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The Drosophila G protein-coupled receptor, Methuselah, exhibits a promiscuous response to peptides.

ABSTRACT: Methuselah (Mth) is a G protein-coupled receptor (GPCR) associated with longevity in Drosophila melanogaster. Previously, Stunted (Sun) was identified as a peptide agonist of Mth. Here, we identify two additional activators of Mth signaling: Drosophila Sex Peptide (SP) and a novel peptide (Serendipitous Peptide Activator of Mth, SPAM). Minimal functional sequences and key residues were identified from Sun and SPAM by studying truncation and alanine-scanning mutations. These peptide agonists share little sequence homology and illustrate the promiscuity of Mth for activation. mth mutants exhibit no defects in behaviors controlled by SP, casting doubt on the biological significance of Mth activation by any of these agonists, and illustrating the difficulty in applying in vitro studies to their relevance in vivo. Future studies of Mth ligands will help further our understanding of the functional interaction of agonists and GPCRs.

SUBMITTER: Ja WW

PROVIDER: S-EPMC2788275 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature

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The Drosophila G protein-coupled receptor, Methuselah, exhibits a promiscuous response to peptides.

Ja William W WW Carvalho Gil B GB Madrigal Marisol M Roberts Richard W RW Benzer Seymour S

Protein science : a publication of the Protein Society 20091101 11

Methuselah (Mth) is a G protein-coupled receptor (GPCR) associated with longevity in Drosophila melanogaster. Previously, Stunted (Sun) was identified as a peptide agonist of Mth. Here, we identify two additional activators of Mth signaling: Drosophila Sex Peptide (SP) and a novel peptide (Serendipitous Peptide Activator of Mth, SPAM). Minimal functional sequences and key residues were identified from Sun and SPAM by studying truncation and alanine-scanning mutations. These peptide agonists shar ...[more]

PMID: 19672878

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Project description:Transient receptor potential melastatin 3 (TRPM3) is a nonselective cation channel that is inhibited by Gβγ subunits liberated following activation of Gαi/o protein-coupled receptors. Here, we demonstrate that TRPM3 channels are also inhibited by Gβγ released from Gαs and Gαq Activation of the Gs-coupled adenosine 2B receptor and the Gq-coupled muscarinic acetylcholine M1 receptor inhibited the activity of TRPM3 heterologously expressed in HEK293 cells. This inhibition was prevented when the Gβγ sink βARK1-ct (C terminus of β-adrenergic receptor kinase-1) was coexpressed with TRPM3. In neurons isolated from mouse dorsal root ganglion (DRG), native TRPM3 channels were inhibited by activating Gs-coupled prostaglandin-EP2 and Gq-coupled bradykinin B2 (BK2) receptors. The Gi/o inhibitor pertussis toxin and inhibitors of PKA and PKC had no effect on EP2- and BK2-mediated inhibition of TRPM3, demonstrating that the receptors did not act through Gαi/o or through the major protein kinases activated downstream of G-protein-coupled receptor (GPCR) activation. When DRG neurons were dialyzed with GRK2i, which sequesters free Gβγ protein, TRPM3 inhibition by EP2 and BK2 was significantly reduced. Intraplantar injections of EP2 or BK2 agonists inhibited both the nocifensive response evoked by TRPM3 agonists, and the heat hypersensitivity produced by Freund's Complete Adjuvant (FCA). Furthermore, FCA-induced heat hypersensitivity was completely reversed by the selective TRPM3 antagonist ononetin in WT mice and did not develop in Trpm3-/- mice. Our results demonstrate that TRPM3 is subject to promiscuous inhibition by Gβγ protein in heterologous expression systems, primary neurons and in vivo, and suggest a critical role for this ion channel in inflammatory heat hypersensitivity.SIGNIFICANCE STATEMENT The ion channel TRPM3 is widely expressed in the nervous system. Recent studies showed that Gαi/o-coupled GPCRs inhibit TRPM3 through a direct interaction between Gβγ subunits and TRPM3. Since Gβγ proteins can be liberated from other Gα subunits than Gαi/o, we examined whether activation of Gs- and Gq-coupled receptors also influence TRPM3 via Gβγ. Our results demonstrate that activation of Gs- and Gq-coupled GPCRs in recombinant cells and sensory neurons inhibits TRPM3 via Gβγ liberation. We also demonstrated that Gs- and Gq-coupled receptors inhibit TRPM3 in vivo, thereby reducing pain produced by activation of TRPM3, and inflammatory heat hypersensitivity. Our results identify Gβγ inhibition of TRPM3 as an effector mechanism shared by the major Gα subunits.

Dataset Information

The Drosophila G protein-coupled receptor, Methuselah, exhibits a promiscuous response to peptides.

Publications

The Drosophila G protein-coupled receptor, Methuselah, exhibits a promiscuous response to peptides.

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