title: Natural and synthetic modulators of SK (K(ca)2) potassium channels inhibit magnesium-dependent activity of the kinase-coupled cation channel TRPM7.
abstract: OBJECTIVE
  Transient receptor potential cation channel subfamily M member 7 (TRPM7) is a bifunctional protein comprising a TRP ion channel segment linked to an α-type protein kinase domain. TRPM7 is essential for proliferation and cell growth. Up-regulation of TRPM7 function is involved in anoxic neuronal death, cardiac fibrosis and tumour cell proliferation. The goal of this work was to identify non-toxic inhibitors of the TRPM7 channel and to assess the effect of blocking endogenous TRPM7 currents on the phenotype of living cells.
  
  
  METHODS
  We developed an aequorin bioluminescence-based assay of TRPM7 channel activity and performed a hypothesis-driven screen for inhibitors of the channel. The candidates identified were further assessed electrophysiologically and in cell biological experiments.
  
  
  RESULTS
  TRPM7 currents were inhibited by modulators of small conductance Ca²⁺ -activated K⁺ channels (K(Ca)2.1-2.3; SK) channels, including the antimalarial plant alkaloid quinine, CyPPA, dequalinium, NS8593, SKA31 and UCL 1684. The most potent compound NS8593 (IC₅₀ 1.6 µM) specifically targeted TRPM7 as compared with other TRP channels, interfered with Mg²⁺ -dependent regulation of TRPM7 channel and inhibited the motility of cultured cells. NS8593 exhibited full and reversible block of native TRPM7-like currents in HEK 293 cells, freshly isolated smooth muscle cells, primary podocytes and ventricular myocytes.
  
  
  CONCLUSIONS
  This study reveals a tight overlap in the pharmacological profiles of TRPM7 and K(Ca)2.1-2.3 channels. NS8593 acts as a negative gating modulator of TRPM7 and is well-suited to study functional features and cellular roles of endogenous TRPM7.
authors.affiliation: Walther-Straub-Institute of Pharmacology and Toxicology, University of Munich, Munich, Germany. vladimir.chubanov@lrz.uni-muenchen.de
authors.forename: V
authors.initials: V
authors.lastname: Chubanov
authors.forename: M
authors.initials: M
authors.lastname: Mederos y Schnitzler
authors.forename: M
authors.initials: M
authors.lastname: Meißner
authors.forename: S
authors.initials: S
authors.lastname: Schäfer
authors.forename: K
authors.initials: K
authors.lastname: Abstiens
authors.forename: T
authors.initials: T
authors.lastname: Hofmann
authors.forename: T
authors.initials: T
authors.lastname: Gudermann
mesh_terms: D015057:1-Naphthylamine / Q000009:adverse effects / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D055808:Drug Discovery; D057809:HEK293 Cells; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D049990:Membrane Transport Modulators / Q000009:adverse effects / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D050199:Podocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000009:adverse effects / Q000494:pharmacology*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors*; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: C515166:(R)-N-(benzimidazol-2-yl)-1,2,3,4-tetrahydro-1-naphthylamine; D049990:Membrane Transport Modulators; D026902:Potassium Channel Blockers; D020033:Protein Isoforms; D011994:Recombinant Proteins; D051640:Small-Conductance Calcium-Activated Potassium Channels; D050053:TRPM Cation Channels; D015057:1-Naphthylamine; C421903:Trpm7 protein, mouse; D017346:Protein Serine-Threonine Kinases; C486583:TRPM7 protein, human; D008274:Magnesium