Fig. 5: Inhibition of CAP-induced calcium influx via direct interaction with TRPV1 via GLP-1 analogs and exendin 9–39 in HEK293T cells transfected with rat TRPV1 and CHO K1 cells expressing human TRPV1. | Experimental & Molecular Medicine

Fig. 5: Inhibition of CAP-induced calcium influx via direct interaction with TRPV1 via GLP-1 analogs and exendin 9–39 in HEK293T cells transfected with rat TRPV1 and CHO K1 cells expressing human TRPV1.

From: GLP-1 and its derived peptides mediate pain relief through direct TRPV1 inhibition without affecting thermoregulation

Fig. 5

a Sequence alignment, molecular weight, and function of GLP-1 analogs and exendin 9–39. b–e Mean normalized calcium influx in HEK293T cells transfected with rat TRPV1. Calcium increases were elicited by CAP (100 nM) in the presence of GLP-1 analogs (100 nM each), GLP-1(7–36) (b), exendin-4 (c), liraglutide (d), or exendin 9–39 (Exe 9–39) (e) (mean ± S.E.M.). Two-tailed unpaired t test (****p < 0.0001, compared with each control CAP). f Mean normalized calcium influx in CHO K1 cells expressing human TRPV1. Calcium increases were elicited by CAP (100 nM) in the absence (control CAP) and presence of GLP-1 analogs (100 nM) or exendin 9–39 (100 nM) (mean ± S.E.M.). One-way ANOVA followed by Dunnett’s multiple comparison test (****p < 0.0001, compared with the control, CAP). g Curves were fitted via a logistic function to show concentration-dependent inhibition of CAP-induced TRPV1 currents by 100 nM GLP-1, exendin-4, liraglutide, or exendin 9–39. h IC50 values of GLP-1, exendin-4, liraglutide, and exendin 9–39 (178.6 ± 23.40 nM, 62.19 ± 5.12 nM, 64.49 ± 10.19 nM, and 28.18 ± 3.92 nM, respectively). i Pull-down assay using His-tagged exendin 9–39 and cell lysates from CHO K1 cells expressing human TRPV1 (‘T’) and naïve CHO K1 cells (‘C’). Detection of the interaction between exendin 9–39 and TRPV1 via western blotting with an anti-human TRPV1 antibody. j Confocal images of FITC-labeled exendin 9–39 in CHO K1 cells expressing human TRPV1 (upper) compared with naïve CHO K1 cells (lower). Overlap of FITC-exendin 9–39 (green), anti-human TRPV1 antibody (red), and Hoechst (blue) in the merged image. Scale bar: 5 µm. ANOVA analysis of variance, CAP capsaicin, CHO K1 Chinese hamster ovary, FITC fluorescein isothiocyanate, GLP-1 glucagon-like peptide-1, S.E.M. standard error of the mean, TRPV1 transient receptor potential vanilloid 1.

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