Identification of the fructose transporter GLUT5 (SLC2A5) as a novel target of nuclear receptor LXR.
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ABSTRACT:
SUBMITTER: Zwarts I
PROVIDER: S-EPMC6594926 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundFructose is an abundant source of carbon and energy for cells to use for metabolism, but only certain cell types use fructose to proliferate. Tumor cells that acquire the ability to metabolize fructose have a fitness advantage over their neighboring cells, but the proteins that mediate fructose metabolism in this context are unknown. Here, we investigated the determinants of fructose-mediated cell proliferation.MethodsLive cell imaging and crystal violet assays were used to characterize the ability of several cell lines (RKO, H508, HepG2, Huh7, HEK293T (293T), A172, U118-MG, U87, MCF-7, MDA-MB-468, PC3, DLD1 HCT116, and 22RV1) to proliferate in fructose (i.e., the fructolytic ability). Fructose metabolism gene expression was determined by RT-qPCR and western blot for each cell line. A positive selection approach was used to "train" non-fructolytic PC3 cells to utilize fructose for proliferation. RNA-seq was performed on parental and trained PC3 cells to find key transcripts associated with fructolytic ability. A CRISPR-cas9 plasmid containing KHK-specific sgRNA was transfected in 293T cells to generate KHK-/- cells. Lentiviral transduction was used to overexpress empty vector, KHK, or GLUT5 in cells. Metabolic profiling was done with seahorse metabolic flux analysis as well as LC/MS metabolomics. Cell Titer Glo was used to determine cell sensitivity to 2-deoxyglucose in media containing either fructose or glucose.ResultsWe found that neither the tissue of origin nor expression level of any single gene related to fructose catabolism determine the fructolytic ability. However, cells cultured chronically in fructose can develop fructolytic ability. SLC2A5, encoding the fructose transporter, GLUT5, was specifically upregulated in these cells. Overexpression of GLUT5 in non-fructolytic cells enabled growth in fructose-containing media across cells of different origins. GLUT5 permitted fructose to flux through glycolysis using hexokinase (HK) and not ketohexokinase (KHK).ConclusionsWe show that GLUT5 is a robust and generalizable driver of fructose-dependent cell proliferation. This indicates that fructose uptake is the limiting factor for fructose-mediated cell proliferation. We further demonstrate that cellular proliferation with fructose is independent of KHK.
| S-EPMC7992954 | biostudies-literature
Project description:BackgroundWhile role of ALDOB-related gene variants for hereditary fructose intolerance is well established, contribution of gene variants for acquired fructose malabsorption (e.g. SLC2A5, GLUT5) is not well understood.MethodsPatients referred to fructose breath test were further selected to identify those having acquired fructose malabsorption. Molecular analysis of genomic DNA included (I) exclusion of 3 main ALDOB gene variants causing hereditary fructose intolerance and (II) sequencing analysis of SLC2A5 gene comprising complete coding region, at least 20 bp of adjacent intronic regions and 700 bp of proximal promoter.ResultsAmong 494 patients, 35 individuals with acquired fructose malabsorption were identified based on pathological fructose-breath test and normal lactose-breath test. Thirty four of them (97%) had negative tissue anti-transglutaminase and/or deamidated gliadin antibodies in their medical records. Molecular analysis of SLC2A5 gene of all 35 subjects identified 5 frequent and 5 singular gene variants mostly in noncoding regions (promoter and intron). Allele frequencies of gene variants were similar to those reported in public databases strongly implying that none of them was associated with acquired fructose malabsorption.ConclusionsGene variants of coding exons, adjacent intronic regions and proximal promoter region of SLC2A5 gene are unlikely to contribute to genetic predisposition of acquired fructose malabsorption.
| S-EPMC8985300 | biostudies-literature
Project description:The identity of the transporter responsible for fructose absorption in the intestine in vivo and its potential role in fructose-induced hypertension remain speculative. Here we demonstrate that Glut5 (Slc2a5) deletion reduced fructose absorption by approximately 75% in the jejunum and decreased the concentration of serum fructose by approximately 90% relative to wild-type mice on increased dietary fructose. When fed a control (60% starch) diet, Glut5(-/-) mice had normal blood pressure and displayed normal weight gain. However, whereas Glut5(+/+) mice showed enhanced salt absorption in their jejuna in response to luminal fructose and developed systemic hypertension when fed a high fructose (60% fructose) diet for 14 weeks, Glut5(-/-) mice did not display fructose-stimulated salt absorption in their jejuna, and they experienced a significant impairment of nutrient absorption in their intestine with accompanying hypotension as early as 3-5 days after the start of a high fructose diet. Examination of the intestinal tract of Glut5(-/-) mice fed a high fructose diet revealed massive dilatation of the caecum and colon, consistent with severe malabsorption, along with a unique adaptive up-regulation of ion transporters. In contrast to the malabsorption of fructose, Glut5(-/-) mice did not exhibit an absorption defect when fed a high glucose (60% glucose) diet. We conclude that Glut5 is essential for the absorption of fructose in the intestine and plays a fundamental role in the generation of fructose-induced hypertension. Deletion of Glut5 results in a serious nutrient-absorptive defect and volume depletion only when the animals are fed a high fructose diet and is associated with compensatory adaptive up-regulation of ion-absorbing transporters in the colon.
| S-EPMC2643499 | biostudies-literature
Project description:Intestinal fructose uptake is mainly mediated by glucose transporter 5 (GLUT5/SLC2A5). Its closest relative, GLUT7, is also expressed in the intestine but does not transport fructose. For rat Glut5, a change of glutamine to glutamic acid at codon 166 (p.Q166E) has been reported to alter the substrate-binding specificity by shifting Glut5-mediated transport from fructose to glucose. Using chimeric proteins of GLUT5 and GLUT7, here we identified amino acid residues of GLUT5 that define its substrate specificity. The proteins were expressed in NIH-3T3 fibroblasts, and their activities were determined by fructose radiotracer flux. We divided the human GLUT5 sequence into 26 fragments and then replaced each fragment with the corresponding region in GLUT7. All fragments that yielded reduced fructose uptake were analyzed further by assessing the role of individual amino acid residues. Various positions in the first extracellular loop, in the fifth, seventh, eighth, ninth, and tenth transmembrane domains (TMDs), and in the regions between the ninth and tenth TMDs and tenth and 11th TMDs were identified as being important for proper fructose uptake. Although the p.Q167E change did not render the human protein into a glucose transporter, molecular dynamics simulations revealed a drastic change in the dynamics and a movement of the intracellular loop connecting the sixth and seventh TMDs, which covers the exit of the ligand. Finally, we generated a GLUT7-GLUT5 chimera consisting of the N-terminal part of GLUT7 and the C-terminal part of GLUT5. Although this chimera was inactive, we demonstrate fructose transport after introduction of four amino acids derived from GLUT5.
| S-EPMC5808771 | biostudies-literature
Project description:The altered activity of the fructose transporter GLUT5, an isoform of the facilitated-diffusion glucose transporter family, has been linked to disorders such as type 2 diabetes and obesity. GLUT5 is also overexpressed in certain tumour cells, and inhibitors are potential drugs for these conditions. Here we describe the crystal structures of GLUT5 from Rattus norvegicus and Bos taurus in open outward- and open inward-facing conformations, respectively. GLUT5 has a major facilitator superfamily fold like other homologous monosaccharide transporters. On the basis of a comparison of the inward-facing structures of GLUT5 and human GLUT1, a ubiquitous glucose transporter, we show that a single point mutation is enough to switch the substrate-binding preference of GLUT5 from fructose to glucose. A comparison of the substrate-free structures of GLUT5 with occluded substrate-bound structures of Escherichia coli XylE suggests that, in addition to global rocker-switch-like re-orientation of the bundles, local asymmetric rearrangements of carboxy-terminal transmembrane bundle helices TM7 and TM10 underlie a 'gated-pore' transport mechanism in such monosaccharide transporters.
| S-EPMC4618315 | biostudies-literature
Project description:The recent dramatic increase in fructose consumption is tightly correlated with an equally dramatic surge in the incidence of type 2 diabetes and obesity in children, but little is known about dietary fructose metabolism and absorption in neonates. The expression of the rat intestinal fructose transporter GLUT5 [Slc2A5, a member of the glucose transporter family (GLUT)] can be specifically induced by its substrate fructose, but only after weaning begins at 14 d of age. In suckling rats younger than 14 d old, dietary fructose cannot enhance GLUT5 expression. The aim of this study was to identify the mechanisms allowing fructose to stimulate GLUT5 during weaning. After intestines were perfused with fructose or glucose (control), using microarray hybridization we showed that of 5K genes analyzed in 10-d-old pups, only 13 were fructose responsive. Previous work found approximately 50 fructose-responsive genes in 20-d-old pups. To identify fructose-responsive genes whose expression also changed with age, intestines of 10- and 20-d-old littermate pups perfused with fructose were compared by microarray. Intestines of 10- and 20-d-old pups perfused with glucose were used to segregate age- but not fructose-responsive genes. About 28 genes were up- and 22 down-regulated in 20- relative to 10-d-old pups, under conditions of fructose perfusion, and many were found, by cluster analysis, to be regulated by corticosterone. When dexamethasone was injected into suckling pups before fructose perfusion, the expression of GLUT5 but not that of the sodium glucose cotransporter (SGLT) 1 and of GLUT2, as well as the uptake of fructose but not of glucose increased dramatically. Thus, dexamethasone, which allows dietary fructose to precociously stimulate intestinal fructose absorption, can mimic the effect of age and modify developmental timing mechanisms regulating GLUT5.
| S-EPMC2194616 | biostudies-literature
Project description:In mammals, glucose transporters (GLUT) control organism-wide blood-glucose homeostasis. In human, this is accomplished by 14 different GLUT isoforms, that transport glucose and other monosaccharides with varying substrate preferences and kinetics. Nevertheless, there is little difference between the sugar-coordinating residues in the GLUT proteins and even the malarial Plasmodium falciparum transporter PfHT1, which is uniquely able to transport a wide range of different sugars. PfHT1 was captured in an intermediate 'occluded' state, revealing how the extracellular gating helix TM7b has moved to break and occlude the sugar-binding site. Sequence difference and kinetics indicated that the TM7b gating helix dynamics and interactions likely evolved to enable substrate promiscuity in PfHT1, rather than the sugar-binding site itself. It was unclear, however, if the TM7b structural transitions observed in PfHT1 would be similar in the other GLUT proteins. Here, using enhanced sampling molecular dynamics simulations, we show that the fructose transporter GLUT5 spontaneously transitions through an occluded state that closely resembles PfHT1. The coordination of D-fructose lowers the energetic barriers between the outward- and inward-facing states, and the observed binding mode for D-fructose is consistent with biochemical analysis. Rather than a substrate-binding site that achieves strict specificity by having a high affinity for the substrate, we conclude GLUT proteins have allosterically coupled sugar binding with an extracellular gate that forms the high-affinity transition-state instead. This substrate-coupling pathway presumably enables the catalysis of fast sugar flux at physiological relevant blood-glucose concentrations.
| S-EPMC10322154 | biostudies-literature
Project description:Receptors for antipsychotics in the hypothalamus contribute to antipsychotics-induced weight gain; however, many of these receptors are also expressed in the intestine. The role of these intestinally-expressed receptors, and their potential modulation of nutrient absorption, have not been investigated in the context of antipsychotics-induced weight gain. Here we tested the effect of dietary fructose and intestinal fructose uptake on clozapine-induced weight gain in mice. Weight gain was determined in wild type mice and mice lacking the GLUT5 fructose transporter that were "orally-administered" 20mg/kg clozapine for 28 days. To assess the role of dietary fructose, clozapine-treated mice were fed controlled diets with different levels of fructose. Effect of clozapine treatment on intestinal fructose transport activity and expression levels of various receptors that bind clozapine, as well as several genes involved in gluconeogenesis and lipogenesis were measured using real-time RT-PCR and western blotting. Oral administration of clozapine significantly increased body weight in wild type C57BL/6 mice but not in GLUT5 null mice. The clozapine-induced weight gain was proportional to the percentage of fructose in the diet. Clozapine-treated mice increased intestinal fructose uptake without changing the intestinal expression level of GLUT5. Clozapine-treated mice expressed significantly higher levels of intestinal H1 histamine receptor in the wild type but not GLUT5 null mice. Clozapine also increased the intestinal expression of fructokinase and several genes involved in gluconeogenesis and lipogenesis. Our results suggest that increased intestinal absorption and metabolism of fructose contributes to clozapine-induced weight gain. Eliminating dietary fructose might prevent antipsychotics-induced weight gain.
| S-EPMC4988743 | biostudies-literature
Project description:Recent studies suggest that the jejunal/kidney-type facilitative glucose transporter (GLUT5) functions as a high-affinity D-fructose transporter. However, its precise role in the small intestine is not clear. In an attempt to identify the fructose transporter in the small intestine, we measured fructose uptake in Xenopus oocytes expressing jejunal mRNA from five species (rat, mouse, rabbit, hamster and guinea-pig). Only jejunal mRNA from the rabbit significantly increased fructose uptake. We also cloned a rabbit GLUT5 cDNA from a jejunal library The predicted amino acid sequence of the 487-residue rabbit GLUT5 showed 72.3 and 67.1% identity with human and rat GLUT5 respectively. Northern-blot analysis revealed GLUT5 transcripts in rabbit duodenum, jejunum and, to a lesser extent, kidney. After separation of rabbit jejunal mRNA on a sucrose density gradient, the fractions that conferred D-fructose transport activity in oocytes also hybridized with rabbit GLUT5 cDNA. Hybrid depletion of jejunal mRNA with a GLUT5 antisense oligonucleotide markedly inhibited the mRNA-induced fructose uptake in oocytes. Immunoblot analysis indicated that GLUT5 (49 kDa) is located in the brush-border membrane of rabbit intestinal epithelial cells. Xenopus oocytes injected with rabbit GLUT5 cRNA exhibited fructose uptake activity with a Km of 11 mM for D-fructose. D-Fructose transport by GLUT5 was significantly inhibited by D-glucose and D-galactose. D-Fructose uptake in brush-border membrane vesicles shows a Km similar to that of GLUT5, but was not inhibited by D-glucose or D-galactose. Finally, cytochalasin B photolabelled a 49 kDa protein in rabbit brush-border-membrane preparations that was immunoprecipitated by antibodies to GLUT5. Our results suggest that GLUT5 functions as a fructose transporter in rabbit small intestine. However, biochemical properties of fructose transport in Xenopus oocytes injected with GLUT5 cRNA differed from those in rabbit jejunal vesicles.
| S-EPMC1137628 | biostudies-other
Project description:Fructose, a naturally occurring monosaccharide, is increasingly used as an added sweetener in processed foods in the form of high fructose corn syrup. Increased fructose intake combined with the identification of children with clinical evidence of isolated fructose malabsorption (IFM) has stimulated interest in possible disorders of fructose absorption. The intestinal absorption of fructose is carried out by the facilitative hexose transporter, which has been designated as GLUT5. Functional properties and tissue distribution of GLUT5 suggest that IFM might be due to mutations in the GLUT5 gene. To test this hypothesis, we screened the GLUT5 gene for mutations in a group of eight patients with IFM and in one subject with global malabsorption, as compared with 15 healthy parents of subjects and up to 6 unrelated controls. No mutations were found in the protein coding region of this gene in any of the subjects. A single G to A substitution in the 5' untranslated region of exon 1 was identified in the subject with global malabsorption. This subject and her healthy mother were heterozygous for the variant sequence, suggesting that it was unlikely to be clinically significant. In addition, sequence analysis of each of the 12 GLUT5 exons was performed in the index case and confirmed the negative single-strand conformation polymorphism findings. These studies demonstrate that IFM does not result from the expression of mutant GLUT5 protein.
| S-EPMC507692 | biostudies-other