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J. Biol. Chem., Vol. 279, Issue 35, 36720-36731, August 27, 2004
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From the Novartis Institute for Biomedical Research, Autoimmunity, and Transplantation, Novartis Pharma AG, CH-4002 Basel, Switzerland
Sphingolipids are signaling molecules that influence diverse cellular functions from control of the cell cycle to degradation of plasma membrane proteins. The synthetic sphingolipid-like compound FTY720 is an immunomodulating agent in clinical trials for transplant graft maintenance. In this report, we compare the effects of the natural yeast sphingolipid phytosphingosine with FTY720 in Saccharomyces cerevisiae. We show that the multicopy suppressor genes that induce growth resistance to FTY720 also confer resistance to growth-inhibitory concentrations of phytosphingosine. In addition, mutants for ubiquitination pathway proteins are shown to be resistant to the growth-inhibiting effect of both FTY720 and phytosphingosine. We observe fewer similarities between sphingosine and FTY720 than between FTY720 and phytosphingosine as revealed by genetic studies. Yeast cells lacking the specific sphingosine kinase LCB4 are sensitive to phytosphingosine and FTY720 but resistant to sphingosine, suggesting that FTY720 and phytosphingosine have a more related mechanism of action. Gene expression profile comparisons of sensitive and resistant yeast cells exposed to FTY720 and phytosphingosine highlight a number of similarities. In response to treatment with these compounds,
77% of the genes that are regulated >2-fold by FTY720 also respond to phytosphingosine in the same direction in the parent strain. In addition, a close inspection of TAT1 and TAT2 transporters following exposure to phytosphingosine indicates that TAT1 protein is degraded in a similar fashion upon treatment with FTY720 and phytosphingosine. There were differences, however, with respect to the TAT2 protein level and the expression profiles of a subset of genes. The genetic, transcriptional, and biochemical data together indicate that FTY720 and phytosphingosine influence similar pathways in yeast cells. These findings offer further insights into the physiological pathways influenced by these compounds in all eukaryotic cells and help us to understand the therapeutic consequences of FTY720 in humans.
Received for publication, June 3, 2004
* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The on-line version of this article (available at http://www.jbc.org) contains four supplemental tables concerning the effect of FTY720 treatment on genes in the parent and the bul1 mutant as well as the effect of PHS on genes in the parent and the bul1 mutant.
To whom correspondence should be addressed: Transplantation Research, Novartis Pharma AG, WSJ 386-906, CH-4002 Basel, Switzerland. Tel.: 0041-61-3247995; Fax: 0041-61-3247429; E-mail: rao.movva{at}pharma.novartis.com.
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