5 research outputs found
Extremely conserved ATP- or ADP-dependent enzymatic system for nicotinamide nucleotide repair
No full textpeer reviewedThe reduced forms of NAD and NADP, two major nucleotides playing a central role in metabolism, are continuously damaged by enzymatic or heat-dependent hydration. We report the molecular identification of the eukaryotic dehydratase that repairs these nucleotides and show that this enzyme (Carkd in mammals, YKL151C in yeast) catalyzes the dehydration of the S form of NADHX and NADPHX, at the expense of ATP, which is converted to ADP. Surprisingly, the Escherichia coli homolog, YjeF, a bidomain protein, catalyzes a similar reaction, but using ADP instead of ATP. The latter reaction is ascribable to the C-terminal domain of YjeF. This represents an unprecedented example of orthologous enzymes using either ADP or ATP as phosphoryl donor. We also show that eukaryotic proteins homologous to the N-terminal domain of YjeF (apolipoprotein A-1-binding protein (AIBP) in mammals, YNL200C in yeast) catalyze the epimerization of the S and R forms of NAD(P)HX, thereby allowing, in conjunction with the energy-dependent dehydratase, the repair of both epimers of NAD(P)HX. Both enzymes are very widespread in eukaryotes, prokaryotes, and archaea, which together with the ADP dependence of the dehydratase in some species indicates the ancient origin of this repair system
Occurrence and subcellular distribution of the NAD(P)HX repair system in mammals.
No full textpeer reviewedHydration of NAD(P)H to NAD(P)HX, which inhibits several dehydrogenases, is corrected by an ATP-dependent dehydratase and an epimerase recently identified as the products of the vertebrate Carkd (carbohydrate kinase domain) and Aibp (apolipoprotein AI-binding protein) genes respectively. The purpose of the present study was to assess the presence of these enzymes in mammalian tissues and determine their subcellular localization. The Carkd gene encodes proteins with a predicted mitochondrial propeptide (mCARKD), a signal peptide (spCARKD) or neither of them (cCARKD). Confocal microscopy analysis of transfected CHO (Chinese-hamster ovary) cells indicated that cCARKD remains in the cytosol, whereas mCARKD and spCARKD are targeted to the mitochondria and the endoplasmic reticulum respectively. Unlike the other two forms, spCARKD is N-glycosylated, supporting its targeting to the endoplasmic reticulum. The Aibp gene encodes two different proteins, which we show to be targeted to the mitochondria (mAIBP) and the cytosol (cAIBP). Quantification of the NAD(P)HX dehydratase and epimerase activities in rat tissues, performed after partial purification, indicated that both enzymes are widely distributed, with total activities of approximately 3-10 nmol/min per g of tissue. Liver fractionation by differential centrifugation confirmed the presence of the dehydratase and the epimerase in the cytosol and in mitochondria. These data support the notion that NAD(P)HX repair is extremely widespread
Recurrence of focal glomerulosclerosis despite cyclosporin treatment after renal transplantation.
No full textAuthor Correction: Early endosome autoantigen 1 regulates IL-1β release upon caspase-1 activation independently of gasdermin D membrane permeabilization
No full textInternational audienceBackground: Inflammasome-activated IL-1β plays a major role in lung neutrophilic inflammation induced by inhaled silica. However, the exact mechanisms that contribute to the initial production of precursor IL-1β (pro-IL-1β) are still unclear. Here, we assessed the implication of alarmins (IL-1α, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1α is a master cytokine that regulates IL-1β expression. Methods: Pro-and mature IL-1β as well as alarmins were assessed by ELISA, Western Blot or qRT-PCR in macrophage cultures and in mouse lung following nano-and micrometric silica exposure. Implication of these immune mediators in the establishment of lung inflammatory responses to silica was investigated in knockout mice or after antibody blockade by evaluating pulmonary neutrophil counts, CXCR2 expression and degree of histological injury. Results: We found that the early release of IL-1α and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1β and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1β by alveolar macrophages was significantly induced by recombinant IL-1α but not by IL-33. Neutralization or deletion of IL-1α reduced IL-1β production and neutrophil accumulation after silica in mice. Finally, IL-1α released by J774 macrophages after in vitro exposure to a range of micro-and nanoparticles of silica was correlated with the degree of lung inflammation induced in vivo by these particles. Conclusions: We demonstrated that in response to silica exposure, IL-1α is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1β production. Moreover, we demonstrated that in vitro IL-1α release from macrophages can be used to predict the acute inflammogenic activity of silica micro-and nanoparticles
