Cloning and expression of a cDNA for the human prostanoid IP receptor.

Abstract

A cDNA clone coding for a functional human prostanoid IP receptor has been isolated from a lung cDNA library.The human IP receptor consists of 386 amino acid residues with a predicted molecular mass of 40,961, and has the seven putative transmembrane domains characteristic of G-protein-coupled receptors.Challenge of Xenopus oocytes co-expressing the IP receptor and the cystic fibrosis transmembrane conductance regulator (CAMP-activated C1-channel) with the stable prostacyclin analog iloprost resulted in specific inward C1-currents, demonstrating that the cDNA encoded a functional IP prostanoid receptor coupled to elevation in CAMP.Radioreceptor binding studies using membranes prepared from mammalian COS cells transfected with the IP receptor cDNA showed that the rank order of potency for prostaglandins and prostaglandin analogs in competition for [SH]iloprost specific binding sites was as predicted for the IP receptor, with iloprost >> carbacyclin >> prostaglandin (PG) E, > PGF,, = PGD, = U46619.Northern blot analysis showed that IP mRNA was most abundantly expressed in kidney, with lesser amounts detected in lung and liver.In summary, we have cloned and expressed a cDNA for the human prostanoid IP receptor that is functionally coupled to a signaling pathway involving stimulation of intracellular C A M P production.Prostacyclin (PGI,)' is a labile metabolite of arachidonic acid produced in concert with the bis-enoic prostaglandins via the cyclooxygenase pathway (1).PGI, plays a major physiological role as a potent mediator of vasodilation and inhibitor of platelet activation (2, 3).Thus, PGI, causes relaxation of arterial smooth muscle and inhibition of platelet aggregation, degranulation and shape change and is, therefore, thought to be important in maintaining vascular homeostasis (4).Other potential roles for PGI, are not well established but include regulation of renal blood flow, renin release and glomerular filtration rate in the kidney cortex (2), modulation of neurotransmitter release in the heart (5), and stimulation of secretion in the stomach and