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The neuronal K+Cl- co-transporter 2 (Slc12a5) modulates insulin secretion.

ABSTRACT: Intracellular chloride concentration ([Cl-]i) in pancreatic ?-cells is kept above electrochemical equilibrium due to the predominant functional presence of Cl- loaders such as the Na+K+2Cl- co-transporter 1 (Slc12a2) over Cl-extruders of unidentified nature. Using molecular cloning, RT-PCR, Western blotting, immunolocalization and in vitro functional assays, we establish that the "neuron-specific" K+Cl- co-transporter 2 (KCC2, Slc12a5) is expressed in several endocrine cells of the pancreatic islet, including glucagon secreting ?-cells, but particularly in insulin-secreting ?-cells, where we provide evidence for its role in the insulin secretory response. Three KCC2 splice variants were identified: the formerly described KCC2a and KCC2b along with a novel one lacking exon 25 (KCC2a-S25). This new variant is undetectable in brain or spinal cord, the only and most abundant known sources of KCC2. Inhibition of KCC2 activity in clonal MIN6 ?-cells increases basal and glucose-stimulated insulin secretion and Ca2+ uptake in the presence of glibenclamide, an inhibitor of the ATP-dependent potassium (KATP)-channels, thus suggesting a possible mechanism underlying KCC2-dependent insulin release. We propose that the long-time considered "neuron-specific" KCC2 co-transporter is expressed in pancreatic islet ?-cells where it modulates Ca2+-dependent insulin secretion.

SUBMITTER: Kursan S

PROVIDER: S-EPMC5431760 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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The neuronal K+Cl- co-transporter 2 (Slc12a5) modulates insulin secretion.

Kursan Shams S McMillen Timothy S TS Beesetty Pavani P Dias-Junior Eduardo E Almutairi Mohammed M MM Sajib Abu A AA Kozak J Ashot JA Aguilar-Bryan Lydia L Di Fulvio Mauricio M

Scientific reports 20170511 1

Intracellular chloride concentration ([Cl-]i) in pancreatic β-cells is kept above electrochemical equilibrium due to the predominant functional presence of Cl- loaders such as the Na+K+2Cl- co-transporter 1 (Slc12a2) over Cl-extruders of unidentified nature. Using molecular cloning, RT-PCR, Western blotting, immunolocalization and in vitro functional assays, we establish that the "neuron-specific" K+Cl-< ...[more]

PMID: 28496181

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Project description:BackgroundA significant mechanism of salt-tolerance in rice is the ability to remove Na+ and Cl- in the leaf sheath, which limits the entry of these toxic ions into the leaf blade. The leaf sheath removes Na+ mainly in the basal parts, and Cl- mainly in the apical parts. These ions are unloaded from the xylem vessels in the peripheral part and sequestered into the fundamental parenchyma cells at the central part of the leaf sheath.ResultsThis study aimed to identify associated Na+ and Cl- transporter genes with this salt removal ability in the leaf sheath of rice variety FL 478. From 21 known candidate Na+ and Cl- transporter rice genes, we determined the salt responsiveness of the expression of these genes in the basal and apical parts, where Na+ or Cl- ions were highly accumulated under salinity. We also compared the expression levels of these transporter genes between the peripheral and central parts of leaf sheaths. The expression of 8 Na+ transporter genes and 3 Cl- transporter genes was up-regulated in the basal and apical parts of leaf sheaths under salinity. Within these genes, OsHKT1;5 and OsSLAH1 were expressed highly in the peripheral part, indicating the involvement of these genes in Na+ and Cl- unloading from xylem vessels. OsNHX2, OsNHX3, OsNPF2.4 were expressed highly in the central part, which suggests that these genes may function in sequestration of Na+ and Cl- in fundamental parenchyma cells in the central part of leaf sheaths under salinity. Furthermore, high expression levels of 4 candidate genes under salinity were associated with the genotypic variation of salt removal ability in the leaf sheath.ConclusionsThese results indicate that the salt removal ability in rice leaf sheath may be regulated by expressing various Na+ or Cl- transporter genes tissue-specifically in peripheral and central parts. Moreover, some genes were identified as candidates whose expression levels were associated with the genotypic variation of salt removal ability in the leaf sheath. These findings will enhance the understanding of the molecular mechanism of salt removal ability in rice leaf sheath, which is useful for breeding salt-tolerant rice varieties.

Project description:Photochemical CO2 reduction catalysed by trans(Cl)-Ru(bpy)(CO)2Cl2 (bpy = 2,2'-bipyridine) efficiently produces carbon monoxide (CO) and formate (HCOO-) in N,N-dimethylacetamide (DMA)/water containing [Ru(bpy)3]2+ as a photosensitizer and 1-benzyl-1,4-dihydronicotinamide (BNAH) as an electron donor. We have unexpectedly found catalyst concentration dependence of the product ratio (CO/HCOO-) in the photochemical CO2 reduction: the ratio of CO/HCOO- decreases with increasing catalyst concentration. The result has led us to propose a new mechanism in which HCOO- is selectively produced by the formation of a Ru(i)-Ru(i) dimer as the catalyst intermediate. This reaction mechanism predicts that the Ru-Ru bond dissociates in the reaction of the dimer with CO2, and that the insufficient electron supply to the catalyst results in the dominant formation of HCOO-. The proposed mechanism is supported by the result that the time-course profiles of CO and HCOO- in the photochemical CO2 reduction catalysed by [Ru(bpy)(CO)2Cl]2 (0.05 mM) are very similar to those of the reduction catalysed by trans(Cl)-Ru(bpy)(CO)2Cl2 (0.10 mM), and that HCOO- formation becomes dominant under low-intensity light. The kinetic analyses based on the proposed mechanism could excellently reproduce the unusual catalyst concentration effect on the product ratio. The catalyst concentration effect observed in the photochemical CO2 reduction using [Ru(4dmbpy)3]2+ (4dmbpy = 4,4'-dimethyl-2,2'-bipyridine) instead of [Ru(bpy)3]2+ as the photosensitizer is also explained with the kinetic analyses, reflecting the smaller quenching rate constant of excited [Ru(4dmbpy)3]2+ by BNAH than that of excited [Ru(bpy)3]2+. We have further synthesized trans(Cl)-Ru(6Mes-bpy)(CO)2Cl2 (6Mes-bpy = 6,6'-dimesityl-2,2'-bipyridine), which bears bulky substituents at the 6,6'-positions in the 2,2'-bipyridyl ligand, so that the ruthenium complex cannot form the dimer due to the steric hindrance. We have found that this ruthenium complex selectively produces CO, which strongly supports the catalytic mechanism proposed in this work.

Dataset Information

The neuronal K+Cl- co-transporter 2 (Slc12a5) modulates insulin secretion.

Publications

The neuronal K<sup>+</sup>Cl<sup>-</sup> co-transporter 2 (Slc12a5) modulates insulin secretion.

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