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Dobson L, Zeke A, Tusnády GE. PolarProtPred: Predicting apical and basolateral localization of transmembrane proteins using putative short linear motifs and deep learning. Bioinformatics 2021; 37:4328-4335. [PMID: 34185052 PMCID: PMC8384406 DOI: 10.1093/bioinformatics/btab480] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/03/2021] [Accepted: 06/28/2021] [Indexed: 11/13/2022] Open
Abstract
Motivation Cell polarity refers to the asymmetric organization of cellular components in various cells. Epithelial cells are the best-known examples of polarized cells, featuring apical and basolateral membrane domains. Mounting evidence suggests that short linear motifs play a major role in protein trafficking to these domains, although the exact rules governing them are still elusive. Results In this study we prepared neural networks that capture recurrent patterns to classify transmembrane proteins localizing into apical and basolateral membranes. Asymmetric expression of drug transporters results in vectorial drug transport, governing the pharmacokinetics of numerous substances, yet the data on how proteins are sorted in epithelial cells is very scattered. The provided method may offer help to experimentalists to identify or better characterize molecular networks regulating the distribution of transporters or surface receptors (including viral entry receptors like that of COVID-19). Availability The prediction server PolarProtPred is available at http://polarprotpred.ttk.hu. Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Laszlo Dobson
- Institute of Enzymology, Research Centre for Natural Sciences, Magyar Tudósok Körútja 2, Budapest, 1117, Hungary.,Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, Heidelberg, 69117, Germany
| | - András Zeke
- Institute of Enzymology, Research Centre for Natural Sciences, Magyar Tudósok Körútja 2, Budapest, 1117, Hungary
| | - Gábor E Tusnády
- Institute of Enzymology, Research Centre for Natural Sciences, Magyar Tudósok Körútja 2, Budapest, 1117, Hungary
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2
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Libby CJ, Gc S, Benavides GA, Fisher JL, Williford SE, Zhang S, Tran AN, Gordon ER, Jones AB, Tuy K, Flavahan W, Gordillo J, Long A, Cooper SJ, Lasseigne BN, Augelli-Szafran CE, Darley-Usmar V, Hjelmeland AB. A role for GLUT3 in glioblastoma cell invasion that is not recapitulated by GLUT1. Cell Adh Migr 2021; 15:101-115. [PMID: 33843470 PMCID: PMC8043167 DOI: 10.1080/19336918.2021.1903684] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The multifaceted roles of metabolism in invasion have been investigated across many cancers. The brain tumor glioblastoma (GBM) is a highly invasive and metabolically plastic tumor with an inevitable recurrence. The neuronal glucose transporter 3 (GLUT3) was previously reported to correlate with poor glioma patient survival and be upregulated in GBM cells to promote therapeutic resistance and survival under restricted glucose conditions. It has been suggested that the increased glucose uptake mediated by GLUT3 elevation promotes survival of circulating tumor cells to facilitate metastasis. Here we suggest a more direct role for GLUT3 in promoting invasion that is not dependent upon changes in cell survival or metabolism. Analysis of glioma datasets demonstrated that GLUT3, but not GLUT1, expression was elevated in invasive disease. In human xenograft derived GBM cells, GLUT3, but not GLUT1, elevation significantly increased invasion in transwell assays, but not growth or migration. Further, there were no changes in glycolytic metabolism that correlated with invasive phenotypes. We identified the GLUT3 C-terminus as mediating invasion: substituting the C-terminus of GLUT1 for that of GLUT3 reduced invasion. RNA-seq analysis indicated changes in extracellular matrix organization in GLUT3 overexpressing cells, including upregulation of osteopontin. Together, our data suggest a role for GLUT3 in increasing tumor cell invasion that is not recapitulated by GLUT1, is separate from its role in metabolism and survival as a glucose transporter, and is likely broadly applicable since GLUT3 expression correlates with metastasis in many solid tumors.
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Affiliation(s)
- Catherine J Libby
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Sajina Gc
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Gloria A Benavides
- Mitochondria Medicine Laboratory, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jennifer L Fisher
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Sarah E Williford
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Sixue Zhang
- Chemistry Department, Drug Discovery Division, Southern Research, Birmingham, AL, USA
| | - Anh Nhat Tran
- Department of Neurosurgery, Northwestern University, Chicago, IL, USA
| | - Emily R Gordon
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA
| | - Amber B Jones
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Kaysaw Tuy
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - William Flavahan
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worchester, MA, USA
| | - Juan Gordillo
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Ashlee Long
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Sara J Cooper
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA
| | - Brittany N Lasseigne
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA.,O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA.,Hugh Kaul Precision Medicine Institute, University of Alabama at Birmingham, Birmingham, AL, USA.,The Center for Clinical and Translational Science, University of Alabama at Birmingham, Birmingham, AL, USA.,UAB IMPACT Fund, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - Victor Darley-Usmar
- Mitochondria Medicine Laboratory, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Anita B Hjelmeland
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA.,O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL, USA
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3
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Abstract
Cell nutrition, detoxification, signalling, homeostasis and response to drugs, processes related to cell growth, differentiation and survival are all mediated by plasma membrane (PM) proteins called transporters. Despite their distinct fine structures, mechanism of function, energetic requirements, kinetics and substrate specificities, all transporters are characterized by a main hydrophobic body embedded in the PM as a series of tightly packed, often intertwined, α-helices that traverse the lipid bilayer in a zigzag mode, connected with intracellular or extracellular loops and hydrophilic N- and C-termini. Whereas longstanding genetic, biochemical and biophysical evidence suggests that specific transmembrane segments, and also their connecting loops, are responsible for substrate recognition and transport dynamics, emerging evidence also reveals the functional importance of transporter N- and C-termini, in respect to transport catalysis, substrate specificity, subcellular expression, stability and signalling. This review highlights selected prototypic examples of transporters in which their termini play important roles in their functioning.
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Affiliation(s)
- Emmanuel Mikros
- Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis, 15771 Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, 15781 Athens, Greece
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4
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Borges MH, Pullockaran J, Catalano PM, Baumann MU, Zamudio S, Illsley NP. Human placental GLUT1 glucose transporter expression and the fetal insulin-like growth factor axis in pregnancies complicated by diabetes. Biochim Biophys Acta Mol Basis Dis 2019; 1865:2411-2419. [PMID: 31175930 DOI: 10.1016/j.bbadis.2019.06.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 04/30/2019] [Accepted: 06/03/2019] [Indexed: 12/14/2022]
Abstract
We have previously described regulation of syncytial GLUT1 glucose transporters by IGF-I. Despite this, it is not clear what signal regulates transplacental glucose transport. In this report we asked whether changes in GLUT1 expression and glucose transport activity in diabetic pregnancies were associated with alterations in the fetal IGF axis. Cord blood samples and paired syncytial microvillous and basal membranes were isolated from normal term pregnancies and pregnancies characterized by gestational diabetes type A2 (GDM A2) and pre-existing insulin-dependent diabetes mellitus (IDDM). Circulating IGF-I, basal membrane GLUT1 expression and glucose transporter activity were correlated with birth weight, but only in control, not diabetic groups. Basal membrane GLUT1 and transporter activity were correlated with IGF-I concentrations in control, but not diabetic groups. IGF binding protein (IGFBP) binding capacity showed a ≥50% reduction in the diabetic groups compared to control; both showed a higher level of free IGF-I. The absence of a correlation between birth weight and factors such as fetal IGF-I or GLUT1 expression in the diabetic groups suggests that IGF-I-stimulated effects may have reached a limiting threshold, such that further increases in IGF-I (or GLUT1) are without effect. These data support that fetal IGF-I acts as a fetal nutritional signal, modulating placental GLUT1 expression and birth weight via altered levels of fetal circulating IGFBPs. Diabetes appears to exert its effects on fetal and placental factors prior to the third trimester and, despite good glycemic control immediately prior to, and in the third trimester, these effects persist to term.
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Affiliation(s)
- Marcus H Borges
- Department of Obstetrics, Gynecology and Women's Health, Rutgers-New Jersey Medical School, Newark, NJ, United States of America
| | - Janet Pullockaran
- Department of Obstetrics, Gynecology and Women's Health, Rutgers-New Jersey Medical School, Newark, NJ, United States of America
| | - Patrick M Catalano
- Department of Obstetrics and Gynecology, MetroHealth Medical Center, Cleveland, OH, United States of America
| | - Marc U Baumann
- Department of Obstetrics, Gynecology and Women's Health, Rutgers-New Jersey Medical School, Newark, NJ, United States of America
| | - Stacy Zamudio
- Department of Obstetrics and Gynecology, Hackensack University Medical Center, Hackensack, NJ, United States of America
| | - Nicholas P Illsley
- Department of Obstetrics and Gynecology, Hackensack University Medical Center, Hackensack, NJ, United States of America.
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5
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Enogieru OJ, Ung PMU, Yee SW, Schlessinger A, Giacomini KM. Functional and structural analysis of rare SLC2A2 variants associated with Fanconi-Bickel syndrome and metabolic traits. Hum Mutat 2019; 40:983-995. [PMID: 30950137 DOI: 10.1002/humu.23758] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 03/01/2019] [Accepted: 03/23/2019] [Indexed: 02/06/2023]
Abstract
Deleterious variants in SLC2A2 cause Fanconi-Bickel Syndrome (FBS), a glycogen storage disorder, whereas less common variants in SLC2A2 associate with numerous metabolic diseases. Phenotypic heterogeneity in FBS has been observed, but its causes remain unknown. Our goal was to functionally characterize rare SLC2A2 variants found in FBS and metabolic disease-associated variants to understand the impact of these variants on GLUT2 activity and expression and establish genotype-phenotype correlations. Complementary RNA-injected Xenopus laevis oocytes were used to study mutant transporter activity and membrane expression. GLUT2 homology models were constructed for mutation analysis using GLUT1, GLUT3, and XylE as templates. Seventeen FBS variants were characterized. Only c.457_462delCTTATA (p.Leu153_Ile154del) exhibited residual glucose uptake. Functional characterization revealed that only half of the variants were expressed on the plasma membrane. Most less common variants (except c.593 C>A (p.Thr198Lys) and c.1087 G>T (p.Ala363Ser)) exhibited similar GLUT2 transport activity as the wild type. Structural analysis of GLUT2 revealed that variants affect substrate-binding, steric hindrance, or overall transporter structure. The mutant transporter that is associated with a milder FBS phenotype, p.Leu153_Ile154del, retained transport activity. These results improve our overall understanding of the underlying causes of FBS and impact of GLUT2 function on various clinical phenotypes ranging from rare to common disease.
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Affiliation(s)
- Osatohanmwen J Enogieru
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California
| | - Peter M U Ung
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Sook Wah Yee
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California
| | - Avner Schlessinger
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Kathleen M Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California.,Institute for Human Genetics, University of California, San Francisco, San Francisco, California
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6
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Illsley NP, Baumann MU. Human placental glucose transport in fetoplacental growth and metabolism. Biochim Biophys Acta Mol Basis Dis 2018; 1866:165359. [PMID: 30593896 DOI: 10.1016/j.bbadis.2018.12.010] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 11/13/2018] [Accepted: 12/06/2018] [Indexed: 02/07/2023]
Abstract
While efficient glucose transport is essential for all cells, in the case of the human placenta, glucose transport requirements are two-fold; provision of glucose for the growing fetus in addition to the supply of glucose required the changing metabolic needs of the placenta itself. The rapidly evolving environment of placental cells over gestation has significant consequences for the development of glucose transport systems. The two-fold transport requirement of the placenta means also that changes in expression will have effects not only for the placenta but also for fetal growth and metabolism. This review will examine the localization, function and evolution of placental glucose transport systems as they are altered with fetal development and the transport and metabolic changes observed in pregnancy pathologies.
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Affiliation(s)
- Nicholas P Illsley
- Center for Abnormal Placentation, Department of Obstetrics and Gynecology, Hackensack University Medical Center, Hackensack, NJ, USA.
| | - Marc U Baumann
- Department of Obstetrics and Gynaecology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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7
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Bibee KP, Augustin R, Gazit V, Moley KH. The apical sorting signal for human GLUT9b resides in the N-terminus. Mol Cell Biochem 2013; 376:163-73. [PMID: 23361362 DOI: 10.1007/s11010-013-1564-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Accepted: 01/18/2013] [Indexed: 12/11/2022]
Abstract
The two splice variants of human glucose transporter 9 (hGLUT9) are targeted to different polarized membranes. hGLUT9a traffics to the basolateral membrane, whereas hGLUT9b traffics to the apical region. This study examines the sorting mechanism of these variants, which differ only in their N-terminal domain. Mutating a di-leucine motif unique to GLUT9a did not affect targeting. Chimeric proteins were made using GLUT1, a basolaterally targeted transporter, and GLUT3, an apically targeted protein whose signal lies in the C-terminus. Overexpression of the chimeric proteins in polarized cells demonstrates that the N-terminus of hGLUT9b contains a signal capable of redirecting GLUT1 to the apical membrane. The N-terminus of hGLUT9a, however, does not contain a basolateral signal sufficient enough to redirect GLUT3. Portions of the GLUT9a N-terminus were substituted with corresponding portions of the GLUT9b N-terminus to determine the motif responsible for apical targeting. The first 16 amino acids were not found to be a sufficient apical signal. The last ten amino acids of the N-termini differ only in amino-acid class at one location. In the B-form, leucine, a hydrophobic residue, is substituted for lysine, a basic residue, found in the A-form. However, mutation of the leucine in hGLUT9b to a lysine resulted in retention of the apical signal. We therefore believe the apical signal exists as an interplay between the final ten amino acids of the N-terminus and another motif within the protein such as the intracellular loop or other motifs within the N-terminus.
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Affiliation(s)
- Kristin P Bibee
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
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8
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Bhonsle JB, Causey R, Oyler BL, Bartolucci C, Lamba D, Pesaresi A, Bhamare NK, Soojhawon I, Garcia GE. Evaluation and computational characterization of the facilitated transport of Glc carbon C-1 oxime reactivators across a blood brain barrier model. Chem Biol Interact 2012; 203:129-34. [PMID: 23073172 DOI: 10.1016/j.cbi.2012.09.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 09/04/2012] [Accepted: 09/25/2012] [Indexed: 10/27/2022]
Abstract
We are evaluating a facilitative transport strategy to move oximes across the blood brain barrier (BBB) to reactivate inhibited brain acetylcholinesterase (AChE). We selected glucose (Glc) transporters (GLUT) for this purpose as these transporters are highly represented in the BBB. Glc conjugates have successfully moved drugs across the BBB and previous work has shown that Glc-oximes (sugar-oximes, SOxs) can reduce the organophosphonate induced hypothermia response. We previously evaluated the reactivation potential of Glc carbon C-1 SOxs. Here we report the reactivation parameters for VX- and GB-inhibited human (Hu) AChE of the best SOx (13c) and our findings that the kinetics are similar to those of the parent oxime. Although crystals of Torpedo californica AChE were produced, neither soaked or co-crystallized experiments were successful at concentrations below 20mM 13c, and higher concentrations cracked the crystals. 13c was non-toxic to neuroblastoma and kidney cell lines at 12-18 mM, allowing high concentrations to be used in a BBB kidney cell model. The transfer of 13c from the donor side was asymmetric with the greatest loss of 13c from the apical- or luminal-treated side. There was no apparent transfer from the basolateral side. The 13cP(app) results indicate a 'low' transport efficiency; however, mass accounting revealed only a 20% recovery from the apical dose in which high concentrations were found in the cell lysate fraction. Molecular modeling of 13c through the GLUT-1 channel demonstrated that transport of 13c was more restricted than Glc. Selected sites were compared and the 13c binding energies were greater than two times those of Glc.
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Affiliation(s)
- Jayendra B Bhonsle
- Astha Drug Discovery & Research, 5284 Randolph Road #262, Rockville, MD 20852, USA
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9
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Ikegami Y, Inukai K, Imai K, Sakamoto Y, Katagiri H, Kurihara S, Awata T, Katayama S. Adiponectin upregulates ferritin heavy chain in skeletal muscle cells. Diabetes 2009; 58:61-70. [PMID: 18931039 PMCID: PMC2606894 DOI: 10.2337/db07-0690] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 10/08/2008] [Indexed: 01/21/2023]
Abstract
OBJECTIVE Adiponectin is an adipocyte-derived protein that acts to reduce insulin resistance in the liver and muscle and also inhibits atherosclerosis. Although adiponectin reportedly enhances AMP-activated protein kinase and inhibits tumor necrosis factor-alpha action downstream from the adiponectin signal, the precise physiological mechanisms by which adiponectin acts on skeletal muscles remain unknown. RESEARCH DESIGN AND METHODS We treated murine primary skeletal muscle cells with recombinant full-length human adiponectin for 12 h and searched, using two-dimensional electrophoresis, for proteins upregulated more than threefold by adiponectin compared with untreated cells. RESULTS We found one protein that was increased 6.3-fold with adiponectin incubation. MALDI-TOF (matrix-assisted laser desorption/ionization-top of flight) mass spectrometric analysis identified this protein as ferritin heavy chain (FHC). When murine primary skeletal muscle cells were treated with adiponectin, IkappaB-alpha phosphorylation was observed, suggesting that adiponectin stimulates nuclear factor (NF)-kappaB activity. In addition, FHC upregulation by adiponectin was inhibited by NF-kappaB inhibitors. These results suggest NF-kappaB activation to be involved in FHC upregulation by adiponectin. Other NF-kappaB target genes, manganese superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS), were also increased by adiponectin treatment. We performed a reactive oxygen species (ROS) assay using CM-H(2)DCFDA fluorescence and found that ROS-reducing effects of adiponectin were abrogated by FHC or MnSOD small-interfering RNA induction. CONCLUSIONS We have demonstrated that adiponectin upregulates FHC in murine skeletal muscle tissues, suggesting that FHC elevation might partially explain how adiponectin protects against oxidative stress in skeletal muscles.
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Affiliation(s)
- Yuichi Ikegami
- Department of Endocrinology and Diabetes, School of Medicine, Saitama Medical University, Saitama, Japan
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10
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Carmosino M, Giménez I, Caplan M, Forbush B. Exon loss accounts for differential sorting of Na-K-Cl cotransporters in polarized epithelial cells. Mol Biol Cell 2008; 19:4341-51. [PMID: 18667527 DOI: 10.1091/mbc.e08-05-0478] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The renal Na-K-Cl cotransporter (NKCC2) is selectively expressed in the apical membranes of cells of the mammalian kidney, where it is the target of the clinically important loop diuretics. In contrast, the "secretory" NKCC1 cotransporter is localized in the basolateral membranes of many epithelia. To identify the sorting signal(s) that direct trafficking of NKCCs, we generated chimeras between the two isoforms and expressed these constructs in polarized renal epithelial cell lines. This analysis revealed an amino acid stretch in NKCC2 containing apical sorting information. The NKCC1 C terminus contains a dileucine motif that constitutes the smallest essential component of its basolateral sorting signal. NKCC1 lacking this motif behaves as an apical protein. Examination of the NKCC gene structure reveals that this dileucine motif is encoded by an additional exon in NKCC1 absent in NKCC2. Phylogenetic analysis of this exon suggests that the evolutionary loss of this exon from the gene encoding the basolateral NKCC1 constitutes a novel mechanism that accounts for the apical sorting of the protein encoded by the NKCC2 gene.
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Affiliation(s)
- Monica Carmosino
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA.
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11
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Wilson-O'Brien AL, Dehaan CL, Rogers S. Mitogen-stimulated and rapamycin-sensitive glucose transporter 12 targeting and functional glucose transport in renal epithelial cells. Endocrinology 2008; 149:917-24. [PMID: 18039784 DOI: 10.1210/en.2007-0985] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We hypothesized that glucose transporter 12 (GLUT12) is involved in regulation of glucose flux in distal renal tubules in response to elevated glucose. We used the Madin-Darby canine kidney polarized epithelial cell model and neutralizing antibodies to analyze GLUT12 targeting and directional GLUT12-mediated glucose transport. At physiological glucose concentrations, GLUT12 was localized to a perinuclear position. High glucose and serum treatment resulted in GLUT12 localization to the apical membrane. This mitogen-stimulated targeting of GLUT12 was inhibited by rapamycin, the specific inhibitor of mammalian target of rapamycin (mTOR). The functional role of GLUT12 was also examined. We constructed a GLUT12 cDNA containing a c-Myc epitope tag in the fifth exofacial loop. Assays of glucose transport at the apical membrane were performed using Transwell filters. By comparing transport assays in the presence of neutralizing anti-c-Myc monoclonal antibody, we specifically measured GLUT12-mediated glucose transport at the apical surface. GLUT12-mediated glucose transport was mitogen dependent and rapamycin sensitive. Our results implicate mTOR signaling in a novel pathway of glucose transporter protein targeting and glucose transport. Activity of the mTOR pathway has been associated with diabetic kidney disease. Our results provide evidence for a link between GLUT12 protein trafficking, glucose transport and signaling molecules central to the control of metabolic disease processes.
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Affiliation(s)
- Amy L Wilson-O'Brien
- The University of Melbourne, Department of Medicine, St. Vincent's Hospital, Melbourne, Fitzroy, Victoria 3065, Australia
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12
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Duffield A, Caplan MJ, Muth TR. Chapter 4 Protein Trafficking in Polarized Cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 270:145-79. [DOI: 10.1016/s1937-6448(08)01404-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Ikegami Y, Inukai K, Awata T, Asano T, Katayama S. SH3 domain of the phosphatidylinositol 3-kinase regulatory subunit is responsible for the formation of a sequestration complex with insulin receptor substrate-1. Biochem Biophys Res Commun 2007; 365:433-8. [PMID: 17991427 DOI: 10.1016/j.bbrc.2007.10.187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Accepted: 10/29/2007] [Indexed: 11/30/2022]
Abstract
Class IA phosphatidylinositol 3-kinase (PI 3-kinase), which is composed of a 110kDa catalytic subunit and a regulatory subunit, plays a key role in most insulin dependent cellular responses. To date, five mammalian regulatory subunit isoforms have been identified, including two 85kDa proteins (p85alpha and p85beta), two 55kDa proteins (p55gamma and p55alpha), and one 50kDa protein (p50alpha). In the present study, we overexpressed these recombinant proteins, tagged with green fluorescent proteins (GFP), in CHO-IR cells and investigated intracellular localizations in both the presence and the absence of insulin stimulation. Interestingly, in response to insulin, only p85alpha and p85beta redistributed to isolated foci in the cells, while both were present throughout the cytoplasm in quiescent cells. In contrast, p55s accumulated in the perinuclear region irrespective of insulin stimulation, while p50alpha behaved similarly to control GFP. Immunofluorescent antibodies against endogenous IRS-1 revealed IRS-1 to be co-localized in the p85 foci in response to insulin. As both insulin receptors and p110alpha catalytic subunits were absent from these foci on immunofluorescence study, only p85 and IRS-1 were suggested to form a sequestration complex in response to insulin. To determine the domain responsible for IRS-1 complex formation, we prepared and overexpressed the SH3 domain deletion mutant of p85alpha in CHO-IR cells. This mutant failed to form foci, suggesting the SH3 domain of regulatory subunits to be responsible for formation of the p85-IRS-1 sequestration complex. In conclusion, our study revealed the SH3 domain of PI 3-kinase to play a critical role in intracellular localizations, including formation of foci with IRS-1 in response to insulin.
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Affiliation(s)
- Yuichi Ikegami
- Division of Endocrinology and Diabetes, Department of Medicine, Saitama Medical University, Morohongo 38, Moroyama, Iruma-gun, Saitama 350-0495, Japan
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14
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Sakyo T, Naraba H, Teraoka H, Kitagawa T. The intrinsic structure of glucose transporter isoforms Glut1 and Glut3 regulates their differential distribution to detergent-resistant membrane domains in nonpolarized mammalian cells. FEBS J 2007; 274:2843-53. [PMID: 17459098 DOI: 10.1111/j.1742-4658.2007.05814.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The hexose transporter family, which mediates facilitated uptake in mammalian cells, consists of more than 10 members containing 12 membrane-spanning segments with a single N-glycosylation site. We previously demonstrated that glucose transporter 1 is organized into a raft-like detergent-resistant membrane domain but that glucose transporter 3 distributes to fluid membrane domains in nonpolarized mammalian cells. In this study, we further examined the structural basis responsible for the distribution by using a series of chimeric constructs. Glucose transporter 1 and glucose transporter 3 with a FLAG-tagged N-terminus were expressed in detergent-resistant membranes and non-detergent-resistant membranes of CHO-K1 cells, respectively. Replacement of either the C-terminal or N-terminal cytosolic portion of FLAG-tagged glucose transporter 1 and glucose transporter 3 did not affect the membrane distribution. However, a critical sorting signal may exist within the N-terminal half of the isoforms without affecting transport activity and its inhibition by cytochalasin B. Further shortening of these regions altered the critical distribution, suggesting that a large proportion or several parts of the intrinsic structure, including the N-terminus of each isoform, are involved in the regulation.
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Affiliation(s)
- Tomoko Sakyo
- Pharmaceutical Research Center, School of Pharmacy, Iwate Medical University, Morioka, Iwate 028-3694, Japan
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Imai K, Inukai K, Ikegami Y, Awata T, Katayama S. LKB1, an upstream AMPK kinase, regulates glucose and lipid metabolism in cultured liver and muscle cells. Biochem Biophys Res Commun 2006; 351:595-601. [PMID: 17083919 DOI: 10.1016/j.bbrc.2006.10.056] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 10/11/2006] [Indexed: 01/21/2023]
Abstract
LKB1 is a 50 kDa serine/threonine kinase that phosphorylates and activates the catalytic subunit of AMPK at its T-loop residue Thr 172. We prepared adenoviruses expressing the constitutive active (wild-type) form (CA) or dominant negative (kinase inactive, D194A mutant) form (DN) of LKB1 and overexpressed these proteins in cultured myotubes (C2C12 cells) and rat hepatoma cells (FAO cells). When analyzed by immunoblotting with the antibody against Thr172-phosphorylated AMPK, the phosphorylation of AMPK was increased (2.5-fold) and decreased (0.4-fold) in cells expressing CA and DN LKB1, respectively, as compared with Lac-Z expressing control cells. Immunoprecipitation experiments, using isoform-specific antibody, revealed these alterations of AMPK phosphorylation to be attributable to altered phosphorylation of AMPK alpha2, but not alpha1 catalytic subunits, strongly suggesting the alpha2 catalytic subunit to be the major substrate for LKB1 in mammalian cells. In addition, adiponectin or AICAR-stimulated AMPK phosphorylation was inhibited by overexpression of DN LKB1, while phenformin-stimulated phosphorylation was unaffected. These results may explain the difference in AMPK activation mechanisms between AMP and phenformin, and also indicate that AMPK phosphorylation by LKB1 is involved in AMP-stimulated AMPK activation. As a downstream target for AMPK, AICAR-induced glucose uptake and ACCbeta phosphorylation were found to be significantly reduced in DN LKB1 expressing C2C12 cells. The expression of key enzymes for gluconeogenesis, glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, was also dependent on LKB1 activities in FAO cells. These results demonstrate that LKB1 is a crucial regulator of AMPK activation in muscle and liver cells and, therefore, that LKB1 activity is potentially of importance to our understanding of glucose and lipid metabolism.
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Affiliation(s)
- Kenta Imai
- Division of Endocrinology and Diabetes, Department of Medicine, Saitama Medical School, Iruma-gun, Saitama 350-0495, Japan
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16
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Chmelar RS, Nathanson NM. Identification of a novel apical sorting motif and mechanism of targeting of the M2 muscarinic acetylcholine receptor. J Biol Chem 2006; 281:35381-96. [PMID: 16968700 DOI: 10.1074/jbc.m605954200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Previous studies have shown that the M2 receptor is localized at steady state to the apical domain in Madin-Darby canine kidney (MDCK) epithelial cells. In this study, we identify the molecular determinants governing the localization and the route of apical delivery of the M2 receptor. First, by confocal analysis of a transiently transfected glycosylation mutant in which the three putative glycosylation sites were mutated, we determined that N-glycans are not necessary for the apical targeting of the M2 receptor. Next, using a chimeric receptor strategy, we found that two independent sequences within the M2 third intracellular loop can confer apical targeting to the basolaterally targeted M4 receptor, Val270-Lys280 and Lys280-Ser350. Experiments using Triton X-100 extraction followed by OptiPrep density gradient centrifugation and cholera toxin beta-subunit-induced patching demonstrate that apical targeting is not because of association with lipid rafts. 35S-Metabolic labeling experiments with domain-specific surface biotinylation as well as immunocytochemical analysis of the time course of surface appearance of newly transfected confluent MDCK cells expressing FLAG-M2-GFP demonstrate that the M2 receptor achieves its apical localization after first appearing on the basolateral domain. Domain-specific application of tannic acid of newly transfected cells indicates that initial basolateral plasma membrane expression is required for subsequent apical localization. This is the first demonstration that a G-protein-coupled receptor achieves its apical localization in MDCK cells via transcytosis.
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Affiliation(s)
- Renée S Chmelar
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington 98195-7750, USA
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17
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Hodson CA, Ambrogi IG, Scott RO, Mohler PJ, Milgram SL. Polarized apical sorting of guanylyl cyclase C is specified by a cytosolic signal. Traffic 2006; 7:456-64. [PMID: 16536743 DOI: 10.1111/j.1600-0854.2006.00398.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Receptor guanylyl cyclases respond to ligand stimulation by increasing intracellular cGMP, thereby initiating a variety of cell-signaling pathways. Furthermore, these proteins are differentially localized at the apical and basolateral membranes of epithelial cells. We have identified a region of 11 amino acids in the cytosolic COOH terminus of guanylyl cyclase C (GCC) required for normal apical localization in Madin-Darby canine kidney (MDCK) cells. These amino acids share no significant sequence homology with previously identified cytosolic apical sorting determinants. However, these amino acids are highly conserved and are sufficient to confer apical polarity to the interleukin-2 receptor alpha-chain (Tac). Additionally, we find two molecular weight species of GCC in lysates prepared from MDCK cells over-expressing GCC but observe only the fully mature species on the cell surface. Using pulse-chase analysis in polarized MDCK cells, we followed the generation of this mature species over time finding it to be detectable only at the apical cell surface. These data support the hypothesis that selective apical sorting can be determined using short, cytosolic amino acid motifs and argue for the existence of apical sorting machinery comparable with the machinery identified for basolateral protein traffic.
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Affiliation(s)
- Caleb A Hodson
- Graduate Program in Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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18
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Hill JK, Williams DE, LeMasurier M, Dumont RA, Strehler EE, Gillespie PG. Splice-site A choice targets plasma-membrane Ca2+-ATPase isoform 2 to hair bundles. J Neurosci 2006; 26:6172-80. [PMID: 16763025 PMCID: PMC2204085 DOI: 10.1523/jneurosci.0447-06.2006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Localization of mechanotransduction in sensory hair cells to hair bundles requires selective targeting of essential proteins to specific locations. Isoform 2 of the plasma-membrane Ca2+-ATPase (PMCA2), required for hearing and balance, is found exclusively in hair bundles. We determined the contribution of splicing at the two major splicing sites (A and C) to hair-cell targeting of PMCA2. When PMCA2 isoforms were immunoprecipitated from purified hair bundles of rat utricle, 2w was the only site A variant detected; moreover, immunocytochemistry for 2w in rat vestibular and cochlear tissues indicated that this splice form was located solely in bundles. To demonstrate the necessity of the 2w sequence, we transfected hair cells with PMCA2 containing different variants at splice sites A and C. Although native hair bundles exclusively use the 2a form at splice-site C, epitope-tagged PMCA2w/a and PMCA2w/b were both concentrated in bundles, indicating that site C is not involved in bundle targeting. In contrast, PMCA2z/a was excluded from bundles and was instead targeted to the basolateral plasma membrane. Bundle-specific targeting of PMCA2w/a tagged with green fluorescent protein (GFP) was diminished, suggesting that GFP interfered with splice-site A. Together, these data demonstrate that PMCA2w/a is the hair-bundle isoform of PMCA in rat hair cells and that 2w targets PMCA2 to bundles. The 2w sequence is thus the first targeting signal identified for a hair-bundle membrane protein; moreover, the striking distribution of inner-ear PMCA isoforms dictated by selective targeting suggests a critical functional role for segregated pathways of Ca2+ transport.
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Cleasby ME, Davey JR, Reinten TA, Graham MW, James DE, Kraegen EW, Cooney GJ. Acute bidirectional manipulation of muscle glucose uptake by in vivo electrotransfer of constructs targeting glucose transporter genes. Diabetes 2005; 54:2702-11. [PMID: 16123360 DOI: 10.2337/diabetes.54.9.2702] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Analysis of conventional germ-line or tissue-specific gene manipulation in vivo is potentially confounded by developmental adaptation of animal physiology. We aimed to adapt the technique of in vivo electrotransfer (IVE) to alter local gene expression in skeletal muscle of rodents as a means of investigating the role of specific proteins in glucose metabolism in vivo. We utilized a square-wave electroporator to induce intracellular electrotransfer of DNA constructs injected into rat or mouse muscles and investigated the downstream effects. In initial studies, expression of green fluorescent protein reporter was induced in 53 +/- 10% of muscle fibers peaking at 7 days, and importantly, the electrotransfer procedure itself did not impact upon the expression of stress proteins or our ability to detect a reduction in 2-deoxyglucose tracer uptake by electroporated muscle of high-fat-fed rats during hyperinsulinemic-euglycemic clamp. To demonstrate functional effects of electrotransfer of constructs targeting glucose transporters, we administered vectors encoding GLUT-1 cDNA and GLUT-4 short hairpin RNAs (shRNAs) to rodent muscles. IVE of the GLUT-1 gene resulted in a 57% increase in GLUT-1 protein, accompanied by a proportionate increase in basal 2-deoxyglucose tracer uptake into muscles of starved rats. IVE of vectors expressing two shRNAs for GLUT-4 demonstrated to reduce specific protein expression and 2-deoxyglucose tracer uptake in 3T3-L1 adipocytes into mouse muscle caused a 51% reduction in GLUT-4 protein, associated with attenuated clearance of tracer to muscle after a glucose load. These results confirm that glucose transporter expression is largely rate limiting for glucose uptake in vivo and highlight the utility of IVE for the acute manipulation of muscle gene expression in the study of the role of specific proteins in glucose metabolism.
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Affiliation(s)
- Mark E Cleasby
- Diabetes and Obesity Program, Garvan Institute of Medical Research, 384 Victoria St., Darlinghurst, NSW 2010, Australia.
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20
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Manel N, Battini JL, Sitbon M. Human T Cell Leukemia Virus Envelope Binding and Virus Entry Are Mediated by Distinct Domains of the Glucose Transporter GLUT1. J Biol Chem 2005; 280:29025-9. [PMID: 15955807 DOI: 10.1074/jbc.m504549200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The glucose transporter GLUT1, a member of the multimembrane-spanning facilitative nutrient transporter family, serves as a receptor for human T cell leukemia virus (HTLV) infection. Here, we show that the 7 amino acids of the extracellular loop 6 of GLUT1 (ECL6) placed in the context of the related GLUT3 transporter were sufficient for HTLV envelope binding. Glutamate residue 426 in ECL6 was identified as critical for binding. However, binding to ECL6 was not sufficient for HTLV envelope-driven infection. Infection required two additional determinants located in ECL1 and ECL5, which otherwise did not influence HTLV envelope binding. Moreover the single N-glycosylation chain located in ECL1 was not required for HTLV infection. Therefore, binding involves a discrete determinant in the carboxyl terminal ECL6, whereas post-binding events engage extracellular sequences in the amino and carboxyl terminus of GLUT1.
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Affiliation(s)
- Nicolas Manel
- Institut de Génétique Moléculaire de Montpellier, CNRS UMR 5535, IFR 122, 1919 route de Mende, F-34293 Montpellier Cedex 5, France
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21
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Reed BC, Cefalu C, Bellaire BH, Cardelli JA, Louis T, Salamon J, Bloecher MA, Bunn RC. GLUT1CBP(TIP2/GIPC1) interactions with GLUT1 and myosin VI: evidence supporting an adapter function for GLUT1CBP. Mol Biol Cell 2005; 16:4183-201. [PMID: 15975910 PMCID: PMC1196329 DOI: 10.1091/mbc.e04-11-0978] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We identified a novel interaction between myosin VI and the GLUT1 transporter binding protein GLUT1CBP(GIPC1) and first proposed that as an adapter molecule it might function to couple vesicle-bound proteins to myosin VI movement. This study refines the model by identifying two myosin VI binding domains in the GIPC1 C terminus, assigning respective oligomerization and myosin VI binding functions to separate N- and C-terminal domains, and defining a central region in the myosin VI tail that binds GIPC1. Data further supporting the model demonstrate that 1) myosin VI and GIPC1 interactions do not require a mediating protein; 2) the myosin VI binding domain in GIPC1 is necessary for intracellular interactions of GIPC1 with myosin VI and recruitment of overexpressed myosin VI to membrane structures, but not for the association of GIPC1 with such structures; 3) GIPC1/myosin VI complexes coordinately move within cellular extensions of the cell in an actin-dependent and microtubule-independent manner; and 4) blocking either GIPC1 interactions with myosin VI or GLUT1 interactions with GIPC1 disrupts normal GLUT1 trafficking in polarized epithelial cells, leading to a reduction in the level of GLUT1 in the plasma membrane and concomitant accumulation in internal membrane structures.
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Affiliation(s)
- Brent C Reed
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
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