title: Cross-reactivity of ryanodine receptors with plasma membrane ion channel modulators.
abstract: Various pharmacological agents designed to modulate plasma membrane ion channels seem to significantly affect intracellular Ca²⁺ signaling when acting on their target receptor. Some agents could also cross-react (modulate channels or receptors beyond their putative target) with intracellular Ca²⁺ transporters. This study investigated the potential of thirty putative modulators of either plasma membrane K⁺, Na⁺, or transient receptor potential (TRP) channels to cross-react with intracellular Ca²⁺ release channels [i.e., ryanodine receptors (RyRs)] from skeletal muscle sarcoplasmic reticulum (SR). Screening for cross-reactivity of these various agents was performed by measuring the rate of spontaneous Ca²⁺ leak or caffeine-induced Ca²⁺ release from SR microsomes. Four of the agents displayed a strong cross-reactivity and were further evaluated with skeletal RyR (RyR1) reconstituted into planar bilayers. 6,12,19,20,25,26-Hexahydro-5,27:13,18:21,24-trietheno-11,7-metheno-7H-dibenzo [b,n][1,5,12,16]tetraazacyclotricosine-5, 13-diium dibromide (UCL 1684; K⁺ channel antagonist) and lamotrigine (Na⁺ channel antagonist) were found to significantly inhibit the RyR1-mediated caffeine-induced Ca²⁺ release. TRP channel agonists anandamide and (-)menthol were found to inhibit and activate RyR1, respectively. High concentrations of nine other agents produced partial inhibition of RyR1-mediated Ca²⁺ release from SR microsomes. Various pharmacological agents, especially TRP modulators, also inhibited a minor RyR1-independent component of the SR Ca²⁺ leak. Overall, ∼43% of the agents selected cross-reacted with RyR1-mediated and/or RyR1-independent Ca²⁺ leak from intracellular stores. Thus, cross-reactivity should be considered when using these classes of pharmacological agents to determine the role of plasmalemmal channels in Ca²⁺ homeostasis.
authors.affiliation: Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois, USA.
authors.forename: Jake T
authors.initials: JT
authors.lastname: Neumann
authors.forename: Julio A
authors.initials: JA
authors.lastname: Copello
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D003429:Cross Reactions; D007473:Ion Channels / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D019837:Ryanodine Receptor Calcium Release Channel