scholarly journals Reconstitution of CO2 Regulation of SLAC1 Anion Channel and Function of CO2-Permeable PIP2;1 Aquaporin as CARBONIC ANHYDRASE4 Interactor

2016 ◽  
Vol 28 (2) ◽  
pp. 568-582 ◽  
Author(s):  
Cun Wang ◽  
Honghong Hu ◽  
Xue Qin ◽  
Brian Zeise ◽  
Danyun Xu ◽  
...  
Keyword(s):  
Anion Channel ◽  
And Function ◽  
Co2 Regulation

scholarly journals A 30-year journey from volume-regulated anion currents to molecular structure of the LRRC8 channel

2019 ◽  
Vol 151 (2) ◽  
pp. 100-117 ◽  
Author(s):  
Kevin Strange ◽  
Toshiki Yamada ◽  
Jerod S. Denton
Keyword(s):  
Structure Function ◽  
Cell Volume ◽  
Cell Volume Regulation ◽  
Anion Channel ◽  
Clear Understanding ◽  
Physiological Processes ◽  
Heteromeric Channel ◽  
Key Aspects ◽  
And Function ◽  
Vexing Problem

The swelling-activated anion channel VRAC has fascinated and frustrated physiologists since it was first described in 1988. Multiple laboratories have defined VRAC’s biophysical properties and have shown that it plays a central role in cell volume regulation and possibly other fundamental physiological processes. However, confusion and intense controversy surrounding the channel’s molecular identity greatly hindered progress in the field for >15 yr. A major breakthrough came in 2014 with the demonstration that VRAC is a heteromeric channel encoded by five members of the Lrrc8 gene family, Lrrc8A–E. A mere 4 yr later, four laboratories described cryo-EM structures of LRRC8A homomeric channels. As the melee of structure/function and physiology studies begins, it is critical that this work be framed by a clear understanding of VRAC biophysics, regulation, and cellular physiology as well as by the field’s past confusion and controversies. That understanding is essential for the design and interpretation of structure/function studies, studies of VRAC physiology, and studies aimed at addressing the vexing problem of how the channel detects cell volume changes. In this review we discuss key aspects of VRAC biophysics, regulation, and function and integrate these into our emerging understanding of LRRC8 protein structure/function.

scholarly journals Structure and function of the voltage dependent anion channel

2010 ◽  
Vol 1797 ◽  
pp. 66 ◽  
Author(s):  
Sebastian Hiller ◽  
Thomas Raschle ◽  
Tsyr-Yan Yu ◽  
Amanda J. Rice ◽  
Thomas Walz ◽  
...  
Keyword(s):  
Anion Channel ◽  
Structure And Function ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
And Function

scholarly journals Leucine-rich repeat containing 8A (LRRC8A) –dependent volume-regulated anion channel activity is dispensable for T-cell development and function

2017 ◽  
Vol 140 (6) ◽  
pp. 1651-1659.e1 ◽  
Author(s):  
Craig D. Platt ◽  
Janet Chou ◽  
Patrick Houlihan ◽  
Yousef R. Badran ◽  
Lalit Kumar ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Development ◽  
Anion Channel ◽  
Cell Development ◽  
Leucine Rich Repeat ◽  
Channel Activity ◽  
And Function

scholarly journals Reconstitution of CO2 regulation of SLAC1 anion channel and function of CO2-permeable PIP2;1 aquaporin as carbonic anhydrase 4 interactor

2015 ◽  
Author(s):  
Cun Wang ◽  
Honghong Hu ◽  
Xue Qin ◽  
Brian Zeise ◽  
Danyun Xu ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Xenopus Oocytes ◽  
Stomatal Closure ◽  
Anion Channel ◽  
Co2 Concentration ◽  
Bimolecular Fluorescence Complementation ◽  
Molecular Signaling ◽  
Carbonic Anhydrases ◽  
Ion Channel Regulation ◽  
Co2 Regulation

Daily dark periods cause an increase in the leaf CO2 concentration (Ci) and the continuing atmospheric [CO2] rise also increases Ci. Elevated Ci causes closing of stomatal pores thus regulating gas exchange of plants. The molecular signaling mechanisms leading to CO2-induced stomatal closure are only partially understood. Here we demonstrate that high intracellular CO2/HCO3- enhances currents mediated by the guard cell S-type anion channel SLAC1 when co-expressing either of the protein kinases OST1, CPK6 or CPK23 in Xenopus oocytes. Split-ubiquitin screening identified the PIP2;1 aquaporin as an interactor of the βCA4 carbonic anhydrase, which was confirmed in split luciferase, bimolecular fluorescence complementation and co-immunoprecipitation experiments. PIP2;1 exhibited CO2 permeability. Co-expression of βCA4 and PIP2;1 with OST1-SLAC1 or CPK6/23-SLAC1 enabled extracellular CO2 enhancement of SLAC1 anion channel activity. An inactive PIP2;1 point mutation was identified which abrogated water and CO2 permeability and extracellular CO2 regulation of SLAC1 activity in Xenopus oocytes. These findings identify the CO2-permeable PIP2;1 aquaporin as key interactor of carbonic anhydrases, show functional reconstitution of extracellular CO2 signaling to ion channel regulation and implicate SLAC1 as a bicarbonate-responsive protein in CO2 regulation of S-type anion channels.

Intracellular CFTR: Localization and Function

1999 ◽  
Vol 79 (1) ◽  
pp. S175-S191 ◽  
Author(s):  
NEIL A. BRADBURY
Keyword(s):  
Cystic Fibrosis ◽  
Molecular Mechanisms ◽  
Apical Membrane ◽  
Membrane Vesicle ◽  
Clinical Manifestations ◽  
Anion Channel ◽  
Integral Membrane Protein ◽  
Normal Function ◽  
Intracellular Compartments ◽  
And Function

Bradbury, Neil A. Intracellular CFTR: Localization and Function. Physiol. Rev. 79, Suppl.: S175–S191, 1999. — There is considerable evidence that CFTR can function as a chloride-selective anion channel. Moreover, this function has been localized to the apical membrane of chloride secretory epithelial cells. However, because cystic fibrosis transmembrane conductance regulator (CFTR) is an integral membrane protein, it will also be present, to some degree, in a variety of other membrane compartments (including endoplasmic reticulum, Golgi stacks, endosomes, and lysosomes). An incomplete understanding of the molecular mechanisms by which alterations in an apical membrane chloride conductance could give rise to the various clinical manifestations of cystic fibrosis has prompted the suggestion that CFTR may also play a role in the normal function of certain intracellular compartments. A variety of intracellular functions have been attributed to CFTR, including regulation of membrane vesicle trafficking and fusion, acidification of organelles, and transport of small anions. This paper aims to review the evidence for localization of CFTR in intracellular organelles and the potential physiological consequences of that localization.

scholarly journals Clinical development of triple-combination CFTR modulators for cystic fibrosis patients with one or two F508del alleles

2019 ◽  
Vol 5 (2) ◽  
pp. 00082-2019 ◽  
Author(s):  
Jennifer L. Taylor-Cousar ◽  
Marcus A. Mall ◽  
Bonnie W. Ramsey ◽  
Edward F. McKone ◽  
Elizabeth Tullis ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Anion Channel ◽  
Triple Combination ◽  
Open Label ◽  
Cftr Protein ◽  
Trafficking Defects ◽  
Cf Transmembrane Conductance Regulator ◽  
And Function ◽  
Cftr Modulators

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator gene (CFTR) that result in diminished quantity and/or function of the CFTR anion channel. F508del-CFTR, the most common CF-causing mutation (found in ∼90% of patients), causes severe processing and trafficking defects, resulting in decreased CFTR quantity and function. CFTR modulators are medications that increase the amount of mature CFTR protein (correctors) or enhance channel function (potentiators) at the cell surface.Combinations of CFTR correctors and potentiators (i.e. lumacaftor/ivacaftor, tezacaftor/ivacaftor) have demonstrated clinical benefit in subsets of patients. However, none are approved for patients with CF heterozygous for F508del-CFTR and a minimal function mutation, i.e. a mutation that produces either no protein or protein that is unresponsive to currently approved CFTR modulators. Next-generation CFTR correctors VX-659 and VX-445, each in triple combination with tezacaftor and ivacaftor, improve CFTR processing, trafficking and function in vitro and have demonstrated clinical improvements in phase 2 studies in patients with CF with one or two F508del-CFTR alleles.Here, we present the rationale and design of four randomised phase 3 studies, and their open-label extensions, evaluating VX-659 (ECLIPSE) or VX-445 (AURORA) plus tezacaftor and ivacaftor in patients with one or two F508del-CFTR alleles.

scholarly journals On the role of tubulin, plectin, desmin, and vimentin in the regulation of mitochondrial energy fluxes in muscle cells

2019 ◽  
Vol 316 (5) ◽  
pp. C657-C667 ◽  
Author(s):  
Kati Mado ◽  
Vladimir Chekulayev ◽  
Igor Shevchuk ◽  
Marju Puurand ◽  
Kersti Tepp ◽  
...  
Keyword(s):  
Striated Muscle ◽  
Adenine Nucleotides ◽  
Anion Channel ◽  
Muscle Cells ◽  
Eukaryotic Cell ◽  
Cytoskeletal Proteins ◽  
Energy Fluxes ◽  
Voltage Dependent Anion Channel ◽  
And Function

Mitochondria perform a central role in life and death of the eukaryotic cell. They are major players in the generation of macroergic compounds and function as integrated signaling pathways, including the regulation of Ca2+ signals and apoptosis. A growing amount of evidence is demonstrating that mitochondria of muscle cells use cytoskeletal proteins (both microtubules and intermediate filaments) not only for their movement and proper cellular positioning, but also to maintain their biogenesis, morphology, function, and regulation of energy fluxes through the outer mitochondrial membrane (MOM). Here we consider the known literature data concerning the role of tubulin, plectin, desmin and vimentin in bioenergetic function of mitochondria in striated muscle cells, as well as in controlling the permeability of MOM for adenine nucleotides (ADNs). This is of great interest since dysfunctionality of these cytoskeletal proteins has been shown to result in severe myopathy associated with pronounced mitochondrial dysfunction. Further efforts are needed to uncover the pathways by which the cytoskeleton supports the functional capacity of mitochondria and transport of ADN(s) across the MOM (through voltage-dependent anion channel).

VDAC1 cysteine residues: topology and function in channel activity and apoptosis

2010 ◽  
Vol 427 (3) ◽  
pp. 445-454 ◽  
Author(s):  
Lior Aram ◽  
Shay Geula ◽  
Nir Arbel ◽  
Varda Shoshan-Barmatz
Keyword(s):  
Apoptotic Cell ◽  
Anion Channel ◽  
Cross Linking ◽  
Cysteine Residues ◽  
Channel Activity ◽  
Voltage Dependent Anion Channel ◽  
Oxidation Reduction ◽  
Voltage Dependent ◽  
And Function ◽  
Interfering Rna

The VDAC (voltage-dependent anion channel) is proposed to control metabolic cross-talk between mitochondria and the cytosol, as well as apoptotic cell death. It has been suggested that apoptosis is modulated by the oxidation state of VDAC. Since cysteine residues are the major target for oxidation/reduction, we verified whether one or both VDAC1 cysteine residues are involved in VDAC1-mediated transport or apoptosis activities. To assess the function of VDAC1 cysteine residues in channel activity and to probe cysteine topology with respect to facing the pore or the bilayer, we used thiol-modifying agents, namely membrane-permeable NEM (N-ethylmaleimide), bulky charged 5-FM (fluorescein-5-maleimide) and the cross-linking reagent BMOE [bis(maleimido)ethane]. Bilayer-reconstituted VDAC conductance was decreased by 5-FM, but not by NEM, whereas 5-FM had no effect on NEM-labelled VDAC conductance. BMOE caused the formation of dimeric VDAC1, suggesting that one of the two VDAC1 cysteine residues is exposed and available for cross-linking. The results thus suggest that one of the VDAC1 cysteine residues faces the VDAC pore, whereas the second is oriented towards the lipid bilayer. Mutated rat VDAC1 in which the two cysteine residues, Cys127 and Cys232, were replaced by alanine residues showed channel activity like native VDAC1 and, when expressed in cells, was localized to mitochondria. Human VDAC1-shRNA (small hairpin RNA)- or -siRNA (small interfering RNA)-treated cells, expressing low levels of endogenous human VDAC1 together with native or cysteine-less rat VDAC1, undergo apoptosis as induced by overexpression of these VDAC1 or upon treatment with reactive oxygen species-producing agents, H2O2, As2O3 or selenite, suggesting that the two cysteine residues are not required for apoptosis or VDAC1 oligomerization.

scholarly journals KLF4 Acts as a wt-CFTR Suppressor through an AKT-Mediated Pathway

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1607 ◽  
Author(s):  
Luis Sousa ◽  
Ines Pankonien ◽  
Luka A Clarke ◽  
Iris Silva ◽  
Karl Kunzelmann ◽  
...  
Keyword(s):  
Glycogen Synthase ◽  
Anion Channel ◽  
Stem Cell Differentiation ◽  
Epithelial Differentiation ◽  
Negative Regulator ◽  
Main Function ◽  
Serine Threonine Kinase ◽  
Cf Transmembrane Conductance Regulator ◽  
Differentiation And Proliferation ◽  
And Function

Cystic Fibrosis (CF) is caused by >2000 mutations in the CF transmembrane conductance regulator (CFTR) gene, but one mutation—F508del—occurs in ~80% of patients worldwide. Besides its main function as an anion channel, the CFTR protein has been implicated in epithelial differentiation, tissue regeneration, and, when dysfunctional, cancer. However, the mechanisms that regulate such relationships are not fully elucidated. Krüppel-like factors (KLFs) are a family of transcription factors (TFs) playing central roles in development, stem cell differentiation, and proliferation. Herein, we hypothesized that these TFs might have an impact on CFTR expression and function, being its missing link to differentiation. Our results indicate that KLF4 (but not KLF2 nor KLF5) is upregulated in CF vs. non-CF cells and that it negatively regulates wt-CFTR expression and function. Of note, F508del–CFTR expressing cells are insensitive to KLF4 modulation. Next, we investigated which KLF4-related pathways have an effect on CFTR. Our data also show that KLF4 modulates wt-CFTR (but not F508del–CFTR) via both the serine/threonine kinase AKT1 (AKT) and glycogen synthase kinase 3 beta (GSK3β) signaling. While AKT acts positively, GSK3β is a negative regulator of CFTR. This crosstalk between wt-CFTR and KLF4 via AKT/ GSK3β signaling, which is disrupted in CF, constitutes a novel mechanism linking CFTR to the epithelial differentiation.

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