title: CCDI: a new ligand that modulates mammalian type 1 ryanodine receptor (RyR1).
abstract: OBJECTIVE
  Ryanodine receptors (RyRs) are Ca(2+)-release channels on the sarco(endo)plasmic reticulum that modulate a wide array of physiological functions. Three RyR isoforms are present in cells: RyR1, RyR2 and RyR3. To date, there are no reports on ligands that modulate RyR in an isoform-selective manner. Such ligands are not only valuable research tools, but could serve as intermediates for development of therapeutics.
  
  
  METHODS
  Pyrrole-2-carboxylic acid and 1,3-dicyclohexylcarbodiimide were allowed to react in carbon tetrachloride for 24 h at low temperatures and pressures. The chemical structures of the two products isolated were elucidated using NMR spectrometry, mass spectrometry and elemental analyses. [(3) H]-ryanodine binding, lipid bilayer and time-lapsed confocal imaging were used to determine their effects on RyR isoforms.
  
  
  RESULTS
  The major product, 2-cyclohexyl-3-cyclohexylimino-2, 3, dihydro-pyrrolo[1,2-c]imidazol-1-one (CCDI) dose-dependently potentiated Ca(2+)-dependent binding of [(3)H]-ryanodine to RyR1, with no significant effects on [(3)H]-ryanodine binding to RyR2 or RyR3. CCDI also reversibly increased the open probability (P(o)) of RyR1 with minimal effects on RyR2 and RyR3. CCDI induced Ca(2+) transients in C2C12 skeletal myotubes, but not in rat ventricular myocytes. This effect was blocked by pretreating cells with ryanodine. The minor product 2-cyclohexyl-pyrrolo[1,2-c]imidazole-1,3-dione had no effect on either [(3)H]-ryanodine binding or P(o) of RyR1, RyR2 and RyR3.
  
  
  CONCLUSIONS
  A new ligand that preferentially modulates RyR1 was identified. In addition to being an important research tool, the pharmacophore of this small molecule could serve as a template for the synthesis of other isoform-selective modulators of RyRs.
authors.affiliation: Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Chengju
authors.initials: C
authors.lastname: Tian
authors.forename: Chun Hong
authors.initials: CH
authors.lastname: Shao
authors.forename: Christina
authors.initials: C
authors.lastname: Padanilam
authors.forename: Edward
authors.initials: E
authors.lastname: Ezell
authors.forename: Jaipaul
authors.initials: J
authors.lastname: Singh
authors.forename: Shelby
authors.initials: S
authors.lastname: Kutty
authors.forename: Keshore R
authors.initials: KR
authors.lastname: Bidasee
mesh_terms: D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D057809:HEK293 Cells; D006801:Humans; D007097:Imines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D008024:Ligands; D008297:Male; D051379:Mice; D015394:Molecular Structure; D011817:Rabbits; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: C000597214:2-cyclohexyl-3-cyclohexylimino-2,3-dihydropyrrolo(1,2-c)imidazol-1-one; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002121:Calcium Channel Blockers; D007097:Imines; D008024:Ligands; D019837:Ryanodine Receptor Calcium Release Channel
keywords: 2-cyclohexyl-3-cyclohexylimino-2,3-dihydro-pyrrolo[1,2-c]imidazol-1-one (CCDI); isoforms-selective; ryanodine receptor; sarcoplasmic reticulum