Lipid Signaling LaboratoryEducation
- B.S., 1992, University of Tampa
- Ph.D., 1997, University of South Florida College of Medicine
- National Research Service Award, Postdoctoral Fellow, Duke University
- Medical University of South Carolina, Advisor: Yusuf Hannun, M.D.
The Chalfant laboratory is currently focused on two major areas of cell signaling and human pathophysiologies. Specifically, the laboratory focuses on: 1) lipid and oncogenic regulation of alternative splicing; and 2) the regulation of eicosanoid synthesis in inflammation and cancer. In regards to the former area, our laboratory focuses on the alternative splicing of caspase 9 and Bcl-x, major regulators of apoptosis and chemotherapy sensitivity of non-small cell lung cancer (NSCLC) cells. NSCLC represents the majority of lung cancers and carries a poor prognosis with a median survival of less than 12 months. Therefore, new strategies are needed in the treatment of NSCLC in order to impact this disease. In regards to caspase 9 RNA splicing and new NSCLC therapies, the expression of caspase 9 is regulated, in one aspect, by alternative RNA splicing via the inclusion or exclusion of an exonic cassette (exons 3, 4, 5, and 6). Inclusion of this exonic cassette into the mature transcript produces the pro-apoptotic caspase 9 (caspase 9a) while the exclusion produces the anti-apoptotic caspase 9, which is regulated by the production of the apoptotic lipid, ceramide. Studies from our laboratory have shown that the regulation of the inclusion of this four exon cassette is a critical factor in determining whether a cell is susceptible or resistant to apoptosis, and thus oncogenic transformation. Currently the laboratory is focused on determining the mechanism regulating caspase 9b formation as well as the downstream cell signaling modulated by this novel splice variant. The overall goal of the research is to determine whether this distal mechanism is a new target for anti-cancer therapeutics.
Our second line of research is also very exciting examining the biological function of a relatively new addition to bioactive sphingolipids, ceramide-1-phosphate (C1P). Specifically, we are examining the role of this bioactive lipid in inflammatory diseases (e.g. trauma-induced coagulopathy, sepsis, anaphylaxis) and cancer via regulation of eicosanoid biosynthesis. Sepsis, for example, is a term used to describe a severe illness arising from serious infection. The mortality rate of sepsis is >215,000 patients a year, and sepsis is the tenth leading cause of death in the US. As such, numerous clinical trials for the treatment of this disease have been undertaken, but unfortunately, these trials have shown limited success. Thus, there is a major need for new therapeutics to treat the disease. As for new therapeutics to combat this disease, products of arachidonic acid (AA), eicosanoids, are well-established mediators of inflammatory responses with major roles in the pathogenesis of the above disease states including sepsis. The production of AA by phospholipases is the initial rate-limiting step in eicosanoid biosynthesis, and the major phospholipase that regulates eicosanoid synthesis in response to inflammatory agonists is group IVA cytosolic phospholipase A2 (cPLA2α). The Chalfant laboratory was the first to demonstrate that C1P generated by ceramide kinase was a novel and specific activator of cPLA2α. Our recent findings also demonstrated that the specific interaction site for C1P is localized to the calcium binding loop II of the C2 domain of cPLA2α making our laboratory group the first to fully characterize a specific interaction site for a bioactive sphingolipid. The Chalfant laboratory also demonstrated that mutagenesis of critical amino acids for the C1P interaction inhibited the ability of cPLA2α to translocate in response to inflammatory agonists. Lastly, our new knockin mouse with this interaction site ablated is generating new insights as to how this lipid:protein interaction regulates the formation of bioactive lipids in vivo. Overall, our data are suggesting that the C1P/cPLA2α interaction is a new target for the development of a new generation of anti-inflammatory mediators, and this line of research is a major focus of the laboratory.