Phospholipase D signaling in serotonin-induced mitogenesis of pulmonary artery smooth muscle cells

• Published in: American journal of physiology. Lung cellular and molecular physiology 2008-09, Vol.295 (3), p.L471-L478
• Main Authors: Liu, Y, Fanburg, B. L
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Cell Proliferation - drug effects; Cells; Cells, Cultured; Enzyme Activation - drug effects; Humans; Kinases; Models, Biological; Mutation; Myocytes, Smooth Muscle - cytology; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - metabolism; Phosphatidic Acids - metabolism; Phosphatidic Acids - pharmacology; Phospholipase D - antagonists & inhibitors; Phospholipase D - genetics; Phospholipase D - metabolism; Pulmonary arteries; Pulmonary Artery - cytology; Pulmonary Artery - drug effects; Pulmonary Artery - metabolism; Receptor, Serotonin, 5-HT2A - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Serotonin - metabolism; Serotonin - pharmacology; Signal transduction; Signal Transduction - drug effects; Studies
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00071.2008

Tufts Medical Center, Boston, Massachusetts Submitted 14 February 2008 ; accepted in final form 8 July 2008 We have previously reported the participation of mitogen-activated protein, Rho, and phosphoinositide-3 (PI3) kinases in separate pathways in serotonin (5-HT)-induced proliferation of pulmonary artery smooth muscle cells (SMCs). In this study, we investigated the possible participation of phospholipase D (PLD) and phosphatidic acid (PA) in this growth process. 5-HT stimulated a time-dependent increase in [ 3 H]phosphatidylbutanol and PA generation. Exposure of SMCs to 1-butanol or overexpression of an inactive mutant of human PLD1R898R blocked 5-HT-induced proliferation. Furthermore, 1-butanol inhibited 5-HT activation of S6K1 and S6 protein, downstream effectors of mammalian target of rapamycin (mTOR), by 80 and 72%, respectively, and partially blocked activation of extracellular signal-regulated kinase (ERK) by 30% but had no effect on other associated signaling pathways. Exogenous PA caused cellular proliferation and revitalized cyclin D1 expression by 5-HT of the 1-butanol-treated cells. PA also reproduced activations by 5-HT of mTOR, S6K1, and ERK. Transfection with inactive human PLD1 reduced 5-HT-induced activation of S6K1 by 50%. Inhibition of 5-HT receptor 2A (R 2A) with ketaserin blocked PLD activation by 5-HT. Inhibition with PI3-kinase inhibitor failed to block either activation of PLD by 5-HT or PA-dependent S6K1 phosphorylation. Taken together, these results indicate that ligation of the 5-HTR 2A by 5-HT initiates PLD activation in SMCs, and that its product, PA, is an early signaling molecule in 5-HT-induced pulmonary artery SMC proliferation. Signaling by PA produces its downstream effects primarily through the mTOR/S6K1 pathway and to a lesser extent through the ERK pathway. Hydrolysis of cell membrane lipid may be important in vascular effects of 5-HT. pulmonary artery smooth muscle cell proliferation; serotonin; phospholipase D; phosphatidic acid; cell signal transduction Address for reprint requests and other correspondence: B. L. Fanburg, Tufts Medical Center, 750 Washington St., Boston, MA 02111 (e-mail: bfanburg{at}tuftsmedicalcenter.org )