Studies from the laboratory of the PI have focused on elucidating the components, mechanisms, and roles of bioactive sphingolipids, especially ceramide. These have resulted in identification of stress (TNF, heat, chemotherapy agents)- induced activation of neutral sphingomyelinase (SMase). Recent advances have included identification of the orthologue of SMase in S. cerevisiae, ISC1 which acts on membrane inositolphosphoceramide (IPC) to liberate ceramide. This enzyme shows homology to a mammalian enzyme, nSMase2, which is poorly characterized. We propose the overall hypothesis that these enzymes define a family of sphingolipid phosphodiesterases with similar mechanisms of action in vitro and with roles in regulating the levels of SM/1PC/ceramide in yeast and mammals. This hypothesis has generated the following specific aims: (1) To determine the physiologic function of nSMase 2.
This aim will test the specific hypothesis that nSMase2 functions as an endogenous SMase. This will be determined through a detailed investigation of the effects of this enzyme on basal and agonist-stimulated sphingolipid metabolism. (2) To determine in vitro mechanisms of ISC1 and nSMase 2.
This aim will adopt a combination of molecular and biochemical approaches to determine specific domains in the enzymes that interact with substrate, the specific determinants of substrate selectivity, and domains responsible for regulation by phosphatidylserine. (3) To determine cellular roles of ISC1, This aim will test the spedfie hypothesis that ISC1 launches a sphingolipid-mediated pathway that functions in response to heat stress in yeast. This will be investigated by employing a combination of microarray expression, biochemical studies, and molecular genetic approaches to define specific and general pathways regulated by ISC1 and its product ceramide. Understanding the mechanisms, regulation, and function of these enzymes is critical for the study of bioactive lipids in general and sphingolipids in particular. These novel and important enzymes will therefore open up a novel area of research, hitherto resistant to molecular approaches. These pathways are of direct significance to the biology of stress responses and specifically to cancer therapeutics.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Physiological Chemistry Study Section (PC)
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Chin, Jean
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Medical University of South Carolina
Schools of Medicine
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Lu, Zhongyang; Li, Yanchun; Jin, Junfei et al. (2015) GPR40/FFA1 and neutral sphingomyelinase are involved in palmitate-boosted inflammatory response of microvascular endothelial cells to LPS. Atherosclerosis 240:163-73
Rajagopalan, Vinodh; Canals, Daniel; Luberto, Chiara et al. (2015) Critical determinants of mitochondria-associated neutral sphingomyelinase (MA-nSMase) for mitochondrial localization. Biochim Biophys Acta 1850:628-39
Shamseddine, A A; Clarke, C J; Carroll, B et al. (2015) P53-dependent upregulation of neutral sphingomyelinase-2: role in doxorubicin-induced growth arrest. Cell Death Dis 6:e1947
Spincemaille, Pieter; Matmati, Nabil; Hannun, Yusuf A et al. (2014) Sphingolipids and mitochondrial function in budding yeast. Biochim Biophys Acta 1840:3131-7
Matmati, Nabil; Metelli, Alessandra; Tripathi, Kaushlendra et al. (2013) Identification of C18:1-phytoceramide as the candidate lipid mediator for hydroxyurea resistance in yeast. J Biol Chem 288:17272-84
Khavandgar, Zohreh; Poirier, Christophe; Clarke, Christopher J et al. (2011) A cell-autonomous requirement for neutral sphingomyelinase 2 in bone mineralization. J Cell Biol 194:277-89
Clarke, Christopher J; Cloessner, Emily A; Roddy, Patrick L et al. (2011) Neutral sphingomyelinase 2 (nSMase2) is the primary neutral sphingomyelinase isoform activated by tumour necrosis factor-? in MCF-7 cells. Biochem J 435:381-90
Barbosa, Antonio Daniel; Osorio, Hugo; Sims, Kellie J et al. (2011) Role for Sit4p-dependent mitochondrial dysfunction in mediating the shortened chronological lifespan and oxidative stress sensitivity of Isc1p-deficient cells. Mol Microbiol 81:515-27
Wu, Bill X; Clarke, Christopher J; Matmati, Nabil et al. (2011) Identification of novel anionic phospholipid binding domains in neutral sphingomyelinase 2 with selective binding preference. J Biol Chem 286:22362-71
Hernandez-Corbacho, Maria Jose; Jenkins, Russell W; Clarke, Christopher J et al. (2011) Accumulation of long-chain glycosphingolipids during aging is prevented by caloric restriction. PLoS One 6:e20411

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