Uehara, T. et al. S-Nitrosylated protein-disulphide isomerase links protein misfolding to neurodegeneration. Nature 441, 513-517

Center for Neuroscience and Aging, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.
Nature (Impact Factor: 41.46). 06/2006; 441(7092):513-7. DOI: 10.1038/nature04782
Source: PubMed


Stress proteins located in the cytosol or endoplasmic reticulum (ER) maintain cell homeostasis and afford tolerance to severe insults. In neurodegenerative diseases, several chaperones ameliorate the accumulation of misfolded proteins triggered by oxidative or nitrosative stress, or of mutated gene products. Although severe ER stress can induce apoptosis, the ER withstands relatively mild insults through the expression of stress proteins or chaperones such as glucose-regulated protein (GRP) and protein-disulphide isomerase (PDI), which assist in the maturation and transport of unfolded secretory proteins. PDI catalyses thiol-disulphide exchange, thus facilitating disulphide bond formation and rearrangement reactions. PDI has two domains that function as independent active sites with homology to the small, redox-active protein thioredoxin. During neurodegenerative disorders and cerebral ischaemia, the accumulation of immature and denatured proteins results in ER dysfunction, but the upregulation of PDI represents an adaptive response to protect neuronal cells. Here we show, in brains manifesting sporadic Parkinson's or Alzheimer's disease, that PDI is S-nitrosylated, a reaction transferring a nitric oxide (NO) group to a critical cysteine thiol to affect protein function. NO-induced S-nitrosylation of PDI inhibits its enzymatic activity, leads to the accumulation of polyubiquitinated proteins, and activates the unfolded protein response. S-nitrosylation also abrogates PDI-mediated attenuation of neuronal cell death triggered by ER stress, misfolded proteins or proteasome inhibition. Thus, PDI prevents neurotoxicity associated with ER stress and protein misfolding, but NO blocks this protective effect in neurodegenerative disorders through the S-nitrosylation of PDI.

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    • "Because the chaperone activity of PDI1 is independent of its isomerase activity (Wang et al., 1997), we next determined the extent to which the decreased apoB lipidation was due to reduced MTP activity in Pdi1-knockdown cells. For this purpose, we delivered adenoviruses expressing either wild-type human PDI1 or a catalytically inactive PDI1 in which all four redox-active cysteines are mutated to alanines (Uehara et al., 2006) into Pdi1-knockdown cells. These experiments revealed that expression of either wildtype or catalytically inactive PDI1 fully restored MTP activity, yet TG secretion was only partially restored by the catalytically inactive PDI1 in Pdi1-knockdown cells (Figure 3, G–I). "
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    ABSTRACT: Apolipoprotein (apo) B is an obligatory component of very low-density lipoprotein (VLDL), whose co- and posttranslational modifications are important in VLDL synthesis, secretion and hepatic lipid homeostasis. ApoB100 contains 25 cysteine residues and 8 disulfide bonds. Although these disulfide bonds were suggested to be important in maintaining apoB100 function, neither the specific oxidoreductase involved nor the direct role of these disulfide bonds in apoB100-lipidation are known. Herein, we used RNA knockdown to evaluate both MTP-dependent and -independent roles of PDI1 in apoB100 synthesis and lipidation in McA-RH7777 cells. Pdi1-knockdown did not elicit any discernible detrimental effect under normal, unstressed conditions. However, it decreased apoB100 synthesis with attenuated MTP activity, delayed apoB100 oxidative folding and reduced apoB100 lipidation, leading to defective VLDL secretion. The oxidative folding-impaired apoB100 was secreted mainly associated with LDL instead of VLDL particles from PDI1-deficient cells, a phenotype which was fully rescued by overexpression of wildtype but not a catalytically inactive PDI1 that fully restored MTP activity. Further, we demonstrate that PDI1 directly interacts with apoB100 via its redox-active CXXC motifs and assist in the oxidative folding of apoB100. Taken together, these findings reveal an unsuspected, yet, key role for PDI1 in oxidative folding of apoB100 and VLDL assembly. © 2014 by The American Society for Cell Biology.
    Full-text · Article · Dec 2014 · Molecular Biology of the Cell
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    • "Because orexin-A has two intramolecular disulfide bonds that are located closely to each other, errors in formation of disulfide pairs may occur frequently in the course of biosynthesis of mature peptide. PDI plays a critical role in the repair of disulfide bonds (Andreu et al., 2012), but this enzyme is inactivated by S-nitrosation (Uehara et al., 2006). Therefore, under conditions associated with overproduction of NO, misfolded (pro-)orexin accumulates and neurodegeneration occurs selectively in orexin neurons (Obukuro et al., 2013). "
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    ABSTRACT: Loss of orexin neurons in the hypothalamus is a prominent feature of narcolepsy and several other neurological conditions. We have recently demonstrated that sleep deprivation stimulates local nitric oxide (NO) production by neuronal NO synthase in the lateral hypothalamus, which leads to selective degeneration of orexin neurons accompanied by formation of orexin-immunoreactive aggregates. Here we analyzed whether lifestyle-related conditions other than sleep deprivation could trigger similar pathological changes in orexin neurons. Male C57BL/6 mice were fed with high fat diet (HFD) for 8 weeks from 4 weeks old. Immunohistochemical analysis revealed that the number of orexin-immunopositive neurons was significantly decreased by HFD intake, whereas the number of melanin-concentrating hormone-immunopositive neurons was unchanged. In addition, HFD promoted formation of intracellular orexin-immunoreactive aggregates in a subset of orexin neurons. We also confirmed that expression of inducible NO synthase (iNOS) in the hypothalamus was upregulated in response to HFD intake. Notably, loss of orexin-immunopositive neurons and formation of orexin-immunoreactive aggregates were not observed in iNOS knockout mice fed with HFD. These results indicate that inappropriate dietary conditions could trigger specific neuropathological events in orexin neurons in an iNOS-dependent manner.
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    • "2.6. Detection of nitrosylated-PTEN using biotin switch assays PTEN S-nitrosylation was detected using biotin switch assays as described previously [13] [16] "
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    ABSTRACT: Hydrogen sulfide (H2S) is a gaseous regulatory factor produced by several enzymes, and plays a pivotal role in processes such as proliferation or vasodilation. Recent reports demonstrated the physiological and pathophysiological functions of H2S in neurons. PTEN is a target of nitric oxide (NO) or hydrogen peroxide, and the oxidative modification of cysteine (Cys) residue(s) attenuates its enzymatic activity. In the present study, we assessed the effect of H2S on the direct modification of PTEN and the resulting downstream signaling. A modified biotin switch assay in SH-SY5Y human neuroblastoma cells revealed that PTEN is S-sulfhydrated endogenously. Subsequently, site-directed mutagenesis demonstrated that both Cys71 and Cys124 in PTEN are targets for S-sulfhydration. Further, the knockdown of cystathionine β-synthetase (CBS) using siRNA decreased this modification in a manner that was correlated to amount of H2S. PTEN was more sensitive to NO under these conditions. These results suggest that the endogenous S-sulfhydration of PTEN via CBS/H2S plays a role in preventing the S-nitrosylation that would inhibition its enzymatic activity under physiological conditions.
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