title: Sphingosine and FTY720 are potent inhibitors of the transient receptor potential melastatin 7 (TRPM7) channels.
abstract: OBJECTIVE
  Transient receptor potential melastatin 7 (TRPM7) is a unique channel kinase which is crucial for various physiological functions. However, the mechanism by which TRPM7 is gated and modulated is not fully understood. To better understand how modulation of TRPM7 may impact biological processes, we investigated if TRPM7 can be regulated by the phospholipids sphingosine (SPH) and sphingosine-1-phosphate (S1P), two potent bioactive sphingolipids that mediate a variety of physiological functions. Moreover, we also tested the effects of the structural analogues of SPH, N,N-dimethyl-D-erythro-sphingosine (DMS), ceramides and FTY720 on TRPM7.
  
  
  METHODS
  HEK293 cells stably expressing TRPM7 were used for whole-cell, single-channel and macropatch current recordings. Cardiac fibroblasts were used for native TRPM7 current recording.
  
  
  RESULTS
  SPH potently inhibited TRPM7 in a concentration-dependent manner, whereas S1P and other ceramides did not produce noticeable effects. DMS also markedly inhibited TRPM7. Moreover, FTY720, an immunosuppressant and the first oral drug for treatment of multiple sclerosis, inhibited TRPM7 with a similar potency to that of SPH. In contrast, FTY720-P has no effect on TRPM7. It appears that SPH and FTY720 inhibit TRPM7 by reducing channel open probability. Furthermore, endogenous TRPM7 in cardiac fibroblasts was markedly inhibited by SPH, DMS and FTY720.
  
  
  CONCLUSIONS
  This is the first study demonstrating that SPH and FTY720 are potent inhibitors of TRPM7. Our results not only provide a new modulation mechanism of TRPM7, but also suggest that TRPM7 may serve as a direct target of SPH and FTY720, thereby mediating S1P-independent physiological/pathological functions of SPH and FTY720.
authors.affiliation: Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, CT 06030, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Qin
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Yue
authors.forename: Baonan
authors.initials: B
authors.lastname: Sun
authors.forename: Wenzhong
authors.initials: W
authors.lastname: Yang
authors.forename: Jia
authors.initials: J
authors.lastname: Xie
authors.forename: Eric
authors.initials: E
authors.lastname: Ni
authors.forename: Yi
authors.initials: Y
authors.lastname: Feng
authors.forename: Rafat
authors.initials: R
authors.lastname: Mahmood
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lixia
authors.initials: L
authors.lastname: Yue
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000068876:Fingolimod Hydrochloride; D057809:HEK293 Cells; D006801:Humans; D007166:Immunosuppressive Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D049990:Membrane Transport Modulators / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010755:Organophosphates / Q000494:pharmacology; D010766:Phosphorylation; D011409:Propylene Glycols / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: C525008:FTY 720P; D007166:Immunosuppressive Agents; D049990:Membrane Transport Modulators; D010755:Organophosphates; D011409:Propylene Glycols; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; D050053:TRPM Cation Channels; C459082:TRPM6 protein, human; C530168:Trpm6 protein, mouse; C421903:Trpm7 protein, mouse; D017346:Protein Serine-Threonine Kinases; C486583:TRPM7 protein, human; D000068876:Fingolimod Hydrochloride; C061800:N,N-dimethylsphingosine; D013110:Sphingosine