Cloning, functional expression and role in cell growth regulation of a hamster 5-HT2 receptor subtype.
We have isolated a hamster fibroblast cDNA clone that encodes a serotoninergic receptor whose deduced amino acid sequence displays 94% identity with the rat brain serotonin (5-HT) type 2 receptor. When expressed in Xenopus oocytes, the hamster receptor efficiently couples to the phosphoinositide second messenger system and leads to intracellular Ca2+ mobilization in response to 5-HT. To determine the pharmacological properties of this receptor, and to evaluate the role of phospholipase C (PLC) activation in growth modulation by 5-HT, we have expressed it in hamster fibroblasts. Transfected cells that express 5-HT receptors were selected using a novel method based on coexpression of the Na+/H+ antiporter gene as a selectable marker. After co-transfection of the 5-HT receptor and Na+/H+ antiporter cDNAs in fibroblasts lacking antiporter activity (variants of the CCL39 line), 50% of the clones resistant to an acute acid load express functional receptors. The pharmacological profile of the transfected receptor is consistent with it being of the 5-HT2 subtype, and the extent of 5-HT-stimulated PLC activation in independent clones correlates with their relative level of cRNA expression. In cells in where addition of 5-HT leads to strong activation of PLC, and inhibition of adenylate cyclase via endogenous 5-HT1b receptors, 5-HT alone has little effect on DNA synthesis stimulation. Thus we conclude that activation of the PLC signalling pathway in these cells is not sufficient to trigger G0/G1 to S phase transition. Strong activation of PLC via 5-HT2 receptors does however contribute to the synergy observed between 5-HT (Gi-coupled pathway) and fibroblast growth factor (tyrosine kinase-activated pathway) on DNA synthesis reinitiation in transfected cells.
Van Obberghen-Schilling
E
E
Centre de Biochimie CNRS, Nice, France.
Vouret-Craviari
V
V
Haslam
R J
RJ
Chambard
J C
JC
Pouysségur
J
J
D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000096:biosynthesis; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011985:Receptors, Serotonin / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism; D014981:Xenopus
D012333:RNA, Messenger; D011985:Receptors, Serotonin; D004247:DNA; D010738:Type C Phospholipases