Which taste signal transduction proteins are expressed in the mouse and human GIs?
We performed RT-PCR on polyA enriched RNA from human stomach, duodenum, jejunum, ileum, and colon. We found that T1R1, T1R2, T1R3, PLCß2, -gustducin, and TrpM5 were expressed in every GI tissue tested, with the exception of T1R2, which was not detected in the stomach and was very weakly expressed in the other tissues (Figure 1a). In general, the expression levels of each gene are in the same order of magnitude throughout the GI. There are, however, marked differences from gene to gene, with 4 orders of magnitude difference between PLCß2 and T1R2 (Figure 1b). RT-PCR with mouse GI total RNA showed that T1r3 and Trpm5 are expressed in all the tested compartments of the GI, T1r1 is expressed in the antrum, duodenum, ileum, and colon, but not in the jejunum, and T1r2 is expressed only in the ileum (not shown). The relative levels of expression between genes were consistent with those of the human genes.
