Office: 843-792-9318
Lab: 843-876-5177
Fax: 843-792-4322
Email: hannun@musc.edu
 

Research Interests

Our laboratory is focused on studies on sphingolipid-mediated signal transduction. These studies have allowed us to propose a critical role for sphingolipids in eukaryotic stress responses. In the yeast, S. cerevisiae, we find that sphingolipids are essential for the adaptation to heat and other stresses. Heat induces transient changes in sphingoid bases and in ceramide involving distinct metabolic pathways. These lipid signals then act to regulate ubiquitin-dependent proteolysis and phosphatase-dependent targets, respectively. Our goals are to use a combination of biochemical and molecular approaches to define the specific roles, mechanisms and functions of sphingolipids in the yeast responses to stress. In mammalian cells, ceramide has emerged as a key regulator of cell growth, differentiation and apoptosis. Many stimuli (such as TNF, heat, and chemotherapeutic agents) activate multiple pathways of sphingolipid metabolism culminating in elevations in ceramide levels. In turn, ceramide can induce apoptosis, cell cycle arrest or terminal differentiation through the activation of serine/threonine phosphatases and subsequent modulation of specific downstream phosphorylated targets such as the retinoblastoma gene product and protein kinase C. These specific responses then couple ceramide action to distinct cellular effects. Our current goals are to provide a biochemical and molecular foundation for the study of these ceramide-dependent pathways. Therefore, we are currently focussing on key enzymes of ceramide metabolism (such as sphingomyelinase, ceramidase and sphingomyelin synthase) that serve to regulate ceramide levels. We are also studying ceramide-activated protein phosphatases in vitro and in cells. For all these studies, we use a combination of chemical, biochemical, molecular, and cellular studies. Furthermore, we are developing inhibitors of these enzymes and targets as novel agents in cancer chemotherapy.

Selected Publications

• Chalfant, C. Rathman, K., Ogretmen, B., and Hannun, Y. A. (2002)  De Novo ceramide regulates the alternative splicing of caspase 9 and Bcl-x in A549 lung adenocarcinoma cells. Dependence on protein phosphatase-1.  J. Biol. Chem. 277: 12587-12595.

• Jones, J. A. and Hannun, Y. A. (2002) Tight binding inhibition of protein phosphatase-1 by phosphatidic acid: specificity of inhibition by the phospholipid.  J. Biol. Chem.277: 15530-15538.

•  Hannun, Y. A. and Obeid, L. M. (2002) The ceramide-centric universe of lipid-mediated cell regulation: stress encounters of the lipid kind.  J. Biol. Chem.277: 15847-25850.

•  Jenkins, G. M., Cowart, L. A., Signorelli, P., Pettus, B. J., Chalfant, C. E., and Hannun, Y. A. (2002) Acute Activation of De Novo Sphingolipid Biosynthesis upon Heat Shock Causes an Accumulation of Ceramide and Subsequent Dephosphorylation of SR Proteins. J. Biol. Chem.277: 42572-42578.

• Okamoto, Y., Vaena de Avalos, S., and Hannun, Y. A. (2002) Structural requirements for selective binding of ISC1 to anionic phospholipids.  J. Biol. Chem.277: 46470-46477

•  Pettus, B. J., Chalfant, C.E., and Hannun, Y. A. (2002).  Ceramide in apoptosis: an overview and current perspectives. Biochim. Biophys. Acta 1585: 114-125.

•  Marchesini, N., Luberto, C., Hannun, Y.A. (2003) Mammalian neutral sphingomyelinase2: biochemical properties and its role in sphingolipid metabolism. J. Biol. Chem.278: 13775-13783.

•  Kroesen, B-J., Jacobs, S., Pettus, B., Sietsma, H., Kok, J-W., Hannun, Y. A., and de Leij, L. (2003) BcR-induced apoptosis involves differential regulation of C₁₆-and C₂₄-ceramide formation and sphingolipid dependent activation of the proteasome. J. Biol. Chem.278: 14723-14731.

•  Pettus, B.J., Bielawska, A., Kroesen, B., Moeller, P.D.R., Szulc, Z. M., Hannun, Y. A., and Busman, M. (2003) Observation of different ceramide species from crude cellular extracts by normal phase high performance liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry.  Rapid communications in Mass Spectrometry 17: 1203-1211.

•  Pettus, B.J., Bielawski, J., Porcelli, A.M., Reames, D.L., Johnson, K.R., Morrow, J., Chalfant, C.E., Obeid, L. M., and Hannun, Y.A. (2003) The sphingosine kinase 1/sphingosine-1-phosphate pathway mediates COX-2 induction and PGE2 production in response to TNFa.  FASEB J. 17: 1411-1421.

•  Cowart, L. A., Okamoto, Y., Pinto, F. R., Gandy, J. L., Almeida, J., and Hannun, Y. A. (2003) Roles for Sphingolipid Biosynthesis in Mediation of Specific Programs of the Heat Stress Response Determined Through Gene Expression Profiling J. Biol. Chem.278: 30328-30338.

•  Okamoto, Y., Vaena de Avalos, S., Hannun, Y. A. (2003) Functional analysis of ISC1 by site-directed mutagenesis.  Biochemistry 42: 7855-7862.

•  Pettus, B. J., Bielawska, A., Spiegel, S., Roddy, P., Hannun, Y. A., and Chalfant, C. E. (2003) Ceramide Kinase Mediates Cytokine and Calcium Ionophore-induced Arachidonic Acid Release. J. Biol. Chem. 278: 38206 - 38213.

•  Alvarez-Vasquez, F., Sims, K. J., Hannun, Y. A., and Voit, E. O. (2003) Integration of Kinetic Information on Yeast Sphingolipid Metabolism in Dynamical Pathway Models.  J. of  Theoretical Biology  226: 265-291.

•  Becker, K. and Hannun, Y. A. (2003) cPKC-dependent sequestration of membrane recycling components in a subset of recycling endosomes. J. Biol. Chem. 278: 52747 - 52754.

•  Pettus, B. J., Bielawska, A., Subramanian, P., Wijesinghe, D., S., Maceyka, M., Leslie, C. C., Evans, J. H., Freiberg, J., Roddy, R., Hannun,  Y. A., and Chalfant, C. E., (2004) Ceramide-1-phosphate is a direct activator of cytosolic phospholipase A2. J. Biol. Chem.279: 11320-11326.

•  Vaena de Avalos, S., Okamoto, Y., and Hannun, Y. A. (2004) Activation and localization of Inositol phosphosphingolipid phospholipase C, Isc1p, to the mitochondria during growth of S. cerevisiae. J. Biol. Chem.279: 11537-11545.

•  Pettus, B.J., Kroesen, B., Szulc, Z. M., Bielawska, A., Bielawski, J., Hannun, Y. A., and Busman, M. (2004) Quantitative measurement of different ceramide species from crude cellular extracts by normal phase high performance liquid chromatography (NP-HPLC) coupled to atmospheric pressure ionization mass spectrometry (APCI-MS). Rapid communications in Mass Spectrometry  18: 577–583.

•  Pettus, B. J., Chalfant, C. E., and Hannun, Y. A. (2004) Sphingolipids in Inflammation: Roles and Implications. Current  Molecular Medicine 4: 405-418.

•  Marchesini, N., Osta, W., Bielawski, J., Luberto, C., Obeid, L. M., and Hannun, Y. A. (2004) Role for Mammalian Neutral Sphingomyelinase2 in Confluence-induced Growth Arrest of MCF7 Cells. J. Biol. Chem.279: 25101-25111.

•  Becker, K. P. and Hannun, Y. A. (2004) Isoenzyme-Specific Translocation of  PKCßII and not PKCßI to a Juxtanuclear Subset of Recycling Endosomes. Involvement of Phospholipase D. J. Biol. Chem.279: (in press)

•  Futerman, A. H, and Hannun, Y. A. (2004) The complex life of simple sphingolipids.  EMBO Reports.  (in press)

• Ogretmen, B. and Hannun, Y. A. (2004) Bioactive Sphingolipids in Cancer Pathogenesis and Treatment.  Nature Reviews Cancer (in press).