Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activation of the transcription factor Nrf2 regulates expression of phase II enzymes and other adaptive responses to electrophile and oxidant stress. Nrf2 concentrations are regulated by the thiol-rich sensor protein Keap1, which is an adaptor protein for Cul3-dependent ubiquitination and degradation of Nrf2. However, the links between site specificity of Keap1 modification by electrophiles and mechanisms of Nrf2 activation are poorly understood. We studied the actions of the prototypical Nrf2 inducer tert-butylhydroquinone (tBHQ) and two biotin-tagged, thiol-reactive electrophiles, N-iodoacetyl-N-biotinylhexylenediamine (IAB) and 1-biotinamido-4-(4'-[maleimidoethyl-cyclohexane]-carboxamido)butane (BMCC). Both IAB and tBHQ induced antioxidant response element (ARE)-directed green fluorescent protein (GFP) expression in ARE/thymidine kinase GFP HepG2 cells, and both initiated nuclear Nrf2 accumulation and induction of heme oxygenase 1 in HEK293 cells. In contrast, BMCC produced none of these effects. Liquid chromatography tandem mass spectrometry (MS-MS) analysis of human Keap1 modified by IAB or BMCC in vitro indicated that IAB adduction occurred primarily in the central linker domain, whereas BMCC modified other Keap1 domains. Treatment of FLAG-Keap1-transfected HEK293 with the Nrf2-activating compounds IAB and tBHQ generated high molecular weight Keap1 forms, which were identified as K-48-linked polyubiquitin conjugates by immunoblotting and liquid chromatography MS-MS. Keap1 polyubiquitination coincided with Nrf2 stabilization and nuclear accumulation. In contrast, BMCC did not induce Keap1 polyubiquitination. Our results suggest that Nrf2 activation is regulated through the polyubiquitination of Keap1, which in turn is triggered by specific patterns of electrophile modification of the Keap1 central linker domain. These results suggest that Keap1 adduction triggers a switching of Cul3-dependent ubiquitination from Nrf2 to Keap1, leading to Nrf2 activation.
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PMID:Specific patterns of electrophile adduction trigger Keap1 ubiquitination and Nrf2 activation. 1598 29

ABSTRUCT: Parkinson's disease (PD) is associated with progressive degeneration of melanin-containing dopamine neuron cell bodies arising in the substantia nigra pars compacta (SNpc) and projecting terminals to the striatum. The disease is best characterized biochemically as a deficiency of striatal dopamine. The mechanism of neurodegeneration remains an enigma despite a large body of investigation and several hypotheses (1-5). In the past decade much has been learned about the chemical pathology of the disease. This progress has been helped by elucidation of the mechanism of the neurotoxic actions of 6-hydroxydopamine (6-OHDA) and N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which are used to induce animal models of this disease. Thus, the most valid current hypothesis concerning the pathogenesis of idiopathic PD is progressive oxidative stress (OS), which can generate excessive reactive oxygen species (ROS) selectively in the SNpc (1-9), and subsequent biochemical abnormalities (Table 1). In addition, the ROS scavenging system may also diminish, which would exaggerate the condition leading to accumulation of ROS. In PD, it is thought that both these events occur; Table 1 gives a summary of the biochemical changes identified to date in the SNpc of PD patients. Iron, monoamine oxidase B (MAO-B), copper/zinc superoxide dismutase (Cu/Zn-SOD), and heme oxygenase (radical producing) are increased; reduced glutathione (GSH) and vitamin C (radical scavenging) are decreased. Whether OS is a primary or secondary event in PD has not been established, but when it does occur, OS can lead to a cascade of events resulting in the demise of the nigrostriatal dopaminergic neurons. One approach toward protection of such neurons is the use of radical scavengers or iron chelators as neuroprotective drugs (10). Table 1 Biochemical Alterations in Substantia Nigra of Parkinson's Disease Indicating Oxidative Stress Elevated Decreased Iron (in microglia, astrocytes, oligodendrocytes, and melanized dopamine neurons and mitochondria) GSH (GSSG unchanged); GSH/GSSG ratio decreased Mitochondrial complex I Ferritin Calcium binding protein (calbindin 28) Mitochondrial monoamine oxidase B Transferrin and transferrin receptor Lipofuscin Vitamins E and C Ubiquitin Copper Cu/Zn-superoxide dismutase Cytotoxic cytokines (TNF-a, IL-1, IL-6) Inflammatory transcription factor NFKB Heme oxygenase-1 Ratio of oxidized to reduced glutathione (GSSG/GSH) Nitric oxide Neuromelanin.
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PMID:Oxidative stress indices in Parkinson's disease : biochemical determination. 2131 73