Inhibition of Transient Receptor Potential Melastatin 3 ion channels by G-protein βγ subunits.

Doreen Badheka,Aysenur Yazici,Tibor Rohacs,Istvan Borbiro,Yevgen Yudin,Cassandra M Hartle,Tooraj Mirshahi

doi:10.7554/elife.26147

Abstract

Transient receptor potential melastatin 3 (TRPM3) channels are activated by heat, and chemical ligands such as pregnenolone sulphate (PregS) and CIM0216. Here, we show that activation of receptors coupled to heterotrimeric Gi/o proteins inhibits TRPM3 channels. This inhibition was alleviated by co-expression of proteins that bind the βγ subunits of heterotrimeric G-proteins (Gβγ). Co-expression of Gβγ, but not constitutively active Gαi or Gαo, inhibited TRPM3 currents. TRPM3 co-immunoprecipitated with Gβ, and purified Gβγ proteins applied to excised inside-out patches inhibited TRPM3 currents, indicating a direct effect. Baclofen and somatostatin, agonists of Gi-coupled receptors, inhibited Ca2+ signals induced by PregS and CIM0216 in mouse dorsal root ganglion (DRG) neurons. The GABAB receptor agonist baclofen also inhibited inward currents induced by CIM0216 in DRG neurons, and nocifensive responses elicited by this TRPM3 agonist in mice. Our data uncover a novel signaling mechanism regulating TRPM3 channels.

Highlights

Transient receptor potential melastatin 3 (TRPM3) channels are activated by heat (Vriens et al, 2011), and a number of chemical ligands such as pregnenolone sulphate (PregS) (Oberwinkler and Philipp, 2014) and the newly described synthetic agonist CIM0216 (Held et al, 2015)
Activation of heterologously expressed Gq-coupled receptors inhibited TRPM3 via Gbg, but we focused on Gi-coupled receptors here to avoid confounding effects of concurrent phospholipase C (PLC) activation
We found that in dorsal root ganglion (DRG) neurons Ca2+ signals evoked by TRPM3 agonists were inhibited in a subset of cells by activating Gi-coupled receptors with somatostatin, or the GABAB receptor agonist baclofen

Summary

Introduction

Transient receptor potential melastatin 3 (TRPM3) channels are activated by heat (Vriens et al, 2011), and a number of chemical ligands such as pregnenolone sulphate (PregS) (Oberwinkler and Philipp, 2014) and the newly described synthetic agonist CIM0216 (Held et al, 2015). All GIRK channels (Kir3.1–3.4) are activated by cell surface receptors that couple to heterotrimeric Gi/o proteins, via direct binding of Gbg to the channel This effect plays roles in slowing the heart rate by muscarinic stimulation, and in the analgesic effects of opioids (Hibino et al, 2010)

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