G protein βγ subunits inhibit TRPM3 ion channels in sensory neurons

2020

Preprint

Transient Receptor Potential Melastatin 3 (TRPM3) is a Ca 2+ permeable non-selective cation channel activated by heat and chemical agonists such as pregnenolone sulfate and CIM0216. TRPM3 mutations in humans were recently reported to be associated with intellectual disability and epilepsy; the functional effects of those mutations however were not reported. Here we show that both disease-associated mutations of TRPM3 render the channel overactive, but likely via different mechanisms. The Val to Met substitution in the S4-S5 loop induced a larger increase in basal activity and agonist sensitivity at room temperature than the Pro to Gln substitution in the extracellular segment of S6. In contrast, heat activation was increased more by the S6 mutant than by the S4-S5 segment mutant. Both mutants were inhibited by the TRPM3 antagonist primidone, suggesting a potential therapeutic intervention to treat this disease.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Disease-associated mutations in TRPM3 render the channel overactive via two distinct mechanisms

Zhao

2020

Preprint

“…G βγ subunits have multiple targets including G‐protein‐coupled inwardly rectifying potassium channels (K ir 3; Logothetis, Kurachi, Galper, Neer, & Clapham, ) and voltage‐gated Ca 2+ channels (N‐type and P/Q‐type; Currie, ). A recently described target of G i signalling is the TRPM3 ion channel, which is robustly inhibited by G βγ subunits (Badheka et al, ; Dembla et al, ; Quallo et al, ). Non‐ion channel targets of G βγ include phosphoinositide 3‐kinase‐γ (PI3Kγ) and MAPKs (Clapham & Neer, ; Khan et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…We and others recently identified transient receptor potential melastatin 3 (TRPM3) as a novel ion channel target of G βγ subunits; these channels are robustly inhibited by activation of a variety of G αi -coupled receptors, including μ receptors in dorsal root ganglion (DRG) neurons, as well as in expression systems (Badheka et al, 2017;Dembla et al, 2017;Quallo, Alkhatib, Gentry, Andersson, & Bevan, 2017). TRPM3 is a heat-activated Ca 2+ permeable nonselective cation channel; its genetic deletion in mice results in reduced heat sensitivity (Vandewauw et al, 2018;Vriens et al, 2011).…”

mentioning

confidence: 99%

The G‐protein‐biased agents PZM21 and TRV130 are partial agonists of μ‐opioid receptor‐mediated signalling to ion channels

2019

British J Pharmacology

Background and Purpose Opioids remain the most efficient medications against severe pain; they act on receptors that couple to heterotrimeric G‐proteins in the Gαi/o family. Opioids exert many of their acute effects through modulating ion channels via Gβγ subunits. Many of their side effects are attributed to β‐arrestin recruitment. Several biased agonists that do not recruit β‐arrestins, but activate G‐protein‐dependent pathways, have recently been developed. While these compounds have been proposed to be full agonists of G‐protein signalling in several high throughput pharmacological assays, their effects were not studied on ion channel targets. Experimental Approach Here, we used patch‐clamp electrophysiology and Ca2+ imaging to test the effects of TRV130, PZM21, and herkinorin, three G‐protein‐biased agonists of μ‐opioid receptors, on ion channel targets of Gαi/o/Gβγ signalling. We also studied G‐protein dissociation using a FRET‐based assay. Key Results All three biased agonists induced smaller activation of G‐protein‐coupled inwardly rectifying K+ channels (Kir3.2) and smaller inhibition of transient receptor potential melastatin (TRPM3) channels than the full μ receptor agonist DAMGO. Co‐application of TRV130 or PZM21, but not herkinorin, alleviated the effects of DAMGO on both channels. PZM21 and TRV130 also decreased the effect of morphine on Kir3.2 channels. The CaV2.2 channel was also inhibited less by PZM21 and TRV130 than by DAMGO. We also found that TRV130, PZM21, and herkinorin were less effective than DAMGO at inducing dissociation of the Gαi/Gβγ complex. Conclusion and Implications TRV130, PZM21, and potentially herkinorin are partial agonists of μ receptors.

“…We and others recently identified Transient Receptor Potential Melastatin 3 (TRPM3) as a novel ion channel target of G βγ subunits; these channels are robustly inhibited by activation of a variety of G αi -coupled receptors, including μOR in dorsal root ganglion (DRG) neurons, as well as in expression systems (Badheka et al, 2017;Dembla et al, 2017;Quallo et al, 2017). TRPM3 is a heat-activated Ca 2+ permeable non-selective cation channel; its genetic deletion in mice results in reduced heat sensitivity (Vriens et al, 2011;Vandewauw et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

The G protein-biased PZM21 and TRV130 act as partial agonists of μ-opioid receptors signaling to ion channel targets

2018

Preprint

Opioids exert many of their acute effects through modulating ion channels via G βγ subunits. Some of their side effects are attributed to β-arrestin recruitment, and several biased agonists that do not activate this pathway have been developed recently. Here we tested the effects of TRV130, PZM21 and herkinorin, three G-protein biased agonists of μ-opioid receptors (μOR), on ion channel targets. Compared to the full μOR agonist DAMGO, all three biased agonists induced smaller activation of G proteincoupled inwardly rectifying potassium channels (GIRK2), and smaller inhibition of Transient Receptor Potential Melastatin (TRPM3) channels. Furthermore, co-application of TRV130 or PZM21, but not herkinorin reduced the effects of DAMGO on both ion channels. Ca V 2.2 was also inhibited less by PZM21 and TRV130 than by DAMGO.TRV130, PZM21 and herkinorin were also less effective than DAMGO in inducing dissociation of the G αi /G βγ complex. We conclude that TRV130, PZM21 are partial agonists of μOR.