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Prasad H. Genes for endosomal pH regulators NHE6 and NHE9 are dysregulated in the substantia nigra in Parkinson's disease. Gene 2024; 927:148737. [PMID: 38945311 DOI: 10.1016/j.gene.2024.148737] [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: 01/11/2024] [Revised: 06/10/2024] [Accepted: 06/27/2024] [Indexed: 07/02/2024]
Abstract
Endosomal acid base balance functions as a master orchestrator within the cell, engaging with many cellular pathways to maintain homeostasis. Mutations in the endosomal pH regulator Na+/H+ exchanger NHE6 may disrupt this delicate balancing act and cause monogenic Parkinsonism. Here, gene expression studies in post-mortem substantia nigra of Parkinson's disease (PD) patients and normal controls were performed to investigate whether NHE6 represents a pathophysiological link between monogenic and sporadic PD. The substantia nigra in PD displayed down-regulation of NHE6, coincident with a loss of expression of several SNARE signalling pathway members, suggesting impaired membrane fusion and vesicle-recycling. Increased abundance of related NHE9 was also identified in the parkinsonian nigra that could reflect compensatory changes or be a consequence of neuronal dysfunction. The current model suggests the possibility that neurons expressing low levels of NHE6 are more susceptible to injury in PD, potentially directly contributing to the loss of nigral dopaminergic neurons and the genesis of the disease. These results have important implications for disease-modifying therapies as they suggest that endosomal pH correctors, including epigenetic modifiers that regulate NHE6 expression, may be beneficial for PD. Thus, aberrant endosomal acidification in the nigrostriatal pathway is a possible unifying pathomechanism in both monogenic and sporadic PD, with implications for understanding and treating this disorder. Replication of these observations in the post-mortem brains of Alzheimer's disease and frontotemporal dementia patients supports a model of conserved mechanisms underlying injury and death of neurons.
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Affiliation(s)
- Hari Prasad
- Department of Developmental Biology and Genetics, Indian Institute of Science, Bengaluru 560012, India.
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2
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Ma L, Kasula RK, Ouyang Q, Schmidt M, Morrow EM. GGA1 interacts with the endosomal Na+/H+ exchanger NHE6 governing localization to the endosome compartment. J Biol Chem 2024; 300:107552. [PMID: 39002678 PMCID: PMC11375261 DOI: 10.1016/j.jbc.2024.107552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 06/20/2024] [Accepted: 06/27/2024] [Indexed: 07/15/2024] Open
Abstract
Mutations in the endosomal Na+/H+ exchanger 6 (NHE6) cause Christianson syndrome, an X-linked neurological disorder. NHE6 functions in regulation of endosome acidification and maturation in neurons. Using yeast two-hybrid screening with the NHE6 carboxyl terminus as bait, we identify Golgi-associated, gamma adaptin ear-containing, ADP-ribosylation factor (ARF) binding protein 1 (GGA1) as an interacting partner for NHE6. We corroborated the NHE6-GGA1 interaction using: coimmunoprecipitation; overexpressed constructs in mammalian cells; and coimmunoprecipitation of endogenously expressed GGA1 and NHE6 from neuroblastoma cells, as well as from the mouse brain. We demonstrate that GGA1 interacts with organellar NHEs (NHE6, NHE7, and NHE9) and that there is significantly less interaction with cell-surface localized NHEs (NHE1 and NHE5). By constructing hybrid NHE1/NHE6 exchangers, we demonstrate the cytoplasmic tail of NHE6 interacts most strongly with GGA1. We demonstrate the colocalization of NHE6 and GGA1 in cultured, primary hippocampal neurons, using super-resolution microscopy. We test the hypothesis that the interaction of NHE6 and GGA1 functions in the localization of NHE6 to the endosome compartment. Using subcellular fractionation experiments, we show that NHE6 is mislocalized in GGA1 KO cells, wherein we find less NHE6 in endosomes, but more NHE6 transport to lysosomes, and more Golgi retention of NHE6, with increased exocytosis to the surface plasma membrane. Consistent with NHE6 mislocalization, and Golgi retention, we find the intraluminal pH in Golgi to be alkalinized in GGA1-null cells. Our study demonstrates a new interaction between NHE6 and GGA1 which functions in the localization of this intracellular NHE to the endosome compartment.
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Affiliation(s)
- Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Ravi Kiran Kasula
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, USA; Center for Translational Neuroscience, Brown University, Providence, Rhode Island, USA.
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3
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Wu Q, Ma L, Joesch-Cohen L, Schmidt M, Uzun EDG, Morrow EM. Targeting NHE6 gene expression identifies lysosome and neurodevelopmental mechanisms in a haploid in vitro cell model. Biol Open 2023; 12:bio059778. [PMID: 37747131 PMCID: PMC10695175 DOI: 10.1242/bio.059778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 09/06/2023] [Indexed: 09/26/2023] Open
Abstract
Christianson syndrome (CS) is an X-linked disorder resulting from loss-of-function (LoF) mutations in SLC9A6 encoding the endosomal Na+/H+ exchanger 6 (NHE6). CS presents with developmental delay, seizures, intellectual disability, nonverbal status, postnatal microcephaly, and ataxia. To define transcriptome signatures of NHE6 LoF, we conducted in-depth RNA-sequencing (RNA-seq) analysis on a haploid NHE6 null cell model. CRIPSR/Cas9 genome editing introduced multiple LoF mutations into SLC9A6 in the near haploid human cell line Hap1. Isogenic, paired parental controls were also studied. NHE6 mutant cell lines were confirmed to have intra-endosomal over-acidification as was seen in other NHE6 null cells. RNA-seq analysis was performed by two widely used pipelines: HISAT2-StringTie-DEseq2 and STAR-HTseq-DEseq2. We identified 1056 differentially expressed genes in mutant NHE6 lines, including genes associated with neurodevelopment, synapse function, voltage-dependent calcium channels, and neuronal signaling. Weighted gene co-expression network analysis was then applied and identified a critical module enriched for genes governing lysosome function. By identifying significantly changed gene expression that is associated with lysosomal mechanisms in NHE6-null cells, our analyses suggest that loss of NHE6 function may converge on mechanisms implicated in lysosome-related neurologic disease. Further, this haploid cell model will serve as an important tool for translational science in CS.
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Affiliation(s)
- Qing Wu
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
| | - Li Ma
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Lena Joesch-Cohen
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
| | - Michael Schmidt
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Ece D. Gamsiz Uzun
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
- Department of Pathology and Laboratory Medicine, Alpert Medical School of Brown University, Providence, RI 02912, USA
| | - Eric M. Morrow
- Center for Translational Neuroscience, Carney Institute for Brain Science and Brown Institute for Translational Science, Brown University, Providence, RI 02912, USA
- Center for Computational Molecular Biology, Brown University, Center for Computational Molecular Biology, Providence, RI 02912, USA
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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4
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Ma L, Kasula RK, Ouyang Q, Schmidt M, Morrow EM. GGA1 interacts with the endosomal Na+/H+ Exchanger NHE6 governing localization to the endosome compartment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.565997. [PMID: 37986849 PMCID: PMC10659387 DOI: 10.1101/2023.11.08.565997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Mutations in the endosomal Na+/H+ exchanger (NHE6) cause Christianson syndrome (CS), an X-linked neurological disorder. Previous studies have shown that NHE6 functions in regulation of endosome acidification and maturation in neurons. Using yeast two-hybrid screening with the NHE6 carboxyl-terminus as bait, we identify Golgi-associated, Gamma adaptin ear containing, ARF binding protein 1 (GGA1) as an interacting partner for NHE6. We corroborated the NHE6-GGA1 interaction using co-immunoprecipitation (co-IP): using over-expressed constructs in mammalian cells; and co-IP of endogenously-expressed GGA1 and NHE6 from neuroblastoma cells, as well as from mouse brain. We demonstrate that GGA1 interacts with organellar NHEs (NHE6, NHE7 and NHE9) but not with cell-surface localized NHEs (NHE1 and NHE5). By constructing hybrid NHE1/NHE6 exchangers, we demonstrate that the cytoplasmic tail of NHE6 is necessary and sufficient for interactions with GGA1. We demonstrate the co-localization of NHE6 and GGA1 in cultured, primary hippocampal neurons, using super-resolution microscopy. We test the hypothesis that the interaction of NHE6 and GGA1 functions in the localization of NHE6 to the endosome compartment. Using subcellular fractionation experiments, we show that NHE6 is mis-localized in GGA1 knockout cells wherein we find less NHE6 in endosomes but more NHE6 transport to lysosomes, and more Golgi retention of NHE6 with increased exocytosis to the surface plasma membrane. Consistent with NHE6 mis-localization, and Golgi retention, we find the intra-luminal pH in Golgi to be alkalinized. Our study demonstrates a new interaction between NHE6 and GGA1 which functions in the localization of this intra-cellular NHE to the endosome compartment.
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Holling T, Brylka L, Scholz T, Bierhals T, Herget T, Meinecke P, Schinke T, Oheim R, Kutsche K. TMCO3, a Putative K + :Proton Antiporter at the Golgi Apparatus, Is Important for Longitudinal Growth in Mice and Humans. J Bone Miner Res 2023; 38:1334-1349. [PMID: 37554015 DOI: 10.1002/jbmr.4827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 04/27/2023] [Accepted: 05/07/2023] [Indexed: 08/10/2023]
Abstract
Isolated short stature, defined as short stature without any other abnormalities, is a common heterogeneous condition in children. Exome sequencing identified the homozygous nonsense variant c.1832G>A/p.(Trp611*) in TMCO3 in two sisters with isolated short stature. Radiological studies, biochemical measurements, assessment of the skeletal status, and three-dimensional bone microarchitecture revealed no relevant skeletal and bone abnormalities in both sisters. The homozygous TMCO3 variant segregated with short stature in the family. TMCO3 transcript levels were reduced by ~50% in leukocyte-derived RNA of both sisters compared with controls, likely due to nonsense-mediated mRNA decay. In primary urinary cells of heterozygous family members, we detected significantly reduced TMCO3 protein levels. TMCO3 is functionally uncharacterized. We ectopically expressed wild-type TMCO3 in HeLa and ATDC5 chondrogenic cells and detected TMCO3 predominantly at the Golgi apparatus, whereas the TMCO3W611* mutant did not reach the Golgi. Coordinated co-expression of TMCO3W611* -HA and EGFP in HeLa cells confirmed intrinsic instability and/or degradation of the mutant. Tmco3 is expressed in all relevant mouse skeletal cell types. Highest abundance of Tmco3 was found in chondrocytes of the prehypertrophic zone in mouse and minipig growth plates where it co-localizes with a Golgi marker. Knockdown of Tmco3 in differentiated ATDC5 cells caused reduced and increased expression of Pthlh and Ihh, respectively. Measurement of long bones in Tmco3tm1b(KOMP)Wtsi knockout mice revealed significant shortening of forelimbs and hindlimbs. TMCO3 is a potential member of the monovalent cation:proton antiporter 2 (CPA2) family. By in silico tools and homology modeling, TMCO3 is predicted to have an N-terminal secretory signal peptide, forms a dimer localized to the membrane, and is organized in a dimerization and a core domain. The core domain contains the CPA2 motif essential for K+ binding and selectivity. Collectively, our data demonstrate that loss of TMCO3 causes growth defects in both humans and mice. © 2023 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Tess Holling
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Laura Brylka
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tasja Scholz
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tatjana Bierhals
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Theresia Herget
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Peter Meinecke
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Thorsten Schinke
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ralf Oheim
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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6
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Shum D, Bhinder B, Mahida J, Radu C, Calder PA, Djaballah H. A Genome-Wide RNAi Screen Reveals Common Host-Virus Gene Signatures: Implication for Dengue Antiviral Drug Discovery. GEN BIOTECHNOLOGY 2023; 2:133-148. [PMID: 37928776 PMCID: PMC10623629 DOI: 10.1089/genbio.2023.0001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/02/2023] [Indexed: 11/07/2023]
Abstract
Dengue is the most common mosquito-borne viral disease that in recent years has become a major international public health concern. Dengue is a tropical neglected disease with increasing global incidences, affecting millions of people worldwide, and without the availability of specific treatments to combat it. The identification of host-target genes essential for the virus life cycle, for which effective modulators may already exist, would provide an alternative path to a rapid drug development of the much needed antidengue agents. For this purpose, we performed the first genome-wide RNAi screen, combining two high-content readouts for dengue virus infection (DENV E infection intensity) and host cell toxicity (host cell stained nuclei), against an arrayed lentiviral-based short hairpin RNA library covering 16,000 genes with a redundancy of at least 5 hairpins per gene. The screen identified 1924 gene candidates in total; of which, 1730 gene candidates abrogated dengue infection, whereas 194 gene candidates were found to enhance its infectivity in HEK293 cells. A first pass clustering analysis of hits revealed a well-orchestrated gene-network dependency on host cell homeostasis and physiology triggering distinct cellular pathways for infectivity, replication, trafficking, and egress; a second analysis revealed a comprehensive gene signature of 331 genes common to hits identified in 28 published RNAi host-viral interaction screens. Taken together, our findings provide novel antiviral molecular targets with the potential for drug discovery and development.
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Affiliation(s)
- David Shum
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Bhavneet Bhinder
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Jeni Mahida
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Constantin Radu
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Paul A. Calder
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Hakim Djaballah
- HTS Core Facility, Memorial Sloan Kettering Cancer Center, New York, New York, USA; Memorial Sloan Kettering Cancer Center, New York, New York, USA
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
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7
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Altered distribution and localization of organellar Na +/H + exchangers in postmortem schizophrenia dorsolateral prefrontal cortex. Transl Psychiatry 2023; 13:34. [PMID: 36732328 PMCID: PMC9895429 DOI: 10.1038/s41398-023-02336-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/20/2023] [Accepted: 01/24/2023] [Indexed: 02/04/2023] Open
Abstract
Schizophrenia is a complex and multifactorial disorder associated with altered neurotransmission as well as numerous signaling pathway and protein trafficking disruptions. The pH of intracellular organelles involved in protein trafficking is tightly regulated and impacts their functioning. The SLC9A family of Na+/H+ exchangers (NHEs) plays a fundamental role in cellular and intracellular pH homeostasis. Four organellar NHE isoforms (NHE6-NHE9) are targeted to intracellular organelles involved in protein trafficking. Increased interactions between organellar NHEs and receptor of activated protein C kinase 1 (RACK1) can lead to redistribution of NHEs to the plasma membrane and hyperacidification of target organelles. Given their role in organelle pH regulation, altered expression and/or localization of organellar NHEs could be an underlying cellular mechanism contributing to abnormal intracellular trafficking and disrupted neurotransmitter systems in schizophrenia. We thus characterized organellar NHE expression, co-immunoprecipitation with RACK1, and Triton X-114 (TX-114) phase partitioning in dorsolateral prefrontal cortex of 25 schizophrenia and 25 comparison subjects by Western blot analysis. In schizophrenia after controlling for subject age at time of death, postmortem interval, tissue pH, and sex, there was significantly decreased total expression of NHE8, decreased co-immunoprecipitation of NHE8 (64%) and NHE9 (56%) with RACK1, and increased TX-114 detergent phase partitioning of NHE6 (283%), NHE9 (75%), and RACK1 (367%). Importantly, none of these dependent measures was significantly impacted when comparing those in the schizophrenia group on antipsychotics to those off of antipsychotics for at least 6 weeks at their time of death and none of these same proteins were affected in rats chronically treated with haloperidol. In summary, we characterized organellar NHE expression and distribution in schizophrenia DLPFC and identified abnormalities that could represent a novel mechanism contributing to disruptions in protein trafficking and neurotransmission in schizophrenia.
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Wu J, Li X, Wang Q, Wang S, He W, Wu Q, Dong C. LncRNA/miRNA/mRNA ceRNA network analysis in spinal cord injury rat with physical exercise therapy. PeerJ 2022; 10:e13783. [PMID: 35923891 PMCID: PMC9341448 DOI: 10.7717/peerj.13783] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 07/05/2022] [Indexed: 01/22/2023] Open
Abstract
Noncoding RNAs have been implicated in the pathophysiology of spinal cord injury (SCI), including cell death, glial scar formation, axonal collapse and demyelination, and inflammation. The evidence suggests that exercise therapy is just as effective as medical treatment in SCI. However, studies of competing endogenous RNA (ceRNA)-mediated regulation mechanisms in the therapy of SCI with exercise are rare. The focus of this research was to investigate the effect of exercise therapy on the expression levels of long noncoding RNA (lncRNA), microRNA (miRNA), and mRNA in rats with SCI. The RNA-seq technology has been used to examine the differentially expressed circRNAs (DECs), lncRNAs (DELs), miRNAs (DEMs), and genes (DEGs) between SCI and exercise therapy rats. The ceRNA network was established using interactions between miRNAs and mRNAs, as well as between miRNAs and lncRNAs/circRNAs. The Database for Annotation, Visualization, and Integrated Discovery was used to anticipate the underlying functions of mRNAs. Our current study identified 76 DELs, 33 DEMs, and 30 DEGs between groups of SCI rats and exercise therapy rats. Subsequently, these newly discovered ceRNA interaction axes could be important targets for the exercise treatment of SCI.
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Affiliation(s)
- Jiahuan Wu
- Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Rehabilitation Medical Center, Suzhou, China
| | - Xiangzhe Li
- Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Rehabilitation Medical Center, Suzhou, China
| | - Qinghua Wang
- Nantong University, Experimental Animal Center, Nantong, China
| | - Sheng Wang
- Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Rehabilitation Medical Center, Suzhou, China
| | - Wenhua He
- Medical College of Nantong University, Department of Anatomy, Nantong, China
| | - Qinfeng Wu
- Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Rehabilitation Medical Center, Suzhou, China
| | - Chuanming Dong
- Medical College of Nantong University, Department of Anatomy, Nantong, China
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Gao AYL, Lourdin-De Filippis E, Orlowski J, McKinney RA. Roles of Endomembrane Alkali Cation/Proton Exchangers in Synaptic Function and Neurodevelopmental Disorders. Front Physiol 2022; 13:892196. [PMID: 35547574 PMCID: PMC9081726 DOI: 10.3389/fphys.2022.892196] [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: 03/08/2022] [Accepted: 03/30/2022] [Indexed: 12/25/2022] Open
Abstract
Endomembrane alkali cation (Na+, K+)/proton (H+) exchangers (eNHEs) are increasingly associated with neurological disorders. These eNHEs play integral roles in regulating the luminal pH, processing, and trafficking of cargo along the secretory (Golgi and post-Golgi vesicles) and endocytic (early, recycling, and late endosomes) pathways, essential regulatory processes vital for neuronal development and plasticity. Given the complex morphology and compartmentalization of multipolar neurons, the contribution of eNHEs in maintaining optimal pH homeostasis and cargo trafficking is especially significant during periods of structural and functional development and remodeling. While the importance of eNHEs has been demonstrated in a variety of non-neuronal cell types, their involvement in neuronal function is less well understood. In this review, we will discuss their emerging roles in excitatory synaptic function, particularly as it pertains to cellular learning and remodeling. We will also explore their connections to neurodevelopmental conditions, including intellectual disability, autism, and attention deficit hyperactivity disorders.
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Affiliation(s)
- Andy Y L Gao
- Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.,Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
| | | | - John Orlowski
- Department of Physiology, McGill University, Montreal, QC, Canada
| | - R Anne McKinney
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
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Nwia SM, Li XC, Leite APDO, Hassan R, Zhuo JL. The Na +/H + Exchanger 3 in the Intestines and the Proximal Tubule of the Kidney: Localization, Physiological Function, and Key Roles in Angiotensin II-Induced Hypertension. Front Physiol 2022; 13:861659. [PMID: 35514347 PMCID: PMC9062697 DOI: 10.3389/fphys.2022.861659] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/25/2022] [Indexed: 01/29/2023] Open
Abstract
The sodium (Na+)/hydrogen (H+) exchanger 3 (NHE3) is one of the most important Na+/H+ antiporters in the small intestines of the gastrointestinal tract and the proximal tubules of the kidney. The roles of NHE3 in the regulation of intracellular pH and acid-base balance have been well established in cellular physiology using in vitro techniques. Localized primarily on the apical membranes in small intestines and proximal tubules, the key action of NHE3 is to facilitate the entry of luminal Na+ and the extrusion of intracellular H+ from intestinal and proximal tubule tubular epithelial cells. NHE3 is, directly and indirectly, responsible for absorbing the majority of ingested Na+ from small and large intestines and reabsorbing >50% of filtered Na+ in the proximal tubules of the kidney. However, the roles of NHE3 in the regulation of proximal tubular Na+ transport in the integrative physiological settings and its contributions to the basal blood pressure regulation and angiotensin II (Ang II)-induced hypertension have not been well studied previously due to the lack of suitable animal models. Recently, novel genetically modified mouse models with whole-body, kidney-specific, or proximal tubule-specific deletion of NHE3 have been generated by us and others to determine the critical roles and underlying mechanisms of NHE3 in maintaining basal body salt and fluid balance, blood pressure homeostasis, and the development of Ang II-induced hypertension at the whole-body, kidney, or proximal tubule levels. The objective of this invited article is to review, update, and discuss recent findings on the critical roles of intestinal and proximal tubule NHE3 in maintaining basal blood pressure homeostasis and their potential therapeutic implications in the development of angiotensin II (Ang II)-dependent hypertension.
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Affiliation(s)
- Sarah M. Nwia
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Xiao Chun Li
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Ana Paula de Oliveira Leite
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Rumana Hassan
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Jia Long Zhuo
- Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, LA, United States,Department of Physiology, Tulane University School of Medicine, New Orleans, LA, United States,*Correspondence: Jia Long Zhuo,
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11
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Ko M, Makena MR, Schiapparelli P, Suarez-Meade P, Mekile AX, Lal B, Lopez-Bertoni H, Kozielski KL, Green JJ, Laterra J, Quiñones-Hinojosa A, Rao R. The endosomal pH regulator NHE9 is a driver of stemness in glioblastoma. PNAS NEXUS 2022; 1:pgac013. [PMID: 35387234 PMCID: PMC8974362 DOI: 10.1093/pnasnexus/pgac013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 09/26/2021] [Accepted: 02/14/2022] [Indexed: 11/25/2022]
Abstract
A small population of self-renewing stem cells initiate tumors and maintain therapeutic resistance in glioblastoma (GBM). Given the limited treatment options and dismal prognosis for this disease, there is urgent need to identify drivers of stem cells that could be druggable targets. Previous work showed that the endosomal pH regulator NHE9 is upregulated in GBM and correlates with worse survival prognosis. Here, we probed for aberrant signaling pathways in patient-derived GBM cells and found that NHE9 increases cell surface expression and phosphorylation of multiple receptor tyrosine kinases (RTKs) by promoting their escape from lysosomal degradation. Downstream of NHE9-mediated receptor activation, oncogenic signaling pathways converged on the JAK2-STAT3 transduction axis to induce pluripotency genes Oct4 and Nanog and suppress markers of glial differentiation. We used both genetic and chemical approaches to query the role of endosomal pH in GBM phenotypes. Loss-of-function mutations in NHE9 that failed to alkalinize endosomal lumen did not increase self-renewal capacity of gliomaspheres in vitro. However, monensin, a chemical mimetic of Na+/H+ exchanger activity, and the H+ pump inhibitor bafilomycin bypassed NHE9 to directly alkalinize the endosomal lumen resulting in stabilization of RTKs and induction of Oct4 and Nanog. Using orthotopic models of primary GBM cells we found that NHE9 increased tumor initiation in vivo. We propose that NHE9 initiates inside-out signaling from the endosomal lumen, distinct from the established effects of cytosolic and extracellular pH on tumorigenesis. Endosomal pH may be an attractive therapeutic target that diminishes stemness in GBM, agnostic of specific receptor subtype.
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Affiliation(s)
- Myungjun Ko
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Department of Neurosurgery, Mayo Clinic College of Medicine, Jacksonville, FL, 32224, USA
| | - Monish R Makena
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Paula Schiapparelli
- Department of Neurosurgery, Mayo Clinic College of Medicine, Jacksonville, FL, 32224, USA
| | - Paola Suarez-Meade
- Department of Neurosurgery, Mayo Clinic College of Medicine, Jacksonville, FL, 32224, USA
| | - Allatah X Mekile
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Bachchu Lal
- Hugo W. Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Hernando Lopez-Bertoni
- Hugo W. Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Kristen L Kozielski
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany
| | - Jordan J Green
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - John Laterra
- Hugo W. Moser Research Institute at Kennedy Krieger, Baltimore, MD, USA
- Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | | | - Rajini Rao
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
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12
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Schnyder D, Albano G, Kucharczyk P, Dolder S, Siegrist M, Anderegg M, Pathare G, Hofstetter W, Baron R, Fuster DG. Deletion of the sodium/hydrogen exchanger 6 causes low bone volume in adult mice. Bone 2021; 153:116178. [PMID: 34508879 DOI: 10.1016/j.bone.2021.116178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 09/04/2021] [Accepted: 09/05/2021] [Indexed: 11/18/2022]
Abstract
The sodium/hydrogen exchanger 6 (NHE6) localizes to recycling endosomes, where it mediates endosomal alkalinization through K+/H+ exchange. Mutations in the SLC9A6 gene encoding NHE6 cause severe X-linked mental retardation, epilepsy, autism and corticobasal degeneration in humans. Patients with SLC9A6 mutations exhibit skeletal malformations, and a previous study suggested a key role of NHE6 in osteoblast-mediated mineralization. The goal of this study was to explore the role of NHE6 in bone homeostasis. To this end, we studied the bone phenotype of NHE6 knock-out mice by microcomputed tomography, quantitative histomorphometry and complementary ex vivo and in vitro studies. We detected NHE6 transcript and protein in both differentiated osteoclasts and mineralizing osteoblasts. In vitro studies with osteoclasts and osteoblasts derived from NHE6 knock-out mice demonstrated normal osteoclast differentiation and osteoblast proliferation without an impairment in mineralization capacity. Microcomputed tomography and bone histomorphometry studies showed a significantly reduced bone volume and trabecular number as well as an increased trabecular space at lumbar vertebrae of 6 months old NHE6 knock-out mice. The bone degradation marker c-terminal telopeptides of type I collagen was unaltered in NHE6 knock-out mice. However, we observed a reduction of the bone formation marker procollagen type 1 N-terminal propeptide, and increased circulating sclerostin levels in NHE6 knock-out mice. Subsequent studies revealed a significant upregulation of sclerostin transcript expression in both primary calvarial cultures and femora derived from NHE6 knock-out mice. Thus, loss of NHE6 in mice causes an increase of sclerostin expression associated with reduced bone formation and low bone volume.
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Affiliation(s)
- Daniela Schnyder
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Giuseppe Albano
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Patrycja Kucharczyk
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Silvia Dolder
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Mark Siegrist
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Manuel Anderegg
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Ganesh Pathare
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Willy Hofstetter
- National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Roland Baron
- Division of Bone and Mineral Research, Harvard Medical School and Harvard School of Dental Medicine, Boston, MA, USA; Department of Oral Medicine, Infection and Immunity, Harvard Medical School and Harvard School of Dental Medicine, Boston, MA, USA
| | - Daniel G Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; National Centre of Competence in Research (NCCR) TransCure, University of Bern, Bern, Switzerland; Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland.
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13
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Pohlkamp T, Xian X, Wong CH, Durakoglugil MS, Werthmann GC, Saido TC, Evers BM, White CL, Connor J, Hammer RE, Herz J. NHE6 depletion corrects ApoE4-mediated synaptic impairments and reduces amyloid plaque load. eLife 2021; 10:72034. [PMID: 34617884 PMCID: PMC8547963 DOI: 10.7554/elife.72034] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 09/19/2021] [Indexed: 11/13/2022] Open
Abstract
Apolipoprotein E4 (ApoE4) is the most important and prevalent risk factor for late-onset Alzheimer’s disease (AD). The isoelectric point of ApoE4 matches the pH of the early endosome (EE), causing its delayed dissociation from ApoE receptors and hence impaired endolysosomal trafficking, disruption of synaptic homeostasis, and reduced amyloid clearance. We have shown that enhancing endosomal acidification by inhibiting the EE-specific sodium-hydrogen exchanger 6 (NHE6) restores vesicular trafficking and normalizes synaptic homeostasis. Remarkably and unexpectedly, loss of NHE6 (encoded by the gene Slc9a6) in mice effectively suppressed amyloid deposition even in the absence of ApoE4, suggesting that accelerated acidification of EEs caused by the absence of NHE6 occludes the effect of ApoE on amyloid plaque formation. NHE6 suppression or inhibition may thus be a universal, ApoE-independent approach to prevent amyloid buildup in the brain. These findings suggest a novel therapeutic approach for the prevention of AD by which partial NHE6 inhibition reverses the ApoE4-induced endolysosomal trafficking defect and reduces plaque load.
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Affiliation(s)
- Theresa Pohlkamp
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States
| | - Xunde Xian
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States.,Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China
| | - Connie H Wong
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States
| | - Murat S Durakoglugil
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States
| | - Gordon Chandler Werthmann
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States
| | - Takaomi C Saido
- Laboratory for Proteolytic Neuroscience, Riken Center for Brain Science, Wako, Japan
| | - Bret M Evers
- Center for Translational Neurodegeneration Research, Dallas, United States
| | - Charles L White
- Pathology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Jade Connor
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States
| | - Robert E Hammer
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
| | - Joachim Herz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, United States.,Center for Translational Neurodegeneration Research, Dallas, United States.,Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, United States
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14
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Abstract
Supplemental Digital Content is Available in the Text. Patients diagnosed with Christianson syndrome have intellectual disability, epilepsy, ataxia, and mutism, as well as hyposensitivity to pain. In this study, we use a mouse model of Christianson syndrome to demonstrate that this pain hyposensitivity is due in part to a decrease in excitability of nociceptors. Children diagnosed with Christianson syndrome (CS), a rare X-linked neurodevelopmental disorder characterized by intellectual disability, epilepsy, ataxia, and mutism, also suffer from hyposensitivity to pain. This places them at risk of sustaining serious injuries that often go unattended. Christianson syndrome is caused by mutations in the alkali cation/proton exchanger SLC9A6/NHE6 that regulates recycling endosomal pH homeostasis and trafficking. Yet, it remains unclear how defects in this transporter lead to altered somatosensory functions. In this study, we validated a Nhe6 knockout (KO) mouse as a model of CS and used it to identify the cellular mechanisms underlying the elevated pain tolerance observed in CS patients. Within the central nervous system, NHE6 immunolabelling is detected in a small percentage of cortical neurons involved in pain processing, including those within the primary somatosensory and the anterior cingulate cortices as well as the periaqueductal gray. Interestingly, it is expressed in a larger percentage of nociceptors. Behaviourally, Nhe6 KO mice have decreased nocifensive responses to acute noxious thermal, mechanical, and chemical (ie, capsaicin) stimuli. The reduced capsaicin sensitivity in the KO mice correlates with a decreased expression of the transient receptor potential channel TRPV1 at the plasma membrane and capsaicin-induced Ca2+ influx in primary cultures of nociceptors. These data indicate that NHE6 is a significant determinant of nociceptor function and pain behaviours, vital sensory processes that are impaired in CS.
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15
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Chebotarev AS, Pochechuev MS, Lanin AA, Kelmanson IV, Kotova DA, Fetisova ES, Panova AS, Bilan DS, Fedotov AB, Belousov VV, Zheltikov AM. Enhanced-contrast two-photon optogenetic pH sensing and pH-resolved brain imaging. JOURNAL OF BIOPHOTONICS 2021; 14:e202000301. [PMID: 33205577 DOI: 10.1002/jbio.202000301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/29/2020] [Accepted: 11/16/2020] [Indexed: 06/11/2023]
Abstract
We present experiments on cell cultures and brain slices that demonstrate two-photon optogenetic pH sensing and pH-resolved brain imaging using a laser driver whose spectrum is carefully tailored to provide the maximum contrast of a ratiometric two-photon fluorescence readout from a high-brightness genetically encoded yellow-fluorescent-protein-based sensor, SypHer3s. Two spectrally isolated components of this laser field are set to induce two-photon-excited fluorescence (2PEF) by driving SypHer3s through one of two excitation pathways-via either the protonated or deprotonated states of its chromophore. With the spectrum of the laser field accurately adjusted for a maximum contrast of these two 2PEF signals, the ratio of their intensities is shown to provide a remarkably broad dynamic range for pH measurements, enabling high-contrast optogenetic deep-brain pH sensing and pH-resolved 2PEF imaging within a vast class of biological systems, ranging from cell cultures to the living brain.
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Affiliation(s)
- Artem S Chebotarev
- Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Matvei S Pochechuev
- Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Aleksandr A Lanin
- Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Moscow, Russia
- Russian Quantum Center, Moscow, Russia
- Kazan Quantum Center, A.N. Tupolev Kazan National Research Technical University, Kazan, Russia
| | - Ilya V Kelmanson
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - Daria A Kotova
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Elena S Fetisova
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Anastasiya S Panova
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Dmitry S Bilan
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - Andrei B Fedotov
- Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Moscow, Russia
- Russian Quantum Center, Moscow, Russia
- Kazan Quantum Center, A.N. Tupolev Kazan National Research Technical University, Kazan, Russia
- National University of Science and Technology "MISiS,", Moscow, Russia
| | - Vsevolod V Belousov
- M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Pirogov Russian National Research Medical University, Moscow, Russia
- Federal Center of Brain Research and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russia
| | - Aleksei M Zheltikov
- Physics Department, International Laser Center, M.V. Lomonosov Moscow State University, Moscow, Russia
- Russian Quantum Center, Moscow, Russia
- Kazan Quantum Center, A.N. Tupolev Kazan National Research Technical University, Kazan, Russia
- Department of Physics and Astronomy, Texas A&M University, College Station, Texas, USA
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16
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Du X, Zuo X, Meng F, Han C, Ouyang W, Han Y, Gu Y, Zhao X, Xu F, Qin FX. Direct inhibitory effect on viral entry of influenza A and SARS-CoV-2 viruses by azithromycin. Cell Prolif 2020; 54:e12953. [PMID: 33211371 PMCID: PMC7744835 DOI: 10.1111/cpr.12953] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 10/13/2020] [Accepted: 10/21/2020] [Indexed: 12/22/2022] Open
Abstract
Objectives Using strategy of drug repurposing, antiviral agents against influenza A virus (IAV) and newly emerging SARS‐coronavirus 2 (SARS‐CoV‐2, also as 2019‐nCoV) could be quickly screened out. Materials and Methods A previously reported engineered replication‐competent PR8 strain carrying luciferase reporter gene (IAV‐luc) and multiple pseudotyped IAV and SARS‐CoV‐2 virus was used. To specifically evaluate the pH change of vesicles containing IAV, we constructed an A549 cell line with endosomal and lysosomal expression of pHluorin2. Results Here, we identified azithromycin (AZ) as an effective inhibitor against multiple IAV and SARS‐CoV‐2 strains. We found that AZ treatment could potently inhibit IAV infection in vitro. Moreover, using pseudotyped virus model, AZ could also markedly block the entry of SARS‐CoV‐2 in HEK293T‐ACE2 and Caco2 cells. Mechanistic studies further revealed that such effect was independent of interferon signalling. AZ treatment neither impaired the binding and internalization of IAV virions, nor the viral replication, but rather inhibited the fusion between viral and vacuolar membranes. Using a NPC1‐pHluorin2 reporter cell line, we confirmed that AZ treatment could alkalize the vesicles containing IAV virions, thereby preventing pH‐dependent membrane fusion. Conclusions Overall, our findings demonstrate that AZ can exert broad‐spectrum antiviral effects against IAV and SARS‐CoV‐2, and could be served as a potential clinical anti‐SARS‐CoV‐2 drug in emergency as well as a promising lead compound for the development of next‐generation anti‐IAV drugs.
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Affiliation(s)
- Xiaohong Du
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China.,Institute of Clinical Medicine Research, the Affiliated Suzhou Hospital of Nanjing Medical University, Suzhou Science and Technology Town Hospital, Suzhou, China
| | - Xiangyang Zuo
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
| | - Fang Meng
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
| | - Chenfeng Han
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
| | - Wei Ouyang
- Department of Infectious Diseases, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
| | - Yu Han
- Department of Infectious Diseases, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
| | - Yayun Gu
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
| | - Xin Zhao
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
| | - Feng Xu
- Department of Infectious Diseases, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
| | - Frank Xiaofeng Qin
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.,Suzhou Institute of Systems Medicine, Suzhou, China
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17
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Zheng T, Jäättelä M, Liu B. pH gradient reversal fuels cancer progression. Int J Biochem Cell Biol 2020; 125:105796. [DOI: 10.1016/j.biocel.2020.105796] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 06/19/2020] [Accepted: 06/24/2020] [Indexed: 12/18/2022]
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18
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Ilie A, Boucher A, Park J, Berghuis AM, McKinney RA, Orlowski J. Assorted dysfunctions of endosomal alkali cation/proton exchanger SLC9A6 variants linked to Christianson syndrome. J Biol Chem 2020; 295:7075-7095. [PMID: 32277048 PMCID: PMC7242699 DOI: 10.1074/jbc.ra120.012614] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/07/2020] [Indexed: 12/15/2022] Open
Abstract
Genetic screening has identified numerous variants of the endosomal solute carrier family 9 member A6 (SLC9A6)/(Na+,K+)/H+ exchanger 6 (NHE6) gene that cause Christianson syndrome, a debilitating X-linked developmental disorder associated with a range of neurological, somatic, and behavioral symptoms. Many of these variants cause complete loss of NHE6 expression, but how subtler missense substitutions or nonsense mutations that partially truncate its C-terminal cytoplasmic regulatory domain impair NHE6 activity and endosomal function are poorly understood. Here, we describe the molecular and cellular consequences of six unique mutations located in the N-terminal cytoplasmic segment (A9S), the membrane ion translocation domain (L188P and G383D), and the C-terminal regulatory domain (E547*, R568Q, and W570*) of human NHE6 that purportedly cause disease. Using a heterologous NHE6-deficient cell expression system, we show that the biochemical, catalytic, and cellular properties of the A9S and R568Q variants were largely indistinguishable from those of the WT transporter, which obscured their disease significance. By contrast, the L188P, G383D, E547*, and W570* mutants exhibited variable deficiencies in biosynthetic post-translational maturation, membrane sorting, pH homeostasis in recycling endosomes, and cargo trafficking, and they also triggered apoptosis. These findings broaden our understanding of the molecular dysfunctions of distinct NHE6 variants associated with Christianson syndrome.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - Jaeok Park
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada
| | | | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec H3G 0B1, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Montreal, Quebec H3G 0B1, Canada
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19
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Kerner-Rossi M, Gulinello M, Walkley S, Dobrenis K. Pathobiology of Christianson syndrome: Linking disrupted endosomal-lysosomal function with intellectual disability and sensory impairments. Neurobiol Learn Mem 2019; 165:106867. [PMID: 29772390 PMCID: PMC6235725 DOI: 10.1016/j.nlm.2018.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 05/04/2018] [Accepted: 05/12/2018] [Indexed: 11/18/2022]
Abstract
Christianson syndrome (CS) is a recently described rare neurogenetic disorder presenting early in life with a broad range of neurological symptoms, including severe intellectual disability with nonverbal status, hyperactivity, epilepsy, and progressive ataxia due to cerebellar atrophy. CS is due to loss-of-function mutations in SLC9A6, encoding NHE6, a sodium-hydrogen exchanger involved in the regulation of early endosomal pH. Here we review what is currently known about the neuropathogenesis of CS, based on insights from experimental models, which to date have focused on mechanisms that affect the CNS, specifically the brain. In addition, parental reports of sensory disturbances in their children with CS, including an apparent insensitivity to pain, led us to explore sensory function and related neuropathology in Slc9a6 KO mice. We present new data showing sensory deficits in Slc9a6 KO mice, which had reduced behavioral responses to noxious thermal and mechanical stimuli (Hargreaves and Von Frey assays, respectively) compared to wild type (WT) littermates. Immunohistochemical and ultrastructural analysis of the spinal cord and peripheral nervous system revealed intracellular accumulation of the glycosphingolipid GM2 ganglioside in KO but not WT mice. This cellular storage phenotype was most abundant in neurons of lamina I-II of the dorsal horn, a major relay site in the processing of painful stimuli. Spinal cords of KO mice also exhibited changes in astroglial and microglial populations throughout the gray matter suggestive of a neuroinflammatory process. Our findings establish the Slc9a6 KO mouse as a relevant tool for studying the sensory deficits in CS, and highlight selective vulnerabilities in relevant cell populations that may contribute to this phenotype. How NHE6 loss of function leads to such a multifaceted neurological syndrome is still undefined, and it is likely that NHE6 is involved with many cellular processes critical to normal nervous system development and function. In addition, the sensory issues exhibited by Slc9a6 KO mice, in combination with our neuropathological findings, are consistent with NHE6 loss of function impacting the entire nervous system. Sensory dysfunction in intellectually disabled individuals is challenging to assess and may impair patient safety and quality of life. Further mechanistic studies of the neurological impairments underlying CS and other genetic intellectual disability disorders must also take into account mechanisms affecting broader nervous system function in order to understand the full range of associated disabilities.
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Affiliation(s)
- Mallory Kerner-Rossi
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Maria Gulinello
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA; IDDRC Behavioral Core Facility, Neuroscience Department, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Steven Walkley
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Kostantin Dobrenis
- Dominick P. Purpura Dept. of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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20
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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Zhang X, Min Q, Li M, Liu X, Li M, Wang D. Mutation of
cyp19a1b
results in sterile males due to efferent duct obstruction in Nile tilapia. Mol Reprod Dev 2019; 86:1224-1235. [DOI: 10.1002/mrd.23237] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 06/28/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Xianbo Zhang
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
- Guizhou Fisheries Research InstituteGuizhou Academy of Agriculture Sciences Guiyang Guizhou China
| | - Qianwen Min
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
| | - Mengru Li
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
| | - Xingyong Liu
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
| | - Minghui Li
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
| | - Deshou Wang
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life SciencesSouthwest University Chongqing China
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22
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A Christianson syndrome-linked deletion mutation (Δ287ES288) in SLC9A6 impairs hippocampal neuronal plasticity. Neurobiol Dis 2019; 130:104490. [PMID: 31175985 DOI: 10.1016/j.nbd.2019.104490] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/25/2019] [Accepted: 06/04/2019] [Indexed: 02/07/2023] Open
Abstract
Christianson Syndrome is a rare but increasingly diagnosed X-linked intellectual disability disorder that arises from mutations in SLC9A6/NHE6, a pH-regulating transporter that localizes to early and recycling endosomes. We have recently reported that one of the originally identified disease-causing mutations in NHE6 (p.E287-S288del, or ΔES) resulted in a loss of its pH regulatory function. However, the impact of this mutation upon neuronal synapse formation and plasticity is unknown. Here, we investigate the consequences of the ΔES mutant upon mouse hippocampal pyramidal neurons by expressing a fluorescently-labeled ΔES NHE6 construct into primary hippocampal neurons. Neurons expressing the ΔES mutant showed significant reductions in mature dendritic spine density with a concurrent increase in immature filopodia. Furthermore, compared to wild-type (WT), ΔES-containing endosomes are redirected away from early and recycling endosomes toward lysosomes. In parallel, the ΔES mutant reduced the trafficking of glutamatergic AMPA receptors to excitatory synapses and increased their accumulation within lysosomes for potential degradation. Upon long-term potentiation (LTP), neurons expressing ΔES failed to undergo significant structural and functional changes as observed in controls and WT transfectants. Interestingly, synapse density and LTP-induced synaptic remodeling in ΔES-expressing neurons were partially restored by bafilomycin, a vesicular alkalinisation agent, or by leupeptin, an inhibitor of lysosomal proteolytic degradation. Overall, our results demonstrate that the ∆ES mutation attenuates synapse density and structural and functional plasticity in hippocampal neurons. These deficits may be partially due to the mistargeting of AMPA receptors and other cargos to lysosomes, thereby preventing their trafficking during synaptic remodeling. This mechanism may contribute to the cognitive learning deficits observed in patients with Christianson Syndrome and suggests a potential therapeutic strategy for treatment.
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23
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Sun H, Chen L, Cao S, Liang Y, Xu Y. Warburg Effects in Cancer and Normal Proliferating Cells: Two Tales of the Same Name. GENOMICS PROTEOMICS & BIOINFORMATICS 2019; 17:273-286. [PMID: 31071451 PMCID: PMC6818181 DOI: 10.1016/j.gpb.2018.12.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 11/19/2018] [Accepted: 12/21/2018] [Indexed: 01/07/2023]
Abstract
It has been observed that both cancer tissue cells and normal proliferating cells (NPCs) have the Warburg effect. Our goal here is to demonstrate that they do this for different reasons. To accomplish this, we have analyzed the transcriptomic data of over 7000 cancer and control tissues of 14 cancer types in TCGA and data of five NPC types in GEO. Our analyses reveal that NPCs accumulate large quantities of ATPs produced by the respiration process before starting the Warburg effect, to raise the intracellular pH from ∼6.8 to ∼7.2 and to prepare for cell division energetically. Once cell cycle starts, the cells start to rely on glycolysis for ATP generation followed by ATP hydrolysis and lactic acid release, to maintain the elevated intracellular pH as needed by cell division since together the three processes are pH neutral. The cells go back to the normal respiration-based ATP production once the cell division phase ends. In comparison, cancer cells have reached their intracellular pH at ∼7.4 from top down as multiple acid-loading transporters are up-regulated and most acid-extruding ones except for lactic acid exporters are repressed. Cancer cells use continuous glycolysis for ATP production as way to acidify the intracellular space since the lactic acid secretion is decoupled from glycolysis-based ATP generation and is pH balanced by increased expressions of acid-loading transporters. Co-expression analyses suggest that lactic acid secretion is regulated by external, non-pH related signals. Overall, our data strongly suggest that the two cell types have the Warburg effect for very different reasons.
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Affiliation(s)
- Huiyan Sun
- The China-Japan Union Hospital, Jilin University, Changchun 130033, China; MOE Key Laboratory of Symbolic Computation and Knowledge Engineering, College of Computer Science and Technology, Jilin University, Changchun 130012, China; Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
| | - Liang Chen
- Faculty of Health Sciences, University of Macau, Taipa, Macau SAR 999078, China
| | - Sha Cao
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA; Department of Biostatistics, School of Medicine, Indiana University, Indianapolis, IN 46202, USA
| | - Yanchun Liang
- MOE Key Laboratory of Symbolic Computation and Knowledge Engineering, College of Computer Science and Technology, Jilin University, Changchun 130012, China; Zhuhai Laboratory of MOE Key Laboratory of Symbolic Computation and Knowledge Engineering, Zhuhai College of Jilin University, Zhuhai 519041, China
| | - Ying Xu
- The China-Japan Union Hospital, Jilin University, Changchun 130033, China; MOE Key Laboratory of Symbolic Computation and Knowledge Engineering, College of Computer Science and Technology, Jilin University, Changchun 130012, China; Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA.
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A potential gain-of-function variant of SLC9A6 leads to endosomal alkalinization and neuronal atrophy associated with Christianson Syndrome. Neurobiol Dis 2019; 121:187-204. [DOI: 10.1016/j.nbd.2018.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 09/18/2018] [Accepted: 10/03/2018] [Indexed: 11/24/2022] Open
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25
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A mouse model of autism implicates endosome pH in the regulation of presynaptic calcium entry. Nat Commun 2018; 9:330. [PMID: 29362376 PMCID: PMC5780507 DOI: 10.1038/s41467-017-02716-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 12/19/2017] [Indexed: 11/21/2022] Open
Abstract
Psychoactive compounds such as chloroquine and amphetamine act by dissipating the pH gradient across intracellular membranes, but the physiological mechanisms that normally regulate organelle pH remain poorly understood. Interestingly, recent human genetic studies have implicated the endosomal Na+/H+ exchanger NHE9 in both autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD). Plasma membrane NHEs regulate cytosolic pH, but the role of intracellular isoforms has remained unclear. We now find that inactivation of NHE9 in mice reproduces behavioral features of ASD including impaired social interaction, repetitive behaviors, and altered sensory processing. Physiological characterization reveals hyperacidic endosomes, a cell-autonomous defect in glutamate receptor expression and impaired neurotransmitter release due to a defect in presynaptic Ca2+ entry. Acute inhibition of synaptic vesicle acidification rescues release but without affecting the primary defect due to loss of NHE9. The Na+/H+ exchanger NHE9 is proposed to regulate the H+ electrochemical gradient across endosomal membranes. Here, the authors find that NHE9 knockout mice show autism spectrum disorder-like behaviors and disrupted synaptic vesicle exocytosis due to impaired presynaptic calcium entry.
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26
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Podinovskaia M, Spang A. The Endosomal Network: Mediators and Regulators of Endosome Maturation. ENDOCYTOSIS AND SIGNALING 2018; 57:1-38. [DOI: 10.1007/978-3-319-96704-2_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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27
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Ma L, Ouyang Q, Werthmann GC, Thompson HM, Morrow EM. Live-cell Microscopy and Fluorescence-based Measurement of Luminal pH in Intracellular Organelles. Front Cell Dev Biol 2017; 5:71. [PMID: 28871281 PMCID: PMC5566985 DOI: 10.3389/fcell.2017.00071] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/04/2017] [Indexed: 11/16/2022] Open
Abstract
Luminal pH is an important functional feature of intracellular organelles. Acidification of the lumen of organelles such as endosomes, lysosomes, and the Golgi apparatus plays a critical role in fundamental cellular processes. As such, measurement of the luminal pH of these organelles has relevance to both basic research and translational research. At the same time, accurate measurement of intraorganellar pH in living cells can be challenging and may be a limiting hurdle for research in some areas. Here, we describe three powerful methods to measure rigorously the luminal pH of different intracellular organelles, focusing on endosomes, lysosomes, and the Golgi apparatus. The described methods are based on live imaging of pH-sensitive fluorescent probes and include: (1) A protocol based on quantitative, ratiometric measurement of endocytosis of pH-sensitive and pH-insensitive fluorescent conjugates of transferrin; (2) A protocol for the use of proteins tagged with a ratiometric variant of the pH-sensitive intrinsically fluorescent protein pHluorin; and (3) A protocol using the fluorescent dye LysoSensor™. We describe necessary reagents, key procedures, and methods and equipment for data acquisition and analysis. Examples of implementation of the protocols are provided for cultured cells derived from a cancer cell line and for primary cultures of mouse hippocampal neurons. In addition, we present strengths and weaknesses of the different described intraorganellar pH measurement methods. These protocols are likely to be of benefit to many researchers, from basic scientists to those conducting translational research with a focus on diseases in patient-derived cells.
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Affiliation(s)
- Li Ma
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversityProvidence, RI, United States.,Brown Institute for Brain Science, Brown UniversityProvidence, RI, United States
| | - Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversityProvidence, RI, United States.,Brown Institute for Brain Science, Brown UniversityProvidence, RI, United States
| | - Gordon C Werthmann
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversityProvidence, RI, United States
| | - Heather M Thompson
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversityProvidence, RI, United States.,Brown Institute for Brain Science, Brown UniversityProvidence, RI, United States.,Hassenfeld Child Health Innovation Institute, Brown UniversityProvidence, RI, United States
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown UniversityProvidence, RI, United States.,Brown Institute for Brain Science, Brown UniversityProvidence, RI, United States.,Hassenfeld Child Health Innovation Institute, Brown UniversityProvidence, RI, United States
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28
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Hypoxia-induced mobilization of NHE6 to the plasma membrane triggers endosome hyperacidification and chemoresistance. Nat Commun 2017. [PMID: 28635961 PMCID: PMC5482059 DOI: 10.1038/ncomms15884] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The pH-dependent partitioning of chemotherapeutic drugs is a fundamental yet understudied drug distribution mechanism that may underlie the low success rates of current approaches to counter multidrug resistance (MDR). This mechanism is influenced by the hypoxic tumour microenvironment and results in selective trapping of weakly basic drugs into acidified compartments such as the extracellular environment. Here we report that hypoxia not only leads to acidification of the tumour microenvironment but also induces endosome hyperacidification. The acidity of the vesicular lumen, together with the alkaline pH of the cytoplasm, gives rise to a strong intracellular pH gradient that drives intravesicular drug trapping and chemoresistance. Endosome hyperacidification is due to the relocalization of the Na+/H+ exchanger isoform 6 (NHE6) from endosomes to the plasma membrane, an event that involves binding of NHE6 to the activated protein kinase C-receptor for activated C kinase 1 complex. These findings reveal a novel mechanism of hypoxia-induced MDR that involves the aberrant intracellular distribution of NHE6.
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29
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Oberheide K, Puchkov D, Jentsch TJ. Loss of the Na +/H + exchanger NHE8 causes male infertility in mice by disrupting acrosome formation. J Biol Chem 2017; 292:10845-10854. [PMID: 28476888 DOI: 10.1074/jbc.m117.784108] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/04/2017] [Indexed: 01/02/2023] Open
Abstract
Mammalian sperm feature a specialized secretory organelle on the anterior part of the sperm nucleus, the acrosome, which is essential for male fertility. It is formed by a fusion of Golgi-derived vesicles. We show here that the predominantly Golgi-resident Na+/H+ exchanger NHE8 localizes to the developing acrosome of spermatids. Similar to wild-type mice, Nhe8-/- mice generated Golgi-derived vesicles positive for acrosomal markers and attached to nuclei, but these vesicles failed to form large acrosomal granules and the acrosomal cap. Spermatozoa from Nhe8-/- mice completely lacked acrosomes, were round-headed, exhibited abnormal mitochondrial distribution, and displayed decreased motility, resulting in selective male infertility. Of note, similar features are also found in globozoospermia, one of the causes of male infertility in humans. Germ cell-specific, but not Sertoli cell-specific Nhe8 disruption recapitulated the globozoospermia phenotype, demonstrating that NHE8's role in spermiogenesis is germ cell-intrinsic. Our work has uncovered a crucial role of NHE8 in acrosome biogenesis and suggests that some forms of human globozoospermia might be caused by a loss of function of this Na+/H+ exchanger. It points to NHE8 as a candidate gene for human globozoospermia and a possible drug target for male contraception.
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Affiliation(s)
- Karina Oberheide
- From the Leibniz-Forschungsinstitut für Molekulare Pharmakologie, D-13125 Berlin and.,Max-Delbrück-Centrum für Molekulare Medizin, D-13125 Berlin, Germany
| | - Dmytro Puchkov
- From the Leibniz-Forschungsinstitut für Molekulare Pharmakologie, D-13125 Berlin and
| | - Thomas J Jentsch
- From the Leibniz-Forschungsinstitut für Molekulare Pharmakologie, D-13125 Berlin and .,Max-Delbrück-Centrum für Molekulare Medizin, D-13125 Berlin, Germany
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30
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Kim J, You YJ. Regulation of organelle function by metformin. IUBMB Life 2017; 69:459-469. [PMID: 28444922 DOI: 10.1002/iub.1633] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/02/2017] [Indexed: 12/30/2022]
Abstract
Metformin ameliorates hyperglycemia without the side effects of lactic acidosis or hypoglycemia. Metformin lowers the blood glucose level by decreasing hepatic glucose production in the liver and by increasing glucose uptake in the muscle. Recent studies show that metformin induces cell death in certain cancer cell lines by interfering with the metabolism of the cancer cells. Therefore, understanding the mechanisms of action for metformin will provide insights into how to better treat diabetes and other metabolic disorders and also into the development of new therapeutic drugs. One of the best understood molecular targets of metformin is the mitochondrial complex I. However, given metformin's broad effects on metabolism, it could act on multiple targets. In this review, we summarize current findings in metformin's mechanisms of action regarding its known targets in mitochondria and known effects in cancer cell lines. Then, we introduce endosomal Na+ /H+ exchangers and the V-ATPase as new potential targets of metformin's action. Finally, we will discuss the hypothesis that metformin directly acts on endosome/lysosome regulation so as to regulate metabolism and ultimately alleviate type 2 diabetes. © 2017 IUBMB Life, 69(7):459-469, 2017.
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Affiliation(s)
- Jeongho Kim
- Department of Biological Sciences, Inha University, Incheon, South Korea
| | - Young-Jai You
- Nagoya Research Center for Brain and Neural Circuits, Graduate School of Science, Nagoya University, Nagoya, Japan
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31
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Larson CL, Heinzen RA. High-Content Imaging Reveals Expansion of the Endosomal Compartment during Coxiella burnetii Parasitophorous Vacuole Maturation. Front Cell Infect Microbiol 2017; 7:48. [PMID: 28293541 PMCID: PMC5329641 DOI: 10.3389/fcimb.2017.00048] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 02/07/2017] [Indexed: 11/18/2022] Open
Abstract
Coxiella burnetii is an obligate intracellular pathogen and the causative agent of human Q fever. Replication of the bacterium within a large parasitophorous vacuole (PV) resembling a host phagolysosome is required for pathogenesis. PV biogenesis is a pathogen driven process that requires engagement of several host cell vesicular trafficking pathways to acquire vacuole components. The goal of this study was to determine if infection by C. burnetii modulates endolysosomal flux to potentially benefit PV formation. HeLa cells, infected with C. burnetii or left uninfected, were incubated with fluorescent transferrin (Tf) for 0–30 min, and the amount of Tf internalized by cells quantitated by high-content imaging. At 3 and 5 days, but not 1 day post-infection, the maximal amounts of fluorescent Tf internalized by infected cells were significantly greater than uninfected cells. The rates of Tf uptake and recycling were the same for infected and uninfected cells; however, residual Tf persisted in EEA.1 positive compartments adjacent to large PV after 30 min of recycling in the absence of labeled Tf. On average, C. burnetii-infected cells contained significantly more CD63-positive endosomes than uninfected cells. In contrast, cells containing large vacuoles generated by Chlamydia trachomatis exhibited increased rates of Tf internalization without increased CD63 expression. Our results suggest that C. burnetii infection expands the endosomal system to increase capacity for endocytic material. Furthermore, this study demonstrates the power of high-content imaging for measurement of cellular responses to infection by intracellular pathogens.
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Affiliation(s)
- Charles L Larson
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health Hamilton, MT, USA
| | - Robert A Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health Hamilton, MT, USA
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Ilie A, Gao AYL, Reid J, Boucher A, McEwan C, Barrière H, Lukacs GL, McKinney RA, Orlowski J. A Christianson syndrome-linked deletion mutation (∆(287)ES(288)) in SLC9A6 disrupts recycling endosomal function and elicits neurodegeneration and cell death. Mol Neurodegener 2016; 11:63. [PMID: 27590723 PMCID: PMC5010692 DOI: 10.1186/s13024-016-0129-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 08/27/2016] [Indexed: 01/19/2023] Open
Abstract
Background Christianson Syndrome, a recently identified X-linked neurodevelopmental disorder, is caused by mutations in the human gene SLC9A6 encoding the recycling endosomal alkali cation/proton exchanger NHE6. The patients have pronounced limitations in cognitive ability, motor skills and adaptive behaviour. However, the mechanistic basis for this disorder is poorly understood as few of the more than 20 mutations identified thus far have been studied in detail. Methods Here, we examined the molecular and cellular consequences of a 6 base-pair deletion of amino acids Glu287 and Ser288 (∆ES) in the predicted seventh transmembrane helix of human NHE6 expressed in established cell lines (CHO/AP-1, HeLa and neuroblastoma SH-SY5Y) and primary cultures of mouse hippocampal neurons by measuring levels of protein expression, stability, membrane trafficking, endosomal function and cell viability. Results In the cell lines, immunoblot analyses showed that the nascent mutant protein was properly synthesized and assembled as a homodimer, but its oligosaccharide maturation and half-life were markedly reduced compared to wild-type (WT) and correlated with enhanced ubiquitination leading to both proteasomal and lysosomal degradation. Despite this instability, a measurable fraction of the transporter was correctly sorted to the plasma membrane. However, the rates of clathrin-mediated endocytosis of the ∆ES mutant as well as uptake of companion vesicular cargo, such as the ligand-bound transferrin receptor, were significantly reduced and correlated with excessive endosomal acidification. Notably, ectopic expression of ∆ES but not WT induced apoptosis when examined in AP-1 cells. Similarly, in transfected primary cultures of mouse hippocampal neurons, membrane trafficking of the ∆ES mutant was impaired and elicited marked reductions in total dendritic length, area and arborization, and triggered apoptotic cell death. Conclusions These results suggest that loss-of-function mutations in NHE6 disrupt recycling endosomal function and trafficking of cargo which ultimately leads to neuronal degeneration and cell death in Christianson Syndrome. Electronic supplementary material The online version of this article (doi:10.1186/s13024-016-0129-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Andy Y L Gao
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Jonathan Reid
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Cassandra McEwan
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Hervé Barrière
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada.
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33
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Zhao H, Carney KE, Falgoust L, Pan JW, Sun D, Zhang Z. Emerging roles of Na⁺/H⁺ exchangers in epilepsy and developmental brain disorders. Prog Neurobiol 2016; 138-140:19-35. [PMID: 26965387 DOI: 10.1016/j.pneurobio.2016.02.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/03/2016] [Accepted: 02/27/2016] [Indexed: 12/15/2022]
Abstract
Epilepsy is a common central nervous system (CNS) disease characterized by recurrent transient neurological events occurring due to abnormally excessive or synchronous neuronal activity in the brain. The CNS is affected by systemic acid-base disorders, and epileptic seizures are sensitive indicators of underlying imbalances in cellular pH regulation. Na(+)/H(+) exchangers (NHEs) are a family of membrane transporter proteins actively involved in regulating intracellular and organellar pH by extruding H(+) in exchange for Na(+) influx. Altering NHE function significantly influences neuronal excitability and plays a role in epilepsy. This review gives an overview of pH regulatory mechanisms in the brain with a special focus on the NHE family and the relationship between epilepsy and dysfunction of NHE isoforms. We first discuss how cells translocate acids and bases across the membrane and establish pH homeostasis as a result of the concerted effort of enzymes and ion transporters. We focus on the specific roles of the NHE family by detailing how the loss of NHE1 in two NHE mutant mice results in enhanced neuronal excitability in these animals. Furthermore, we highlight new findings on the link between mutations of NHE6 and NHE9 and developmental brain disorders including epilepsy, autism, and attention deficit hyperactivity disorder (ADHD). These studies demonstrate the importance of NHE proteins in maintaining H(+) homeostasis and their intricate roles in the regulation of neuronal function. A better understanding of the mechanisms underlying NHE1, 6, and 9 dysfunctions in epilepsy formation may advance the development of new epilepsy treatment strategies.
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Affiliation(s)
- Hanshu Zhao
- Department of Neurology, The First Affiliated Hospital of the Harbin Medical University, Harbin, China.,Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Karen E Carney
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lindsay Falgoust
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jullie W Pan
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Dandan Sun
- Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, PA 15213, USA
| | - Zhongling Zhang
- Department of Neurology, The First Affiliated Hospital of the Harbin Medical University, Harbin, China
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Alfarouk KO. Tumor metabolism, cancer cell transporters, and microenvironmental resistance. J Enzyme Inhib Med Chem 2016; 31:859-66. [PMID: 26864256 DOI: 10.3109/14756366.2016.1140753] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Cancer cells reprogram their metabolic machineries to enter into permanent glycolytic pathways. The full reason for such reprogramming takes place is unclear. However, this metabolic switch is not made in vain for the lactate that is generated and exported outside cells is reused by other cells. This results in the generation of a pH gradient between the low extracellular pH that is acidic (pHe) and the higher cytosolic alkaline or near neutral pH (pHi) environments that are tightly regulated by the overexpression of several pumps and ion channels (e.g. NHE-1, MCT-1, V-ATPase, CA9, and CA12). The generation of this unique pH gradient serves as a determining factor in defining "tumor fitness". Tumor fitness is the capacity of the tumor to invade and metastasize due to its ability to reduce the efficiency of the immune system and confer resistance to chemotherapy. In this article, we highlight the importance of tumor microenvironment in mediating the failure of chemotherapeutic agents.
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Affiliation(s)
- Khalid O Alfarouk
- a Department of Pharmacology , Faculty of Pharmacy, AL-Neelain University , Khartoum , Sudan
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Jinadasa T, Josephson CB, Boucher A, Orlowski J. Determinants of Cation Permeation and Drug Sensitivity in Predicted Transmembrane Helix 9 and Adjoining Exofacial Re-entrant Loop 5 of Na+/H+ Exchanger NHE1. J Biol Chem 2015; 290:18173-18186. [PMID: 26063808 DOI: 10.1074/jbc.m115.642199] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Indexed: 12/25/2022] Open
Abstract
Mammalian Na(+)/H(+) exchangers (NHEs) regulate numerous physiological processes and are involved in the pathogenesis of several diseases, including tissue ischemia and reperfusion injuries, cardiac hypertrophy and failure, and cancer progression. Hence, NHEs are being targeted for pharmaceutical-based clinical therapies, but pertinent information regarding the structural elements involved in cation translocation and drug binding remains incomplete. Molecular manipulations of the prototypical NHE1 isoform have implicated several predicted membrane-spanning (M) helices, most notably M4, M9, and M11, as important determinants of cation permeation and drug sensitivity. Here, we have used substituted-cysteine accessibility mutagenesis and thiol-modifying methanethiosulfonate (MTS) reagents to further probe the involvement of evolutionarily conserved sites within M9 (residues 342-363) and the adjacent exofacial re-entrant loop 5 between M9 and M10 (EL5; residues 364-415) of a cysteine-less variant of rat NHE1 on its kinetic and pharmacological properties. MTS treatment significantly reduced the activity of mutants containing substitutions within M9 (H353C, S355C, and G356C) and EL5 (G403C and S405C). In the absence of MTS, mutants S355C, G403C, and S405C showed modest to significant decreases in their apparent affinities for Na(+) o and/or H(+) i. In addition, mutations Y370C and E395C within EL5, whereas failing to confer sensitivity to MTS, nevertheless, reduced the affinity for Na(+) o, but not for H(+) i. The Y370C mutant also exhibited higher affinity for ethylisopropylamiloride, a competitive antagonist of Na(+) o transport. Collectively, these results further implicate helix M9 and EL5 of NHE1 as important elements involved in cation transport and inhibitor sensitivity, which may inform rational drug design.
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Affiliation(s)
- Tushare Jinadasa
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6
| | - Colin B Josephson
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6; Division of Clinical Neurosciences, University of Calgary Foothills Medical Centre, Calgary, Alberta T2N 2T9, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6
| | - John Orlowski
- Department of Physiology, McGill University, Montréal, Québec H3G 1Y6.
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Hunter JM, Kiefer J, Balak CD, Jooma S, Ahearn ME, Hall JG, Baumbach-Reardon L. Review of X-linked syndromes with arthrogryposis or early contractures-aid to diagnosis and pathway identification. Am J Med Genet A 2015; 167A:931-73. [DOI: 10.1002/ajmg.a.36934] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/05/2014] [Indexed: 02/03/2023]
Affiliation(s)
- Jesse M. Hunter
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Jeff Kiefer
- Knowledge Mining; Translational Genomics Research Institute; Phoenix Arizona
| | - Christopher D. Balak
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Sonya Jooma
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Mary Ellen Ahearn
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
| | - Judith G. Hall
- Departments of Medical Genetics and Pediatrics; University of British Columbia and BC Children's Hospital Vancouver; British Columbia Canada
| | - Lisa Baumbach-Reardon
- Integrated Functional Cancer Genomics; Translational Genomics Research Institute; Phoenix Arizona
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Kondapalli KC, Llongueras JP, Capilla-González V, Prasad H, Hack A, Smith C, Guerrero-Cázares H, Quiñones-Hinojosa A, Rao R. A leak pathway for luminal protons in endosomes drives oncogenic signalling in glioblastoma. Nat Commun 2015; 6:6289. [PMID: 25662504 PMCID: PMC4354686 DOI: 10.1038/ncomms7289] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 01/12/2015] [Indexed: 12/15/2022] Open
Abstract
Epidermal growth factor receptor (EGFR) signalling is a potent driver of glioblastoma, a malignant and lethal form of brain cancer. Disappointingly, inhibitors targeting receptor tyrosine kinase activity are not clinically effective and EGFR persists on the plasma membrane to maintain tumour growth and invasiveness. Here we show that endolysosomal pH is critical for receptor sorting and turnover. By functioning as a leak pathway for protons, the Na(+)/H(+) exchanger NHE9 limits luminal acidification to circumvent EGFR turnover and prolong downstream signalling pathways that drive tumour growth and migration. In glioblastoma, NHE9 expression is associated with stem/progenitor characteristics, radiochemoresistance, poor prognosis and invasive growth in vitro and in vivo. Silencing or inhibition of NHE9 in brain tumour-initiating cells attenuates tumoursphere formation and improves efficacy of EGFR inhibitor. Thus, NHE9 mediates inside-out control of oncogenic signalling and is a highly druggable target for pan-specific receptor clearance in cancer therapy.
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Affiliation(s)
- Kalyan C. Kondapalli
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Jose P. Llongueras
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Vivian Capilla-González
- Department of Neurosurgery, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Hari Prasad
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Anniesha Hack
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Christopher Smith
- Department of Neurosurgery, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Hugo Guerrero-Cázares
- Department of Neurosurgery, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Alfredo Quiñones-Hinojosa
- Department of Neurosurgery, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
| | - Rajini Rao
- Department of Physiology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
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Prasad H, Rao R. The Na+/H+ exchanger NHE6 modulates endosomal pH to control processing of amyloid precursor protein in a cell culture model of Alzheimer disease. J Biol Chem 2015; 290:5311-27. [PMID: 25561733 DOI: 10.1074/jbc.m114.602219] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Early intervention may be key to safe and effective therapies in patients with Alzheimer disease. Endosomal dysfunction is an early step in neurodegeneration. Endosomes are a major site of production of Aβ peptide from the processing of amyloid precursor protein (APP) by clipping enzymes (β- and γ-secretases). The β-secretase enzyme BACE1 requires acidic lumen pH for optimum function, and acid pH promotes Aβ aggregation. The Na(+)/H(+) exchanger NHE6 provides a leak pathway for protons, limiting luminal acidification by proton pumps. Like APP, NHE6 expression was induced upon differentiation of SH-SY5Y neuroblastoma cells and localized to an endosomal compartment. Therefore, we investigated whether NHE6 expression altered APP localization and processing in a stably transfected cell culture model of human APP expression. We show that co-expression with NHE6 or treatment with the Na(+)/H(+) ionophore monensin shifted APP away from the trans-Golgi network into early and recycling endosomes in HEK293 cells. NHE6 alkalinized the endosomal lumen, similar to monensin, and significantly attenuated APP processing and Aβ secretion. In contrast, Aβ production was elevated upon NHE6 knockdown. We show that NHE6 transcript and protein levels are lowered in Alzheimer brains relative to control. These findings, taken together with emerging genetic evidence linking endosomal Na(+)/H(+) exchangers with Alzheimer disease, suggest that proton leak pathways may regulate Aβ generation and contribute to disease etiology.
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Affiliation(s)
- Hari Prasad
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Rajini Rao
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Tan WH, Bird LM, Thibert RL, Williams CA. If not Angelman, what is it? A review of Angelman-like syndromes. Am J Med Genet A 2014; 164A:975-92. [PMID: 24779060 DOI: 10.1002/ajmg.a.36416] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Angelman syndrome (AS) is caused by a lack of expression of the maternally inherited UBE3A gene in the brain. However, about 10% of individuals with a clinical diagnosis of AS do not have an identifiable molecular defect. It is likely that most of those individuals have an AS-like syndrome that is clinically and molecularly distinct from AS. These AS-like syndromes can be broadly classified into chromosomal microdeletion and microduplication syndromes, and single-gene disorders. The microdeletion/microduplication syndromes are now easily identified by chromosomal microarray analysis and include Phelan–McDermid syndrome (chromosome 22q13.3 deletion), MBD5 haploinsufficiency syndrome (chromosome 2q23.1 deletion), and KANSL1 haploinsufficiency syndrome (chromosome 17q21.31 deletion). The single-gene disorders include Pitt–Hopkins syndrome (TCF4), Christianson syndrome (SLC9A6), Mowat–Wilson syndrome (ZEB2), Kleefstra syndrome (EHMT1), and Rett (MECP2) syndrome. They also include disorders due to mutations in HERC2, adenylosuccinase lyase (ADSL), CDKL5, FOXG1, MECP2 (duplications), MEF2C, and ATRX. Although many of these single-gene disorders can be caused by chromosomal microdeletions resulting in haploinsufficiency of the critical gene, the individual disorders are often caused by intragenic mutations that cannot be detected by chromosomal microarray analysis. We provide an overview of the clinical features of these syndromes, comparing and contrasting them with AS, in the hope that it will help guide clinicians in the diagnostic work-up of individuals with AS-like syndromes.
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Ilie A, Weinstein E, Boucher A, McKinney RA, Orlowski J. Impaired posttranslational processing and trafficking of an endosomal Na+/H+ exchanger NHE6 mutant (Δ370WST372) associated with X-linked intellectual disability and autism. Neurochem Int 2014; 73:192-203. [DOI: 10.1016/j.neuint.2013.09.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/23/2013] [Accepted: 09/24/2013] [Indexed: 01/23/2023]
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Kondapalli KC, Prasad H, Rao R. An inside job: how endosomal Na(+)/H(+) exchangers link to autism and neurological disease. Front Cell Neurosci 2014; 8:172. [PMID: 25002837 PMCID: PMC4066934 DOI: 10.3389/fncel.2014.00172] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 06/04/2014] [Indexed: 12/02/2022] Open
Abstract
Autism imposes a major impediment to childhood development and a huge emotional and financial burden on society. In recent years, there has been rapidly accumulating genetic evidence that links the eNHE, a subset of Na(+)/H(+) exchangers that localize to intracellular vesicles, to a variety of neurological conditions including autism, attention deficit hyperactivity disorder (ADHD), intellectual disability, and epilepsy. By providing a leak pathway for protons pumped by the V-ATPase, eNHE determine luminal pH and regulate cation (Na(+), K(+)) content in early and recycling endosomal compartments. Loss-of-function mutations in eNHE cause hyperacidification of endosomal lumen, as a result of imbalance in pump and leak pathways. Two isoforms, NHE6 and NHE9 are highly expressed in brain, including hippocampus and cortex. Here, we summarize evidence for the importance of luminal cation content and pH on processing, delivery and fate of cargo. Drawing upon insights from model organisms and mammalian cells we show how eNHE affect surface expression and function of membrane receptors and neurotransmitter transporters. These studies lead to cellular models of eNHE activity in pre- and post-synaptic neurons and astrocytes, where they could impact synapse development and plasticity. The study of eNHE has provided new insight on the mechanism of autism and other debilitating neurological disorders and opened up new possibilities for therapeutic intervention.
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Affiliation(s)
| | | | - Rajini Rao
- Department of Physiology, The Johns Hopkins University School of MedicineBaltimore, MD, USA
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Zanni G, Barresi S, Cohen R, Specchio N, Basel-Vanagaite L, Valente EM, Shuper A, Vigevano F, Bertini E. A novel mutation in the endosomal Na+/H+ exchanger NHE6 (SLC9A6) causes Christianson syndrome with electrical status epilepticus during slow-wave sleep (ESES). Epilepsy Res 2014; 108:811-5. [PMID: 24630051 DOI: 10.1016/j.eplepsyres.2014.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/23/2014] [Accepted: 02/02/2014] [Indexed: 11/26/2022]
Abstract
Mutations in the solute carrier family 9, subfamily A member 6 (SLC9A6) gene, encoding the endosomal Na+/H+ exchanger 6 (NHE6) are associated with Christianson syndrome, a syndromic form of X-linked intellectual disability characterized by microcephaly, severe global developmental delay, autistic behavior, early onset seizures and ataxia. In a 7-year-old boy with characteristic clinical and neuroimaging features of Christianson syndrome and epileptic encephalopathy with continuous spikes and waves during sleep, we identified a novel splice site mutation (IVS10-1G>A) in SLC9A6. These findings expand the clinical spectrum of the syndrome and indicate NHE6 dysfunction as a new cause of electrical status epilepticus during slow-wave sleep (ESES).
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Affiliation(s)
- Ginevra Zanni
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative disorders, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.
| | - Sabina Barresi
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative disorders, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Roni Cohen
- Schneider's Children Medical Center of Israel and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Nicola Specchio
- Division of Neurology, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Lina Basel-Vanagaite
- Schneider's Children Medical Center of Israel and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Enza Maria Valente
- Unit of Neurogenetics, Mendel Laboratory, IRCCS Casa Sollievo della Sofferenza Institute, San Giovanni Rotondo, Italy
| | - Avinoam Shuper
- Schneider's Children Medical Center of Israel and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Federico Vigevano
- Division of Neurology, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Enrico Bertini
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative disorders, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
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44
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Diering GH, Numata M. Endosomal pH in neuronal signaling and synaptic transmission: role of Na(+)/H(+) exchanger NHE5. Front Physiol 2014; 4:412. [PMID: 24454292 PMCID: PMC3888932 DOI: 10.3389/fphys.2013.00412] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 12/27/2013] [Indexed: 12/27/2022] Open
Abstract
Neuronal precursor cells extend multiple neurites during development, one of which extends to form an axon whereas others develop into dendrites. Chemical stimulation of N-methyl D-aspartate (NMDA) receptor in fully-differentiated neurons induces projection of dendritic spines, small spikes protruding from dendrites, thereby establishing another layer of polarity within the dendrite. Neuron-enriched Na+/H+ exchanger NHE5 contributes to both neurite growth and dendritic spine formation. In resting neurons and neuro-endocrine cells, neuron-enriched NHE5 is predominantly associated with recycling endosomes where it colocalizes with nerve growth factor (NGF) receptor TrkA. NHE5 potently acidifies the lumen of TrkA-positive recycling endosomes and regulates cell-surface targeting of TrkA, whereas chemical stimulation of NMDA receptors rapidly recruits NHE5 to dendritic spines, alkalinizes dendrites and down-regulates the dendritic spine formation. Possible roles of NHE5 in neuronal signaling via proton movement in subcellular compartments are discussed.
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Affiliation(s)
- Graham H Diering
- Department of Neuroscience, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Masayuki Numata
- Department of Biochemistry and Molecular Biology, University of British Columbia Vancouver, BC, Canada
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45
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Fuster DG, Alexander RT. Traditional and emerging roles for the SLC9 Na+/H+ exchangers. Pflugers Arch 2013; 466:61-76. [PMID: 24337822 DOI: 10.1007/s00424-013-1408-8] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 11/14/2013] [Accepted: 11/20/2013] [Indexed: 10/25/2022]
Abstract
The SLC9 gene family encodes Na(+)/H(+) exchangers (NHEs). These transmembrane proteins transport ions across lipid bilayers in a diverse array of species from prokaryotes to eukaryotes, including plants, fungi, and animals. They utilize the electrochemical gradient of one ion to transport another ion against its electrochemical gradient. Currently, 13 evolutionarily conserved NHE isoforms are known in mammals [22, 46, 128]. The SLC9 gene family (solute carrier classification of transporters: www.bioparadigms.org) is divided into three subgroups [46]. The SLC9A subgroup encompasses plasmalemmal isoforms NHE1-5 (SLC9A1-5) and the predominantly intracellular isoforms NHE6-9 (SLC9A6-9). The SLC9B subgroup consists of two recently cloned isoforms, NHA1 and NHA2 (SLC9B1 and SLC9B2, respectively). The SLC9C subgroup consist of a sperm specific plasmalemmal NHE (SLC9C1) and a putative NHE, SLC9C2, for which there is currently no functional data [46]. NHEs participate in the regulation of cytosolic and organellar pH as well as cell volume. In the intestine and kidney, NHEs are critical for transepithelial movement of Na(+) and HCO3(-) and thus for whole body volume and acid-base homeostasis [46]. Mutations in the NHE6 or NHE9 genes cause neurological disease in humans and are currently the only NHEs directly linked to human disease. However, it is becoming increasingly apparent that members of this gene family contribute to the pathophysiology of multiple human diseases.
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Affiliation(s)
- Daniel G Fuster
- Division of Nephrology, Hypertension and Clinical Pharmacology and Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland,
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46
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Ouyang Q, Lizarraga SB, Schmidt M, Yang U, Gong J, Ellisor D, Kauer JA, Morrow EM. Christianson syndrome protein NHE6 modulates TrkB endosomal signaling required for neuronal circuit development. Neuron 2013; 80:97-112. [PMID: 24035762 DOI: 10.1016/j.neuron.2013.07.043] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2013] [Indexed: 12/21/2022]
Abstract
Neuronal arborization is regulated by cell-autonomous and nonautonomous mechanisms including endosomal signaling via BDNF/TrkB. The endosomal Na⁺/H⁺ exchanger 6 (NHE6) is mutated in a new autism-related disorder. NHE6 functions to permit proton leak from endosomes, yet the mechanisms causing disease are unknown. We demonstrate that loss of NHE6 results in overacidification of the endosomal compartment and attenuated TrkB signaling. Mouse brains with disrupted NHE6 display reduced axonal and dendritic branching, synapse number, and circuit strength. Site-directed mutagenesis shows that the proton leak function of NHE6 is required for neuronal arborization. We find that TrkB receptor colocalizes to NHE6-associated endosomes. TrkB protein and phosphorylation are reduced in NHE6 mutant neurons in response to BDNF signaling. Finally, exogenous BDNF rescues defects in neuronal arborization. We propose that NHE6 mutation leads to circuit defects that are in part due to impoverished neuronal arborization that may be treatable by enhanced TrkB signaling.
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Affiliation(s)
- Qing Ouyang
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Sofia B Lizarraga
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Michael Schmidt
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Unikora Yang
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Jingyi Gong
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Debra Ellisor
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA
| | - Julie A Kauer
- Departments of Molecular Pharmacology, Physiology and Biotechnology, and Neuroscience, Brown University, Providence, Rhode Island 02912, USA
| | - Eric M Morrow
- Department of Molecular Biology, Cell Biology and Biochemistry, and Institute for Brain Science, Brown University, Laboratory for Molecular Medicine, 70 Ship Street, Providence, RI 02903, USA.,Developmental Disorders Genetics Research Program, Emma Pendleton Bradley Hospital and Department of Psychiatry and Human Behavior, Brown University Medical School, 1011 Veteran Memorial Pkwy., East Providence, RI 02915, USA
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47
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Donowitz M, Ming Tse C, Fuster D. SLC9/NHE gene family, a plasma membrane and organellar family of Na⁺/H⁺ exchangers. Mol Aspects Med 2013; 34:236-51. [PMID: 23506868 DOI: 10.1016/j.mam.2012.05.001] [Citation(s) in RCA: 185] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 03/09/2012] [Indexed: 12/24/2022]
Abstract
This brief review of the human Na/H exchanger gene family introduces a new classification with three subgroups to the SLC9 gene family. Progress in the structure and function of this gene family is reviewed with structure based on homology to the bacterial Na/H exchanger NhaA. Human diseases which result from genetic abnormalities of the SLC9 family are discussed although the exact role of these transporters in causing any disease is not established, other than poorly functioning NHE3 in congenital Na diarrhea.
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Affiliation(s)
- Mark Donowitz
- Departments of Medicine and Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
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Mulet JM, Llopis-Torregrosa V, Primo C, Marqués MC, Yenush L. Endocytic regulation of alkali metal transport proteins in mammals, yeast and plants. Curr Genet 2013; 59:207-30. [PMID: 23974285 DOI: 10.1007/s00294-013-0401-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 07/24/2013] [Accepted: 07/29/2013] [Indexed: 12/30/2022]
Abstract
The relative concentrations of ions and solutes inside cells are actively maintained by several classes of transport proteins, in many cases against their concentration gradient. These transport processes, which consume a large portion of cellular energy, must be constantly regulated. Many structurally distinct families of channels, carriers, and pumps have been characterized in considerable detail during the past decades and defects in the function of some of these proteins have been linked to a growing list of human diseases. The dynamic regulation of the transport proteins present at the cell surface is vital for both normal cellular function and for the successful adaptation to changing environments. The composition of proteins present at the cell surface is controlled on both the transcriptional and post-translational level. Post-translational regulation involves highly conserved mechanisms of phosphorylation- and ubiquitylation-dependent signal transduction routes used to modify the cohort of receptors and transport proteins present under any given circumstances. In this review, we will summarize what is currently known about one facet of this regulatory process: the endocytic regulation of alkali metal transport proteins. The physiological relevance, major contributors, parallels and missing pieces of the puzzle in mammals, yeast and plants will be discussed.
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Affiliation(s)
- José Miguel Mulet
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avd. de los Naranjos s/n, 46022, Valencia, Spain
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Sodium/hydrogen exchanger NHA2 is critical for insulin secretion in β-cells. Proc Natl Acad Sci U S A 2013; 110:10004-9. [PMID: 23720317 DOI: 10.1073/pnas.1220009110] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
NHA2 is a sodium/hydrogen exchanger with unknown physiological function. Here we show that NHA2 is present in rodent and human β-cells, as well as β-cell lines. In vivo, two different strains of NHA2-deficient mice displayed a pathological glucose tolerance with impaired insulin secretion but normal peripheral insulin sensitivity. In vitro, islets of NHA2-deficient and heterozygous mice, NHA2-depleted Min6 cells, or islets treated with an NHA2 inhibitor exhibited reduced sulfonylurea- and secretagogue-induced insulin secretion. The secretory deficit could be rescued by overexpression of a wild-type, but not a functionally dead, NHA2 transporter. NHA2 deficiency did not affect insulin synthesis or maturation and had no impact on basal or glucose-induced intracellular Ca(2+) homeostasis in islets. Subcellular fractionation and imaging studies demonstrated that NHA2 resides in transferrin-positive endosomes and synaptic-like microvesicles but not in insulin-containing large dense core vesicles in β-cells. Loss of NHA2 inhibited clathrin-dependent, but not clathrin-independent, endocytosis in Min6 and primary β-cells, suggesting defective endo-exocytosis coupling as the underlying mechanism for the secretory deficit. Collectively, our in vitro and in vivo studies reveal the sodium/proton exchanger NHA2 as a critical player for insulin secretion in the β-cell. In addition, our study sheds light on the biological function of a member of this recently cloned family of transporters.
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Enhanced recruitment of endosomal Na+/H+ exchanger NHE6 into Dendritic spines of hippocampal pyramidal neurons during NMDA receptor-dependent long-term potentiation. J Neurosci 2013; 33:595-610. [PMID: 23303939 DOI: 10.1523/jneurosci.2583-12.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Postsynaptic endosomal trafficking has emerged as a principal regulatory mechanism of structural and functional plasticity of glutamatergic synapses. Recycling endosomes perform activity-dependent transport of AMPA receptors (AMPARs) and lipids to the postsynaptic membrane, activities that are known to contribute to long-term synaptic potentiation and hypothesized to subserve learning and memory processes in the brain. Recently, genetic defects in a widely expressed vesicular pH-regulating transporter, the Na(+)/H(+) exchanger NHE6 isoform, have been implicated in neurodevelopmental disorders including severe X-linked mental retardation and autism. However, little information is available regarding the cellular properties of this transporter in the CNS. Here, we show by quantitative light microscopy that the protein abundance of NHE6 is developmentally regulated in area CA1 of the mouse hippocampus. Within pyramidal neurons, NHE6 was found to localize to discrete puncta throughout the soma and neurites, with noticeable accumulation at dendritic spines and presynaptic terminals. Dual immunolabeling of dendritic spines revealed that NHE6 partially colocalizes with typical markers of early and recycling endosomes as well as with the AMPAR subunit GluA1. Significantly, NHE6-containing vesicles exhibited enhanced translocation to dendritic spine heads during NMDA receptor (NMDAR)-dependent long-term potentiation. These data suggest that NHE6 may play a unique, previously unrecognized, role at glutamatergic synapses that are important for learning and memory.
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