title: Triphenylphosphine oxide is a potent and selective inhibitor of the transient receptor potential melastatin-5 ion channel.
abstract: Transient receptor potential melastatin-5 (TRPM5) is a calcium-gated monovalent cation channel expressed in highly specialized cells of the taste bud and gastrointestinal tract, as well as in pancreatic β-cells. Well established as a critical signaling protein for G protein-coupled receptor-mediated taste pathways, TRPM5 also has recently been implicated as a regulator of incretin and insulin secretion. To date, no inhibitors of practical use have been described that could facilitate investigation of TRPM5 functions in taste or secretion of metabolic hormones. Using recombinant TRPM5-expressing cells in a fluorescence imaging plate reader-based membrane potential assay, we identified triphenylphosphine oxide (TPPO) as a selective and potent inhibitor of TRPM5. TPPO inhibited both human (IC₅₀ = 12 μM) and murine TRPM5 (IC₅₀ = 30 μM) heterologously expressed in HEK293 cells, but had no effect (up to 100 μM) on the membrane potential responses of TRPA1, TRPV1, or TRPM4b. TPPO also inhibited a calcium-gated TRPM5-dependent conductance in taste cells isolated from the tongues of transgenic TRPM5(+/)⁻ mice. In contrast, TPP had no effect on TRPM5 responses, indicating a strict requirement of the oxygen atom for activity. Sixteen additional TPPO derivatives also inhibited TRPM5 but none more potently than TPPO. Structure-activity relationship of tested compounds was used for molecular modeling-based analysis to clarify the positive and negative structural contributions to the potency of TPPO and its derivatives. TPPO is the most potent TRPM5 inhibitor described to date and is the first demonstrated to exhibit selectivity over other channels.
authors.affiliation: Redpoint Bio Inc., Ewing, New Jersey 08628, USA. kpalmer@redpointbio.com
authors.forename: R Kyle
authors.initials: RK
authors.lastname: Palmer
authors.forename: Karnail
authors.initials: K
authors.lastname: Atwal
authors.forename: Ivona
authors.initials: I
authors.lastname: Bakaj
authors.forename: Stacy
authors.initials: S
authors.lastname: Carlucci-Derbyshire
authors.forename: M Tulu
authors.initials: MT
authors.lastname: Buber
authors.forename: Rok
authors.initials: R
authors.lastname: Cerne
authors.forename: Rosa Y
authors.initials: RY
authors.lastname: Cortés
authors.forename: Heather R
authors.initials: HR
authors.lastname: Devantier
authors.forename: Vincent
authors.initials: V
authors.lastname: Jorgensen
authors.forename: Aaron
authors.initials: A
authors.lastname: Pawlyk
authors.forename: S Paul
authors.initials: SP
authors.lastname: Lee
authors.forename: Dennis G
authors.initials: DG
authors.lastname: Sprous
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Robert
authors.initials: R
authors.lastname: Bryant
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008163:Luminescent Measurements; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008822:Mice, Transgenic; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D013329:Structure-Activity Relationship; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors* / Q000235:genetics; D013649:Taste; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology
chemical_list: D009943:Organophosphorus Compounds; D050053:TRPM Cation Channels; C404409:TRPM5 protein, human; C498617:Trpm5 protein, mouse; D002118:Calcium; C063888:triphenylphosphine oxide