title: Structural determinants of 4-chloro-m-cresol required for activation of ryanodine receptor type 1.
abstract: 4-Chloro-m-cresol (4-CmC) is a clinically relevant activator of the intracellular Ca2+ release channel, the ryanodine receptor isoform 1 (RyR1). In this study, the chemical moieties on the 4-CmC molecule required for its activation of RyR1 were determined using structure-activity relationship analysis with a set of commercially available 4-CmC analogs. Separate compounds each lacking one of the three functional groups of 4-CmC (1-hydroxyl, 3-methyl, or 4-chloro) were poor activators of RyR1. Substitution of different chemical groups for the 1-hydroxyl of 4-CmC resulted in compounds that were poor activators of RyR1, suggesting that the hydroxyl group is preferred at this position. Substitution of hydrophobic groups at the 3-position enhanced bioactivity of the compound relative to 4-CmC, whereas substitution with hydrophilic groups abolished bioactivity. Likewise, 4-CmC analogs with hydrophobic groups substituted into the 4-position enhanced bioactivity, whereas hydrophilic or charged groups diminished bioactivity. 4-CmC analogs containing a single hydrophobic group at either the 3- or 4-position as well as 3,5-disubstituted or 3,4,5-trisubstituted phenols were also effective activators of RyR1. These results indicate that the 1-hydroxyl group of 4-CmC is required for activation of RyR1 and that hydrophobic groups at the 3,4- and 5-positions are preferred. These findings suggest that the 4-CmC binding site on RyR1 most likely consists of a hydrophilic region to interact with the 1-hydroxyl as well as a hydrophobic region(s) to interact with chemical groups at the 3- and/or 4-positions of 4-CmC.
authors.affiliation: Absolute Science Inc., Cambridge, Massachusetts, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Jacobson
authors.forename: Scott T
authors.initials: ST
authors.lastname: Moe
authors.forename: P D
authors.initials: PD
authors.lastname: Allen
authors.forename: James D
authors.initials: JD
authors.lastname: Fessenden
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D003408:Cresols / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011869:Radioligand Assay; D012433:Ryanodine / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014316:Tritium
chemical_list: D003408:Cresols; D019837:Ryanodine Receptor Calcium Release Channel; D014316:Tritium; D012433:Ryanodine; C006984:chlorocresol