共查询到20条相似文献,搜索用时 15 毫秒
1.
Eun Sil Kang Jaeyong Lee Takujiro Homma Toshihiro Kurahashi Sho Kobayashi Atsunori Nabeshima 《Free radical research》2017,51(1):80-90
Cystine, an oxidized form of cysteine (Cys), is imported into cells via the protein xCT, which is also associated with the export of glutamate as the counter amino acid. In the current study, we attempted to rationalize roles of xCT in the livers of male mice. While xCT was not expressed in the livers of ordinary mice, it was induced under conditions of glutathione depletion, caused by the administration of acetaminophen (AAP). To differentiate the role between xCT and the transsulfuration pathway on the supply of Cys, we employed an inhibitor of the enzyme cystathionine γ-lyase, propargylglycine (PPG). This inhibitor caused a marked aggravation in AAP-induced hepatic damage and the mortality of the xCT?/? mice was increased to a greater extent than that for the xCT+/+ mice. While a PPG pretreatment had no effect on liver condition or Cys levels, the administration of AAP to the PPG-pretreated mice reduced the levels of Cys as well as glutathione to very low levels in both the xCT+/+ and xCT?/? mice. These findings indicate that the transsulfuration pathway plays a major role in replenishing Cys when glutathione levels are low. Moreover, an ascorbic acid insufficiency, induced by Akr1a ablation, further aggravated the AAP-induced liver damage in the case of the xCT deficiency, indicating that glutathione and ascorbic acid function cooperatively in protecting the liver. In conclusion, while the transsulfuration pathway plays a primary role in supplying Cys to the redox system in the liver, xCT is induced in cases of emergencies, by compensating for Cys supply systems. 相似文献
2.
3.
The oxidative stress-inducible cystine/glutamate exchange system, system xc−, transports one molecule of cystine, the oxidized form of cysteine, into cells and thereby releases one molecule of glutamate
into the extracellular space. It consists of two protein components, the 4F2 heavy chain, necessary for membrane location
of the heterodimer, and the xCT protein, responsible for transport activity. Previously, system xc− has been regarded to be a mere supplier of cysteine to cells for the synthesis of proteins and the antioxidant glutathione
(GSH). In that sense, oxygen, electrophilic agents, and bacterial lipopolysaccharide trigger xCT expression to accommodate
with increased oxidative stress by stimulating GSH biosynthesis. However, emerging evidence established that system xc− may act on its own as a GSH-independent redox system by sustaining a redox cycle over the plasma membrane. Hallmarks of this
cycle are cystine uptake, intracellular reduction to cysteine and secretion of the surplus of cysteine into the extracellular
space. Consequently, increased levels of extracellular cysteine provide a reducing microenvironment required for proper cell
signaling and communication, e.g. as already shown for the mechanism of T cell activation. By contrast, the enhanced release
of glutamate in exchange with cystine may trigger neurodegeneration due to glutamate-induced cytotoxic processes. This review
aims to provide a comprehensive picture from the early days of system xc− research up to now. 相似文献
4.
5.
Sho Kobayashi Mami Sato Takayuki Kasakoshi Takumi Tsutsui Masahiro Sugimoto Mitsuhiko Osaki Futoshi Okada Kiharu Igarashi Jun Hiratake Takujiro Homma Marcus Conrad Junichi Fujii Tomoyoshi Soga Shiro Bannai Hideyo Sato 《The Journal of biological chemistry》2015,290(14):8778-8788
The cystine/glutamate transporter, designated as system xc−, is important for maintaining intracellular glutathione levels and extracellular redox balance. The substrate-specific component of system xc−, xCT, is strongly induced by various stimuli, including oxidative stress, whereas it is constitutively expressed only in specific brain regions and immune tissues, such as the thymus and spleen. Although cystine and glutamate are the well established substrates of system xc− and the knockout of xCT leads to alterations of extracellular redox balance, nothing is known about other potential substrates. We thus performed a comparative metabolite analysis of tissues from xCT-deficient and wild-type mice using capillary electrophoresis time-of-flight mass spectrometry. Although most of the analyzed metabolites did not show significant alterations between xCT-deficient and wild-type mice, cystathionine emerged as being absent specifically in the thymus and spleen of xCT-deficient mice. No expression of either cystathionine β-synthase or cystathionine γ-lyase was observed in the thymus and spleen of mice. In embryonic fibroblasts derived from wild-type embryos, cystine uptake was significantly inhibited by cystathionine in a concentration-dependent manner. Wild-type cells showed an intracellular accumulation of cystathionine when incubated in cystathionine-containing buffer, which concomitantly stimulated an increased release of glutamate into the extracellular space. By contrast, none of these effects could be observed in xCT-deficient cells. Remarkably, unlike knock-out cells, wild-type cells could be rescued from cystine deprivation-induced cell death by cystathionine supplementation. We thus conclude that cystathionine is a novel physiological substrate of system xc− and that the accumulation of cystathionine in immune tissues is exclusively mediated by system xc−. 相似文献
6.
Tadayuki Tsujita Vivian Peirce Liam Baird Yuka Matsuyama Misaki Takaku Shawn V. Walsh Julian L. Griffin Akira Uruno Masayuki Yamamoto John D. Hayes 《Molecular and cellular biology》2014,34(20):3800-3816
Liver-specific Nrf1 (NF-E2-p45-related factor 1) knockout mice develop nonalcoholic steatohepatitis. To identify postnatal mechanisms responsible for this phenotype, we generated an inducible liver-specific Nrf1 knockout mouse line using animals harboring an Nrf1flox allele and a rat CYP1A1-Cre transgene (Nrf1flox/flox::CYP1A1-Cre mice). Administration of 3-methylcholanthrene (3-MC) to these mice (Nrf1flox/flox::CYP1A1-Cre+3MC mice) resulted in loss of hepatic Nrf1 expression. The livers of mice lacking Nrf1 accumulated lipid, and the hepatic fatty acid (FA) composition in such animals differed significantly from that in the Nrf1flox/flox::CYP1A1-Cre control. This change was provoked by upregulation of several FA metabolism genes. Unexpectedly, we also found that the level of glutathione was increased dramatically in livers of Nrf1flox/flox::CYP1A1-Cre+3MC mice. While expression of glutathione biosynthetic enzymes was unchanged, xCT, a component of the cystine/glutamate antiporter system xc−, was significantly upregulated in livers of Nrf1flox/flox::CYP1A1-Cre+3MC mice, suggesting that Nrf1 normally suppresses xCT. Thus, stress-inducible expression of xCT is a two-step process: under homeostatic conditions, Nrf1 effectively suppresses nonspecific transactivation of xCT, but when cells encounter severe oxidative/electrophilic stress, Nrf1 is displaced from an antioxidant response element (ARE) in the gene promoter while Nrf2 is recruited to the ARE. Thus, Nrf1 controls both the FA and the cystine/cysteine content of hepatocytes by participating in an elaborate regulatory network. 相似文献
7.
Dun Y Mysona B Van Ells T Amarnath L Ola MS Ganapathy V Smith SB 《Cell and tissue research》2006,324(2):189-202
The cystine-glutamate exchanger, system xc
−, mediates the Na+-independent exchange of cystine into cells, coupled to the efflux of intracellular glutamate. System xc
− plays a critical role in glutathione homeostasis. Early studies of brain suggested that system xc
− was present primarily in astrocytes but not neurons. More recent work indicates that certain brain neurons have an active system xc
−. In the retina, system xc
− has been demonstrated in Müller and retinal pigment epithelial cells. We have recently suggested that two protein components of system xc
−, xCT and 4F2hc, are present in ganglion cells of the intact retina. Here, we have used (1) molecular and immunohistochemical assays to determine whether system xc
− is present in primary ganglion cells isolated from neonatal mouse retinas and (2) functional assays to determine whether its activity is regulated by oxidative stress in a retinal ganglion cell line (RGC–5). Primary mouse ganglion cells and RGC–5 cells express xCT and 4F2hc. RGC–5 cells take up [3H]glutamate in the absence of Na+, and this uptake is blocked by known substrates of system xc
− (glutamate, cysteine, cystine, quisqualic acid). Treatment of RGC–5 cells with NO and reactive oxygen species donors leads to increased activity of system xc
− associated with an increase in the maximal velocity of the transporter with no significant change in the substrate affinity. This is the first report of system xc
− in primary retinal ganglion cells and RGC–5 cells. Oxidative stress upregulates this transport system in RGC–5 cells, and the process is associated with an increase in xCT mRNA and protein but no change in 4F2hc mRNA or protein. This work was supported by National Institutes of Health grants EY014560 and EY012830. 相似文献
8.
The cystine/glutamate exchanger (antiporter xc−) is a membrane transporter involved in the uptake of cystine, the rate-limiting amino acid in the synthesis of glutathione.
Recent studies suggest that the antiporter plays a role in the slow oxidative excitotoxity and in the pathological effects
of β-N-oxalylamino-l-alanine, the molecule responsible for neurolathyrism, a neurotoxic upper motor neuron disease. The mouse cystine/glutamate
exchanger has been cloned and showed to be composed of two distinct proteins, one of which being a novel protein, named xCT,
of 502 amino acids and 12 putative trans-membrane domains. We have generated and purified a polyclonal antibody to mouse xCT
and studied its expression in rat brain and in different cultured cells (astrocytes, fibroblasts and neurons) using Western
blot and immunocytochemical techniques. Expression of xCT was also studied in rat brain and muscle at different developmental
stages. Parallel experiments were carried out with antibodies to the heavy chain of 4F2 surface antigen, the non-specific
subunit of the antiporter xc−. xCT antibody detected in all cell and tissue extracts a specific band of about 40 kDa. Subcellular fractionation demonstrated
that xCT is concentrated mainly in the microsomal-mitochondrial fraction, in accord with its structure as transmembrane protein.
Immunocytochemical analysis showed a strong staining in all cells examined, included neurons. Furthermore, both xCT and the
heavy chain of 4F2 surface antigen increased in the brain during development, reaching the highest expression in adulthood.
The study of the expression and developmental profile of xCT represents a first step towards a better characterization of
its biochemical properties and function, which in turn may help to understand the relative contribution of the xc− antiporter in the pathogenesis of certain neurodegenerative diseases. 相似文献
9.
McBean GJ 《Amino acids》2012,42(1):199-205
Astrocyte cells require cysteine as a substrate for glutamate cysteine ligase (γ-glutamylcysteine synthase; EC 6.3.2.2) catalyst
of the rate-limiting step of the γ-glutamylcycle leading to formation of glutathione (l-γ-glutamyl-l-cysteinyl-glycine; GSH). In both astrocytes and glioblastoma/astrocytoma cells, the majority of cysteine originates from
reduction of cystine imported by the xc− cystine-glutamate exchanger. However, the transsulfuration pathway, which supplies cysteine from the indispensable amino
acid, methionine, has recently been identified as a significant contributor to GSH synthesis in astrocytes. The purpose of
this review is to evaluate the importance of the transsulfuration pathway in these cells, particularly in the context of a
reserve pathway that channels methionine towards cysteine when the demand for glutathione is high, or under conditions in
which the supply of cystine by the xc− exchanger may be compromised. 相似文献
10.
Katarzyna Chojnacka Ralph Brehm Karola Weider Anna Hejmej Marta Lydka Ilona Kopera-Sobota Barbara Bilinska 《Reproductive biology》2012,12(4):341-346
Gap junctions are intercellular channels that connect the cytoplasm of adjacent cells, allowing the passage of small molecules (<1 kDa) and thereby the regulation of many different processes. In the male gonad, the most abundant protein that builds gap junctions is connexin 43 (Cx43, GJA1). Specific knock-out of Sertoli cells (SCCx43KO?/?) results in an impaired spermatogenesis up to the Sertoli cell only syndrome. The aim of this study was to compare the testicular expression pattern of the androgen receptor (AR) in wild type (WT) and SCCx43KO?/? mice. In both WT and SCCx43KO?/? testes, the AR staining was restricted to the nuclei of Sertoli, Leydig, and peritubular cells. However, the staining intensity varied between control and mutant mice. In the latter, the AR expression depended on the level of the seminiferous tubule impairment. In tubules with qualitatively normal spermatogenesis, the AR protein expression was similar to that observed in the testes of WT mice. Conversely, seminiferous tubules with an arrest of spermatogenesis at the level of spermatogonial or spermatocyte phase expressed the AR at a lower intensity. In Sertoli cell only tubules (no germ cells in the tubules), the AR immunoreaction was mainly weak or undetectable. Moreover, AR staining was lower in Sertoli and Leydig cells (p < 0.001 and p < 0.05, respectively) of SCCx43KO?/? mice compared to WT mice, as revealed by a semiquantitative analysis. In conclusion, the deletion of Cx43 leads to a partial disruption of the AR signaling pathway, indicating a possible reason for the observed impaired spermatogenesis. 相似文献
11.
12.
Despite longstanding evidence that hypoglycaemic neuronal injury is mediated by glutamate excitotoxicity, the cellular and molecular mechanisms involved remain incompletely defined. Here, we demonstrate that the excitotoxic neuronal death that follows GD (glucose deprivation) is initiated by glutamate extruded from astrocytes via system xc− – an amino acid transporter that imports l-cystine and exports l-glutamate. Specifically, we find that depriving mixed cortical cell cultures of glucose for up to 8 h injures neurons, but not astrocytes. Neuronal death is prevented by ionotropic glutamate receptor antagonism and is partially sensitive to tetanus toxin. Removal of amino acids during the deprivation period prevents – whereas addition of l-cystine restores – GD-induced neuronal death, implicating the cystine/glutamate antiporter, system xc−. Indeed, drugs known to inhibit system xc− ameliorate GD-induced neuronal death. Further, a dramatic reduction in neuronal death is observed in chimaeric cultures consisting of neurons derived from WT (wild-type) mice plated on top of astrocytes derived from sut mice, which harbour a naturally occurring null mutation in the gene (Slc7a11) that encodes the substrate-specific light chain of system xc− (xCT). Finally, enhancement of astrocytic system xc− expression and function via IL-1β (interleukin-1β) exposure potentiates hypoglycaemic neuronal death, the process of which is prevented by removal of l-cystine and/or addition of system xc− inhibitors. Thus, under the conditions of GD, our studies demonstrate that astrocytes, via system xc−, have a direct, non-cell autonomous effect on cortical neuron survival. 相似文献
13.
NF-E2-related factor 2 (Nrf2), known to protect against reactive oxygen species, has recently been reported to resolve acute inflammatory responses in activated macrophages. Consequently, disruption of Nrf2 promotes a proinflammatory macrophage phenotype. In the current study, we addressed the impact of this macrophage phenotype on CD8+ T cell activation by using an antigen-driven coculture model consisting of Nrf2−/− and Nrf2+/+ bone marrow-derived macrophages (BMDMΦ) and transgenic OT-1 CD8+ T cells. OT-1 CD8+ T cells encode a T cell receptor that specifically recognizes MHC class I-presented ovalbumin OVA(257–264) peptide, thereby causing a downstream T cell activation. Interestingly, coculture of OVA(257–264)-pulsed Nrf2−/− BMDMΦ with transgenic OT-1 CD8+ T cells attenuated CD8+ T cell activation, proliferation, and cytotoxic function. Since the provision of low-molecular-weight thiols such as glutathione (GSH) or cysteine (Cys) by macrophages limits antigen-driven CD8+ T cell activation, we quantified the amounts of intracellular and extracellular GSH and Cys in both cocultures. Indeed, GSH levels were strongly decreased in Nrf2−/− cocultures compared to wild-type counterparts. Supplementation of thiols in Nrf2−/− cocultures via addition of glutathione ester, N-acetylcysteine, β-mercaptoethanol, or cysteine itself restored T cell proliferation as well as cytotoxicity by increasing intracellular GSH. Mechanistically, we identified two potential Nrf2-regulated genes involved in thiol synthesis in BMDMΦ: the cystine transporter subunit xCT and the modulatory subunit of the GSH-synthesizing enzyme γ-GCS (GCLM). Pharmacological inhibition of γ-GCS-dependent GSH synthesis as well as knockdown of the cystine antiporter xCT in Nrf2+/+ BMDMΦ mimicked the effect of Nrf2−/− BMDMΦ on CD8+ T cell function. Our findings demonstrate that reduced levels of GCLM as well as xCT in Nrf2−/− BMDMΦ limit GSH availability, thereby inhibiting antigen-induced CD8+ T cell function. 相似文献
14.
15.
Tyrosine phosphorylation as evidence of epididymal cauda participation in the sperm maturation process of Corynorhinus mexicanus bat
下载免费PDF全文
![点击此处可从《Acta zoologica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ahiezer Rodríguez‐Tobón Reyna Fierro Miguel Angel León‐Galván Adolfo Rosado Edith Cortés‐Barberena Edith Arenas‐Ríos 《Acta zoologica》2016,97(3):310-318
The bat Corynorhinus mexicanus provides an interesting experimental model for the study of epididymal sperm maturation because after spermatogenesis and the regression of the testes, this bat stores sperm in the epididymal cauda for several months. Earlier research conducted by our group suggested that sperm maturation in this species must be completed in the caudal region of the epididymis. One of the major signal transduction events during sperm maturation is the tyrosine phosphorylation of sperm proteins. The aim of the present study was to comparatively evaluate tyrosine phosphorylation in spermatozoa obtained from the caput, corpus and cauda of the epididymis during the sperm storage period. The maturation status of the sperm was determined by the percentage of capacitation and tyrosine phosphorylation in sperm obtained from the epididymis. The highest proportion of tyrosine phosphorylation was registered after the sperm had reached the cauda epididymis during the middle of the storage period. In conclusion, in Corynorhinus mexicanus and most likely in other chiropteran species with an asynchronous male reproductive pattern, epididymal sperm maturation ends in the caudal region of the epididymis and is related to the time that the sperm remains in the epididymis before mating activity. 相似文献
16.
S. Schöniger T. Caprile C. R. Yulis Q. Zhang E. M. Rodríguez F. Nürnberger 《Cell and tissue research》2009,336(3):477-488
Elevated glutamate levels have been reported in humans with diabetic retinopathy. Retinal Müller glial cells regulate glutamate
levels via the GLAST transporter and system xc
− (cystine-glutamate exchanger). We have investigated whether transporter function and gene and/or protein expression are altered
in mouse Müller cells cultured under conditions of hyperglycemia or oxidative stress (two factors implicated in diabetic retinopathy).
Cells were subjected to hyperglycemic conditions (35 mM glucose) over an 8-day period or to oxidative stress conditions (induced
by exposure to various concentrations of xanthine:xanthine oxidase) for 6 h. The Na+-dependent and –independent uptake of [3H] glutamate was assessed as a measure of GLAST and system xc
− function, respectively. Hyperglycemia did not alter the uptake of [3H] glutamate by GLAST or system xc
−; neither gene nor protein expression decreased. Oxidative stress (70:14 or 100:20 μM xanthine:mU/ml xanthine oxidase) decreased
GLAST activity by ~10% but increased system xc
− activity by 43% and 89%, respectively. Kinetic analysis showed an oxidative-stress-induced change in Vmax, but not Km. Oxidative stress caused a 2.4-fold increase in mRNA encoding xCT, the unique component of system xc
−. Of the two isoforms of xCT (40 and 50 kDa), oxidative stress induced a 3.6-fold increase in the 40-kDa form localized to
the plasma membrane. This is the first report of the differential expression and localization of xCT isoforms as caused by
cellular stress. Increased system xc
− activity in Müller cells subjected to conditions associated with diabetic retinopathy may be beneficial, as this exchanger
is important for the synthesis of the antioxidant glutathione.
This work was supported by NIH R01 EY014560. 相似文献
17.
Redox imbalance in cystine/glutamate transporter-deficient mice 总被引:1,自引:0,他引:1
Sato H Shiiya A Kimata M Maebara K Tamba M Sakakura Y Makino N Sugiyama F Yagami K Moriguchi T Takahashi S Bannai S 《The Journal of biological chemistry》2005,280(45):37423-37429
Cystine/glutamate transporter, designated as system x(-)(c), mediates cystine entry in exchange for intracellular glutamate in mammalian cells. This transporter consists of two protein components, xCT and 4F2 heavy chain, and the former is predicted to mediate the transport activity. This transporter plays a pivotal role for maintaining the intracellular GSH levels and extracellular cystine/cysteine redox balance in cultured cells. To clarify the physiological roles of this transporter in vivo, we generated and characterized mice lacking xCT. The xCT(-/-) mice were healthy in appearance and fertile. However, cystine concentration in plasma was significantly higher in these mice, compared with that in the littermate xCT(-/-) mice, while there was no significant difference in plasma cysteine concentration. Plasma GSH level in xCT(-/-) mice was lower than that in the xCT(-/-) mice. The embryonic fibroblasts derived from xCT(-/-) mice failed to survive in routine culture medium, and 2-mercaptoethanol was required for survival and growth. When 2-mercaptoethanol was removed from the culture medium, cysteine and GSH in these cells dramatically decreased, and cells started to die within 24 h. N-Acetyl cysteine also rescued xCT(-/-)-derived cells and permitted growth. These results demonstrate that system x(-)(c) contributes to maintaining the plasma redox balance in vivo but is dispensable in mammalian development, although it is vitally important to cells in vitro. 相似文献
18.
Ajit G. Thomas Rita Sattler Karen Tendyke Kara A. Loiacono Hans Hansen Vishal Sahni Yutaka Hashizume Camilo Rojas Barbara S. Slusher 《PloS one》2015,10(8)
The cystine-glutamate antiporter (system xc
-) is a Na+-independent amino acid transporter that exchanges extracellular cystine for intracellular glutamate. It is thought to play a critical role in cellular redox processes through regulation of intracellular glutathione synthesis via cystine uptake. In gliomas, system xc
- expression is universally up-regulated while that of glutamate transporters down-regulated, leading to a progressive accumulation of extracellular glutamate and excitotoxic cell death of the surrounding non-tumorous tissue. Additionally, up-regulation of system xc
- in activated microglia has been implicated in the pathogenesis of several neurodegenerative disorders mediated by excess glutamate. Consequently, system xc
- is a new drug target for brain cancer and neuroinflammatory diseases associated with excess extracellular glutamate. Unfortunately no potent and selective small molecule system xc
- inhibitors exist and to our knowledge, no high throughput screening (HTS) assay has been developed to identify new scaffolds for inhibitor design. To develop such an assay, various neuronal and non-neuronal human cells were evaluated as sources of system xc
-. Human glioma cells were chosen based on their high system xc
- activity. Using these cells, [14C]-cystine uptake and cystine-induced glutamate release assays were characterized and optimized with respect to cystine and protein concentrations and time of incubation. A pilot screen of the LOPAC/NINDS libraries using glutamate release demonstrated that the logistics of the assay were in place but unfortunately, did not yield meaningful pharmacophores. A larger, HTS campaign using the 384-well cystine-induced glutamate release as primary assay and the 96-well 14C-cystine uptake as confirmatory assay is currently underway. Unexpectedly, we observed that the rate of cystine uptake was significantly faster than the rate of glutamate release in human glioma cells. This was in contrast to the same rates of cystine uptake and glutamate release previously reported in normal human fibroblast cells. 相似文献
19.
20.
Sebastien L'hoste Abderrahmen Chargui Radia Belfodil Christophe Duranton Isabelle Rubera Baharia Mograbi Chantal Poujeol Michel Tauc Philippe Poujeol 《Free radical biology & medicine》2009,46(8):1017-1031
The aim of this study was to characterize the role of CFTR during Cd2+-induced apoptosis. For this purpose primary cultures and cell lines originated from proximal tubules (PCT) of wild-type cftr+/+ and cftr?/? mice were used. In cftr+/+ cells, the application of Cd2+ (5 μM) stimulated within 8 min an ERK1/2-activated CFTR-like Cl? conductance sensitive to CFTRinh-172. Thereafter Cd2+ induced an apoptotic volume decrease (AVD) within 6 h followed by caspase-3 activation and apoptosis. The early increase in CFTR conductance was followed by the activation of volume-sensitive outwardly rectifying (VSOR) Cl? and TASK2 K+ conductances. By contrast, cftr?/? cells exposed to Cd2+ were unable to develop VSOR currents, caspase-3 activity, and AVD process and underwent necrosis. Moreover in cftr+/+ cells, Cd2+ enhanced reactive oxygen species (ROS) production and induced a 50% decrease in total glutathione content (major ROS scavenger in PCT). ROS generation and glutathione decrease depended on the presence of CFTR, since they did not occur in the presence of CFTRinh-172 or in cftr?/? cells. Additionally, Cd2+ exposure accelerates effluxes of fluorescent glutathione S-conjugate in cftr+/+ cells. Our data suggest that CFTR could modulate ROS levels to ensure apoptosis during Cd2+ exposure by modulating the intracellular content of glutathione. 相似文献