The long-term goal of this project is to explore the mechanisms and molecular ordering of radiation-induced apoptosis in mammalian cells and the anti-apoptotic signaling systems that constrain this response. The basic hypothesis is that failure to initiate apoptosis in response to radiation results from tight regulation of the apoptotic response by anti-apoptotic mechanisms. The balance between pro- and anti-apoptotic systems determines under any set of circumstances the magnitude of the apoptotic response in vitro and in vivo. While the p53 pathway is the most acclaimed mechanism of radiation-induced apoptosis, we have studied in previous rounds of this research the mechanisms and molecular ordering of ceramide-mediated apoptosis, specifically of the ceramide generated by acid sphingomyelinase activation in response to radiation in vitro and in vivo. Our recent discovery that radiation-induced DNA damage signals apoptosis via activating another enzyme, ceramide synthase (CS), and the identification of the mammalian CS gene, provide new opportunities for mechanistic studies of radiation sensitivity and resistance in normal and tumor tissues. This proposal presents a detailed plan to characterize mammalian CS and the effects of radiation on its structure and function. Specifically, we propose to purify mammalian CS, develop an in vitro assay for its enzymatic activity, characterize its molecular structure, identify post-translational modifications on CS induced by radiation, and explore the mechanisms of ATM-mediated suppression of radiation-induced CS activation. We will also study the mechanisms of CS involvement in mitochondrial apoptosis, focusing on demonstrating a requirement for CS activation in radiation-induced mitochondrial apoptosis, the topology of CS in the mitochondrial membrane, ceramide species generated by CS after irradiation, the interaction between ceramide and BAX, and the effects of CS activation on the MPT complex. Finally we propose to study the involvement of CS in tissue responses to radiation in vivo, specifically focusing on the involvement of CS in the GI tract and tumor responses to single-dose and fractionated irradiation. The proposed Specific Aims are interactive and address new and heretofore unknown mechanisms of radiation-induced cell death and tissue responses. The research plan provides an approach to investigate new hypotheses on the mechanisms of radiation resistance. Improved understanding of these pro- and anti-apoptotic signaling systems and their coordinated function may yield opportunities for pharmacological interventions in in vivo models, with important potentials for clinical applications in the radiation management of human cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA052462-16
Application #
7038378
Study Section
Special Emphasis Panel (ZRG1-SSS-1 (01))
Program Officer
Pelroy, Richard
Project Start
1990-07-15
Project End
2008-03-31
Budget Start
2006-04-01
Budget End
2008-03-31
Support Year
16
Fiscal Year
2006
Total Cost
$386,938
Indirect Cost
Name
Sloan-Kettering Institute for Cancer Research
Department
Type
DUNS #
064931884
City
New York
State
NY
Country
United States
Zip Code
10065
Lee, Hyunmi; Rotolo, Jimmy A; Mesicek, Judith et al. (2011) Mitochondrial ceramide-rich macrodomains functionalize Bax upon irradiation. PLoS One 6:e19783
Rotolo, Jimmy A; Stancevic, Branka; Lu, Sydney X et al. (2009) Cytolytic T cells induce ceramide-rich platforms in target cell membranes to initiate graft-versus-host disease. Blood 114:3693-706
Lahiri, Sujoy; Lee, Hyunmi; Mesicek, Judith et al. (2007) Kinetic characterization of mammalian ceramide synthases: determination of K(m) values towards sphinganine. FEBS Lett 581:5289-94
Tilly, Jonathan L; Kolesnick, Richard N (2002) Sphingolipids, apoptosis, cancer treatments and the ovary: investigating a crime against female fertility. Biochim Biophys Acta 1585:135-8
Li, Chi-Ming; Park, Jae-Ho; Simonaro, Calogera M et al. (2002) Insertional mutagenesis of the mouse acid ceramidase gene leads to early embryonic lethality in homozygotes and progressive lipid storage disease in heterozygotes. Genomics 79:218-24
Haimovitz-Friedman, A; Balaban, N; McLoughlin, M et al. (1994) Protein kinase C mediates basic fibroblast growth factor protection of endothelial cells against radiation-induced apoptosis. Cancer Res 54:2591-7
Haimovitz-Friedman, A; Kan, C C; Ehleiter, D et al. (1994) Ionizing radiation acts on cellular membranes to generate ceramide and initiate apoptosis. J Exp Med 180:525-35
Fuks, Z; Persaud, R S; Alfieri, A et al. (1994) Basic fibroblast growth factor protects endothelial cells against radiation-induced programmed cell death in vitro and in vivo. Cancer Res 54:2582-90
Kolesnick, R N; Haimovitz-Friedman, A; Fuks, Z (1994) The sphingomyelin signal transduction pathway mediates apoptosis for tumor necrosis factor, Fas, and ionizing radiation. Biochem Cell Biol 72:471-4
Fuks, Z; Vlodavsky, I; Andreeff, M et al. (1992) Effects of extracellular matrix on the response of endothelial cells to radiation in vitro. Eur J Cancer 28A:725-31

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