Signaling Pathways for Sphingosylphosphorylcholine-Mediated Mitogenesis in Swiss 3T3 Fibroblasts

• Published in: The Journal of cell biology 1993-06, Vol.121 (6), p.1385-1395
• Main Authors: Desai, Naishadh N., Carlson, Robert O., Mattie, Mark E., Olivera, Ana, Buckley, Nancy E., Seki, Takashi, Brooker, Gary, Spiegel, Sarah
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Arachidonic Acid - metabolism; Biological and medical sciences; Calcium; Calcium - metabolism; Cell Division - physiology; Cell growth; Cell physiology; Cells; Cellular biology; Cultured cells; Cyclic AMP - metabolism; Fibroblasts; Fundamental and applied biological sciences. Psychology; Growth Substances - physiology; Insulin; Lipids; Lysophospholipids; Mice; Mitogens; Molecular and cellular biology; Neurology; Phosphatidylinositols - metabolism; Phosphorylcholine - analogs & derivatives; Phosphorylcholine - metabolism; Protein Kinase C - physiology; Signal transduction; Signal Transduction - physiology; Sphingosine - analogs & derivatives; Sphingosine - metabolism; Swiss 3T3 cells; T lymphocytes
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.121.6.1385

Sphingosylphosphorylcholine (SPC), or lysophingomyelin, a wide-spectrum growth promoting agent for a variety of cell types, stimulates cellular proliferation of quiescent Swiss 3T3 fibroblasts to a greater extent than other known growth factors or than the structurally related molecules, sphingosine and sphingosine-1-phosphate. SPC potentiated the mitogenic effect of an activator of protein kinase C, 12-O-tetradecanoylphorbol 13-acetate, and did not compete with phorbol esters for binding to protein kinase C in intact Swiss 3T3 fibroblasts. However, downregulation of protein kinase C, by prolonged treatment with phorbol ester, reduced, but did not eliminate, the ability of SPC to stimulate DNA synthesis, indicating that SPC may act via both protein kinase C-dependent and -independent signaling path-ways. SPC induced a rapid rise in intracellular free calcium ([Ca2+]i) in viable 3T3 fibroblasts determined with a digital imaging system. Although the increases in [Ca2+]iwere observed even in the absence of calcium in the external medium, no increase in the levels of inositol phosphates could be detected in response to mitogenic concentrations of SPC. Furthermore, in contrast to sphingosine or sphingosine-1-phosphate, the mitogenic effect of SPC was not accompanied by increases in phosphatidic acid levels or changes in cAMP levels. SPC, but not sphingosine or sphingosine-1-phosphate, stimulates the release of arachidonic acid. Therefore, the ability of SPC to act as an extremely potent mitogen may be due to activation of signaling pathway(s) distinct from those used by sphingosine or sphingosine-1-phosphate.