Structure and expression of the TP and EP1 prostanoid receptor genes

Abstract: Prostanoids are ubiquitously distributed lipid signaling molecules derived from arachidonic acid, that exhibit numerous and diverse biological effects in a variety of physiological and pathophysiological conditions. The cell surface receptors for the prostanoids belong to the family of G protein-coupled receptors. In this thesis, the author describes the cloning and structural characterization of two mouse prostanoid receptor genes, namely the thromboxane A2 receptor (TP) and prostaglandin E2 receptor (EP1) genes. Both genes exhibit a similar intron-exon organization; they consist of two introns and three exons of which only the second and third exon contain coding sequence. Neither of the genes have a consensus TATA or CAAT box in their 5’ ends. Ribonuclease protection assay and in situ hybridization were used to determine the tissue distribution of the TP and EP1 genes. The TP gene is expressed in mouse thymus, spleen and in the T cell-like cell line EL4, implying that TP is expressed in thymocytes. EP1 mRNA was found in the paraventricular and supraoptic nuclei of the hypothalamus, as well as in the collecting ducts in kidney. The presence of a second gene, encoding the protein kinase PKN, was identified on the antisense strand of the EP1 gene. The PKN and EP1 genes overlap in a tail to tail manner. The 3’ untranslated region of a long variant of PKN mRNA completely overlaps the EP1 gene. The expression of EP1 and EP4 receptor mRNA in the rat brain was investigated by in situ hybridization. In contrast to the mouse, the rat brain does not express EP1 receptor mRNA. EP4 is expressed in the median preoptic nucleus, the medial preoptic area, the supraoptic nucleus, the magnocellular paraventricular nucleus of the hypothalamus, the parabrachial nucleus, the nucleus of the solitary tract and the ventrolateral medulla. EP4 receptor expression was also seen in neurons of the nodose ganglion.