 nor of insulin-stimulated glucose uptake. Yet the anti-lipolytic action of insulin was markedly impaired in both cultured adipocytes and in mice injected with GSNO prior to administration of insulin. In cells, impaired ability of insulin to diminish phosphorylated PKA substrates in response to isoproterenol suggested impaired insulin-induced activation of PDE3B. Consistently, increased S-nitrosylation of PDE3B was detected in adipose tissue of high fat-fed obese mice. Site-directed mutagenesis revealed that Cys-768 and Cys-1040, two putative sites for S-nitrosylation adjacent to the substrate-binding site of PDE3B, accounted for ∼50% of its GSNO-induced S-nitrosylation. Collectively, PDE3B and the anti-lipolytic action of insulin may constitute novel targets for increased S-nitrosylation of adipose tissue in obesity.
    Journal of Biological Chemistry 07/2011; 286(35):30433-43. · 4.65 Impact Factor
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    ABSTRACT: Reversible protein cysteine nitrosylation (S-nitrosylation) is a common mechanism utilized in signal transduction and other diverse cellular processes. Protein denitrosylation is largely mediated by cysteine denitrosylases, but the functional scope and significance of these enzymes are incompletely defined, in part due to limited information on their cognate substrates. Here, using Jurkat cells, we employed stable isotope labeling by amino acids in cell culture (SILAC), coupled to the biotin switch technique and mass spectrometry, to identify 46 new substrates of one denitrosylase, thioredoxin 1. These substrates are involved in a wide range of cellular functions including cytoskeletal organization, cellular metabolism, signal transduction, and redox homeostasis. We also identified multiple S-nitrosylated proteins that are not substrates of thioredoxin 1. A verification of our principal findings was made in a second cell type (RAW264.7 cells). Our results point to thioredoxin 1 as a major protein denitrosylase in mammalian cells and demonstrate the utility of quantitative proteomics for large-scale identification of denitrosylase substrates.
    Biochemistry 08/2010; 49(32):6963-9. · 3.38 Impact Factor
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    ABSTRACT: S-Nitrosylation, the redox-based modification of Cys thiol side chains by nitric oxide, is a common mechanism in signal transduction. Dysregulated S-nitrosylation contributes to a range of human pathologies. New roles for protein denitrosylation in regulating S-nitrosylation are being revealed. Recently, several denitrosylases - the enzymes that mediate Cys denitrosylation - have been discovered, of which two enzyme systems in particular, the S-nitrosoglutathione reductase and thioredoxin systems, have been shown to be physiologically relevant. These highly conserved enzymes regulate signalling through multiple classes of receptors and influence diverse cellular responses. In addition, they protect from nitrosative stress in microorganisms, mammals and plants, thereby exerting profound effects on host-microbe interactions and innate immunity.
    Nature Reviews Molecular Cell Biology 10/2009; 10(10):721-32. · 37.16 Impact Factor
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    ABSTRACT: Nitric oxide exerts a plethora of biological effects via protein S-nitrosylation, a redox-based reaction that converts a protein Cys thiol to a S-nitrosothiol. However, although the regulation of protein S-nitrosylation has been the subject of extensive study, much less is known about the systems governing protein denitrosylation. Most recently, thioredoxin/thioredoxin reductases were shown to mediate both basal and stimulus-coupled protein denitrosylation. We now demonstrate that protein denitrosylation by thioredoxin is regulated dynamically by thioredoxin-interacting protein (Txnip), a thioredoxin inhibitor. Endogenously synthesized nitric oxide represses Txnip, thereby facilitating thioredoxin-mediated denitrosylation. Autoregulation of denitrosylation thus allows cells to survive nitrosative stress. Our findings reveal that denitrosylation of proteins is dynamically regulated, establish a physiological role for thioredoxin in protection from nitrosative stress, and suggest new approaches to manipulate cellular S-nitrosylation.
    Journal of Biological Chemistry 10/2009; 284(52):36160-6. · 4.65 Impact Factor
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    ABSTRACT: Protein S-nitrosylation, the posttranslational modification of cysteine thiols to form S-nitrosothiols, is a principle mechanism of nitric oxide-based signaling. Studies have demonstrated myriad roles for S-nitrosylation in organisms from bacteria to humans, and recent efforts have greatly advanced our scientific understanding of how this redox-based modification is dynamically regulated during physiological and pathophysiological conditions. The focus of this review is the biotin-switch technique (BST), which has become a mainstay assay for detecting S-nitrosylated proteins in complex biological systems. Potential pitfalls and modern adaptations of the BST are discussed, as are future directions for this assay in the burgeoning field of protein S-nitrosylation.
    Free Radical Biology and Medicine. 01/2009;
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    ABSTRACT: Nitric oxide acts substantially in cellular signal transduction through stimulus-coupled S-nitrosylation of cysteine residues. The mechanisms that might subserve protein denitrosylation in cellular signaling remain uncharacterized. Our search for denitrosylase activities focused on caspase-3, an exemplar of stimulus-dependent denitrosylation, and identified thioredoxin and thioredoxin reductase in a biochemical screen. In resting human lymphocytes, thioredoxin-1 actively denitrosylated cytosolic caspase-3 and thereby maintained a low steady-state amount of S-nitrosylation. Upon stimulation of Fas, thioredoxin-2 mediated denitrosylation of mitochondria-associated caspase-3, a process required for caspase-3 activation, and promoted apoptosis. Inhibition of thioredoxin-thioredoxin reductases enabled identification of additional substrates subject to endogenous S-nitrosylation. Thus, specific enzymatic mechanisms may regulate basal and stimulus-induced denitrosylation in mammalian cells.
    Science 06/2008; 320(5879):1050-4. · 31.20 Impact Factor
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    ABSTRACT: beta-adrenergic receptors (beta-ARs), prototypic G-protein-coupled receptors (GPCRs), play a critical role in regulating numerous physiological processes. The GPCR kinases (GRKs) curtail G-protein signaling and target receptors for internalization. Nitric oxide (NO) and/or S-nitrosothiols (SNOs) can prevent the loss of beta-AR signaling in vivo, but the molecular details are unknown. Here we show in mice that SNOs increase beta-AR expression and prevent agonist-stimulated receptor downregulation; and in cells, SNOs decrease GRK2-mediated beta-AR phosphorylation and subsequent recruitment of beta-arrestin to the receptor, resulting in the attenuation of receptor desensitization and internalization. In both cells and tissues, GRK2 is S-nitrosylated by SNOs as well as by NO synthases, and GRK2 S-nitrosylation increases following stimulation of multiple GPCRs with agonists. Cys340 of GRK2 is identified as a principal locus of inhibition by S-nitrosylation. Our studies thus reveal a central molecular mechanism through which GPCR signaling is regulated.
    Cell 06/2007; 129(3):511-22. · 31.96 Impact Factor
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    ABSTRACT: S-Nitrosylation, the covalent addition of a nitrogen monoxide group to a cysteine thiol, has been shown to modify the function of a broad spectrum of mammalian, plant, and microbial proteins and thereby to convey the ubiquitous influence of nitric oxide on cellular signal transduction and host defense. Accumulating evidence indicates that dysregulated, diminished, or excessive S-nitrosylation may be implicated in a wide range of pathophysiological conditions. A recent study establishes a functional relationship between inhibitory S-nitrosylation of the redox enzyme protein disulfide isomerase (PDI), defects in regulation of protein folding within the endoplasmic reticulum (ER), and neurodegeneration. Further, an examination of human brains afflicted with Parkinson's or Alzheimer's disease supports a causal role for the S-nitrosylation of PDI and consequent ER stress in these prevalent neurodegenerative disorders.
    ACS Chemical Biology 08/2006; 1(6):355-8. · 5.44 Impact Factor
  • Moran Benhar, Jonathan S Stamler
    Nature Cell Biology 08/2005; 7(7):645-6. · 20.76 Impact Factor
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    ABSTRACT: Increasing evidence suggests that enhanced production of reactive oxygen species (ROS) activates the MAP kinases, c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase MAPK (p38). These phosphorylated intermediates at the stress-activated pathway induce expression of matrix metalloproteinases (MMPs), leading to inflammatory responses and pathological damages involved in the etiology of multiple sclerosis (MS). Here we report that N-acetylcysteine amide (AD4) crosses the blood-brain barrier (BBB), chelates Cu(2+), which catalyzes free radical formation, and prevents ROS-induced activation of JNK, p38 and MMP-9. In the myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, oral administration of AD4 drastically reduced the clinical signs, inflammation, MMP-9 activity, and protected axons from demylination damages. In agreement with the in vitro studies, we propose that ROS scavenging by AD4 in MOG-treated animals prevented MMP's induction and subsequent damages through inhibition of MAPK pathway. The low toxicity of AD4 coupled with BBB penetration makes this compound an excellent potential candidate for the therapy of MS and other neurodegenerative disorders.
    Journal of Neurochemistry 07/2004; 89(5):1241-51. · 3.97 Impact Factor
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Publication Stats

680 Citations
79 Downloads
889 Views
152.08 Total Impact Points

Institutions

  • 2010–2013
    • Technion - Israel Institute of Technology
      • • Ruth and Bruce Rappaport Faculty of Medicine
      • • Department of Biochemistry
      H̱efa, Haifa District, Israel
  • 2006–2009
    • Duke University Medical Center
      • • Department of Medicine
      • • Department of Biochemistry
      Durham, North Carolina, United States