title: Tanshinone II-A sodium sulfonate (DS-201) enhances human BKCa channel activity by selectively targeting the pore-forming α subunit.
abstract: OBJECTIVE
  Tanshinone II-A sodium sulfonate (DS-201), a water-soluble derivative of Tanshinone II-A, has been found to induce vascular relaxation and activate BKCa channels. The aim of this study was to explore the mechanisms underlying the action of DS-201 on BKCa channels.
  
  
  METHODS
  Human BKCa channels containing α subunit alone or α plus β1 subunits were expressed in HEK293 cells. BKCa currents were recorded from the cells using patch-clamp technique. The expression and trafficking of BKCa subunits in HEK293 cells or vascular smooth muscle cells (VSMCs) were detected by Western blotting, flow cytometry and confocal microscopy.
  
  
  RESULTS
  DS-201 (40-160 μmol/L) concentration-dependently increased the total open probability of BKCa channels in HEK293 cells, associated with enhancements of Ca(2+) and voltage dependence as well as a delay in deactivation. Coexpression of β1 subunit did not affect the action of DS-201: the values of EC50 for BKCa channels containing α subunit alone and α plus β1 subunit were 66.6±1.5 and 62.0±1.1 μmol/L, respectively. In both HEK293 cells and VSMCs, DS-201 (80 μmol/L) markedly increased the expression of α subunit without affecting β1 subunit. In HEK293 cells, DS-201 enriched the membranous level of α subunit, likely by accelerating the trafficking and suppressing the internalization of α subunit. In both HEK293 cells and VSMCs, DS-201 (≥320 μmol/L) induced significant cytotoxicity.
  
  
  CONCLUSIONS
  DS-201 selectively targets the pore-forming α subunit of human BKCa channels, thus enhancing the channel activities and increasing the subunit expression and trafficking, whereas the β1 subunit does not contribute to the action of DS-201.
authors.affiliation: 1] Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China [2] Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Luzhou Medical College, Luzhou 646000, China.
authors.forename: Xiao-qiu
authors.initials: XQ
authors.lastname: Tan
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China.
authors.forename: Xiu-li
authors.initials: XL
authors.lastname: Cheng
authors.affiliation: Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Luzhou Medical College, Luzhou 646000, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yan
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China.
authors.forename: Jing-li
authors.initials: JL
authors.lastname: Gu
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Luzhou Medical College, Luzhou 646000, China.
authors.forename: Xiao-rong
authors.initials: XR
authors.lastname: Zeng
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing 100005, China.
authors.forename: Ji-min
authors.initials: JM
authors.lastname: Cao
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D007700:Kinetics; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008564:Membrane Potentials; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D010616:Phenanthrenes / Q000494:pharmacology* / Q000633:toxicity; D021381:Protein Transport; D051381:Rats; D014162:Transfection; D014665:Vasodilator Agents / Q000494:pharmacology* / Q000633:toxicity
chemical_list: C494841:KCNMA1 protein, human; C531905:KCNMB1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D010616:Phenanthrenes; D014665:Vasodilator Agents; C024894:tanshinone II A sodium sulfonate; D002118:Calcium