期刊
BIOCHEMICAL JOURNAL
卷 393, 期 -, 页码 733-740出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20050643
关键词
ceramide; de novo synthesis; inositolphosphoceramide-phospholipase C (Isc1p); sphingomyelinase (SMase); sporulation
资金
- NCI NIH HHS [R24CA095841, R24 CA095841] Funding Source: Medline
- NCRR NIH HHS [P20RR016434, P20 RR016434] Funding Source: Medline
- NIGMS NIH HHS [R37 GM043825, R01 GM043825, F32 GM068270, GM 43825, GM068270-01] Funding Source: Medline
- NLM NIH HHS [R01 LM010144] Funding Source: Medline
Saccharomyces cerevisiae produces the sphingolipid ceramide by de novo synthesis as well as by hydrolysis of complex sphingo-lipids by Isc1p (inositotphosphoceramide-phospholipase C), which is homologous with the mammalian neutral sphingomyelinases. Though the roles of sphingolipids in yeast stress responses are well characterized, it has been unclear whether Isc1p contributes to stress-induced sphingolipids. The present study was undertaken in order to distinguish the relative roles of de novo sphingolipid biosynthesis versus Iscip-mediated sphingolipid production in the heat-stress response. Ceramide production was measured at normal and increased temperature in an ISC1 deletion and its parental strain (ISC1 being the gene that codes for Isc1p). The results showed that Isc1p contributes specifically to the formation of the C-24-, C-24:1- and C-26-dihydroceramide species. The interaction between these two pathways of sphingolipid production was confirmed by the finding that ISC1 deletion is synthetically lethal with the IcbI-100 mutation. Interestingly, Isc1p did not contribute significantly to transient cell-cycle arrest or growth at elevated temperature, responses known to be regulated by the de novo pathway. In order to define specific contributions of ISC1, microarray hybridizations were performed, and analyses showed misregulation of genes involved in carbon source utilization and sexual reproduction, which was corroborated by defining a sporulation defect of the isc1 Delta strain. These results indicate that the two pathways of ceramide production in yeast interact, but differ in their regulation of ceramides of distinct molecular species and serve distinct cellular functions.
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