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Osmotic Response of Dorsal Root Ganglion Neurons Expressing Wild-Type and Mutant KCC3 Transporters.
Flores B, Delpire E
(2020) Cell Physiol Biochem 54: 577-590
MeSH Terms: Animals, Axons, Cell Size, Corpus Callosum, Disease Models, Animal, Gain of Function Mutation, Ganglia, Spinal, Hereditary Sensory and Autonomic Neuropathies, Homeostasis, Humans, Membrane Transport Proteins, Mice, Mice, Knockout, Neurons, Osmotic Pressure, Symporters
Show Abstract · Added June 30, 2020
BACKGROUND/AIMS - Loss-of-Function (LOF) of the potassium chloride cotransporter 3 (KCC3) results in hereditary sensorimotor neuropathy with Agenesis of the Corpus Callosum (HSMN/ACC). Our KCC3 knockout mouse recapitulated axonal swelling and tissue vacuolization observed in autopsies of individuals with HSMN/ACC. We previously documented the first human case of a KCC3 gain-of-function (GOF) in which the patient also exhibited severe peripheral neuropathy. Furthermore, the GOF mouse model exhibited shrunken axons implicating the cotransporter in cell volume homeostasis. It is unclear how both KCC3 LOF and GOF lead to peripheral neuropathy. Thus, we sought to study differences in cell volume regulation of dorsal root ganglion neurons isolated from different mouse lines.
METHODS - Using wide-field microscopy, we measured calcein fluorescence intensity through pinhole measurements at the center of cells and compared cell swelling and cell volume regulation/recovery of wild-type, LOF, and GOF dorsal root ganglia neurons, as well as wild-type neurons treated with a KCC-specific inhibitor.
RESULTS - In contrast to control neurons that swell and volume regulate under a hypotonic challenge, neurons lacking KCC3 swell but fail to volume regulate. Similar data were observed in wild-type neurons treated with the KCC inhibitor. We also show that sensory neurons expressing a constitutively active KCC3 exhibited a blunted swelling phase compared to wild-type neurons, questioning the purely osmotic nature of the swelling phase.
CONCLUSION - These findings demonstrate the integral role of KCC3 in cell volume homeostasis and support the idea that cell volume homeostasis is critical to the health of peripheral nerves.
© Copyright by the Author(s). Published by Cell Physiol Biochem Press.
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16 MeSH Terms
Loss of non-canonical KCC2 functions promotes developmental apoptosis of cortical projection neurons.
Mavrovic M, Uvarov P, Delpire E, Vutskits L, Kaila K, Puskarjov M
(2020) EMBO Rep 21: e48880
MeSH Terms: Apoptosis, Chlorides, Epilepsy, Humans, Neurons, Symporters
Show Abstract · Added March 18, 2020
KCC2, encoded in humans by the SLC12A5 gene, is a multifunctional neuron-specific protein initially identified as the chloride (Cl ) extruder critical for hyperpolarizing GABA receptor currents. Independently of its canonical function as a K-Cl cotransporter, KCC2 regulates the actin cytoskeleton via molecular interactions mediated through its large intracellular C-terminal domain (CTD). Contrary to the common assumption that embryonic neocortical projection neurons express KCC2 at non-significant levels, here we show that loss of KCC2 enhances apoptosis of late-born upper-layer cortical projection neurons in the embryonic brain. In utero electroporation of plasmids encoding truncated, transport-dead KCC2 constructs retaining the CTD was as efficient as of that encoding full-length KCC2 in preventing elimination of migrating projection neurons upon conditional deletion of KCC2. This was in contrast to the effect of a full-length KCC2 construct bearing a CTD missense mutation (KCC2 ), which disrupts cytoskeletal interactions and has been found in patients with neurological and psychiatric disorders, notably seizures and epilepsy. Together, our findings indicate ion transport-independent, CTD-mediated regulation of developmental apoptosis by KCC2 in migrating cortical projection neurons.
© 2020 The Authors.
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6 MeSH Terms
Interpreting an apoptotic corpse as anti-inflammatory involves a chloride sensing pathway.
Perry JSA, Morioka S, Medina CB, Iker Etchegaray J, Barron B, Raymond MH, Lucas CD, Onengut-Gumuscu S, Delpire E, Ravichandran KS
(2019) Nat Cell Biol 21: 1532-1543
MeSH Terms: Animals, Apoptosis, Biological Transport, Cell Line, Cell Line, Tumor, Chlorides, Humans, Inflammation, Jurkat Cells, Mice, Mice, Inbred C57BL, Oxidative Stress, Phagocytes, Phagocytosis, Signal Transduction, Sodium-Potassium-Chloride Symporters, Transcription, Genetic
Show Abstract · Added March 18, 2020
Apoptotic cell clearance (efferocytosis) elicits an anti-inflammatory response by phagocytes, but the mechanisms that underlie this response are still being defined. Here, we uncover a chloride-sensing signalling pathway that controls both the phagocyte 'appetite' and its anti-inflammatory response. Efferocytosis transcriptionally altered the genes that encode the solute carrier (SLC) proteins SLC12A2 and SLC12A4. Interfering with SLC12A2 expression or function resulted in a significant increase in apoptotic corpse uptake per phagocyte, whereas the loss of SLC12A4 inhibited corpse uptake. In SLC12A2-deficient phagocytes, the canonical anti-inflammatory program was replaced by pro-inflammatory and oxidative-stress-associated gene programs. This 'switch' to pro-inflammatory sensing of apoptotic cells resulted from the disruption of the chloride-sensing pathway (and not due to corpse overload or poor degradation), including the chloride-sensing kinases WNK1, OSR1 and SPAK-which function upstream of SLC12A2-had a similar effect on efferocytosis. Collectively, the WNK1-OSR1-SPAK-SLC12A2/SLC12A4 chloride-sensing pathway and chloride flux in phagocytes are key modifiers of the manner in which phagocytes interpret the engulfed apoptotic corpse.
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Cryo-EM structures of NKCC1 and hKCC1: a new milestone in the physiology of cation-chloride cotransporters.
Delpire E, Guo J
(2020) Am J Physiol Cell Physiol 318: C225-C237
MeSH Terms: Amino Acid Sequence, Animals, Cations, Chlorides, Cryoelectron Microscopy, Humans, Solute Carrier Family 12, Member 2, Symporters
Show Abstract · Added March 18, 2020
New milestones have been reached in the field of cation-Cl cotransporters with the recently released cryo-electron microscopy (EM) structures of the (zebrafish) Na-K-2Cl cotransporter (NKCC1) and the human K-Cl cotransporter (hKCC1). In this review we provide a brief timeline that identifies the multiple breakthroughs in the field of solute carrier 12 transporters that led to the structure resolution of two of its key members. While cation-Cl cotransporters share the overall architecture of carriers belonging to the amino acid-polyamine-organocation (APC) superfamily and some of their substrate binding sites, several new insights are gained from the two individual structures. A first major feature relates to the largest extracellular domain between transmembrane domain (TMD) 5 and TMD6 of KCC1, which stabilizes the dimer and forms a cap that likely participates in extracellular gating. A second feature is the conservation of the K and Cl binding sites in both structures and evidence of an unexpected second Cl coordination site in the KCC1 structure. Structural data are discussed in the context of previously published studies that examined the basic and kinetics properties of these cotransport mechanisms. A third characteristic is the evidence of an extracellular gate formed by conserved salt bridges between charged residues located toward the end of TMD3 and TMD4 in both transporters and the existence of an additional neighboring bridge in the hKCC1 structure. A fourth feature of these newly solved structures relates to the multiple points of contacts between the monomer forming the cotransporter homodimer units. These involve the TMDs, the COOH-terminal domains, and the large extracellular loop for hKCC1.
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8 MeSH Terms
Cryo-EM structures of the human cation-chloride cotransporter KCC1.
Liu S, Chang S, Han B, Xu L, Zhang M, Zhao C, Yang W, Wang F, Li J, Delpire E, Ye S, Bai XC, Guo J
(2019) Science 366: 505-508
MeSH Terms: Amino Acid Sequence, Animals, Binding Sites, Cryoelectron Microscopy, HEK293 Cells, Humans, Ion Transport, Mice, Molecular Dynamics Simulation, Oocytes, Protein Domains, Protein Multimerization, Protein Structure, Quaternary, Sequence Alignment, Sodium-Potassium-Chloride Symporters, Symporters, Xenopus laevis
Show Abstract · Added March 18, 2020
Cation-chloride cotransporters (CCCs) mediate the coupled, electroneutral symport of cations with chloride across the plasma membrane and are vital for cell volume regulation, salt reabsorption in the kidney, and γ-aminobutyric acid (GABA)-mediated modulation in neurons. Here we present cryo-electron microscopy (cryo-EM) structures of human potassium-chloride cotransporter KCC1 in potassium chloride or sodium chloride at 2.9- to 3.5-angstrom resolution. KCC1 exists as a dimer, with both extracellular and transmembrane domains involved in dimerization. The structural and functional analyses, along with computational studies, reveal one potassium site and two chloride sites in KCC1, which are all required for the ion transport activity. KCC1 adopts an inward-facing conformation, with the extracellular gate occluded. The KCC1 structures allow us to model a potential ion transport mechanism in KCCs and provide a blueprint for drug design.
Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
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17 MeSH Terms
Developmentally regulated KCC2 phosphorylation is essential for dynamic GABA-mediated inhibition and survival.
Watanabe M, Zhang J, Mansuri MS, Duan J, Karimy JK, Delpire E, Alper SL, Lifton RP, Fukuda A, Kahle KT
(2019) Sci Signal 12:
MeSH Terms: Animals, Animals, Newborn, Binding Sites, Cells, Cultured, Central Nervous System, Chlorides, Gene Expression Regulation, Developmental, Male, Mice, 129 Strain, Mice, Inbred C57BL, Mice, Knockout, Neurons, Phosphorylation, Signal Transduction, Symporters, gamma-Aminobutyric Acid
Show Abstract · Added March 18, 2020
Despite its importance for γ-aminobutyric acid (GABA) inhibition and involvement in neurodevelopmental disease, the regulatory mechanisms of the K/Cl cotransporter KCC2 (encoded by ) during maturation of the central nervous system (CNS) are not entirely understood. Here, we applied quantitative phosphoproteomics to systematically map sites of KCC2 phosphorylation during CNS development in the mouse. KCC2 phosphorylation at Thr and Thr, which inhibits KCC2 activity, underwent dephosphorylation in parallel with the GABA excitatory-inhibitory sequence in vivo. Knockin mice expressing the homozygous phosphomimetic KCC2 mutations T906E/T1007E ( ), which prevented the normal developmentally regulated dephosphorylation of these sites, exhibited early postnatal death from respiratory arrest and a marked absence of cervical spinal neuron respiratory discharges. mice also displayed disrupted lumbar spinal neuron locomotor rhythmogenesis and touch-evoked status epilepticus associated with markedly impaired KCC2-dependent Cl extrusion. These data identify a previously unknown phosphorylation-dependent KCC2 regulatory mechanism during CNS development that is essential for dynamic GABA-mediated inhibition and survival.
Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.
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16 MeSH Terms
variants in cause sporadic early-onset progressive sensorimotor neuropathy.
Park J, Flores BR, Scherer K, Kuepper H, Rossi M, Rupprich K, Rautenberg M, Deininger N, Weichselbaum A, Grimm A, Sturm M, Grasshoff U, Delpire E, Haack TB
(2020) J Med Genet 57: 283-288
MeSH Terms: Adolescent, Age of Onset, Agenesis of Corpus Callosum, Charcot-Marie-Tooth Disease, Child, Female, Genotype, Hereditary Sensory and Autonomic Neuropathies, Humans, Infant, Magnetic Resonance Imaging, Male, Mutation, Pedigree, Peripheral Nervous System Diseases, Phenotype, Symporters
Show Abstract · Added March 18, 2020
BACKGROUND - Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous disorder of the peripheral nervous system. Biallelic variants in have been associated with autosomal-recessive hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC). We identified heterozygous de novo variants in in three unrelated patients with intermediate CMT.
METHODS - We evaluated the clinical reports and electrophysiological data of three patients carrying de novo variants in identified by diagnostic trio exome sequencing. For functional characterisation of the identified variants, potassium influx of mutated KCC3 cotransporters was measured in oocytes.
RESULTS - We identified two different de novo missense changes (p.Arg207His and p.Tyr679Cys) in in three unrelated individuals with early-onset progressive CMT. All presented with axonal/demyelinating sensorimotor neuropathy accompanied by spasticity in one patient. Cognition and brain MRI were normal. Modelling of the mutant KCC3 cotransporter in oocytes showed a significant reduction in potassium influx for both changes.
CONCLUSION - Our findings expand the genotypic and phenotypic spectrum associated with variants from autosomal-recessive HMSN/ACC to dominant-acting de novo variants causing a milder clinical presentation with early-onset neuropathy.
© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.
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17 MeSH Terms
SLC12A ion transporter mutations in sporadic and familial human congenital hydrocephalus.
Jin SC, Furey CG, Zeng X, Allocco A, Nelson-Williams C, Dong W, Karimy JK, Wang K, Ma S, Delpire E, Kahle KT
(2019) Mol Genet Genomic Med 7: e892
MeSH Terms: Animals, Cerebral Aqueduct, Genetic Diseases, X-Linked, Humans, Hydrocephalus, Male, Mutation, Neural Cell Adhesion Molecule L1, Symporters, Whole Exome Sequencing, Xenopus laevis
Show Abstract · Added March 18, 2020
BACKGROUND - Congenital hydrocephalus (CH) is a highly morbid disease that features enlarged brain ventricles and impaired cerebrospinal fluid homeostasis. Although early linkage or targeted sequencing studies in large multigenerational families have localized several genes for CH, the etiology of most CH cases remains unclear. Recent advances in whole exome sequencing (WES) have identified five new bona fide CH genes, implicating impaired regulation of neural stem cell fate in CH pathogenesis. Nonetheless, in the majority of CH cases, the pathological etiology remains unknown, suggesting more genes await discovery.
METHODS - WES of family members of a sporadic and familial form of severe L1CAM mutation-negative CH associated with aqueductal stenosis was performed. Rare genetic variants were analyzed, prioritized, and validated. De novo copy number variants (CNVs) were identified using the XHMM algorithm and validated using qPCR. Xenopus oocyte experiments were performed to access mutation impact on protein function and expression.
RESULTS - A novel inherited protein-damaging mutation (p.Pro605Leu) in SLC12A6, encoding the K -Cl cotransporter KCC3, was identified in both affected members of multiplex kindred CHYD110. p.Pro605 is conserved in KCC3 orthologs and among all human KCC paralogs. The p.Pro605Leu mutation maps to the ion-transporting domain, and significantly reduces KCC3-dependent K transport. A novel de novo CNV (deletion) was identified in SLC12A7, encoding the KCC3 paralog and binding partner KCC4, in another family (CHYD130) with sporadic CH.
CONCLUSION - These findings identify two novel, related genes associated with CH, and implicate genetically encoded impairments in ion transport for the first time in CH pathogenesis.
© 2019 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals, Inc.
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11 MeSH Terms
Functional Coupling of K-Cl Cotransporter (KCC) to GABA-Gated Cl Channels in the Central Nervous System of Drosophila melanogaster Leads to Altered Drug Sensitivities.
Chen R, Prael FJ, Li Z, Delpire E, Weaver CD, Swale DR
(2019) ACS Chem Neurosci 10: 2765-2776
MeSH Terms: Animals, Central Nervous System, Chloride Channels, Drosophila Proteins, Drosophila melanogaster, Insecticide Resistance, Neurons, Signal Transduction, Symporters, Synaptic Transmission, gamma-Aminobutyric Acid
Show Abstract · Added April 10, 2019
GABAergic signaling is the cornerstone for fast synaptic inhibition of neural signaling in arthropods and mammals and is the molecular target for insecticides and pharmaceuticals, respectively. The K-Cl cotransporter (KCC) is the primary mechanism by which mature neurons maintain low intracellular Cl concentration, yet the fundamental physiology, comparative physiology, and toxicological relevance of insect KCC is understudied. Considering this, we employed electrophysiological, genetic, and pharmacological methods to characterize the physiological underpinnings of KCC function to the Drosophila CNS. Our data show that genetic ablation or pharmacological inhibition of KCC results in an increased spike discharge frequency and significantly ( P < 0.05) reduces the CNS sensitivity to γ-aminobutyric acid (GABA). Further, simultaneous inhibition of KCC and ligand-gated chloride channel (LGCC) complex results in a significant ( P < 0.001) increase in CNS spontaneous activity over baseline firing rates that supports functional coupling of KCC to LGCC function. Interestingly, 75% reduction in KCC mRNA did not alter basal neurotransmission levels indicating that only a fraction of the KCC population is required to maintain the Cl ionic gradient when at rest, but prolonged synaptic activity increases the threshold for GABA-mediated inhibition and reduces nerve sensitivity to GABA. These data expand current knowledge regarding the physiological role of KCC in a model insect and provides the necessary foundation to develop KCC as a novel biochemical target of insecticides, as well as complements existing research to provide a holistic understanding of the plasticity in mammalian health and disease.
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11 MeSH Terms
Use of chemical probes to explore the toxicological potential of the K/Cl cotransporter (KCC) as a novel insecticide target to control the primary vector of dengue and Zika virus, Aedes aegypti.
Prael FJ, Chen R, Li Z, Reed CW, Lindsley CW, Weaver CD, Swale DR
(2018) Pestic Biochem Physiol 151: 10-17
MeSH Terms: Aedes, Animals, Dengue, Drosophila, Insecticides, Mammals, Mosquito Vectors, Nervous System, Symporters, Zika Virus
Show Abstract · Added April 10, 2019
The majority of commercialized insecticides target the insect nervous system and therefore, neural proteins are well-validated targets for insecticide development. Considering that only a few neural targets are exploited for insecticidal action and the development of insecticide resistance has reduced the efficacy of current insecticidal classes, we sought to test the toxicological potential of the potassium-chloride cotransporter (KCC). In mammals, KCC proteins have seminal roles in shaping GABAergic signaling and inhibitory neurotransmission, thus ion transport through KCC is critical for proper neurotransmission. Therefore, we hypothesized that mosquito KCC represents a putative insecticide target site and that pharmacological inhibition of KCC constructs in Aedes aegypti will be lethal. To test this hypothesis, we developed a robust, cell-based fluorescence assay that enables in vitro characterization of small-molecules against Ae. aegypti KCC and performed a proof-of-concept study employing well characterized mammalian KCC modulators to determine the toxicological potential of Ae. aegypti KCC. The selective inhibitor of mammalian KCC, termed VU0463271, was found to be a potent inhibitor Ae. aegypti KCC and microinjection induced lethality in a concentration-dependent manner to susceptible and pyrethroid resistant strains. Importantly, an analog of VU0463271 was shown to be >40-fold less potent and did not induce toxicity, suggesting that the observed physiological effects and mortality are likely due to KCC inhibition. This proof-of-concept study suggests that Ae. aegypti KCC represents a putative target site for mosquitocide design that can mitigate the current mechanisms of insecticide resistance.
Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.
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