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Inverse agonistic action of 3-iodothyronamine at the human trace amine-associated receptor 5.

Dinter J, Mühlhaus J, Wienchol CL, Yi CX, Nürnberg D, Morin S, Grüters A, Köhrle J, Schöneberg T, Tschöp M, Krude H, Kleinau G, Biebermann H - PLoS ONE (2015)

Bottom Line: In contrast to mTaar5, 3-T1AM application at hTAAR5 resulted in significant reduction in basal IP3 formation and MAP kinase signaling.In conclusion, our data suggest that the human TAAR5 is a target for 3-T1AM, exhibiting inhibitory effects on IP3 formation and MAP kinase signaling pathways, but does not mediate Gs signaling effects as observed for TAAR1.In consequence, 3-T1AM-mediated effects may differ between rodents and humans.

View Article: PubMed Central - PubMed

Affiliation: Institut für Experimentelle Pädiatrische Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany.

ABSTRACT

Objective: Application of 3-iodothyronamine (3-T1AM) results in decreased body temperature and body weight in rodents. The trace amine-associated receptor (TAAR) 1, a family A G protein-coupled receptor, is a target of 3-T1AM. However, 3-T1AM effects still persist in mTaar1 knockout mice, which suggest so far unknown further receptor targets that are of physiological relevance. TAAR5 is a highly conserved TAAR subtype among mammals and we here tested TAAR5 as a potential 3-T1AM target. First, we investigated mouse Taar5 (mTaar5) expression in several brain regions of the mouse in comparison to mTaar1. Secondly, to unravel the full spectrum of signaling capacities, we examined the distinct Gs-, Gi/o-, G12/13-, Gq/11- and MAP kinase-mediated signaling pathways of mouse and human TAAR5 under ligand-independent conditions and after application of 3-T1AM. We found overlapping localization of mTaar1 and mTaar5 in the amygdala and ventromedial hypothalamus of the mouse brain. Second, the murine and human TAAR5 (hTAAR5) display significant basal activity in the Gq/11 pathway but show differences in the basal activity in Gs and MAP kinase signaling. In contrast to mTaar5, 3-T1AM application at hTAAR5 resulted in significant reduction in basal IP3 formation and MAP kinase signaling. In conclusion, our data suggest that the human TAAR5 is a target for 3-T1AM, exhibiting inhibitory effects on IP3 formation and MAP kinase signaling pathways, but does not mediate Gs signaling effects as observed for TAAR1. This study also indicates differences between TAAR5 orthologs with respect to their signaling profile. In consequence, 3-T1AM-mediated effects may differ between rodents and humans.

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Structural homology model of hTAAR5 with highlighted amino acid positions that were substituted to design chimeric human-murine receptors.The design of a structural homology model of hTAAR5 was already reported [43]. We used this 3D information to visualize the amino acids differing between human and mice TAAR5 in accordance to observed differences in the sequence of both species (Fig. 4) with a focus on residues that are in spatial proximity to the extracellular ligand binding part or the intracellular effector binding region. The human wild type amino acids (shown by atom spheres) and the equivalent residues in mouse are provided as mutations in the labels. H1–7 = seven-transmembrane helices 1–7; H8 = eighth intracellular helix; ECL = extracellular loop, ICL = intracellular loop, Ntt = N-terminal tail; Ctt = C-terminal tail.
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pone.0117774.g005: Structural homology model of hTAAR5 with highlighted amino acid positions that were substituted to design chimeric human-murine receptors.The design of a structural homology model of hTAAR5 was already reported [43]. We used this 3D information to visualize the amino acids differing between human and mice TAAR5 in accordance to observed differences in the sequence of both species (Fig. 4) with a focus on residues that are in spatial proximity to the extracellular ligand binding part or the intracellular effector binding region. The human wild type amino acids (shown by atom spheres) and the equivalent residues in mouse are provided as mutations in the labels. H1–7 = seven-transmembrane helices 1–7; H8 = eighth intracellular helix; ECL = extracellular loop, ICL = intracellular loop, Ntt = N-terminal tail; Ctt = C-terminal tail.

Mentions: To unravel the molecular details of these species-specific differences of TAAR function, we generated chimeric receptors based on differences in the amino acid sequence of both receptors. For this purpose an amino acid sequence alignment was used to predict residues that are potentially involved in ligand binding and signaling (for detailed substitutions see Table 2, and Figs. 4, 5). These specific residues were substituted in three multiple combinations from mTaar5 into corresponding positions of hTAAR5. In total, six single mutations were substituted at corresponding positions, three located in the extracellular loop ECL2 and three in the intracellular loop ICL3 (Table 2 and Fig. 5).


Inverse agonistic action of 3-iodothyronamine at the human trace amine-associated receptor 5.

Dinter J, Mühlhaus J, Wienchol CL, Yi CX, Nürnberg D, Morin S, Grüters A, Köhrle J, Schöneberg T, Tschöp M, Krude H, Kleinau G, Biebermann H - PLoS ONE (2015)

Structural homology model of hTAAR5 with highlighted amino acid positions that were substituted to design chimeric human-murine receptors.The design of a structural homology model of hTAAR5 was already reported [43]. We used this 3D information to visualize the amino acids differing between human and mice TAAR5 in accordance to observed differences in the sequence of both species (Fig. 4) with a focus on residues that are in spatial proximity to the extracellular ligand binding part or the intracellular effector binding region. The human wild type amino acids (shown by atom spheres) and the equivalent residues in mouse are provided as mutations in the labels. H1–7 = seven-transmembrane helices 1–7; H8 = eighth intracellular helix; ECL = extracellular loop, ICL = intracellular loop, Ntt = N-terminal tail; Ctt = C-terminal tail.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4382497&req=5

pone.0117774.g005: Structural homology model of hTAAR5 with highlighted amino acid positions that were substituted to design chimeric human-murine receptors.The design of a structural homology model of hTAAR5 was already reported [43]. We used this 3D information to visualize the amino acids differing between human and mice TAAR5 in accordance to observed differences in the sequence of both species (Fig. 4) with a focus on residues that are in spatial proximity to the extracellular ligand binding part or the intracellular effector binding region. The human wild type amino acids (shown by atom spheres) and the equivalent residues in mouse are provided as mutations in the labels. H1–7 = seven-transmembrane helices 1–7; H8 = eighth intracellular helix; ECL = extracellular loop, ICL = intracellular loop, Ntt = N-terminal tail; Ctt = C-terminal tail.
Mentions: To unravel the molecular details of these species-specific differences of TAAR function, we generated chimeric receptors based on differences in the amino acid sequence of both receptors. For this purpose an amino acid sequence alignment was used to predict residues that are potentially involved in ligand binding and signaling (for detailed substitutions see Table 2, and Figs. 4, 5). These specific residues were substituted in three multiple combinations from mTaar5 into corresponding positions of hTAAR5. In total, six single mutations were substituted at corresponding positions, three located in the extracellular loop ECL2 and three in the intracellular loop ICL3 (Table 2 and Fig. 5).

Bottom Line: In contrast to mTaar5, 3-T1AM application at hTAAR5 resulted in significant reduction in basal IP3 formation and MAP kinase signaling.In conclusion, our data suggest that the human TAAR5 is a target for 3-T1AM, exhibiting inhibitory effects on IP3 formation and MAP kinase signaling pathways, but does not mediate Gs signaling effects as observed for TAAR1.In consequence, 3-T1AM-mediated effects may differ between rodents and humans.

View Article: PubMed Central - PubMed

Affiliation: Institut für Experimentelle Pädiatrische Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany.

ABSTRACT

Objective: Application of 3-iodothyronamine (3-T1AM) results in decreased body temperature and body weight in rodents. The trace amine-associated receptor (TAAR) 1, a family A G protein-coupled receptor, is a target of 3-T1AM. However, 3-T1AM effects still persist in mTaar1 knockout mice, which suggest so far unknown further receptor targets that are of physiological relevance. TAAR5 is a highly conserved TAAR subtype among mammals and we here tested TAAR5 as a potential 3-T1AM target. First, we investigated mouse Taar5 (mTaar5) expression in several brain regions of the mouse in comparison to mTaar1. Secondly, to unravel the full spectrum of signaling capacities, we examined the distinct Gs-, Gi/o-, G12/13-, Gq/11- and MAP kinase-mediated signaling pathways of mouse and human TAAR5 under ligand-independent conditions and after application of 3-T1AM. We found overlapping localization of mTaar1 and mTaar5 in the amygdala and ventromedial hypothalamus of the mouse brain. Second, the murine and human TAAR5 (hTAAR5) display significant basal activity in the Gq/11 pathway but show differences in the basal activity in Gs and MAP kinase signaling. In contrast to mTaar5, 3-T1AM application at hTAAR5 resulted in significant reduction in basal IP3 formation and MAP kinase signaling. In conclusion, our data suggest that the human TAAR5 is a target for 3-T1AM, exhibiting inhibitory effects on IP3 formation and MAP kinase signaling pathways, but does not mediate Gs signaling effects as observed for TAAR1. This study also indicates differences between TAAR5 orthologs with respect to their signaling profile. In consequence, 3-T1AM-mediated effects may differ between rodents and humans.

Show MeSH
Related in: MedlinePlus