title: Use-dependent inhibition of the skeletal muscle ryanodine receptor by the suramin analogue NF676.
abstract: The skeletal muscle Ca2+ release channel, the ryanodine receptor, is activated by the trypanocidal drug suramin via the calmodulin-binding site. As calmodulin activates and inhibits the ryanodine receptor depending on whether Ca2+ is absent or present, suramin analogues were screened for inhibition of the ryanodine receptor. Up to 300 microM, the novel suramin analogue, 4,4'-(carbonyl-bis(imino-4,1-phenylene-(2,5-benzimidazolylene)carbonylimino))-bis-benzenesulfonic acid disodium salt (NF676) was not able to significantly inhibit the basal [3H]ryanodine binding. However, kinetic analysis of the high affinity [3H]ryanodine binding elucidates a time-dependent increment of inhibition by NF676, which is indicative for an open channel blocker. Moreover, the ryanodine receptor was much more sensitive towards inhibition by NF676 when preactivated with caffeine or the nonhydrolysable ATP analogue, adenylyl-imidodiphosphate. Nonetheless, the suramin activated ryanodine receptor was not susceptible towards high-affinity NF676 inhibition, indicating an allosteric hindrance between the binding sites of suramin and NF676. In the line of this finding, NF676 per se was not capable to elute the purified ryanodine receptor from a calmodulin-Sepharose, but it prevented the elution by suramin. Other than suramin, NF676 did not inhibit the Ca2+ ATPase of the sarcoplasmic reticulum. However, suramin-induced Ca2+ release from sarcoplasmic reticulum was completely abrogated by preincubation with NF676. Taken together, we conclude from these data that NF676 represents a novel lead compound as a potent use-dependent blocker of the skeletal muscle ryanodine receptor via an allosteric interaction with the suramin-binding site.
authors.affiliation: Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria.
authors.forename: Ilse
authors.initials: I
authors.lastname: Wolner
authors.forename: Matthias U
authors.initials: MU
authors.lastname: Kassack
authors.forename: Heiko
authors.initials: H
authors.lastname: Ullmann
authors.forename: Anton
authors.initials: A
authors.lastname: Karel
authors.forename: Martin
authors.initials: M
authors.lastname: Hohenegger
mesh_terms: D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000494:Allosteric Regulation; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000494:pharmacology*; D020013:Calcium Signaling / Q000187:drug effects*; D002147:Calmodulin / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D011817:Rabbits; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D013498:Suramin / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D002147:Calmodulin; C515094:NF676 compound; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D000266:Adenylyl Imidodiphosphate; D002110:Caffeine; D013498:Suramin; D002118:Calcium