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Batsaikhan T, Choi JS, Ha SM, Ahn Y, Seo YJ. D-Galactose and Hypoxia Induce the Early Onset of Age-Related Hearing Loss Deterioration in a Mouse Model. Tissue Eng Regen Med 2023; 20:779-787. [PMID: 37294515 PMCID: PMC10352183 DOI: 10.1007/s13770-023-00547-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/18/2023] [Accepted: 04/20/2023] [Indexed: 06/10/2023] Open
Abstract
BACKGROUND We previously showed that aging accelerates after 3 months of exposure to hypoxia and environmental change but not genetic modifications. Here, we aimed to simply induce early-onset age-related hearing loss within a short period based on our previous method. METHODS We randomly divided 16 C57BL/6 mice into four groups that were maintained under conditions of normoxia and hypoxia with or without injected D-galactose for 2 months. Deteriorated hearing, the expression of age-related factors, and oxidative stress responses were detected using the click and tone burst auditory brainstem response test, reverse transcription-polymerase chain reaction, and by measuring superoxide dismutase (SOD). RESULTS The group maintained under hypoxia combined with D-galactose lost hearing particularly at 24 Hz and 32 Hz at 6 weeks compared with the other groups. Aging-related factors were also significantly decreased in the hypoxia and D-galactose groups. However, SOD levels did not significantly differ among the groups. CONCLUSION Age-related hearing loss is an environmental disorder induced by chronic oxidative stress associated with genetic backgrounds. Our findings suggested that D-galactose and hypoxia can induce the phenotypes of age-related hearing loss and aging-associated molecules in a murine model within a short time with environmental stimulation alone.
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Affiliation(s)
- Temuulen Batsaikhan
- Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-do, 26426, South Korea
- Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea
| | - Jin Sil Choi
- Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-do, 26426, South Korea
- Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea
| | - Sun Mok Ha
- Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-do, 26426, South Korea
- Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea
| | - Yeji Ahn
- Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-do, 26426, South Korea
- Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea
| | - Young Joon Seo
- Department of Otorhinolaryngology, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, Gangwon-do, 26426, South Korea.
- Research Institute of Hearing Enhancement, Yonsei University Wonju College of Medicine, 20 Ilsan-ro, Wonju, 26426, South Korea.
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Structure of the human heterodimeric transporter 4F2hc-LAT2 in complex with Anticalin, an alternative binding protein for applications in single-particle cryo-EM. Sci Rep 2022; 12:18269. [PMID: 36310334 PMCID: PMC9618567 DOI: 10.1038/s41598-022-23270-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 10/27/2022] [Indexed: 12/31/2022] Open
Abstract
Cryo-EM structure determination of relatively small and flexible membrane proteins at high resolution is challenging. Increasing the size and structural features by binding of high affinity proteins to the biomolecular target allows for better particle alignment and may result in structural models of higher resolution and quality. Anticalins are alternative binding proteins to antibodies, which are based on the lipocalin scaffold and show potential for theranostic applications. The human heterodimeric amino acid transporter 4F2hc-LAT2 is a membrane protein complex that mediates transport of certain amino acids and derivatives thereof across the plasma membrane. Here, we present and discuss the cryo-EM structure of human 4F2hc-LAT2 in complex with the anticalin D11vs at 3.2 Å resolution. Relative high local map resolution (2.8-3.0 Å) in the LAT2 substrate binding site together with molecular dynamics simulations indicated the presence of fixed water molecules potentially involved in shaping and stabilizing this region. Finally, the presented work expands the application portfolio of anticalins and widens the toolset of binding proteins to promote high-resolution structure solution by single-particle cryo-EM.
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Bernardinelli E, Roesch S, Simoni E, Marino A, Rasp G, Astolfi L, Sarikas A, Dossena S. Novel POU3F4 variants identified in patients with inner ear malformations exhibit aberrant cellular distribution and lack of SLC6A20 transcriptional upregulation. Front Mol Neurosci 2022; 15:999833. [PMID: 36245926 PMCID: PMC9558712 DOI: 10.3389/fnmol.2022.999833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/13/2022] [Indexed: 11/14/2022] Open
Abstract
Hearing loss (HL) is the most common sensory defect and affects 450 million people worldwide in a disabling form. Pathogenic sequence alterations in the POU3F4 gene, which encodes a transcription factor, are causative of the most common type of X-linked deafness (X-linked deafness type 3, DFN3, DFNX2). POU3F4-related deafness is characterized by a typical inner ear malformation, namely an incomplete partition of the cochlea type 3 (IP3), with or without an enlargement of the vestibular aqueduct (EVA). The pathomechanism underlying POU3F4-related deafness and the corresponding transcriptional targets are largely uncharacterized. Two male patients belonging to a Caucasian cohort with HL and EVA who presented with an IP3 were submitted to genetic analysis. Two novel sequence variants in POU3F4 were identified by Sanger sequencing. In cell-based assays, the corresponding protein variants (p.S74Afs*8 and p.C327*) showed an aberrant expression and subcellular distribution and lack of transcriptional activity. These two protein variants failed to upregulate the transcript levels of the amino acid transporter gene SLC6A20, which was identified as a novel transcriptional target of POU3F4 by RNA sequencing and RT-qPCR. Accordingly, POU3F4 silencing by siRNA resulted in downregulation of SLC6A20 in mouse embryonic fibroblasts. Moreover, we showed for the first time that SLC6A20 is expressed in the mouse cochlea, and co-localized with POU3F4 in the spiral ligament. The findings presented here point to a novel role of amino acid transporters in the inner ear and pave the way for mechanistic studies of POU3F4-related HL.
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Affiliation(s)
- Emanuele Bernardinelli
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Sebastian Roesch
- Department of Otorhinolaryngology, Head and Neck Surgery, Paracelsus Medical University, Salzburg, Austria
| | - Edi Simoni
- Bioacoustic Research Laboratory, Department of Neuroscience, Biomedical Campus Pietro d’Abano, University of Padua, Padua, Italy
| | - Angela Marino
- Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Messina, Italy
| | - Gerd Rasp
- Department of Otorhinolaryngology, Head and Neck Surgery, Paracelsus Medical University, Salzburg, Austria
| | - Laura Astolfi
- Bioacoustic Research Laboratory, Department of Neuroscience, Biomedical Campus Pietro d’Abano, University of Padua, Padua, Italy
- Interdepartmental Research Center of International Auditory Processing Project in Venice (I-APPROVE), Department of Neurosciences, University of Padova, Santi Giovanni e Paolo Hospital, ULSS3, Venice, Italy
| | - Antonio Sarikas
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
- *Correspondence: Antonio Sarikas,
| | - Silvia Dossena
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
- Silvia Dossena,
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Metabolic Abnormalities Linked to Auditory Pathways in ApoE-Knockout HEI-OC1 Cells: A Transcription-Metabolism Co-Analysis. Biomolecules 2022; 12:biom12091217. [PMID: 36139057 PMCID: PMC9496352 DOI: 10.3390/biom12091217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 08/26/2022] [Accepted: 08/26/2022] [Indexed: 11/16/2022] Open
Abstract
Lipid transporter protein apolipoprotein E (APOE) has contributed to functional studies of various organ functions. Animals with ApoE knockout (KO) have been used to study atherosclerosis and hyperlipidemia while an increasing number of researchers have recently focused on the association of ApoE with hearing loss. A study found that ApoE KO mice experience sensorineural hearing loss and hair cell loss, but the exact mechanism is unclear. To explore the potential relationship between ApoE and hearing loss, we used HEI-OC1 cells (House Ear Institute-Organ of Corti) with Corti apparatus properties to reveal cell changes after ApoE knockout by combined transcriptome and metabolomic analysis. We found that glutamate deficiency, caused by reduced expression of glutamine transporter proteins, was a key correlate of basal metabolism and that inadequate glutamate causes apoptosis by reducing the cells’ resistance to external damage. Our study provides a reference mechanism for hearing loss due to ApoE KO.
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Systematic Investigations on the Metabolic and Transcriptomic Regulation of Lactate in the Human Colon Epithelial Cells. Int J Mol Sci 2022; 23:ijms23116262. [PMID: 35682941 PMCID: PMC9181574 DOI: 10.3390/ijms23116262] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 05/19/2022] [Accepted: 05/31/2022] [Indexed: 02/04/2023] Open
Abstract
Lactate, primarily produced by the gut microbiota, performs as a necessary “information transmission carrier” between the gut and the microbiota. To investigate the role of lactate in the gut epithelium cell–microbiota interactions as a metabolic signal, we performed a combinatory, global, and unbiased analysis of metabolomic and transcriptional profiling in human colon epithelial cells (Caco-2), using a lactate treatment at the physiological concentration (8 mM). The data demonstrated that most of the genes in oxidative phosphorylation were significantly downregulated in the Caco-2 cells due to lactate treatment. Consistently, the levels of fumarate, adenosine triphosphate (ATP), and creatine significantly decreased, and these are the metabolic markers of OXPHOS inhibition by mitochondria dysfunction. The one-carbon metabolism was affected and the polyol pathway was activated at the levels of gene expression and metabolic alternation. In addition, lactate significantly upregulated the expressions of genes related to self-protection against apoptosis. In conclusion, lactate participates in gut–gut microbiota communications by remodeling the metabolomic and transcriptional signatures, especially for the regulation of mitochondrial function. This work contributes comprehensive information to disclose the molecular mechanisms of lactate-mediated functions in human colon epithelial cells that can help us understand how the microbiota communicates with the intestines through the signaling molecule, lactate.
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Rullo-Tubau J, Bartoccioni P, Llorca O, Errasti-Murugarren E, Palacín M. HATs meet structural biology. Curr Opin Struct Biol 2022; 74:102389. [DOI: 10.1016/j.sbi.2022.102389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/31/2022] [Accepted: 04/10/2022] [Indexed: 11/26/2022]
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Slc7a8 Deletion Is Protective against Diet-Induced Obesity and Attenuates Lipid Accumulation in Multiple Organs. BIOLOGY 2022; 11:biology11020311. [PMID: 35205177 PMCID: PMC8869389 DOI: 10.3390/biology11020311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/20/2022] [Accepted: 01/26/2022] [Indexed: 11/22/2022]
Abstract
Simple Summary The development of obesity can be attributed to adipocyte hypertrophy or hyperplasia which lead to increased adiposity. The C57BL/6 mouse is an excellent model to study metabolic syndromes often associated with obesity development. Mice fed on a high-fat diet are susceptible to weight gain, leading to the development of obesity and its associated metabolic syndrome. Here, we report findings from targeting a novel potential human adipogenic gene (SLC7A8) under conditions of obesity development using a mouse model of diet-induced obesity (DIO). The results indicate that deleting slc7a8 in mice significantly protects against DIO and improves glucose metabolism. Deficiency in slc7a8 was observed to significantly attenuate adipocyte hypertrophy in white and brown adipose tissue and to reduce lipid accumulation in many organs. Furthermore, inflammation was significantly reduced in the adipose tissue and liver of slc7a8-deficient mice with DIO. Overall, the results from this study show that slc7a8 is an important molecular regulator of obesity development and mediates its function by reducing lipid accumulation in multiple organs. Hence, SLC7A8 could serve as a potential therapeutic target to combat the development of obesity and other pathophysiological conditions associated with excess lipid accumulation. Abstract Adipogenesis, through adipocyte hyperplasia and/or hypertrophy, leads to increased adiposity, giving rise to obesity. A genome-wide transcriptome analysis of in vitro adipogenesis in human adipose-derived stromal/stem cells identified SLC7A8 (Solute Carrier Family 7 Member 8) as a potential novel mediator. The current study has investigated the role of SLC7A8 in adipose tissue biology using a mouse model of diet-induced obesity. slc7a8 knockout (KO) and wildtype (WT) C57BL/6J mice were fed either a control diet (CD) or a high-fat diet (HFD) for 14 weeks. On the HFD, both WT and KO mice (WTHFD and KOHFD) gained significantly more weight than their CD counterparts. However, KOHFD gained significantly less weight than WTHFD. KOHFD had significantly reduced levels of glucose intolerance compared with those observed in WTHFD. KOHFD also had significantly reduced adipocyte mass and hypertrophy in inguinal, mesenteric, perigonadal, and brown adipose depots, with a corresponding decrease in macrophage infiltration. Additionally, KOHFD had decreased lipid accumulation in the liver, heart, gastrocnemius muscle, lung, and kidney. This study demonstrates that targeting slc7a8 protects against diet-induced obesity by reducing lipid accumulation in multiple organs and suggests that if targeted, has the potential to mitigate the development of obesity-associated comorbidities.
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Wang J, Serratrice N, Lee CJ, François F, Sweedler JV, Puel JL, Mothet JP, Ruel J. Physiopathological Relevance of D-Serine in the Mammalian Cochlea. Front Cell Neurosci 2022; 15:733004. [PMID: 34975405 PMCID: PMC8718999 DOI: 10.3389/fncel.2021.733004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 11/29/2021] [Indexed: 12/02/2022] Open
Abstract
NMDA receptors (NMDARs) populate the complex between inner hair cell (IHC) and spiral ganglion neurons (SGNs) in the developing and mature cochlea. However, in the mature cochlea, activation of NMDARs is thought to mainly occur under pathological conditions such as excitotoxicity. Ototoxic drugs such as aspirin enable cochlear arachidonic-acid-sensitive NMDAR responses, and induced chronic tinnitus was blocked by local application of NMDAR antagonists into the cochlear fluids. We largely ignore if other modulators are also engaged. In the brain, D-serine is the primary physiological co-agonist of synaptic NMDARs. Whether D-serine plays a role in the cochlea had remained unexplored. We now reveal the presence of D-serine and its metabolic enzymes prior to, and at hearing onset, in the sensory and non-neuronal cells of the cochlea of several vertebrate species. In vivo intracochlear perfusion of D-serine in guinea pigs reduces sound-evoked activity of auditory nerve fibers without affecting the receptor potentials, suggesting that D-serine acts specifically on the postsynaptic auditory neurons without altering the functional state of IHC or of the stria vascularis. Indeed, we demonstrate in vitro that agonist-induced activation of NMDARs produces robust calcium responses in rat SGN somata only in the presence of D-serine, but not of glycine. Surprisingly, genetic deletion in mice of serine racemase (SR), the enzyme that catalyzes D-serine, does not affect hearing function, but offers protection against noise-induced permanent hearing loss as measured 3 months after exposure. However, the mechanisms of activation of NMDA receptors in newborn rats may be different from those in adult guinea pigs. Taken together, these results demonstrate for the first time that the neuro-messenger D-serine has a pivotal role in the cochlea by promoting the activation of silent cochlear NMDAR in pathological situations. Thus, D-serine and its signaling pathway may represent a new druggable target for treating sensorineural hearing disorders (i.e., hearing loss, tinnitus).
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Affiliation(s)
- Jing Wang
- Institute for Neurosciences of Montpellier (INM), University Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM), Montpellier, France.,ENT Department, Hospital and University of Montpellier, Montpellier, France
| | - Nicolas Serratrice
- Institute for Neurosciences of Montpellier (INM), University Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM), Montpellier, France
| | - Cindy J Lee
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Florence François
- Institute for Neurosciences of Montpellier (INM), University Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM), Montpellier, France
| | - Jonathan V Sweedler
- Department of Chemistry, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Jean-Luc Puel
- Institute for Neurosciences of Montpellier (INM), University Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM), Montpellier, France
| | - Jean-Pierre Mothet
- Laboratoire LuMin, Biophotonics and Synapse Physiopathology Team, Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS), ENS Paris Saclay, Centrale Supélec, Gif-sur-Yvette, France
| | - Jérôme Ruel
- Institute for Neurosciences of Montpellier (INM), University Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM), Montpellier, France.,Aix-Marseille Université, Centre National de la Recherche Scientifique (CNRS), Laboratoire de Neurosciences Cognitives, Marseille, France
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Structural basis for substrate specificity of heteromeric transporters of neutral amino acids. Proc Natl Acad Sci U S A 2021; 118:2113573118. [PMID: 34848541 DOI: 10.1073/pnas.2113573118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/13/2021] [Indexed: 11/18/2022] Open
Abstract
Despite having similar structures, each member of the heteromeric amino acid transporter (HAT) family shows exquisite preference for the exchange of certain amino acids. Substrate specificity determines the physiological function of each HAT and their role in human diseases. However, HAT transport preference for some amino acids over others is not yet fully understood. Using cryo-electron microscopy of apo human LAT2/CD98hc and a multidisciplinary approach, we elucidate key molecular determinants governing neutral amino acid specificity in HATs. A few residues in the substrate-binding pocket determine substrate preference. Here, we describe mutations that interconvert the substrate profiles of LAT2/CD98hc, LAT1/CD98hc, and Asc1/CD98hc. In addition, a region far from the substrate-binding pocket critically influences the conformation of the substrate-binding site and substrate preference. This region accumulates mutations that alter substrate specificity and cause hearing loss and cataracts. Here, we uncover molecular mechanisms governing substrate specificity within the HAT family of neutral amino acid transporters and provide the structural bases for mutations in LAT2/CD98hc that alter substrate specificity and that are associated with several pathologies.
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Ng L, Liu Y, Liu H, Forrest D. Cochlear Fibrocyte and Osteoblast Lineages Expressing Type 2 Deiodinase Identified with a Dio2CreERt2 Allele. Endocrinology 2021; 162:bqab179. [PMID: 34436572 PMCID: PMC8475715 DOI: 10.1210/endocr/bqab179] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Indexed: 12/16/2022]
Abstract
Type 2 deiodinase (Dio2) amplifies levels of 3,5,3'-L-triiodothyronine (T3), the active form of thyroid hormone, and is essential for cochlear maturation and auditory development. However, cellular routes for endocrine signaling in the compartmentalized, anatomically complex cochlea are little understood. Dio2 generates T3 from thyroxine (T4), a more abundant thyroid hormone precursor in the circulation, and is dramatically induced in the cochlea before the onset of hearing. The evidence implies that specific Dio2-expressing cell types critically mediate T3 signaling but these cell types are poorly defined because Dio2 is expressed transiently at low levels. Here, using a Dio2CreERt2 knockin that activates a fluorescent reporter, we define Dio2-expressing cochlear cell types at high resolution in male or female mice. Dio2-positive cells were detected in vascularized supporting tissues but not in avascular internal epithelia, indicating segregation of T3-generating and T3-responding tissues. In the spiral ligament and spiral limbus, Dio2-positive fibrocytes clustered around vascular networks that convey T4 into cochlear tissues. In the otic capsule, Dio2-positive osteoblasts localized at cartilage surfaces as the bony labyrinth matures. We corroborated the identities of Dio2-positive lineages by RNA-sequencing of individual cells. The results suggest a previously unrecognized role for fibrocytes in mediating hormonal signaling. We discuss a model whereby fibrocytes mediate paracrine-like control of T3 signaling to the organ of Corti and epithelial target tissues.
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Affiliation(s)
- Lily Ng
- Laboratory of Endocrinology and Receptor Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ye Liu
- Laboratory of Endocrinology and Receptor Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hong Liu
- Laboratory of Endocrinology and Receptor Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
| | - Douglas Forrest
- Laboratory of Endocrinology and Receptor Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
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Nicolàs-Aragó A, Fort J, Palacín M, Errasti-Murugarren E. Rush Hour of LATs towards Their Transport Cycle. MEMBRANES 2021; 11:602. [PMID: 34436365 PMCID: PMC8399266 DOI: 10.3390/membranes11080602] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 12/29/2022]
Abstract
The mammalian SLC7 family comprises the L-amino acid transporters (LATs) and the cationic amino acid transporters (CATs). The relevance of these transporters is highlighted by their involvement in several human pathologies, including inherited rare diseases and acquired diseases, such as cancer. In the last four years, several crystal or cryo-EM structures of LATs and CATs have been solved. These structures have started to fill our knowledge gap that previously was based on the structural biology of remote homologs of the amino acid-polyamine-organocation (APC) transporters. This review recovers this structural and functional information to start generating the molecular bases of the transport cycle of LATs. Special attention is given to the known transporter conformations within the transport cycle and the molecular bases for substrate interaction and translocation, including the asymmetric interaction of substrates at both sides of the plasma membrane.
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Affiliation(s)
- Adrià Nicolàs-Aragó
- Laboratory of Amino Acid Transporters and Disease, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10, 08028 Barcelona, Spain; (A.N.-A.); (J.F.)
| | - Joana Fort
- Laboratory of Amino Acid Transporters and Disease, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10, 08028 Barcelona, Spain; (A.N.-A.); (J.F.)
- CIBERER (Centro Español en Red de Biomedicina de Enfermedades Raras), 08028 Barcelona, Spain
- Department of Biochemistry and Molecular Biomedicine, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Manuel Palacín
- Laboratory of Amino Acid Transporters and Disease, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10, 08028 Barcelona, Spain; (A.N.-A.); (J.F.)
- CIBERER (Centro Español en Red de Biomedicina de Enfermedades Raras), 08028 Barcelona, Spain
- Department of Biochemistry and Molecular Biomedicine, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Ekaitz Errasti-Murugarren
- Laboratory of Amino Acid Transporters and Disease, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10, 08028 Barcelona, Spain; (A.N.-A.); (J.F.)
- CIBERER (Centro Español en Red de Biomedicina de Enfermedades Raras), 08028 Barcelona, Spain
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12
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Celaya AM, Rodríguez-de la Rosa L, Bermúdez-Muñoz JM, Zubeldia JM, Romá-Mateo C, Avendaño C, Pallardó FV, Varela-Nieto I. IGF-1 Haploinsufficiency Causes Age-Related Chronic Cochlear Inflammation and Increases Noise-Induced Hearing Loss. Cells 2021; 10:cells10071686. [PMID: 34359856 PMCID: PMC8304185 DOI: 10.3390/cells10071686] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 06/28/2021] [Accepted: 06/28/2021] [Indexed: 12/18/2022] Open
Abstract
Insulin-like growth factor 1 (IGF-1) deficiency is an ultrarare syndromic human sensorineural deafness. Accordingly, IGF-1 is essential for the postnatal maturation of the cochlea and the correct wiring of hearing in mice. Less severe decreases in human IGF-1 levels have been associated with other hearing loss rare genetic syndromes, as well as with age-related hearing loss (ARHL). However, the underlying mechanisms linking IGF-1 haploinsufficiency with auditory pathology and ARHL have not been studied. Igf1-heterozygous mice express less Igf1 transcription and have 40% lower IGF-1 serum levels than wild-type mice. Along with ageing, IGF-1 levels decreased concomitantly with the increased expression of inflammatory cytokines, Tgfb1 and Il1b, but there was no associated hearing loss. However, noise exposure of these mice caused increased injury to sensory hair cells and irreversible hearing loss. Concomitantly, there was a significant alteration in the expression ratio of pro- and anti-inflammatory cytokines in Igf1+/- mice. Unbalanced inflammation led to the activation of the stress kinase JNK and the failure to activate AKT. Our data show that IGF-1 haploinsufficiency causes a chronic subclinical proinflammatory age-associated state and, consequently, greater susceptibility to stressors. This work provides the molecular bases to further understand hearing disorders linked to IGF-1 deficiency.
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Affiliation(s)
- Adelaida M. Celaya
- Institute for Biomedical Research “Alberto Sols” (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), 28029 Madrid, Spain; (A.M.C.); (J.M.B.-M.); (J.M.Z.)
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
| | - Lourdes Rodríguez-de la Rosa
- Institute for Biomedical Research “Alberto Sols” (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), 28029 Madrid, Spain; (A.M.C.); (J.M.B.-M.); (J.M.Z.)
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
- Hospital La Paz Institute for Health Research (IdiPAZ), 28029 Madrid, Spain;
- Correspondence: (L.R.-d.l.R.); (I.V.-N.)
| | - Jose M. Bermúdez-Muñoz
- Institute for Biomedical Research “Alberto Sols” (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), 28029 Madrid, Spain; (A.M.C.); (J.M.B.-M.); (J.M.Z.)
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
| | - José M. Zubeldia
- Institute for Biomedical Research “Alberto Sols” (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), 28029 Madrid, Spain; (A.M.C.); (J.M.B.-M.); (J.M.Z.)
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
- Allergy Service, Gregorio Marañon General University Hospital, 28009 Madrid, Spain
- Gregorio Marañon Health Research Institute (IiSGM), 28009 Madrid, Spain
| | - Carlos Romá-Mateo
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, Spain and FIHCUV-INCLIVA, 46010 Valencia, Spain
| | - Carlos Avendaño
- Hospital La Paz Institute for Health Research (IdiPAZ), 28029 Madrid, Spain;
- Department of Anatomy, Histology & Neuroscience, Medical School, Autonomous University of Madrid, 28029 Madrid, Spain
| | - Federico V. Pallardó
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
- Department of Physiology, Faculty of Medicine and Dentistry, University of Valencia, Spain and FIHCUV-INCLIVA, 46010 Valencia, Spain
| | - Isabel Varela-Nieto
- Institute for Biomedical Research “Alberto Sols” (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), 28029 Madrid, Spain; (A.M.C.); (J.M.B.-M.); (J.M.Z.)
- Rare Diseases Biomedical Research Networking Centre (CIBERER), The Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; (C.R.-M.); (F.V.P.)
- Hospital La Paz Institute for Health Research (IdiPAZ), 28029 Madrid, Spain;
- Correspondence: (L.R.-d.l.R.); (I.V.-N.)
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13
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Yu Y, Yang J, Luan F, Gu G, Zhao R, Wang Q, Dong Z, Tang J, Wang W, Sun J, Lv P, Zhang H, Wang C. Sensorineural Hearing Loss and Mitochondrial Apoptosis of Cochlear Spiral Ganglion Neurons in Fibroblast Growth Factor 13 Knockout Mice. Front Cell Neurosci 2021; 15:658586. [PMID: 34220452 PMCID: PMC8242186 DOI: 10.3389/fncel.2021.658586] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/26/2021] [Indexed: 12/17/2022] Open
Abstract
Deafness is known to occur in more than 400 syndromes and accounts for almost 30% of hereditary hearing loss. The molecular mechanisms underlying such syndromic deafness remain unclear. Furthermore, deafness has been a common feature in patients with three main syndromes, the BÖrjeson-Forssman-Lehmann syndrome, Wildervanck syndrome, and Congenital Generalized Hirsutism, all of which are characterized by loss-of-function mutations in the Fgf13 gene. Whether the pathogenesis of deafness in these syndromes is associated with the Fgf13 mutation is not known. To elucidate its role in auditory function, we generated a mouse line with conditional knockout of the Fgf13 gene in the inner ear (Fgf13 cKO). FGF13 is expressed predominantly in the organ of Corti, spiral ganglion neurons (SGNs), stria vascularis, and the supporting cells. Conditional knockout of the gene in the inner ear led to sensorineural deafness with low amplitude and increased latency of wave I in the auditory brainstem response test but had a normal distortion product otoacoustic emission threshold. Fgf13 deficiency resulted in decreased SGN density from the apical to the basal region without significant morphological changes and those in the number of hair cells. TUNEL and caspase-3 immunocytochemistry assays showed that apoptotic cell death mediated the loss of SGNs. Further detection of apoptotic factors through qRT-PCR suggested the activation of the mitochondrial apoptotic pathway in SGNs. Together, this study reveals a novel role for Fgf13 in auditory function, and indicates that the gene could be a potential candidate for understanding deafness. These findings may provide new perspectives on the molecular mechanisms and novel therapeutic targets for treatment deafness.
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Affiliation(s)
- Yulou Yu
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Jing Yang
- Department of Physiology, Hebei Medical University, Shijiazhuang, China
| | - Feng Luan
- Department of Otolaryngology, The Third Hospital of Hebei Medical University, Shijiazhuang, China
| | - Guoqiang Gu
- Department of Cardiology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Ran Zhao
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Qiong Wang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Zishan Dong
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Junming Tang
- Hubei Key Laboratory of Embryonic Stem Cell Research, Hubei University of Medicine, Shiyan, China
| | - Wei Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, China
| | - Jinpeng Sun
- Key Laboratory Experimental Teratology of the Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Ping Lv
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Hailin Zhang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Chuan Wang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
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14
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Morio H, Reien Y, Hirayama Y, Hashimoto H, Anzai N. Protein kinase C activation upregulates human L-type amino acid transporter 2 function. J Physiol Sci 2021; 71:11. [PMID: 33789576 PMCID: PMC10716992 DOI: 10.1186/s12576-021-00795-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 03/05/2021] [Indexed: 11/10/2022]
Abstract
L-type amino acid transporter 2 (LAT2) is a Na+-independent neutral amino acid transporter, whose function regulation system remains unclarified. Since protein kinase C (PKC) is known to regulate the functions of various transporters, we investigated whether human LAT2 (hLAT2) function is regulated by PKC. In mouse proximal tubule S2 cells, hLAT2 transport activity was upregulated by PKC activation. However, we found that the mRNA and protein expression of hLAT2 was not affected by PKC activation and that the upregulation was independent of the three potential PKC consensus sites in the hLAT2 amino acid sequence. Moreover, we found that PKC activation upregulated the Vmax value for hLAT2-mediated alanine transport, which was not accompanied by the induction of hLAT2 membrane insertion. In conclusion, we showed that hLAT2 function is upregulated by PKC activation, which is not related to either the de novo synthesis, the phosphorylation or the membrane insertion of hLAT2.
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Affiliation(s)
- Hanae Morio
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba, 260-8670, Japan
| | - Yoshie Reien
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba, 260-8670, Japan
| | - Yuri Hirayama
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba, 260-8670, Japan
| | - Hirofumi Hashimoto
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba, 260-8670, Japan
| | - Naohiko Anzai
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba, 260-8670, Japan.
- Department of Pharmacology and Toxicology, School of Medicine, Dokkyo Medical University, 880 Kitakobayashi, Mibu-cho, Shimotsuga-gun, Tochigi, 321-0293, Japan.
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15
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Fairweather SJ, Shah N, Brӧer S. Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 21:13-127. [PMID: 33052588 DOI: 10.1007/5584_2020_584] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H+ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b0,+AT-rBAT and the SLC6 family heteromer B0AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.
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Affiliation(s)
- Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia. .,Resarch School of Chemistry, Australian National University, Canberra, ACT, Australia.
| | - Nishank Shah
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Brӧer
- Research School of Biology, Australian National University, Canberra, ACT, Australia.
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16
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Errasti-Murugarren E, Palacín M. Heteromeric Amino Acid Transporters in Brain: from Physiology to Pathology. Neurochem Res 2021; 47:23-36. [PMID: 33606172 DOI: 10.1007/s11064-021-03261-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/27/2021] [Accepted: 01/30/2021] [Indexed: 12/12/2022]
Abstract
In humans, more than 50 transporters are responsible for the traffic and balance of amino acids within and between cells and tissues, and half of them have been associated with disease [1]. Covering all common amino acids, Heteromeric Amino acid Transporters (HATs) are one class of such transporters. This review first highlights structural and functional studies that solved the atomic structure of HATs and revealed molecular clues on substrate interaction. Moreover, this review focuses on HATs that have a role in the central nervous system (CNS) and that are related to neurological diseases, including: (i) LAT1/CD98hc and its role in the uptake of branched chain amino acids trough the blood brain barrier and autism. (ii) LAT2/CD98hc and its potential role in the transport of glutamine between plasma and cerebrospinal fluid. (iii) y+LAT2/CD98hc that is emerging as a key player in hepatic encephalopathy. xCT/CD98hc as a potential therapeutic target in glioblastoma, and (iv) Asc-1/CD98hc as a potential therapeutic target in pathologies with alterations in NMDA glutamate receptors.
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Affiliation(s)
- Ekaitz Errasti-Murugarren
- Institute for Research in Biomedicine. Institute of Science and Technology (BIST), 08028, Barcelona, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), 08028, Barcelona, Spain.
| | - Manuel Palacín
- Institute for Research in Biomedicine. Institute of Science and Technology (BIST), 08028, Barcelona, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), 08028, Barcelona, Spain. .,Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.
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17
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Affortit C, Casas F, Ladrech S, Ceccato JC, Bourien J, Coyat C, Puel JL, Lenoir M, Wang J. Exacerbated age-related hearing loss in mice lacking the p43 mitochondrial T3 receptor. BMC Biol 2021; 19:18. [PMID: 33526032 PMCID: PMC7852282 DOI: 10.1186/s12915-021-00953-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 01/08/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Age-related hearing loss (ARHL), also known as presbycusis, is the most common sensory impairment seen in elderly people. However, the cochlear aging process does not affect people uniformly, suggesting that both genetic and environmental (e.g., noise, ototoxic drugs) factors and their interaction may influence the onset and severity of ARHL. Considering the potential links between thyroid hormone, mitochondrial activity, and hearing, here, we probed the role of p43, a N-terminally truncated and ligand-binding form of the nuclear receptor TRα1, in hearing function and in the maintenance of hearing during aging in p43-/- mice through complementary approaches, including in vivo electrophysiological recording, ultrastructural assessments, biochemistry, and molecular biology. RESULTS We found that the p43-/- mice exhibit no obvious hearing loss in juvenile stages, but that these mice developed a premature, and more severe, ARHL resulting from the loss of cochlear sensory outer and inner hair cells and degeneration of spiral ganglion neurons. Exacerbated ARHL in p43-/- mice was associated with the early occurrence of a drastic fall of SIRT1 expression, together with an imbalance between pro-apoptotic Bax, p53 expression, and anti-apoptotic Bcl2 expression, as well as an increase in mitochondrial dysfunction, oxidative stress, and inflammatory process. Finally, p43-/- mice were also more vulnerable to noise-induced hearing loss. CONCLUSIONS These results demonstrate for the first time a requirement for p43 in the maintenance of hearing during aging and highlight the need to probe the potential link between human THRA gene polymorphisms and/or mutations and accelerated age-related deafness or some adult-onset syndromic deafness.
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Affiliation(s)
- Corentin Affortit
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - François Casas
- INRA, UMR 866 Dynamique Musculaire et Métabolisme,, 34060, Montpellier, France
| | - Sabine Ladrech
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Jean-Charles Ceccato
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Jérôme Bourien
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Carolanne Coyat
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Jean-Luc Puel
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Marc Lenoir
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France
- Université de Montpellier, 34000, Montpellier, France
| | - Jing Wang
- INSERM - UMR 1051, Institut des Neurosciences de Montpellier, 80 rue Augustin Fliche, 34295, Montpellier, France.
- Université de Montpellier, 34000, Montpellier, France.
- ENT Department, CHU Montpellier, 34295, Montpellier, France.
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18
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Kantipudi S, Jeckelmann JM, Ucurum Z, Bosshart PD, Fotiadis D. The Heavy Chain 4F2hc Modulates the Substrate Affinity and Specificity of the Light Chains LAT1 and LAT2. Int J Mol Sci 2020; 21:ijms21207573. [PMID: 33066406 PMCID: PMC7589757 DOI: 10.3390/ijms21207573] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 10/09/2020] [Accepted: 10/10/2020] [Indexed: 01/23/2023] Open
Abstract
The human L-type amino acid transporters LAT1 and LAT2 mediate the transport of amino acids and amino acid derivatives across plasma membranes in a sodium-independent, obligatory antiport mode. In mammalian cells, LAT1 and LAT2 associate with the type-II membrane N-glycoprotein 4F2hc to form heteromeric amino acid transporters (HATs). The glycosylated ancillary protein 4F2hc is known to be important for successful trafficking of the unglycosylated transporters to the plasma membrane. The heavy (i.e., 4F2hc) and light (i.e., LAT1 and LAT2) chains belong to the solute carrier (SLC) families SLC3 and SLC7, and are covalently linked by a conserved disulfide bridge. Overexpression, absence, or malfunction of certain HATs is associated with human diseases and HATs are therefore considered therapeutic targets. Here, we present a comparative, functional characterization of the HATs 4F2hc-LAT1 and 4F2hc-LAT2, and their light chains LAT1 and LAT2. For this purpose, the HATs and the light chains were expressed in the methylotrophic yeast Pichia pastoris and a radiolabel transport assay was established. Importantly and in contrast to mammalian cells, P. pastoris has proven useful as eukaryotic expression system to successfully express human LAT1 and LAT2 in the plasma membrane without the requirement of co-expressed trafficking chaperone 4F2hc. Our results show a novel function of the heavy chain 4F2hc that impacts transport by modulating the substrate affinity and specificity of corresponding LATs. In addition, the presented data confirm that the light chains LAT1 and LAT2 constitute the substrate-transporting subunits of the HATs, and that light chains are also functional in the absence of the ancillary protein 4F2hc.
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19
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Sub-Nanometer Cryo-EM Density Map of the Human Heterodimeric Amino Acid Transporter 4F2hc-LAT2. Int J Mol Sci 2020; 21:ijms21197094. [PMID: 32993041 PMCID: PMC7584034 DOI: 10.3390/ijms21197094] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/23/2020] [Accepted: 09/23/2020] [Indexed: 12/13/2022] Open
Abstract
Heterodimeric amino acid transporters (HATs) are protein complexes mediating the transport of amino acids and derivatives thereof across biological membranes. HATs are composed of two subunits, a heavy and a light chain subunit belonging to the solute carrier (SLC) families SLC3 and SLC7. The human HAT 4F2hc-LAT2 is composed of the type-II membrane N-glycoprotein 4F2hc (SCL3A2) and the L-type amino acid transporter LAT2 (SLC7A8), which are covalently linked to each other by a conserved disulfide bridge. Whereas LAT2 catalyzes substrate transport, 4F2hc is important for the successful trafficking of the transporter to the plasma membrane. The overexpression, malfunction, or absence of 4F2hc-LAT2 is associated with human diseases, and therefore, this heterodimeric complex represents a potential drug target. The recombinant human 4F2hc-LAT2 can be functionally overexpressed in the methylotrophic yeast Pichia pastoris, and the protein can be purified. Here, we present the cryo-EM density map of the human 4F2hc-LAT2 amino acid transporter at sub-nanometer resolution. A homology model of 4F2hc-LAT2 in the inward-open conformation was generated and fitted into the cryo-EM density and analyzed. In addition, disease-causing point mutations in human LAT2 were mapped on the homology model of 4F2hc-LAT2, and the possible functional implications on the molecular level are discussed.
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20
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Vona B, Doll J, Hofrichter MA, Haaf T. Non-syndromic hearing loss: clinical and diagnostic challenges. MED GENET-BERLIN 2020. [DOI: 10.1515/medgen-2020-2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Abstract
Hereditary hearing loss is clinically and genetically heterogeneous. There are presently over 120 genes that have been associated with non-syndromic hearing loss and many more that are associated with syndromic forms. Despite an increasing number of genes that have been implemented into routine molecular genetic diagnostic testing, the diagnostic yield from European patient cohorts with hereditary hearing loss remains around the 50 % mark. This attests to the many gaps of knowledge the field is currently working toward resolving. It can be expected that many more genes await identification. However, it can also be expected, for example, that the mutational signatures of the known genes are still unclear, especially variants in non-coding or regulatory regions influencing gene expression. This review summarizes several challenges in the clinical and diagnostic setting for hereditary hearing loss with emphasis on syndromes that mimic non-syndromic forms of hearing loss in young children and other factors that heavily influence diagnostic rates. A molecular genetic diagnosis for patients with hearing loss opens several additional avenues, such as patient tailored selection of the best currently available treatment modalities, an understanding of the prognosis, and supporting family planning decisions. In the near future, a genetic diagnosis may enable patients to engage in preclinical trials for the development of therapeutics.
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Affiliation(s)
- Barbara Vona
- Tübingen Hearing Research Centre, Department of Otolaryngology – Head & Neck Surgery , Eberhard Karls University , Elfriede-Aulhorn-Strasse 5 , Tübingen , Germany
| | - Julia Doll
- Institute of Human Genetics , Julius Maximilians University , Würzburg , Germany
| | | | - Thomas Haaf
- Institute of Human Genetics , Julius-Maximilians University Würzburg , Biozentrum, Am Hubland , Würzburg , Germany
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21
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Mu Y, Li W, Wei Z, He L, Zhang W, Chen X. Transcriptome analysis reveals molecular strategies in gills and heart of large yellow croaker (Larimichthys crocea) under hypoxia stress. FISH & SHELLFISH IMMUNOLOGY 2020; 104:304-313. [PMID: 32544557 DOI: 10.1016/j.fsi.2020.06.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/07/2020] [Accepted: 06/12/2020] [Indexed: 06/11/2023]
Abstract
The gills and heart are two major targets of hypoxia in fish. However, the molecular responses in fish gills and heart to hypoxia challenge remain unclear. Here, RNA-Seq technology was used to study the gene expression profiles in gills and heart of large yellow croaker (Larimichthys crocea) at 6, 24, and 48 h after hypoxia stress. A total of 1,546 and 2,746 differentially expressed genes (DEGs) were identified in gills and heart, respectively. Expression changes of nine genes in each tissue were further validated by the qPCR. Based on KEGG and Gene ontology enrichments, we found that various innate immunity-related genes, such as complement components (C1qs, C2, C3, C6, and C7), chemokines (CCL3, CCL17, CCL19, CCL25, and CXCL8_L3), chemokine receptors (CCR9, CXCR1, and CXCR3), and nitric oxide synthase (NOS), were significantly down-regulated in gills and/or heart, suggesting that innate immune processes mediated by these genes may be inhibited by hypoxia. The genes involved in both glycolysis pathway (LDHA) and tricarboxylic acid cycle (IDH2 and OGDH) were up-regulated in gills and heart of hypoxic large yellow croakers, possibly because gill and heart tissues need enough energy to accelerate gas exchange and blood circulation. Hypoxia also affected the ion transport in gills of large yellow croaker, through down-regulating the expression levels of numerous classical ion transporters, including HVCN1, SLC20A2, SLC4A4, RHBG, RHCG, and SCN4A, suggesting an energy conservation strategy to hypoxia stress. All these results indicate that the immune processes, glycolytic pathways, and ion transport were significantly altered in gills and/or heart of large yellow croaker under hypoxia, possibly contributing to maintain cellular energy balance during hypoxia. Our data, therefore, afford new information to understand the tissue-specific molecular responses of bony fish to hypoxia stress.
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Affiliation(s)
- Yinnan Mu
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China
| | - Wanru Li
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China
| | - Zuyun Wei
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China
| | - Lianghua He
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China
| | - Weini Zhang
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China
| | - Xinhua Chen
- Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, Fujian Agriculture and Forestry University, Fuzhou, 350002, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, PR China.
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22
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Enomoto K, Hotomi M. Amino Acid Transporters as Potential Therapeutic Targets in Thyroid Cancer. Endocrinol Metab (Seoul) 2020; 35:227-236. [PMID: 32615707 PMCID: PMC7386108 DOI: 10.3803/enm.2020.35.2.227] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/09/2020] [Indexed: 12/31/2022] Open
Abstract
Thyroid cancer cells have a high amino acid demand for proliferation, invasion, and metastasis. Amino acids are taken up by thyroid cancer cells, both thyroid follicular cell and thyroid parafollicular cells (commonly called "C-cells"), via amino acid transporters. Amino acid transporters up-regulate in many cancers, and their expression level associate with clinical aggressiveness and prognosis. This is the review to discuss the therapeutic potential of amino acid transporters and as molecular targets in thyroid cancer.
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Affiliation(s)
- Keisuke Enomoto
- Department of Otolaryngology-Head and Neck Surgery, Wakayama Medical University, Wakayama, Japan
| | - Muneki Hotomi
- Department of Otolaryngology-Head and Neck Surgery, Wakayama Medical University, Wakayama, Japan
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Groeneweg S, van Geest FS, Peeters RP, Heuer H, Visser WE. Thyroid Hormone Transporters. Endocr Rev 2020; 41:5637505. [PMID: 31754699 DOI: 10.1210/endrev/bnz008] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/07/2019] [Indexed: 02/08/2023]
Abstract
Thyroid hormone transporters at the plasma membrane govern intracellular bioavailability of thyroid hormone. Monocarboxylate transporter (MCT) 8 and MCT10, organic anion transporting polypeptide (OATP) 1C1, and SLC17A4 are currently known as transporters displaying the highest specificity toward thyroid hormones. Structure-function studies using homology modeling and mutational screens have led to better understanding of the molecular basis of thyroid hormone transport. Mutations in MCT8 and in OATP1C1 have been associated with clinical disorders. Different animal models have provided insight into the functional role of thyroid hormone transporters, in particular MCT8. Different treatment strategies for MCT8 deficiency have been explored, of which thyroid hormone analogue therapy is currently applied in patients. Future studies may reveal the identity of as-yet-undiscovered thyroid hormone transporters. Complementary studies employing animal and human models will provide further insight into the role of transporters in health and disease. (Endocrine Reviews 41: 1 - 55, 2020).
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Affiliation(s)
- Stefan Groeneweg
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Ferdy S van Geest
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Robin P Peeters
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Heike Heuer
- Department of Endocrinology, Diabetes and Metabolism, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - W Edward Visser
- Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands Academic Center for Thyroid Diseases, Erasmus Medical Center, Rotterdam, the Netherlands
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24
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Choroid plexus LAT2 and SNAT3 as partners in CSF amino acid homeostasis maintenance. Fluids Barriers CNS 2020; 17:17. [PMID: 32046769 PMCID: PMC7014681 DOI: 10.1186/s12987-020-0178-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 02/01/2020] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Cerebrospinal fluid (CSF) is mainly produced by the choroid plexus (CP) located in brain ventricles. Although derived from blood plasma, it is nearly protein-free (~ 250-fold less) and contains about 2-20-fold less free amino acids, with the exception of glutamine (Gln) which is nearly equal. The aim of this study was to determine which amino acid transporters are expressed in mouse CP epithelium in order to gain understanding about how this barrier maintains the observed amino acid concentration gradient. METHODS Expression of amino acid transporters was assessed in isolated choroid plexuses (CPs) by qRT-PCR followed by localization studies using immunofluorescence with specific antibodies. The impact of LAT2 (Slc7a8) antiporter deletion on CSF amino acids was determined. RESULTS The purity of isolated choroid plexuses was tested on the mRNA level using specific markers, in particular transthyretin (Ttr) that was enriched 330-fold in CP compared to cerebral tissue. In a first experimental round, 14 out of 32 Slc amino acid transporters tested on the mRNA level by qPCR were selected for further investigation. Out of these, five were considered highly expressed, SNAT1 (Slc38a1), SNAT3 (Slc38a3), LAT2 (Slc7a8), ASC1 (Slc7a10) and SIT1 (Slc6a20b). Three of them were visualized by immunofluorescence: SNAT1 (Slc38a1), a neutral amino acid-Na+ symporter, found at the blood side basolateral membrane of CP epithelium, while SNAT3 (Slc38a3), an amino acid-Na+ symporter and H+ antiporter, as well as LAT2 (Slc7a8), a neutral amino acid antiporter, were localized at the CSF-facing luminal membrane. In a LAT2 knock-out mouse model, CSF Gln was unchanged, whereas other amino acids normally 2-20-fold lower than in plasma, were increased, in particular the LAT2 uptake substrates leucine (Leu), valine (Val) and tryptophan (Trp) and some other amino acids such as glutamate (Glu), glycine (Gly) and proline (Pro). CONCLUSION These results suggest that Gln is actively transported by SNAT1 from the blood into CP epithelial cells and then released luminally into CSF via SNAT3 and LAT2. Its efflux via LAT2 may drive the reuptake from the CSF of essential amino acid substrates of this antiporter and thereby participates to maintaining the amino acid gradient between plasma and CSF.
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25
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Krammer EM, Prévost M. Function and Regulation of Acid Resistance Antiporters. J Membr Biol 2019; 252:465-481. [DOI: 10.1007/s00232-019-00073-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 06/08/2019] [Indexed: 01/07/2023]
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26
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Knöpfel EB, Vilches C, Camargo SMR, Errasti-Murugarren E, Stäubli A, Mayayo C, Munier FL, Miroshnikova N, Poncet N, Junza A, Bhattacharya SS, Prat E, Berry V, Berger W, Heon E, Moore AT, Yanes Ó, Nunes V, Palacín M, Verrey F, Kloeckener-Gruissem B. Dysfunctional LAT2 Amino Acid Transporter Is Associated With Cataract in Mouse and Humans. Front Physiol 2019; 10:688. [PMID: 31231240 PMCID: PMC6558864 DOI: 10.3389/fphys.2019.00688] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 05/16/2019] [Indexed: 11/13/2022] Open
Abstract
Cataract, the loss of ocular lens transparency, accounts for ∼50% of worldwide blindness and has been associated with water and solute transport dysfunction across lens cellular barriers. We show that neutral amino acid antiporter LAT2 (Slc7a8) and uniporter TAT1 (Slc16a10) are expressed on mouse ciliary epithelium and LAT2 also in lens epithelium. Correspondingly, deletion of LAT2 induced a dramatic decrease in lens essential amino acid levels that was modulated by TAT1 defect. Interestingly, the absence of LAT2 led to increased incidence of cataract in mice, in particular in older females, and a synergistic effect was observed with simultaneous lack of TAT1. Screening SLC7A8 in patients diagnosed with congenital or age-related cataract yielded one homozygous single nucleotide deletion segregating in a family with congenital cataract. Expressed in HeLa cells, this LAT2 mutation did not support amino acid uptake. Heterozygous LAT2 variants were also found in patients with cataract some of which showed a reduced transport function when expressed in HeLa cells. Whether heterozygous LAT2 variants may contribute to the pathology of cataract needs to be further investigated. Overall, our results suggest that defects of amino acid transporter LAT2 are implicated in cataract formation, a situation that may be aggravated by TAT1 defects.
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Affiliation(s)
- Emilia Boiadjieva Knöpfel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
- Swiss National Centre of Competence in Research Kidney.CH, University of Zurich, Zurich, Switzerland
| | - Clara Vilches
- Genes, Disease and Therapy Program, Molecular Genetics Laboratory – IDIBELL, Barcelona, Spain
- U730 and U731, Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
| | - Simone M. R. Camargo
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Ekaitz Errasti-Murugarren
- U730 and U731, Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Andrina Stäubli
- Institute of Medical Molecular Genetics, University of Zurich, Zurich, Switzerland
- Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Clara Mayayo
- Genes, Disease and Therapy Program, Molecular Genetics Laboratory – IDIBELL, Barcelona, Spain
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Francis L. Munier
- Jules-Gonin Eye Hospital, University of Lausanne, Lausanne, Switzerland
| | | | - Nadège Poncet
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Alexandra Junza
- Metabolomics Platform, IISPV, Department of Electronic Engineering, Universitat Rovira i Virgili, Tarragona, Spain
- CIBER of Diabetes and Associated Metabolic Diseases (CIBERDEM), Madrid, Spain
| | - Shomi S. Bhattacharya
- Andalusian Molecular Biology and Regenerative Medicine Centre – CABIMER, Seville, Spain
- UCL Institute of Ophthalmology, London, United Kingdom
| | - Esther Prat
- Genes, Disease and Therapy Program, Molecular Genetics Laboratory – IDIBELL, Barcelona, Spain
- U730 and U731, Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
- Genetics Section, Department of Physiological Sciences, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain
| | - Vanita Berry
- Andalusian Molecular Biology and Regenerative Medicine Centre – CABIMER, Seville, Spain
| | - Wolfgang Berger
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
- Institute of Medical Molecular Genetics, University of Zurich, Zurich, Switzerland
- Neuroscience Center Zurich – ZNZ, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Elise Heon
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, Toronto, ON, Canada
| | - Anthony T. Moore
- Andalusian Molecular Biology and Regenerative Medicine Centre – CABIMER, Seville, Spain
- Moorfields Eye Hospital, London, United Kingdom
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA, United States
| | - Óscar Yanes
- Metabolomics Platform, IISPV, Department of Electronic Engineering, Universitat Rovira i Virgili, Tarragona, Spain
- CIBER of Diabetes and Associated Metabolic Diseases (CIBERDEM), Madrid, Spain
| | - Virginia Nunes
- Genes, Disease and Therapy Program, Molecular Genetics Laboratory – IDIBELL, Barcelona, Spain
- U730 and U731, Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
- Genetics Section, Department of Physiological Sciences, Faculty of Medicine and Health Sciences, University of Barcelona, Barcelona, Spain
| | - Manuel Palacín
- U730 and U731, Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
- Institute for Research in Biomedicine, The Barcelona Institute of Science and Technology, Barcelona, Spain
- Departament de Bioquímica i Biomedicina Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Francois Verrey
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
- Swiss National Centre of Competence in Research Kidney.CH, University of Zurich, Zurich, Switzerland
| | - Barbara Kloeckener-Gruissem
- Institute of Medical Molecular Genetics, University of Zurich, Zurich, Switzerland
- Department of Biology, ETH Zurich, Zurich, Switzerland
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27
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L amino acid transporter structure and molecular bases for the asymmetry of substrate interaction. Nat Commun 2019; 10:1807. [PMID: 31000719 PMCID: PMC6472337 DOI: 10.1038/s41467-019-09837-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 04/02/2019] [Indexed: 11/26/2022] Open
Abstract
L-amino acid transporters (LATs) play key roles in human physiology and are implicated in several human pathologies. LATs are asymmetric amino acid exchangers where the low apparent affinity cytoplasmic side controls the exchange of substrates with high apparent affinity on the extracellular side. Here, we report the crystal structures of an LAT, the bacterial alanine-serine-cysteine exchanger (BasC), in a non-occluded inward-facing conformation in both apo and substrate-bound states. We crystallized BasC in complex with a nanobody, which blocks the transporter from the intracellular side, thus unveiling the sidedness of the substrate interaction of BasC. Two conserved residues in human LATs, Tyr 236 and Lys 154, are located in equivalent positions to the Na1 and Na2 sites of sodium-dependent APC superfamily transporters. Functional studies and molecular dynamics (MD) calculations reveal that these residues are key for the asymmetric substrate interaction of BasC and in the homologous human transporter Asc-1. L-Amino acid Transporters (LATs) are asymmetric amino acid exchangers. Here the authors determine the crystal structure of a prokaryotic LAT, the alanine-serine-cysteine exchanger (BasC) and identify key residues for asymmetric substrate interaction in both BasC and the homologous human transporter Asc-1 through functional studies.
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28
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Celaya AM, Sánchez-Pérez I, Bermúdez-Muñoz JM, Rodríguez-de la Rosa L, Pintado-Berninches L, Perona R, Murillo-Cuesta S, Varela-Nieto I. Deficit of mitogen-activated protein kinase phosphatase 1 (DUSP1) accelerates progressive hearing loss. eLife 2019; 8:39159. [PMID: 30938680 PMCID: PMC6464786 DOI: 10.7554/elife.39159] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 04/01/2019] [Indexed: 12/12/2022] Open
Abstract
Mitogen-activated protein kinases (MAPK) such as p38 and the c-Jun N-terminal kinases (JNKs) are activated during the cellular response to stress signals. Their activity is regulated by the MAPK-phosphatase 1 (DUSP1), a key component of the anti-inflammatory response. Stress kinases are well-described elements of the response to otic injury and the otoprotective potential of JNK inhibitors is being tested in clinical trials. By contrast, there are no studies exploring the role of DUSP1 in hearing and hearing loss. Here we show that Dusp1 expression is age-regulated in the mouse cochlea. Dusp1 gene knock-out caused premature progressive hearing loss, as confirmed by auditory evoked responses in Dusp1-/- mice. Hearing loss correlated with cell death in hair cells, degeneration of spiral neurons and increased macrophage infiltration. Dusp1-/- mouse cochleae showed imbalanced redox status and dysregulated expression of cytokines. These data suggest that DUSP1 is essential for cochlear homeostasis in the response to stress during ageing.
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Affiliation(s)
- Adelaida M Celaya
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain
| | - Isabel Sánchez-Pérez
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain.,Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain.,Biochemistry Department, Faculty of Medicine, Autonomous University of Madrid, Madrid, Spain.,Biomedicine Unit UCLM-CSIC, Madrid, Spain
| | - Jose M Bermúdez-Muñoz
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain
| | - Lourdes Rodríguez-de la Rosa
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain.,Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
| | - Laura Pintado-Berninches
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
| | - Rosario Perona
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain.,Hospital La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
| | - Silvia Murillo-Cuesta
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain
| | - Isabel Varela-Nieto
- Institute for Biomedical Research "Alberto Sols" (IIBM), Spanish National Research Council-Autonomous University of Madrid (CSIC-UAM), Madrid, Spain.,Centre for Biomedical Network Research on Rare Diseases (CIBERER), CIBER, ISCIII, Madrid, Spain
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29
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Jeckelmann JM, Fotiadis D. Volta Phase Plate Cryo-EM Structure of the Human Heterodimeric Amino Acid Transporter 4F2hc-LAT2. Int J Mol Sci 2019; 20:ijms20040931. [PMID: 30795505 PMCID: PMC6413005 DOI: 10.3390/ijms20040931] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 02/15/2019] [Accepted: 02/18/2019] [Indexed: 01/29/2023] Open
Abstract
Heteromeric amino acid transporters (HATs) are protein complexes that catalyze the transport of amino acids across plasma membranes. HATs are composed of two subunits, a heavy and a light subunit, which belong to the solute carrier (SLC) families SLC3 and SLC7. The two subunits are linked by a conserved disulfide bridge. Several human diseases are associated with loss of function or overexpression of specific HATs making them drug targets. The human HAT 4F2hc-LAT2 (SLC3A2-SLC7A8) is specific for the transport of large neutral L-amino acids and specific amino acid-related compounds. Human 4F2hc-LAT2 can be functionally overexpressed in the methylotrophic yeast Pichia pastoris and pure recombinant protein purified. Here we present the first cryo-electron microscopy (cryo-EM) 3D-map of a HAT, i.e., of the human 4F2hc-LAT2 complex. The structure could be determined at ~13 Å resolution using direct electron detector and Volta phase plate technologies. The 3D-map displays two prominent densities of different sizes. The available X-ray structure of the 4F2hc ectodomain fitted nicely into the smaller density revealing the relative position of 4F2hc with respect to LAT2 and the membrane plane.
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Affiliation(s)
- Jean-Marc Jeckelmann
- Institute of Biochemistry and Molecular Medicine, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern, CH-3012 Bern, Switzerland.
| | - Dimitrios Fotiadis
- Institute of Biochemistry and Molecular Medicine, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern, CH-3012 Bern, Switzerland.
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30
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Bartoccioni P, Fort J, Zorzano A, Errasti-Murugarren E, Palacín M. Functional characterization of the alanine-serine-cysteine exchanger of Carnobacterium sp AT7. J Gen Physiol 2019; 151:505-517. [PMID: 30696726 PMCID: PMC6445583 DOI: 10.1085/jgp.201812195] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 11/16/2018] [Accepted: 01/03/2019] [Indexed: 01/18/2023] Open
Abstract
Proteins of the L-type amino acid transporter (LAT) subfamily take up amino acids from the environment for use in the cell. Bartoccioni et al. show that the bacterial amino acid exchanger BasC is functionally similar to the human LAT Asc1, making BasC a useful model for this class of transporters. Many key cell processes require prior cell uptake of amino acids from the environment, which is facilitated by cell membrane amino acid transporters such as those of the L-type amino acid transporter (LAT) subfamily. Alterations in LAT subfamily amino acid transport are associated with several human diseases, including cancer, aminoacidurias, and neurodegenerative conditions. Therefore, from the perspective of human health, there is considerable interest in obtaining structural information about these transporter proteins. We recently solved the crystal structure of the first LAT transporter, the bacterial alanine-serine-cysteine exchanger of Carnobacterium sp AT7 (BasC). Here, we provide a complete functional characterization of detergent-purified, liposome-reconstituted BasC transporter to allow the extension of the structural insights into mechanistic understanding. BasC is a sodium- and proton-independent small neutral amino acid exchanger whose substrate and inhibitor selectivity are almost identical to those previously described for the human LAT subfamily member Asc-1. Additionally, we show that, like its human counterparts, this transporter has apparent affinity asymmetry for the intra- and extracellular substrate binding sites—a key feature in the physiological role played by these proteins. BasC is an excellent paradigm of human LAT transporters and will contribute to our understanding of the molecular mechanisms underlying substrate recognition and translocation at both sides of the plasma membrane.
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Affiliation(s)
- Paola Bartoccioni
- Institute for Research in Biomedicine, Barcelona Institute of Science and Technology, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain
| | - Joana Fort
- Institute for Research in Biomedicine, Barcelona Institute of Science and Technology, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain.,Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - Antonio Zorzano
- Institute for Research in Biomedicine, Barcelona Institute of Science and Technology, Barcelona, Spain.,Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Ekaitz Errasti-Murugarren
- Institute for Research in Biomedicine, Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Manuel Palacín
- Institute for Research in Biomedicine, Barcelona Institute of Science and Technology, Barcelona, Spain .,Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain.,Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain
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31
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Kandasamy P, Gyimesi G, Kanai Y, Hediger MA. Amino acid transporters revisited: New views in health and disease. Trends Biochem Sci 2018; 43:752-789. [PMID: 30177408 DOI: 10.1016/j.tibs.2018.05.003] [Citation(s) in RCA: 252] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 02/09/2023]
Abstract
Amino acid transporters (AATs) are membrane-bound transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs have diverse functional roles ranging from neurotransmission to acid-base balance, intracellular energy metabolism, and anabolic and catabolic reactions. In cancer cells and diabetes, dysregulation of AATs leads to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer, obesity and diabetes. Indeed, the neutral amino acid transporters (NATs) SLC7A5/LAT1 and SLC1A5/ASCT2 are likely involved in several human malignancies. However, a clinical therapy that directly targets AATs has not yet been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, their diverse physiological roles in different tissues and organs, their wide-ranging implications in human diseases and the emerging strategies and tools that will be necessary to target AATs therapeutically.
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Affiliation(s)
- Palanivel Kandasamy
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Gergely Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
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32
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Vilches C, Boiadjieva-Knöpfel E, Bodoy S, Camargo S, López de Heredia M, Prat E, Ormazabal A, Artuch R, Zorzano A, Verrey F, Nunes V, Palacín M. Cooperation of Antiporter LAT2/CD98hc with Uniporter TAT1 for Renal Reabsorption of Neutral Amino Acids. J Am Soc Nephrol 2018; 29:1624-1635. [PMID: 29610403 DOI: 10.1681/asn.2017111205] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 02/24/2018] [Indexed: 01/01/2023] Open
Abstract
Background Reabsorption of amino acids (AAs) across the renal proximal tubule is crucial for intracellular and whole organism AA homeostasis. Although the luminal transport step is well understood, with several diseases caused by dysregulation of this process, the basolateral transport step is not understood. In humans, only cationic aminoaciduria due to malfunction of the basolateral transporter y+LAT1/CD98hc (SLC7A7/SLC3A2), which mediates the export of cationic AAs, has been described. Thus, the physiologic roles of basolateral transporters of neutral AAs, such as the antiporter LAT2/CD98hc (SLC7A8/SLC3A2), a heterodimer that exports most neutral AAs, and the uniporter TAT1 (SLC16A10), which exports only aromatic AAs, remain unclear. Functional cooperation between TAT1 and LAT2/CD98hc has been suggested by in vitro studies but has not been evaluated in vivoMethods To study the functional relationship of TAT1 and LAT2/CD98hc in vivo, we generated a double-knockout mouse model lacking TAT1 and LAT2, the catalytic subunit of LAT2/CD98hc (dKO LAT2-TAT1 mice).Results Compared with mice lacking only TAT1 or LAT2, dKO LAT2-TAT1 mice lost larger amounts of aromatic and other neutral AAs in their urine due to a tubular reabsorption defect. Notably, dKO mice also displayed decreased tubular reabsorption of cationic AAs and increased expression of y+LAT1/CD98hc.Conclusions The LAT2/CD98hc and TAT1 transporters functionally cooperate in vivo, and y+LAT1/CD98hc may compensate for the loss of LAT2/CD98hc and TAT1, functioning as a neutral AA exporter at the expense of some urinary loss of cationic AAs. Cooperative and compensatory mechanisms of AA transporters may explain the lack of basolateral neutral aminoacidurias in humans.
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Affiliation(s)
- Clara Vilches
- Molecular Genetics Laboratory, Genes Disease and Therapy Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat, Spain
| | - Emilia Boiadjieva-Knöpfel
- Department of Physiology.,Zurich Center for Integrative Human Physiology (ZIHP), and.,Swiss National Centre of Competence in Research (NCCR), Kidney Control of Homeostasis (Kidney.CH), University of Zurich, Zurich, Switzerland
| | - Susanna Bodoy
- Department of Biochemistry and Molecular Medicine, Biology Faculty, University of Barcelona, Barcelona, Spain.,Molecular Medicine Unit, Amino acid transporters and disease group, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain
| | - Simone Camargo
- Department of Physiology.,Zurich Center for Integrative Human Physiology (ZIHP), and.,Swiss National Centre of Competence in Research (NCCR), Kidney Control of Homeostasis (Kidney.CH), University of Zurich, Zurich, Switzerland
| | - Miguel López de Heredia
- Molecular Genetics Laboratory, Genes Disease and Therapy Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and
| | - Esther Prat
- Molecular Genetics Laboratory, Genes Disease and Therapy Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and.,Genetics Section, Physiological Sciences Department, Health Sciences and Medicine Faculty, University of Barcelona, Barcelona, Spain; and
| | - Aida Ormazabal
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and.,Clinical Biochemistry Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Rafael Artuch
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and.,Clinical Biochemistry Department, Institut de Recerca Sant Joan de Déu, Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain
| | - Antonio Zorzano
- Department of Biochemistry and Molecular Medicine, Biology Faculty, University of Barcelona, Barcelona, Spain.,Molecular Medicine Unit, Amino acid transporters and disease group, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) - CB07/08/0017, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - François Verrey
- Department of Physiology.,Zurich Center for Integrative Human Physiology (ZIHP), and.,Swiss National Centre of Competence in Research (NCCR), Kidney Control of Homeostasis (Kidney.CH), University of Zurich, Zurich, Switzerland
| | - Virginia Nunes
- Molecular Genetics Laboratory, Genes Disease and Therapy Program, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat, Spain; .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and.,Genetics Section, Physiological Sciences Department, Health Sciences and Medicine Faculty, University of Barcelona, Barcelona, Spain; and
| | - Manuel Palacín
- Department of Biochemistry and Molecular Medicine, Biology Faculty, University of Barcelona, Barcelona, Spain; .,Molecular Medicine Unit, Amino acid transporters and disease group, Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) - U730, U731, U703, and
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