Deng L.,U.S. Food and Drug Administration |
Luo M.,University of Maryland Institute for Bioscience and Biotechnology Research |
Luo M.,Anhui University of Science and Technology |
Velikovsky A.,University of Maryland Institute for Bioscience and Biotechnology Research |
And 3 more authors.
Annual Review of Biophysics | Year: 2013
The adaptive immune system, which is based on highly diverse antigen receptors that are generated by somatic recombination, arose approximately 500 Mya at the dawn of vertebrate evolution. In jawed vertebrates, adaptive immunity is mediated by antibodies and T cell receptors (TCRs), which are composed of immunoglobulin (Ig) domains containing hypervariable loops that bind antigen. In striking contrast, the adaptive immune receptors of jawless vertebrates, termed variable lymphocyte receptors (VLRs), are constructed from leucine-rich repeat (LRR) modules. Structural studies of VLRs have shown that these LRR-based receptors bind antigens though their concave surface, in addition to a unique hypervariable loop in the C-terminal LRR capping module. These studies have revealed a remarkable example of convergent evolution in which jawless vertebrates adopted the LRR scaffold to recognize as broad a spectrum of antigens as the Ig-based antibodies and TCRs of jawed vertebrates, with altogether comparable affinity and specificity. Copyright © 2013 by Annual Reviews.
PubMed | University of Notre Dame, Loyola University Chicago, University of Massachusetts Medical School and University of Maryland Institute for Bioscience and Biotechnology Research
Type: Journal Article | Journal: Proceedings of the National Academy of Sciences of the United States of America | Year: 2016
How T-cell receptors (TCRs) can be intrinsically biased toward MHC proteins while simultaneously display the structural adaptability required to engage diverse ligands remains a controversial puzzle. We addressed this by examining TCR sequences and structures for evidence of physicochemical compatibility with MHC proteins. We found that human TCRs are enriched in the capacity to engage a polymorphic, positively charged hot-spot region that is almost exclusive to the 1-helix of the common human class I MHC protein, HLA-A*0201 (HLA-A2). TCR binding necessitates hot-spot burial, yielding high energetic penalties that must be offset via complementary electrostatic interactions. Enrichment of negative charges in TCR binding loops, particularly the germ-line loops encoded by the TCR V and V genes, provides this capacity and is correlated with restricted positioning of TCRs over HLA-A2. Notably, this enrichment is absent from antibody genes. The data suggest a built-in TCR compatibility with HLA-A2 that biases receptors toward, but does not compel, particular binding modes. Our findings provide an instructional example for how structurally pliant MHC biases can be encoded within TCRs.
Deng L.,University of Maryland Institute for Bioscience and Biotechnology Research |
Deng L.,University of Maryland University College |
Velikovsky C.A.,University of Maryland Institute for Bioscience and Biotechnology Research |
Velikovsky C.A.,University of Maryland University College |
And 10 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010
Adaptive immunity in jawless vertebrates is mediated by leucine-rich repeat proteins called "variable lymphocyte receptors" (VLRs). Two types of VLR (A and B) are expressed by mutually exclusive lymphocyte populations in lamprey. VLRB lymphocytes resemble the B cells of jawed vertebrates; VLRA lymphocytes are similar to T cells. We determined the structure of a high-affinity VLRA isolated from lamprey immunized with hen egg white lysozyme (HEL) in unbound and antigen-bound forms. The VLRA-HEL complex demonstrates that certain VLRAs, like γδ T-cell receptors (TCRs) but unlike αβ TCRs, can recognize antigens directly, without a requirement for processing orantigen-presenting molecules. Thus, these VLRAs feature the nanomolar affinities of antibodies, the direct recognition of unprocessed antigens of both antibodies and γδ TCRs, and the exclusive expression on the lymphocyte surface that is unique to αβ and γδ TCRs.
PubMed | Integrated Biotherapeutics, Inc., Stanford University, University of Maryland Institute for Bioscience and Biotechnology Research, University of Alberta and 3 more.
Type: Journal Article | Journal: Hepatology (Baltimore, Md.) | Year: 2016
Direct-acting antivirals (DAAs) have led to a high cure rate in treated patients with chronic hepatitis C virus (HCV) infection, but this still leaves a large number of treatment failures secondary to the emergence of resistance-associated variants (RAVs). To increase the barrier to resistance, a complementary strategy is to use neutralizing human monoclonal antibodies (HMAbs) to prevent acute infection. However, earlier efforts with the selected antibodies led to RAVs in animal and clinical studies. Therefore, we identified an HMAb that is less likely to elicit RAVs for affinity maturation to increase potency and, more important, breadth of protection. Selected matured antibodies show improved affinity and neutralization against a panel of diverse HCV isolates. Structural and modeling studies reveal that the affinity-matured HMAb mediates virus neutralization, in part, by inducing conformational change to the targeted epitope, and that the maturated light chain is responsible for the improved affinity and breadth of protection. A matured HMAb protected humanized mice when challenged with an infectious HCV human serum inoculum for a prolonged period. However, a single mouse experienced breakthrough infection after 63 days when the serum HMAb concentration dropped by several logs; sequence analysis revealed no viral escape mutation.The findings suggest that a single broadly neutralizing antibody can prevent acute HCV infection without inducing RAVs and may complement DAAs to reduce the emergence of RAVs. (Hepatology 2016;64:1922-1933).
Holland S.J.,Max Planck Institute of Immunobiology and Epigenetics |
Gao M.,University of Maryland Institute for Bioscience and Biotechnology Research |
Hirano M.,Emory University |
Iyer L.M.,U.S. National Center for Biotechnology Information |
And 8 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014
The alternative adaptive immune system of jawless vertebrates is based on different isotypes of variable lymphocyte receptors (VLRs) that are composed of leucine-rich repeats (LRRs) and expressed by distinct B- and T-like lymphocyte lineages. VLRB is expressed by B-like cells, whereas VLRA and VLRC are expressed by two T-like lineages that develop in the thymoid, a thymus-like structure in lamprey larvae. In each case, stepwise combinatorial insertions of different types of short donor LRR cassettes into incomplete germ-line genes are required to generate functional VLR gene assemblies. It is unknown, however, whether the diverse repertoires of VLRs that are expressed by peripheral blood lymphocytes are shaped by selection after their assembly. Here, we identify signatures of selection in the peripheral repertoire of VLRC antigen receptors that are clonally expressed by one of the T-like cell types in lampreys. Selection strongly favors VLRC molecules containing four internal variable leucine-rich repeat (LRRV) modules, although VLRC assemblies encoding five internal modules are initially equally frequent. In addition to the length selection, VLRC molecules in VLRC+peripheral lymphocytes exhibit a distinct pattern of high entropy sites in the N-terminal LRR1 module, which is inserted next to the germ-line-encoded LRRNT module. This is evident in comparisons to VLRC gene assemblies found in the thymoid and to VLRC gene assemblies found in some VLRA+cells. Our findings are the first indication to our knowledge that selection operates on a VLR repertoire and provide a framework to establish the mechanism by which this selection occurs during development of the VLRC+ lymphocyte lineage. © 2014, National Academy of Sciences. All rights reserved.
Li Y.,University of Maryland Institute for Bioscience and Biotechnology Research |
Li Y.,University of Maryland University College |
Wang Q.,University of Maryland Institute for Bioscience and Biotechnology Research |
Wang Q.,University of Maryland University College |
And 2 more authors.
Journal of Experimental Medicine | Year: 2011
Natural killer (NK) cells are lymphocytes of the innate immune system that participate in the elimination of tumor cells. In humans, the activating natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46 play a major role in NK cell-mediated tumor cell lysis. NKp30 recognizes B7-H6, a member of the B7 family which is expressed on tumor, but not healthy, cells. To understand the basis for tumor surveillance by NCRs, we determined the structure of NKp30, a member of the CD28 family which includes CTLA-4 and PD-1, in complex with B7-H6. The overall organization of the NKp30-B7-H6-activating complex differs considerably from those of the CTLA-4-B7 and PD-1-PD-L T cell inhibitory complexes. Whereas CTLA-4 and PD-1 use only the front β-sheet of their Ig-like domain to bind ligands, NKp30 uses both front and back β-sheets, resulting in engagement of B7-H6 via the side, as well as face, of the β-sandwich. Moreover, B7-H6 contacts NKp30 through the complementarity-determining region (CDR)-like loops of its V-like domain in an antibody-like interaction that is not observed for B7 or PD-L. This first structure of an NCR bound to ligand provides a template for designing molecules to stimulate NKp30-mediated cytolytic activity for tumor immunotherapy. © 2011 Li et al.
PubMed | University of Maryland Institute for Bioscience and Biotechnology Research, Johns Hopkins University, University of Maryland University College, North Carolina State University and Shakti BioResearch
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2015
Prostate-associated gene 4 (PAGE4) is an intrinsically disordered cancer/testis antigen that is up-regulated in the fetal and diseased human prostate. Knocking down PAGE4 expression results in cell death, whereas its overexpression leads to a growth advantage of prostate cancer cells (Zeng, Y., He, Y., Yang, F., Mooney, S. M., Getzenberg, R. H., Orban, J., and Kulkarni, P. (2011) The cancer/testis antigen prostate-associated gene 4 (PAGE4) is a highly intrinsically disordered protein. J. Biol. Chem. 286, 13985-13994). Phosphorylation of PAGE4 at Thr-51 is critical for potentiating c-Jun transactivation, an important factor in controlling cell growth, apoptosis, and stress response. Using NMR spectroscopy, we show that the PAGE4 polypeptide chain has local and long-range conformational preferences that are perturbed by site-specific phosphorylation at Thr-51. The population of transient turn-like structures increases upon phosphorylation in an 20-residue acidic region centered on Thr-51. This central region therefore becomes more compact and more negatively charged, with increasing intramolecular contacts to basic sequence motifs near the N and C termini. Although flexibility is decreased in the central region of phospho-PAGE4, the polypeptide chain remains highly dynamic overall. PAGE4 utilizes a transient helical structure adjacent to the central acidic region to bind c-Jun with low affinity in vitro. The binding interaction is attenuated by phosphorylation at Thr-51, most likely because of masking the effects of the more compact phosphorylated state. Therefore, phosphorylation of PAGE4 leads to conformational shifts in the dynamic ensemble, with large functional consequences. The changes in the structural ensemble induced by posttranslational modifications are similar conceptually to the conformational switching events seen in some marginally stable (metamorphic) folded proteins in response to mutation or environmental triggers.
PubMed | University of Buenos Aires and University of Maryland College Park
Type: | Journal: The Biochemical journal | Year: 2016
Natural Killer (NK) cells are lymphocytes of the innate immune system that eliminate virally infected or malignantly transformed cells. NK cell function is regulated by diverse surface receptors that are both activating and inhibitory. Among them, the homodimeric Ly49 receptors control NK cell cytotoxicity by sensing MHC class I molecules on target cells. Although crystal structures have been reported for Ly49/MHC-I complexes, the underlying binding mechanism has not been elucidated. Accordingly, we carried out thermodynamic and kinetic experiments on the interaction of four Ly49 receptors (Ly49G, Ly49H, Ly49I and Ly49P) with two MHC-I ligands (H-2D
Pierce B.G.,University of Massachusetts Medical School |
Pierce B.G.,University of Maryland Institute for Bioscience and Biotechnology Research |
Vreven T.,University of Massachusetts Medical School |
Weng Z.,University of Massachusetts Medical School
BMC Bioinformatics | Year: 2014
Background: T cell receptors (TCRs) can recognize diverse lipid and metabolite antigens presented by MHC-like molecules CD1 and MR1, and the molecular basis of many of these interactions has not been determined. Here we applied our protein docking algorithm TCRFlexDock, previously developed to perform docking of TCRs to peptide-MHC (pMHC) molecules, to predict the binding of αβ and γδ TCRs to CD1 and MR1, starting with the structures of the unbound molecules. Results: Evaluating against TCR-CD1d complexes with crystal structures, we achieved near-native structures in the top 20 models for two out of four cases, and an acceptable-rated prediction for a third case. We also predicted the structure of an interaction between a MAIT TCR and MR1-antigen that has not been structurally characterized, yielding a top-ranked model that agreed remarkably with a characterized TCR-MR1-antigen structure that has a nearly identical TCR α chain but a different β chain, highlighting the likely dominance of the conserved α chain in MR1-antigen recognition. Docking performance was improved by re-training our scoring function with a set of TCR-pMHC complexes, and for a case with an outlier binding mode, we found that alternative docking start positions improved predictive accuracy. We then performed unbound docking with two mycolyl-lipid specific TCRs that recognize lipid-bound CD1b, which represent a class of interactions that is not structurally characterized. Highly-ranked models of these complexes showed remarkable agreement between their binding topologies, as expected based on their shared germline sequences, while differences in residue-level interactions with their respective antigens point to possible mechanisms underlying their distinct specificities. Conclusions: Together these results indicate that flexible docking simulations can provide accurate models and atomic-level insights into TCR recognition of MHC-like molecules presenting lipid and other small molecule antigens. © 2014 Pierce et al.; licensee BioMed Central Ltd.
PubMed | University of Buenos Aires and University of Maryland Institute for Bioscience and Biotechnology Research
Type: Journal Article | Journal: Immunology | Year: 2015
Peptidoglycan recognition proteins (PGRP) are pattern recognition receptors that can bind or hydrolyse peptidoglycan (PGN). Four human PGRP have been described: PGRP-S, PGRP-L, PGRP-I and PGRP-I. Mammalian PGRP-S has been implicated in intracellular destruction of bacteria by polymorphonuclear cells, PGRP-I and PGRP-I have been found in keratinocytes and epithelial cells, and PGRP-L is a serum protein that hydrolyses PGN. We have expressed recombinant human PGRP and observed that PGRP-S and PGRP-I exist as monomer and disulphide dimer proteins. The PGRP dimers maintain their biological functions. We detected the PGRP-S dimer in human serum and polymorphonuclear cells, from where it is secreted after degranulation; these cells being a possible source of serum PGRP-S. Recombinant PGRP do not act as bactericidal or bacteriostatic agents in the assayed conditions; however, PGRP-S and PGRP-I cause slight damage in the bacterial membrane. Monocytes/macrophages increase Staphylococcus aureus phagocytosis in the presence of PGRP-S, PGRP-I and PGRP-I. All PGRP bind to monocyte/macrophage membranes and are endocytosed by them. In addition, all PGRP protect cells from PGN-induced apoptosis. PGRP increase THP-1 cell proliferation and enhance activation by PGN. PGRP-S-PGN complexes increase the membrane expression of CD14, CD80 and CD86, and enhance secretion of interleukin-8, interleukin-12 and tumour necrosis factor-, but reduce interleukin-10, clearly inducing an inflammatory profile.