Engman Lab Members
| David M. Engman, MD, PhD (Principal Investigator)d-engman@northwestern.edu
|
 | Cheryl L. Olson (Lab Manager) |
 | Melvin D. Daniels (PhD Student)Pathogenesis of autoimmune myocarditis. Myocarditis, inflammation of the heart, is a major cause of morbidity and death throughout the worldwide. It may be caused by infections with viruses, parasites and bacteria, cardiotoxic drugs and infarction. Myocarditis is typically biphasic, with an inflammatory phase followed by a fibrotic phase. Despite its public health importance, much remains to be determined about the involvement of the immune system in the progression and resolution of myocarditis and there is need both for specific markers of cardiac inflammation for diagnostic purposes and for development of specific therapies to alleviate disease. In genetically susceptible individuals, myocarditis may have an autoimmune nature – that is, the immune system inadvertently attacks the heart and causes inflammation. I have developed a novel model of autoimmune myocarditis and my ongoing research focuses on (i) the molecular pathogenesis of the acute and chronic phases of autoimmune myocarditis, (ii) the natural evolution of T cell responses during the inflammatory and resolution phases of disease, and (iii) the contribution of renin-angiotensin system to the severity of autoimmune myocarditis. The information obtained from my research will be used to guide the design and testing of novel immunotherapies to prevent illness and death in patients with myocarditis that may have an autoimmune component. |
 | Brian T. Emmer (MD/PhD Student)Role of calflagin proteins in trypanosome flagellar biology. The calflagins comprise a family of dually-acylated proteins found in the flagellum of the protozoan Trypanosoma brucei, the agent of African sleeping sickness. Modification by myristoylation and palmitoylation is required for flagellar membrane targeting, with myristate-only protein mislocalizing to the cell body (pellicular) membrane. There are two major parts to my thesis research. The first involves the functions of the calflagins, which I am investigating using RNA interference through both in vitro studies and a model of sleeping sickness. The second involves the identification and characterization of enzymes that catalyze the fatty acid modifications that are essential for the normal sorting pathway of these proteins. Unlike N-myristoylation, which is a cotranslational process occurring in the endoplasmic reticulum, protein palmitoylation is a substrate-specific reaction catalyzed by specific palmitoyl acyltransferases (PATs). I have identified the PAT that is specific for the calflagins, and my ongoing studies focus on (i) the pathway by which calflagin palmitoylation promotes trafficking to the flagellar membrane, (ii) the identification of novel T. brucei palmitoyl-proteins and mapping to their cognate PATs and (iii) the function of these palmitoyl proteins in trypanosome biology. |
 | Kevin M. Bonney (PhD Student)Molecular Mimicry in the Pathogenesis of Chagas Disease. The contractile protein cardiac myosin heavy chain is a primary target antigen of autoimmune responses resulting from a number of viral and parasitic infections, cardiotoxic drug treatment, and myocardial infarction. Initial studies of infection with the parasite Trypanosoma cruzi, the cause of Chagas heart disease, implicated antigenic molecular mimicry as one mechanism by which autoimmunity develops during infection. Molecular mimicry is the process by which immunity to a parasite antigen crossreacts with self antigen (in this case, cardiac myosin) to initiate and/or propagate a heart-specific autoimmune response leading to tissue damage and heart failure. My work focuses on questions regarding (i) the involvement of specific T. cruzi antigens in myosin molecular mimicry, (ii) the importance of molecular mimicry to the development of autoimmunity following T. cruzi infection, (iii) the evolution of intra- and intermolecular antigenic spreading during T. cruzi infection and (iv) the contribution of antigen-specific autoimmunity to the pathogenesis of Chagas heart disease. |
 | Danijela Maric (PhD Student)Structure-Function Studies of Flagellar Calcium-Binding Protein. The protozoan Trypanosoma cruzi is the causative agent of Chagas disease, which is a leading case of myocarditis in South and Central America. The flagellar calcium binding protein (FCaBP) of T. cruzi is an abundant, highly immunogenic protein that elicits strong cellular and humoral immune responses in infected humans and experimental animals. We previously demonstrated that FCaBP is a calcium-acyl switch protein whose flagellar membrane association is modulated by its calcium-binding state; however, the function of this protein is still unknown. Further analysis of FCaBP identified a 24 amino acid region at the amino terminus that is necessary and sufficient for such localization. The amino terminus of FCaBP is both myristoylated and palmitoylated; both modifications are required for flagellar membrane targeting. My research involves (i) investigation of the role of the amino terminus as a substrate for protein palmitoylation and as a partial mediator of flagellar membrane association, (ii) function of FCaBP through gene knockout studies and (iii) identification of FCaBP binding partners that are regulated through the calcium-switch mechanism. Finally, I am exploring the possibility that RNA interference, which is operative in the African trypanosome T. brucei, can be introduced to T. cruzi, which will greatly facilitate functional analysis of gene function in this organism. |
 | Teresa K. Schussler (PhD Student)
|
 | Christina Souther (Research Technologist)Global analysis of protein palmitoylation in trypanosomes. Palmitoylation, the addition of a 16-carbon fatty acid to a protein, is a reversible posttranslational modification important for protein trafficking, turnover and signaling. Palmitate is added to proteins by palmitoyl acyl transferases (PATs) and removed by acyl-protein thioesterases. Dynamic palmitoylation is important in regulating calcium channel activation and regulated protein sorting. PATs were first discovered in yeast and more recently in mice and humans. They are found in different locations in the cell and have been shown to have great specificity in the substrate proteins on which they act. My project involves the identification and characterization of PATs and their substrates in the African trypanosome Trypanosoma brucei. Bioinformatic analysis of the T. brucei genome identified twelve proteins containing consensus PAT domains and I am in the process of characterizing these by RNAi knockdown and in vivo tagging. I am also attempting to determine the specific substrate for each PAT in an effort to increase our understanding of the relationships between protein acylation and localization/function and protein sorting processes in this parasite. The specific functions of the acyl proteins are also of interest and this determination will be another valuable byproduct of this investigation. |
 | Deborah A. Pasternack, PhD (Postdoctoral Fellow)In the eukaryotic cell, sphingolipid biogenesis plays an important regulatory role in membrane architecture, protein trafficking, and lipid-mediated signaling. Sphingolipids form specialized membrane microdomains, called lipid rafts, which serve as platforms for signal transduction and for the sorting of acylated and glycosylphosphatidylinositol (GPI)-anchored proteins. Metabolites of sphingolipid biogenesis act as bioactive lipids and potent mediators of cellular proliferation, differentiation, and apoptosis. In the African trypanosome, genetic depletion of serine palymitoyltransferase (SPT2) indicates that de novo sphingolipid biogenesis is essential for parasite viability, kinetoplast segregation, and cytokinesis. Surprisingly, only mild defects in vesicular trafficking were observed, and SPT2 depletion had no effect on the association of calfagin with flagellar lipid rafts. These findings suggest that sphingolipid metabolites may act as lipid-mediators of cell cycle progression and survival in trypanosomes as well. To address this hypothesis, the aims of my research are to target downstream enzymes in the sphingolipid biogenesis pathway to assess the role of de novo sphingolipid biogenesis and metabolism in lipid-mediated cell survival, proliferation, and differentiation in trypanosomes. Genetic depletion of sphingomyelin synthase and sphingomyelinase genes will allow us to dissect the functional role of specialized membrane microdomains, as well as to assess the kinetics and fate of sphingolipid turnover in response to external stimuli accompanied by life cycle differentiation. Proteomic analysis of lipid raft-associated proteins will be essential for the identification of novel signaling cascades operable in these very unique and early branching eukaryotes. |
| Conrad L. Epting, MD (Asst. Professor of Pediatrics, Collaborating Scientist)c-epting@northwestern.edu My laboratory explores the cell surface as a dynamic platform regulating cell behavior. Specifically, we seek to understand how surface glycoproteins regulate cell-cell fusion in muscle cells, and to determine how pathogens target cardiac muscle. Using surface modification, we then hope to re-engineer stem cells to improve tissue targeting and tissue integration. To accomplish these broad aims, our current research projects are exploring the following research issues: (1) Tissue tropism of Trypanosoma cruzi. T. cruzi demonstrates tissue tropism during both the acute and chronic phases of infection, targeting cardiac, skeletal, and smooth muscle. Patients with chronic T. cruzi infection may develop clinical symptoms related to target tissue infection, notably myositis, dilated cardiomyopathy, and megasyndromes. The molecular basis for these clinical observations is incompletely understood. My research hopes to define and characterize the cell surface proteins important during the initial host-parasite interaction enabling myogenic specificity. (2) Cell-cell fusion and GPI-anchored proteins during skeletal myogenesis. Secondary skeletal myogenesis, the process of differentiation of dividing, mononuclear myoblast into quiescent, multinucleate myotubes is critical for maintenance of skeletal muscle during aging and after injury. GPI-anchored cell surface proteins appear to be critical for these regulated membrane-membrane fusion events. Our research hopes to dissect the molecular choreography occurring at the site of opposing membranes which enables cell fusion. (3) RNA interference in Trypanosoma cruzi (with Danijela Maric and Cheryl Olson). A few of the kinetoplastid parasites possess functional RNAi machinery, enabling selective knock-down of target genes to elucidate their function. T. cruzi does not, and several genes required for this process are absent from T. cruzi. We are attempting to reintroduce the RNAi machinery into T. cruzi to apply this powerful technology to the study of T. cruzi biology and pathogenesis of Chagas disease. |