David H. Margulies, M.D., Ph.D.Building 10, Room 11D1210 Center DriveBethesda, MD 20892-1892Phone: 301-496-6429Fax: firstname.lastname@example.org
The Molecular Biology Section (MBS) of the Laboratory of Immunology is directed toward a precise molecular understanding of critical interactions that initiate, control, and perpetuate the immune response. To this aim, this laboratory focuses on
In the past several years, the major accomplishments of MBS have included the development of strategies for expressing and studying soluble analogs of MHC-I molecules, TCR, and NK receptors, and the measurement of the biophysical interactions between MHC-I molecules and cognate TCR as well as between MHC-I molecules and inhibitory NK receptors. The methods used for these measurements include surface plasmon resonance and analytical equilibrium ultracentrifugation.
Through the use of such purified MHC molecules, TCR, and NK receptors we have learned the thresholds of affinity that allow such cell surface receptors to activate or inhibit effector-cell function. We have also learned that the characteristic kinetics of these binding interactions are of moderate association rate and rapid dissociate rate. These studies provide fundamental information on the rules that govern the signals that are conveyed between cells of the immune system and provide insight into the molecular mechanisms that control these signals.
Recent studies have involved the isolation of several monoclonal antibodies directed against specific MHC/peptide complexes and the comparison of the specificity and the affinity of these to the T-cell receptors that they mimic. We have completed the x-ray structure determination of the H-2Dd/P18-I10 complex, the prototype MHC/peptide complex that we have studied functionally and biochemically, as well as that of the Va domain of the T-cell receptor that binds this complex. These structures are illustrated below. Currently, in collaboration with J.-S. Hu and A. Bax, the solution structure of the Va domain is being completed.
More recently, we have been studying the nature of the binding specificity and kinetics of the NK receptor, Ly49A, which is a murine inhibitory receptor that has been shown to interact functionally with the MHC-I molecule, H-2Dd. The kinetics and affinity of binding of Ly49A for H-2Dd are quite similar to that of the previously studied TCR which shows H-2Dd/P18-I10 specificity. However, unlike the TCR that shows exquisite peptide specificity and that discriminates peptide variants that differ by as little as a single amino acid substitution, the NK receptors shows MHC (i.e., H-2Dd) specificity and requires a peptide-conformed molecule but does not discriminate variant peptides as long as they are capable of binding H-2Dd.
In addition to our physical studies of the binding of Ly49A to H-2Dd, we have also examined the function of H-2Dd expressed in transgenic mice in the absence of the expression of other MHC-I molecules. This was accomplished by generating a transgenic mouse that expresses the H-2Dd as a single chain molecule, covalently attached to its obligate light chain, β2-microglobulin. This allows the expression of the H-2Dd/β2-m complex even in the absence of normal β2-m expression as in induced mutant (knockout) β2-m defective animals. We have studied the TCR development and function as well as the NK-receptor function in such animals and find that, although the single chain H-2Dd/ β2-m molecule functions normally in its interactions with a wide repertoire of TCR, the same molecule fails to interact normally with the NK receptor Ly49A. This suggests that the binding site for the NK receptor is structurally distinct from that of the TCR.
Further studies are intended to elucidate the structure/function relationship of a set of NK receptors related to the Ly49A molecule and to further explore the basis of peptide/specific T-cell recognition. These will be performed with a view towards integrating the biochemical and biophysical measurements with the functional immunological behavior of these molecules in cultured cells and in intact animals.
Phi Beta Kappa; U.S. Public Health Service Commendation Medal, 1987; Outstanding Service Medal, 1991; Meritorious Service Medal 1997.
Lisa F. Boyd, Rosalene Carey, Doo Hyun Chung, Kannan Natarajan, Fumito Tani, Jian Wang.
(View list in PubMed.)
Natarajan K, Hicks A, Mans J, Robinson H, Guan R, Mariuzza RA, Margulies DH. Crystal structure of the murine cytomegalovirus MHC-I homolog m144. J Mol Biol. 2006 Apr 21;358(1):157-71.
Hu JS, Plaksin D, Margulies DH. Backbone and side chain resonance assignmentsof a TRAV14-3 mouse T cell receptor domain. J Biomol NMR. 2005 Mar;31(3):271-2.
Margulies DH. Monoclonal antibodies: producing magic bullets by somatic cell hybridization. J Immunol. 2005 Mar 1;174(5):2451-2.
Candon S, McHugh RS, Foucras G, Natarajan K, Shevach EM, Margulies DH. Spontaneous organ-specific Th2-mediated autoimmunity in TCR transgenic mice. J Immunol. 2004 Mar 1;172(5):2917-24.
Margulies DH. Molecular interactions: stiff or floppy (or somewhere in between?). Immunity. 2003 Dec;19(6):772-4.
Dam J, Guan R, Natarajan K, Dimasi N, Chlewicki LK, Kranz DM, Schuck P, Margulies DH, Mariuzza RA. Variable MHC class I engagement by Ly49 natural killer cell receptors demonstrated by the crystal structure of Ly49C bound to H-2K(b). Nat Immunol. 2003 Dec;4(12):1213-22.
Special Interest Groups
Immunology, Molecular Modeling, Molecular Recognition and Quantitative Interaction, Structural Biology
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Last Updated March 27, 2013