Phospholipid and proton modulation of KirBac1.1 channel acitivity

Summary

Principal Investigator: Decha Enkvetchakul
Abstract: The inward rectifying potassium (Kir) channel family consists of several potassium channels that play a central role in many cell types. These channels are notable for a unique cytoplasmic domain containing putative binding sites for regulatory ligands such as protons and membrane phospholipids. Mutations that alter responsiveness to these ligands can result in disease, e.g. Bartter's syndrome secondary to mutations in Kir1.1 that alter sensitivity to either pH or to phosphatidylinositol bisphosphate (PIP2), resulting in decreased channel activity and derangement of salt transport/excretion in the kidney. Recently, the crystal structure of one member of the prokaryotic protein family, KirBad.1, with significant primary sequence similarities with eukaryotic Kirs, was solved. We have shown that purified KirBad.1 reconstituted in liposomes is a potassium selective channel, regulated by protons and PIP2 with functional characteristics similar to eukaryotic Kirs. The unique ability to examine a pure protein preparation in a fully defined milieu, in combination with the crystal structure, provides a valuable tool in elucidating the structural mechanisms of ligand gating. The overall goal of this proposal is to define structural mechanisms of KirBac1.1 proton and phospholipid gating, using electrophysiological and liposomal assays. Results from this proposal will provide insight into proton and PIP2 gating mechanisms of Kir channels in general, and may lead to therapy of diseases caused by altered ligand regulation of Kir function, such as Bartter's syndrome.
Funding Period: ----------------2006 - ---------------2011-
more information: NIH RePORT

Top Publications

  1. pmc Control of inward rectifier K channel activity by lipid tethering of cytoplasmic domains
    Decha Enkvetchakul
    Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
    J Gen Physiol 130:329-34. 2007
  2. pmc Differential roles of blocking ions in KirBac1.1 tetramer stability
    Shizhen Wang
    Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St Louis, MO 63104, USA
    J Biol Chem 284:2854-60. 2009
  3. pmc KirBac1.1: it's an inward rectifying potassium channel
    Wayland W L Cheng
    Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
    J Gen Physiol 133:295-305. 2009
  4. pmc Direct regulation of prokaryotic Kir channel by cholesterol
    Dev K Singh
    Department of Medicine, University of Illinois, Chicago, Illinois 60612, USA
    J Biol Chem 284:30727-36. 2009
  5. pmc Functional complementation and genetic deletion studies of KirBac channels: activatory mutations highlight gating-sensitive domains
    Jennifer J Paynter
    Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PU, United Kingdom
    J Biol Chem 285:40754-61. 2010
  6. pmc Enantioselective protein-sterol interactions mediate regulation of both prokaryotic and eukaryotic inward rectifier K+ channels by cholesterol
    Nazzareno D'Avanzo
    Department of Cell Biology and Physiology, and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St Louis, Missouri, United States of America
    PLoS ONE 6:e19393. 2011
  7. pmc Cholesterol regulates prokaryotic Kir channel by direct binding to channel protein
    Dev K Singh
    Department of Medicine, University of Illinois, Chicago, IL 60612, USA
    Biochim Biophys Acta 1808:2527-33. 2011
  8. ncbi Structural rearrangements underlying ligand-gating in Kir channels
    Shizhen Wang
    Department of Cell Biology and Physiology and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 425 S Euclid Ave, St Louis, Missouri 63110, USA
    Nat Commun 3:617. 2012

Scientific Experts

  • Colin Nichols
  • Dev K Singh
  • Decha Enkvetchakul
  • Shizhen Wang
  • Nazzareno D'Avanzo
  • Jennifer J Paynter
  • Wayland W L Cheng
  • Sun Joo Lee
  • Sarah Heyman
  • Douglas F Covey
  • Krzysztof Hyrc
  • Wayland Cheng
  • Isabelle Andres-Enguix
  • Philip W Fowler
  • Nigel J Robinson
  • Vassiliy N Bavro
  • Stephen Tottey
  • Yoshio Kusakabe
  • Stephen J Tucker
  • Mark S P Sansom
  • Yewande Alimi
  • Ailing Tong
  • Iana Jeliazkova
  • Jaya Bhattacharyya

Detail Information

Publications8

  1. pmc Control of inward rectifier K channel activity by lipid tethering of cytoplasmic domains
    Decha Enkvetchakul
    Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
    J Gen Physiol 130:329-34. 2007
    ..This study establishes a critical role of the slide-helix in Kir channel gating, and directly demonstrates that physical interaction of soluble domains with the membrane can control ion channel activity...
  2. pmc Differential roles of blocking ions in KirBac1.1 tetramer stability
    Shizhen Wang
    Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, St Louis, MO 63104, USA
    J Biol Chem 284:2854-60. 2009
    ..This stabilization was additive with the effect of Ba(2+), consistent with both ions simultaneously occupying the channel: Ba(2+) at the selectivity filter entrance and Cd(2+) coordinated by I138C side chains in the inner cavity...
  3. pmc KirBac1.1: it's an inward rectifying potassium channel
    Wayland W L Cheng
    Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
    J Gen Physiol 133:295-305. 2009
    ....
  4. pmc Direct regulation of prokaryotic Kir channel by cholesterol
    Dev K Singh
    Department of Medicine, University of Illinois, Chicago, Illinois 60612, USA
    J Biol Chem 284:30727-36. 2009
    ..Taken together, these observations demonstrate that cholesterol suppresses Kir channels in a pure protein-lipid environment and suggest that the interaction is direct and specific...
  5. pmc Functional complementation and genetic deletion studies of KirBac channels: activatory mutations highlight gating-sensitive domains
    Jennifer J Paynter
    Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PU, United Kingdom
    J Biol Chem 285:40754-61. 2010
    ..In particular, the mutations identified in TM2 favor a model of KirBac channel gating in which opening of the pore at the helix-bundle crossing plays a far more important role than has recently been proposed...
  6. pmc Enantioselective protein-sterol interactions mediate regulation of both prokaryotic and eukaryotic inward rectifier K+ channels by cholesterol
    Nazzareno D'Avanzo
    Department of Cell Biology and Physiology, and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St Louis, Missouri, United States of America
    PLoS ONE 6:e19393. 2011
    ..These data indicate that cholesterol regulates Kir channels through direct protein-sterol interactions likely taking advantage of an evolutionarily conserved binding pocket...
  7. pmc Cholesterol regulates prokaryotic Kir channel by direct binding to channel protein
    Dev K Singh
    Department of Medicine, University of Illinois, Chicago, IL 60612, USA
    Biochim Biophys Acta 1808:2527-33. 2011
    ..Collectively, results from this study indicate that cholesterol-induced suppression of KirBac1.1 activity is mediated by direct interaction between cholesterol and the channel protein...
  8. ncbi Structural rearrangements underlying ligand-gating in Kir channels
    Shizhen Wang
    Department of Cell Biology and Physiology and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 425 S Euclid Ave, St Louis, Missouri 63110, USA
    Nat Commun 3:617. 2012
    ..The observed ligand-dependent conformational changes in KirBac1.1 provide a general model for ligand-induced Kir channel gating at the molecular level...