Basic—Alimentary TractRelease of Endogenous Opioids From Duodenal Enteroendocrine Cells Requires Trpm5
Section snippets
Mice
Transgenic mice expressing enhanced green fluorescent protein (GFP) from a 10-kilobase-long Trpm5 promoter and Trpm5 knockout (KO) mice were described previously.5, 26 Their genetic background is C57Bl/6. Control wild-type (WT) mice were C57Bl/6 obtained from Charles River Laboratories (Wilmington, MA) or bred at Mount Sinai Animal Facility (New York, NY). All animals were kept on a regular mouse chow and maintained according to the Mount Sinai Institutional Animal Care and Use Committee
Trpm5 Expression in Mouse Intestine
Trpm5 expression in intestinal cells was monitored by immunohistochemistry and expression of a GFP transgene faithfully driven in Trpm5-expressing taste cells by the 12-kilobase-long Trpm5 promoter.26 Both methods revealed a large number of scattered Trpm5-expressing cells throughout the entire gut, from stomach to colon. By comparing GFP transgene fluorescence with Trpm5 immunostaining, we determined that all Trpm5-positive GFP-positive gut cells also expressed endogenous Trpm5 protein (Figure
Discussion
In taste cells, the Trpm5 ion channel is indispensable for propagating chemosensory signals to the nervous system. Its main role appears in assisting membrane depolarization in a final step in signal transmission from activation of G-protein–coupled receptors. Mice deficient in Trpm5 are severely affected in their ability to sense sweet, bitter, and umami compounds, tastants that all activate G protein–coupled receptors.6, 7, 34
In this report, we describe solitary chemosensory cells in mouse
Acknowledgments
Z.K. and D.R. contributed equally to this report.
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Conflicts of interest Dr Margolskee has a personal financial interest in the form of stock ownership in the Redpoint Bio company, receives consulting fees from the Redpoint Bio company, and is an inventor on patents and patent applications that have been licensed to the Redpoint Bio company. The remaining authors disclose no conflicts.
Funding Supported in part by National Institutes of Health grants DC007399 and DK073248 (to B.M.) and DC03055 (to R.F.M.).