[Research Interests] [Representative Publications] [Lab Members] RESEARCH INTERESTSCell membranes are complex two-dimensional arrays of mobile, interacting molecules. My laboratory uses cell biology, biophysics, especially fluorescence methods, biochemistry and immunology to study membrane dynamics and organization in cells ranging from lymphocytes to epithelial cells. All of our work on membranes arises from interests in transplantation immunology, especially in the cell biology of class I MHC molecules. We aim to understand: 1) the intracellular traffic of class I MHC molecules during and after peptide loading, 2) the relationship between plasma membrane biophysics and antigen presentation by class I molecules and 3) the changes in T cell receptors after they bind MHC molecules. Our methods of analysis emphasize quantitative microscopy and image analysis, especially fluorescence recovery after photobleaching, FRAP, to measure lateral diffusion, and fluorescence resonance energy transfer, FRET, to measure molecular proximity and clustering. Work with these techniques as well as with other advanced microscopies, including deconvolution microscopy and total internal reflection microscopy, is done in a strong Departmental imaging facility with ample hardware and technical support. Using genetically fluorescent class I MHC molecules (tagged with GFP and its derivatives) we have dissected the organization of these molecules and their specialized chaperones in the endoplasmic reticulum, ER. Thus far we know that nascent class I molecules remain in the ER after peptide loading and that they interact with a number of factors some of which may carriers for export from the ER. One of these carriers, Bap31, may be important in trafficking stable peptide-loaded MHC molecules along the secretory pathway to the cell surface. We also investigate the way in which antigen presentation to T cells is affected changes in organization of class I MHC molecules at the cell surface. Cholesterol depletion of plasma membranes has large effects on antigen presentation; these effects can be mimicked by drugs that affect the membrane skeleton and by class I MHC molecules that have been engineered so that they can be crosslinked and clustered by small membrane-permeable compounds. We have shown that increasing the size of class I MHC clusters enhances presentation of low concentrations of antigens. We have some evidence that changes in class I MHC clustering occur naturally when cells are activated for antigen presentation. In a collaboration with medical school laboratories we are currently investigating the clustering of T cell receptors for antigen, TCR. We are developing methods of specifically labeling TCR with quantum and using the unique photophysics of the quantum dots labels to report on changes in TCR clustering with time after activation of naïve T cells by antigen. Currently we concentrate on CD8+ T cell responses to class I MHC molecules, but we are also developing reagents for analyzing resposnes of CD4+ T cells. REPRESENTATIVE PUBLICATIONSFooksman, D.R., Shaikh, S.R., Boyle, S. & Edidin, M. Phosphatidylinositol 4,5-bisphosphate concentration at the APC side of the immunological synapse is required for effector T cell function. J. Immunol 182: 5179-5182 (2009). Abe F., Van Prooyen N., Ladasky J.J. & Edidin M. Interaction of Bap31 and class I MHC molecules and their traffic out of the endoplasmic reticulum. J. Immunol. 182: 4776-4783 (2009). Shaikh, SR, Boyle, S., Hua, J., Li, Z. and Edidin M. In Vivo Test of the Vertical Phase Separation Hypothesis: The Display of MHC Class I Molecules on Membranes of B cells from Mice Fed High Fat Diets. British journal of Nutrition 101: 804-809 (2009). Shaikh SR, Mitchell D, Carroll E, Li M, Schneck J and Edidin M. Differential effects of a saturated and a monounsaturated fatty acid on MHC class I antigen presentation. Scand J Immunol. 2008. 68:30-42. Everett, M.W. and Edidin, M. 2007. Tapasin Increases Efficiency of MHC I Assembly in the Endoplasmic Reticulum but Does Not Affect MHC I Stability at the Cell Surface. The Journal of Immunology. 179:7646-52. Fooksman, D.R., Edidin, M., and Barisas, B.G. 2007. Measuring rotational diffusion of MHC class I on live cells by polarized FPR. Biophys Chem. 130:10-6. Shaikh SR, Edidin MA. 2006. Membranes are not just rafts. Chem Phys Lipids.144(1):1-3. Ladasky, J.J., Boyle, S., Seth, M., Li, H., Pentcheva, T., Abe, F., Steinberg, S.J., Edidin, M. (2006). Bap31 enhances the ER export and quality control of human class I MHC molecules. HONORSCole Medal of the Biophysical Society, 1979 Meyerhoff Fellowship of the Weizmann Institute, 1981 MERIT Award, National Institutes of Health, 1988 Fellow of University College London (England) 2004 Doctor, Honoris Causa,, Debrecen University (Hungary) 2004 Fellow, American Association for the Advancement of Science (AAAS), 2006 University of Chicago Alumni Association, Professional Achievement Award, 2009 Fellow of the Biophysical Society, 2010 Lab Members
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