Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 10, 1567
eCollection

GTL-1, a Calcium Activated TRPM Channel, Enhances Nociception

Affiliations

GTL-1, a Calcium Activated TRPM Channel, Enhances Nociception

Emiliano Cohen et al. Front Pharmacol.

Abstract

C. elegans PVD neurons are conserved for morphology, function and molecular determinants with mammalian polymodal nociceptors. Functions of polymodal nociceptors require activities of multiple ion channels and receptors including members of the TRP family. GTL-1, a member of the TRPM subclass of TRP channels, was previously shown to amplify PVD-mediated responses to optogenetic stimuli. Here we characterize effects of GTL-1 on PVD-mediated behavioral responses to noxious stimuli. We show that GTL-1 is required within PVD for the immediate and enduring response to thermal (cold) stimuli. But, find no significant reduction in percent animals responding to single or to repeated noxious mechanical stimuli. Nevertheless, PVD specific knockdown of gtl-1expression reduces the magnitude of responses to noxious mechanical stimuli. To understand GTL-1's mechanism of action we expressed it in HEK293 cells. Our results show GTL-1-dependent currents induced by activation of a Gαq-coupled Designer Receptor Exclusively Activated by Designer Drugs (DREADD). In addition, using excised patches we show that GTL-1 can be activated by internal calcium. Our results are consistent with indirect, calcium dependent, activation of GTL-1 by noxious stimuli. This mechanism explains the GTL-1-dependent amplification of responses to multiple stimuli optogenetic and sensory in PVD.

Keywords: C. elegans; TRPM; behavior; calcium; nociceptors.

Figures

Figure 1
Figure 1
GTL-1 is required within PVD for the effects of temperature on locomotion. Effects of temperature on locomotion were compared between wild type (N2), gtl-1(lf), and trpa-1(lf) animals (A–C) and between wild-type (N2) animals and animals expressing gtl-1dsRNA specifically in PVD (gtl-1;dsRNAPVD) (D–F), at 20°C (black bars) or 15°C (grey bars). Number of animals, 24, 36, 29, 22, 18, and 15 (A–C) and 24, 36, 13, and 12 (D–F) in order of appearance. Significant differences for the same strain at 15°C relative to 20°C were examined using two-way ANOVA with bonferroni’s multiple comparisons correction (*-p < 0.05, ***-p < 0.01, ****-p < 0.0001). Temperature contributes significantly to the variance in A (p < 0.0001), B (p = 0.0018), C (p = 0.0112), D (p < 0.0001) and E (p = 0.042); genotype contributes significantly to the variance only in B (p < 0.0001); and effects of the interaction are significant in A (p = 0.0069), B (p = 0.0476), D (p = 0.0069), E (p = 0.0032), and F (0.026).
Figure 2
Figure 2
GTL-1 is required for the immediate and enduring response to cold temperatures. Number of reversals was counted over 30 sec immediately after the temperature drop (A) and 10 min later (B). n = 16 each. Significant differences relative to controls, maintained at 20°C (black bars) throughout the experiments, were examined using two-way ANOVA **-p< 0.01).
Figure 3
Figure 3
GTL-1 is not essential for the response to single or repeated mechanical stimuli. (A) Percent animals not responding to a single high threshold mechanical stimuli in mec-4(e1611);gtl-1(lf) and in mec-4(1611) animals (20 and 11 plates, respectively, 10 animals each plate). Statistical analysis was performed using n.s, p = 0.086. (B) Responses to repeated high threshold mechanical stimuli in gtl-1(lf) animals (n = 20), wild-type (N2, n = 20), and -PVD (n = 20) animals.
Figure 4
Figure 4
GTL-1 affects the magnitude of the response to noxious mechanical stimuli. Immediate and enduring responses to a noxious mechanical stimulus of wild-type (N2, N = 19, circles) compared to gtl-1(lf) (n = 13, squares) (A–C) and wild-type (N2, n = 19, circles) compared to gtl-1 dsRNAPVD (n = 5, squares) (D–F).
Figure 5
Figure 5
Internal calcium and Gαq activity gate GTL-1. GTL-1 was expressed in HEK293 cells. (A and B) Calcium enhances GTL-1 dependent currents. (A) Representative IV recording with and without calcium applied to the inner side of the excised inside-out patch. (B) Fold effect on current amplitudes of Calcium applied to the excised inside-out patch at +80mV. Effects of calcium are significant, p < 0.05, (n = 8), one-way ANOVA with correction for multiple variables (C and D) GTL-1 is activated by DREADD-Gαq. (C) Representative response. (D) Average response, n = 5. Of note, no currents are detected in the absence of CNO or in cells not expressing GTL-1.
Figure 6
Figure 6
Activation of GTL-1 by internal calcium enables amplification of sensory stimuli. (A) Sensory stimuli via nocisensor activation directly (TRPA-1) or indirectly (GPCRs and MEC-10/DEGT-1) elevate cytosolic calcium. (B) Elevated cytosolic calcium activates GTL-1 channels to amplify the calcium signal.

Similar articles

See all similar articles

References

    1. Albeg A., Smith C. J., Chatzigeorgiou M., Feitelson D. G., Hall D. H., Schafer W. R., et al. (2011). C. elegans multi-dendritic sensory neurons: morphology and function. Mol. Cel Neurosci. 46, 308–317. 10.1016/j.mcn.2010.10.001 - DOI - PMC - PubMed
    1. Babcock D. T., Landry C., Galko M. J. (2009). Cytokine signaling mediates UV-induced nociceptive sensitization in Drosophila larvae. Curr. Biol. 19, 799–806. 10.1016/j.cub.2009.03.062 - DOI - PMC - PubMed
    1. Bautista D. M., Siemens J., Glazer J. M., Tsuruda P. R., Basbaum A. I., Stucky C. L., et al. (2007). The menthol receptor TRPM8 is the principal detector of environmental cold. Nature 448, 204–208. 10.1038/nature05910 - DOI - PubMed
    1. Caterina M. J., Julius D. (1999). Sense and specificity: a molecular identity for nociceptors. Curr. Opin. In Neurobiol. 9, 525–530. 10.1016/S0959-4388(99)00009-4 - DOI - PubMed
    1. Caterina M. J., Leffler A., Malmberg A. B., Martin W. J., Trafton J., Peterses-Zeitz K. R., et al. (2000). Impaired nociceptrion and pain sensation in mice lacking the capsaicin receptor. Science 288, 306–313. 10.1126/science.288.5464.306 - DOI - PubMed

LinkOut - more resources

Feedback