Figure 5
From: HTR4 gene structure and altered expression in the developing lung
Expression profiling of HTR4 in airway cells. RT-PCR and sequencing confirmed expression of HTR4 transcripts a (NM_001040169.2) and b (NM_000870.5) in total brain tissue (a). Sequence encoding exon 1 was found in both transcripts, which contradicts information provided by NCBI for transcript a, however transcripts a and b were differentiated by the presence of exon 13 or 9 respectively. Q-PCR analysis (b) indicated highest expression in total brain tissue, but ≤0.26% relative to this in total lung tissue, HBEC, HASM and the BEAS2B-R1 cell line. Error bars indicate SEM (n ≥3). Radioligand binding experiments (c), using a saturating concentration of [3H]-GR113808 (approx. 1 nM), defined 5-HT4R expression in CHO-K1 cells transiently transfected with pcDNA3-HTR4a, un-transfected CHO-K1 cells, HBEC, HASM and BEAS2B-R1 cells. Error bars indicate SEM (n ≥3). While the pcDNA3-HTR4a-transfected CHO-K1 cells expressed a substantial 5-HT4R population (approx. 460 fmol/mg protein), no other cell type expressed a significant receptor population (all ≤50 fmol/mg protein).