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Partin AC, Bruno R, Shafaattalab S, Vander Mause E, Winters A, Daris M, Gahrs C, Jette CA, DiAndreth B, Sandberg ML, Hamburger AE, Kamb A, Riley TP. Geometric parameters that affect the behavior of logic-gated CAR T cells. Front Immunol 2024; 15:1304765. [PMID: 38343543 PMCID: PMC10853413 DOI: 10.3389/fimmu.2024.1304765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/12/2024] [Indexed: 02/15/2024] Open
Abstract
Clinical applications of CAR-T cells are limited by the scarcity of tumor-specific targets and are often afflicted with the same on-target/off-tumor toxicities that plague other cancer treatments. A new promising strategy to enforce tumor selectivity is the use of logic-gated, two-receptor systems. One well-described application is termed Tmod™, which originally utilized a blocking inhibitory receptor directed towards HLA-I target antigens to create a protective NOT gate. Here we show that the function of Tmod blockers targeting non-HLA-I antigens is dependent on the height of the blocker antigen and is generally compatible with small, membrane-proximal targets. We compensate for this apparent limitation by incorporating modular hinge units to artificially extend or retract the ligand-binding domains relative to the effector cell surface, thereby modulating Tmod activator and blocker function. By accounting for structural differences between activator and blocker targets, we developed a set of simple geometric parameters for Tmod receptor design that enables targeting of blocker antigens beyond HLA-I, thereby broadening the applications of logic-gated cell therapies.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Alexander Kamb
- A2 Biotherapeutics, Inc., Agoura Hills, CA, United States
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2
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Mock JY, Winters A, Riley TP, Bruno R, Naradikian MS, Sharma S, Jette CA, Elshimali R, Gahrs C, Toledo-Warshaviak D, West AP, Kamb A, Hamburger AE. HLA-A∗02-gated safety switch for cancer therapy has exquisite specificity for its allelic target antigen. Mol Ther Oncolytics 2022; 27:157-166. [PMID: 36381658 PMCID: PMC9619369 DOI: 10.1016/j.omto.2022.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/30/2022] [Indexed: 12/02/2022] Open
Abstract
Innovative cell-based therapies are important new weapons in the fight against difficult-to-treat cancers. One promising strategy involves cell therapies equipped with multiple receptors to integrate signals from more than one antigen. We developed a specific embodiment of this approach called Tmod, a two-receptor system that combines activating and inhibitory inputs to distinguish between tumor and normal cells. The selectivity of Tmod is enforced by the inhibitory receptor (blocker) that recognizes an antigen, such as an HLA allele, whose expression is absent from tumors because of loss of heterozygosity. Although unwanted cross-reactivity of the blocker likely reduces efficacy rather than safety, it is important to verify the blocker's specificity. We have tested an A∗02-directed blocker derived from the PA2.1 mouse antibody as a safety mechanism paired with a mesothelin-specific activating CAR in our Tmod construct. We solved the crystal structure of humanized PA2.1 Fab in complex with HLA-A∗02 to determine its binding epitope, which was used to bioinformatically select specific class I HLA alleles to test the blocker's functional specificity in vitro. We found that this A∗02-directed blocker is highly specific for its cognate antigen, with only one cross-reactive allele (A∗69) capable of triggering comparable function.
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Affiliation(s)
- Jee-Young Mock
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | - Aaron Winters
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | - Timothy P. Riley
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | - Richele Bruno
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | | | - Shruti Sharma
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | - Claudia A. Jette
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Ryan Elshimali
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | - Casey Gahrs
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA
| | | | - Anthony P. West
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Alexander Kamb
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA,Corresponding author Alexander Kamb, PhD, A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA.
| | - Agnes E. Hamburger
- A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA,Corresponding author Agnes E. Hamburger, A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301, USA.
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DiAndreth B, Hamburger AE, Xu H, Kamb A. The Tmod cellular logic gate as a solution for tumor-selective immunotherapy. Clin Immunol 2022; 241:109030. [PMID: 35561999 DOI: 10.1016/j.clim.2022.109030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 05/02/2022] [Indexed: 11/03/2022]
Abstract
Immune cells that are engineered with receptors to integrate signals from multiple antigens offer a promising route to achieve the elusive property of therapeutic selectivity in cancer patients. Several types of multi-signal integrators have been described, among them mechanisms that pair activating and inhibitory receptors which are termed NOT gates by analogy to logical operations performed by machines. Here we review one such NOT-gated signal integrator called the Tmod system which is being developed for patients with solid tumors. Coupled with rigorous selection for patients with defined lesions in their tumor genomes (loss of heterozygosity), the Tmod approach presents an unusual opportunity to create truly selective therapies for certain cancer patients. Several of these agents are advancing toward the clinic, supported by a large body of quantitative preclinical data.
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Affiliation(s)
| | | | - Han Xu
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA 91301, USA
| | - Alexander Kamb
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA 91301, USA.
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Tokatlian T, Asuelime GE, Mock JY, DiAndreth B, Sharma S, Toledo Warshaviak D, Daris ME, Bolanos K, Luna BL, Naradikian MS, Deshmukh K, Hamburger AE, Kamb A. Mesothelin-specific CAR-T cell therapy that incorporates an HLA-gated safety mechanism selectively kills tumor cells. J Immunother Cancer 2022; 10:jitc-2021-003826. [PMID: 35091455 PMCID: PMC8804709 DOI: 10.1136/jitc-2021-003826] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2021] [Indexed: 12/31/2022] Open
Abstract
Background Mesothelin (MSLN) is a classic tumor-associated antigen that is expressed in lung cancer and many other solid tumors. However, MSLN is also expressed in normal mesothelium which creates a significant risk of serious inflammation for MSLN-directed therapeutics. We have developed a dual-receptor (Tmod™) system that exploits the difference between tumor and normal tissue in a subset of patients with defined heterozygous gene loss (LOH) in their tumors. Methods T cells engineered with the MSLN CAR Tmod construct described here contain (1) a novel MSLN-activated CAR and (2) an HLA-A*02-gated inhibitory receptor (blocker). A*02 binding is intended to override T-cell cytotoxicity, even in the presence of MSLN. The Tmod system is designed to treat heterozygous HLA class I patients, selected for HLA LOH. When A*02 is absent from tumors selected for LOH, the MSLN Tmod cells are predicted to mediate potent killing of the MSLN(+)A*02(−) malignant cells. Results The sensitivity of the MSLN Tmod cells is comparable with a benchmark MSLN CAR-T that was active but toxic in the clinic. Unlike MSLN CAR-T cells, the Tmod system robustly protects surrogate “normal” cells even in mixed-cell populations in vitro and in a xenograft model. The MSLN CAR can also be paired with other HLA class I blockers, supporting extension of the approach to patients beyond A*02 heterozygotes. Conclusions The Tmod mechanism exemplified by the MSLN CAR Tmod construct provides an alternative route to leverage solid-tumor antigens such as MSLN in safer, more effective ways than previously possible.
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Affiliation(s)
| | | | | | | | - Shruti Sharma
- A2 Biotherapeutics Inc, Agoura Hills, California, USA
| | | | - Mark E Daris
- A2 Biotherapeutics Inc, Agoura Hills, California, USA
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Tokatlian T, Asuelime GE, Naradikian MS, Mock JY, Daris ME, Martin AD, Toledo Warshaviak D, Kamb A, Hamburger AE. Chimeric Antigen Receptors Directed at Mutant KRAS Exhibit an Inverse Relationship Between Functional Potency and Neoantigen Selectivity. Cancer Res Commun 2022; 2:58-65. [PMID: 36860694 PMCID: PMC9973398 DOI: 10.1158/2767-9764.crc-21-0165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/03/2022] [Accepted: 01/13/2022] [Indexed: 11/16/2022]
Abstract
Neoantigens are among the most intriguing potential immuno-oncology targets because, unlike many cancer targets that are expressed on normal tissues, they are by definition restricted to cancer cells. Medicines directed at common neoantigens such as mutant KRAS are especially interesting because they may offer the convenience and cost of an off-the-shelf therapy. However, all common KRAS mutations produce proteins that differ from the wild type at a single amino acid, creating challenges for molecular discrimination. We have undertaken an effort to optimize single-chain variable fragments (scFv) against peptide/major histocompatibility antigen complexes composed of HLA-A*11 and either G12V- or G12D-mutant KRAS peptides. These scFvs could in principle be used in chimeric antigen receptor (CAR) T-cell therapies for selected patients whose tumors bear either of these mutations. Here we show that optimization of such CARs involves a trade-off between potency and selectivity. We further show that targeting this family without high selectivity engenders risks of cross-reactivity against other members of the G-protein family to which KRAS belongs. Significance We report an effort to generate high potency, selective CARs directed at mutant KRAS peptides. Although the heavily optimized CARs maintain high selectivity against wild-type KRAS, they lose selectivity against other KRAS-related peptides derived from human proteins. To our knowledge, this work is the first to examine the trade-off between potency and selectivity with regard to KRAS pMHC-directed CARs, illustrating the challenge to achieve both sufficient potency and high selectivity.
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Affiliation(s)
| | | | | | | | - Mark E. Daris
- Research, A2 Biotherapeutics, Agoura Hills, California
| | | | | | | | - Agnes E. Hamburger
- Research, A2 Biotherapeutics, Agoura Hills, California.,Corresponding Author: Agnes E. Hamburger, Research, A2 Biotherapeutics, 30301 Agoura Road, Agoura Hills, CA 91301. Phone: 805-491-1988; E-mail:
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Hamburger AE, DiAndreth B, Cui J, Daris ME, Munguia ML, Deshmukh K, Mock JY, Asuelime GE, Lim ED, Kreke MR, Tokatlian T, Kamb A. Engineered T cells directed at tumors with defined allelic loss. Mol Immunol 2020; 128:298-310. [DOI: 10.1016/j.molimm.2020.09.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/10/2020] [Accepted: 09/17/2020] [Indexed: 12/30/2022]
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Xu H, Hamburger AE, Mock JY, Wang X, Martin AD, Tokatlian T, Oh J, Daris ME, Negri KR, Gabrelow GB, Wu ML, Nampe DP, Asuelime GE, McElvain ME, Sandberg ML, Kamb A. Structure-function relationships of chimeric antigen receptors in acute T cell responses to antigen. Mol Immunol 2020; 126:56-64. [PMID: 32768859 DOI: 10.1016/j.molimm.2020.07.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/28/2020] [Indexed: 12/31/2022]
Abstract
Chimeric antigen receptors (CARs) and their parent signaling molecule, the T cell receptor (TCR), are fascinating proteins of increasing relevance to disease therapy. Here we use a collection of 1221 pMHC-directed CAR constructs representing 10 pMHC targets to study aspects of CAR structure-activity relationships (SAR), with particular focus on the extracellular and transmembrane structural components. These experiments that involve pMHC targets whose number/cell can be manipulated by peptide dosing in vitro enable systematic analysis of the SAR of CARs in carefully controlled experimental situations (Harris and Kranz, 2016). We find that CARs tolerate a wide range of structural variation, with the ligand-binding domains (LBDs) dominating the SAR of CAR antigen sensitivity. Notwithstanding the critical role of the LBD, CAR antigen-binding on the cell surface, measured by pMHC tetramer staining, is not an effective predictor of functional sensitivity. These results have important implications for the design and testing of CARs aimed toward the clinic.
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Affiliation(s)
- Han Xu
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Agnes E Hamburger
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Jee-Young Mock
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Xueyin Wang
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Aaron D Martin
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Talar Tokatlian
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Julyun Oh
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Mark E Daris
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Kathleen R Negri
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Grant B Gabrelow
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Ming Lun Wu
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Daniel P Nampe
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Grace E Asuelime
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Michele E McElvain
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Mark L Sandberg
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States
| | - Alexander Kamb
- A2 Biotherapeutics, 30301 Agoura Rd., Agoura Hills, CA, 91301, United States.
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Arora T, Padaki R, Liu L, Hamburger AE, Ellison AR, Stevens SR, Louie JS, Kohno T. Differences in binding and effector functions between classes of TNF antagonists. Cytokine 2009; 45:124-31. [PMID: 19128982 DOI: 10.1016/j.cyto.2008.11.008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Revised: 10/06/2008] [Accepted: 11/19/2008] [Indexed: 12/16/2022]
Abstract
There are currently two Food and Drug Administration-approved classes of biologic agents that target tumor necrosis factor-alpha (TNF-alpha): anti-TNF monoclonal antibodies (mAbs) (adalimumab and infliximab), and soluble TNF receptors (etanercept). This study examined the ability of the TNF antagonists to: (1) bind various polymorphic variants of cell surface-expressed Fc receptors (FcgammaRs) and the complement component C1q, and (2) mediate Ab-dependent cellular cytotoxicity (ADCC) and complement-mediated cytotoxicity (CDC) killing of cells expressing membrane-bound TNF (mTNF) in vitro. Both mAbs and the soluble TNF receptor demonstrated low-level binding to the activating receptors FcgammaRI, FcgammaRIIa, and FcgammaRIIIa, and the inhibitory receptor FcgammaRIIb, in the absence of exogenous TNF. However, upon addition of TNF, the mAbs, but not etanercept, showed significantly increased binding, in particular to the FcgammaRII and FcgammaRIII receptors. Infliximab and adalimumab induced ADCC much more potently than etanercept. In the presence of TNF, both mAbs bound C1q in in vitro assays, but etanercept did not bind C1q under any conditions. Infliximab and adalimumab also induced CDC in cells expressing mTNF more potently than etanercept. Differences in the ability to bind ligand and mediate cell death may account for the differences in efficacy and safety of TNF antagonists.
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Affiliation(s)
- Taruna Arora
- Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1799, USA.
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Abstract
The mucosal regions of the body are responsible for defense against environmental pathogens. Particularly in the lumen of the gut, antibody-mediated immune responses are critical for preventing invasion by pathogens. In this chapter, we review structural studies that have illuminated various aspects of mucosal immunity. Crystal structures of IgA1-Fc and IgA-binding fragments of the polymeric immunoglobulin receptor and Fc alphaRI, combined with models of intact IgA and IgM from solution scattering studies, reveal potential mechanisms for immune exclusion and induction of inflammatory responses. Other recent structures yield insights into bacterial mechanisms for evasion of the host immune response.
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Affiliation(s)
- A E Hamburger
- Division of Biology, California Institute of Technology, 114-96, Pasadena, CA 91125, USA
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Hamburger ZA, Hamburger AE, West AP, Weis WI. Crystal structure of the S.cerevisiae exocyst component Exo70p. J Mol Biol 2005; 356:9-21. [PMID: 16359701 DOI: 10.1016/j.jmb.2005.09.099] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 09/29/2005] [Indexed: 11/17/2022]
Abstract
The exocyst is an evolutionarily conserved multiprotein complex required for the targeting and docking of post-Golgi vesicles to the plasma membrane. Through its interactions with a variety of proteins, including small GTPases, the exocyst is thought to integrate signals from the cell and signal that vesicles arriving at the plasma membrane are ready for fusion. Here we describe the three-dimensional crystal structure of one of the components of the exocyst, Exo70p, from Saccharomyces cerevisiae at 3.5A resolution. Exo70p binds the small GTPase Rho3p in a GTP-dependent manner with an equilibrium dissociation constant of approximately 70 microM. Exo70p is an extended rod approximately 155 angstroms in length composed principally of alpha helices, and is a novel fold. The structure provides a first view of the Exo70 protein family and provides a framework to study the molecular function of this exocyst component.
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Affiliation(s)
- Zsuzsa A Hamburger
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA
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Hamburger AE, West AP, Hamburger ZA, Hamburger P, Bjorkman PJ. Crystal Structure of a Secreted Insect Ferritin Reveals a Symmetrical Arrangement of Heavy and Light Chains. J Mol Biol 2005; 349:558-69. [PMID: 15896348 DOI: 10.1016/j.jmb.2005.03.074] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Revised: 03/23/2005] [Accepted: 03/25/2005] [Indexed: 10/25/2022]
Abstract
Ferritins are iron storage proteins made of 24 subunits forming a hollow spherical shell. Vertebrate ferritins contain varying ratios of heavy (H) and light (L) chains; however, known ferritin structures include only one type of chain and have octahedral symmetry. Here, we report the 1.9A structure of a secreted insect ferritin from Trichoplusia ni, which reveals equal numbers of H and L chains arranged with tetrahedral symmetry. The H/L-chain interface includes complementary features responsible for ordered assembly of the subunits. The H chain contains a ferroxidase active site resembling that of vertebrate H chains with an endogenous, bound iron atom. The L chain lacks the residues that form a putative iron core nucleation site in vertebrate L chains. Instead, a possible nucleation site is observed at the L chain 3-fold pore. The structure also reveals inter- and intrasubunit disulfide bonds, mostly in the extended N-terminal regions unique to insect ferritins. The symmetrical arrangement of H and L chains and the disulfide crosslinks reflect adaptations of insect ferritin to its role as a secreted protein.
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Affiliation(s)
- Agnes E Hamburger
- Division of Biology 114-96, California Institute of Technology, Pasadena, CA 91125, USA
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Abstract
During human immunodeficiency virus entry, gp41 undergoes a series of conformational changes that induce membrane fusion. Immediately prior to fusion, gp41 exists in a prehairpin intermediate in which the N- and C-peptide regions of gp41 are exposed. Rearrangement of this intermediate into a six-helix bundle composed of a trimeric coiled coil from the N-peptide region (N-trimer) surrounded by three peptides from the C-peptide region provides the driving force for membrane fusion, whereas prevention of six-helix bundle formation inhibits viral entry. Because of its central role in mediating viral entry, the N-trimer region of gp41 is a key vaccine target. Extensive efforts to discover potent and broadly neutralizing antibodies (Abs) against the N-trimer region have, thus far, been unsuccessful. In this study, we attached a potent C-peptide inhibitor that binds to the N-trimer region to cargo proteins of various sizes to examine the steric accessibility of the N-trimer during fusion. These inhibitors show a progressive loss of potency with increasing cargo size. Extension of the cargo/C-peptide linker partially restores inhibitory potency. These results demonstrate that the human immunodeficiency virus defends its critical hairpin-forming machinery by steric exclusion of large proteins and may explain the current dearth of neutralizing Abs against the N-trimer. In contrast, previous results suggest the C-peptide region is freely accessible during fusion, demonstrating that the N- and C-peptide regions are in structurally distinct environments. Based on these results, we also propose new strategies for the generation of neutralizing Abs that overcome this steric block.
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Affiliation(s)
- Agnes E Hamburger
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Luo R, Mann B, Lewis WS, Rowe A, Heath R, Stewart ML, Hamburger AE, Sivakolundu S, Lacy ER, Bjorkman PJ, Tuomanen E, Kriwacki RW. Solution structure of choline binding protein A, the major adhesin of Streptococcus pneumoniae. EMBO J 2004; 24:34-43. [PMID: 15616594 PMCID: PMC544903 DOI: 10.1038/sj.emboj.7600490] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Accepted: 11/03/2004] [Indexed: 11/09/2022] Open
Abstract
Streptococcus pneumoniae (pneumococcus) remains a significant health threat worldwide, especially to the young and old. While some of the biomolecules involved in pneumococcal pathogenesis are known and understood in mechanistic terms, little is known about the molecular details of bacterium/host interactions. We report here the solution structure of the 'repeated' adhesion domains (domains R1 and R2) of the principal pneumococcal adhesin, choline binding protein A (CbpA). Further, we provide insights into the mechanism by which CbpA binds its human receptor, polymeric immunoglobulin receptor (pIgR). The R domains, comprised of 12 imperfect copies of the leucine zipper heptad motif, adopt a unique 3-alpha-helix, raft-like structure. Each pair of alpha-helices is antiparallel and conserved residues in the loop between Helices 1 and 2 exhibit a novel 'tyrosine fork' structure that is involved in binding pIgR. This and other structural features that we show are conserved in most pneumococcal strains appear to generally play an important role in bacterial adhesion to pIgR. Interestingly, pneumococcus is the only bacterium known to adhere to and invade human cells by binding to pIgR.
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Affiliation(s)
- Rensheng Luo
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Beth Mann
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA
| | - William S Lewis
- Hartwell Center for Bioinformatics and Biotechnology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Arthur Rowe
- National Centre for Macromolecular Hydrodynamics, University of Nottingham, School of Biosciences, Sutton, Bonington, Leicestershire, UK
| | - Richard Heath
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA
- Division of Protein Sciences, Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Michael L Stewart
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
- Department of Molecular Sciences, University of Tennessee Health Sciences Center, Memphis, TN, USA
| | | | - Siva Sivakolundu
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Eilyn R Lacy
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Pamela J Bjorkman
- Division of Biology, Pasadena, CA, USA
- Howard Hughes Medical Institute California Institute of Technology, Pasadena, CA, USA
| | - Elaine Tuomanen
- Department of Infectious Diseases, St Jude Children's Research Hospital, Memphis, TN, USA
- Department of Molecular Sciences, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Pediatrics, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Infectious Diseases, St Jude Children's Research Hospital, 332 N Lauderdale St, Memphis, TN 38105, USA. Tel.: +1 901 495 3486; E-mail:
| | - Richard W Kriwacki
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA
- Department of Molecular Sciences, University of Tennessee Health Sciences Center, Memphis, TN, USA
- Department of Structural Biology, St Jude Children's Research Hospital, Room D1024/Mail Drop 311, 332 N Lauderdale St, Memphis, TN 38105, USA. Tel.: +1 901 495 3290; Fax: +1 901 495 3032; E-mail:
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Hamburger AE, West AP, Bjorkman PJ. Crystal Structure of a Polymeric Immunoglobulin Binding Fragment of the Human Polymeric Immunoglobulin Receptor. Structure 2004; 12:1925-35. [PMID: 15530357 DOI: 10.1016/j.str.2004.09.006] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Revised: 09/02/2004] [Accepted: 09/03/2004] [Indexed: 11/28/2022]
Abstract
The polymeric immunoglobulin receptor (pIgR) is a type I transmembrane protein that delivers dimeric IgA (dIgA) and pentameric IgM to mucosal secretions. Here, we report the 1.9 A resolution X-ray crystal structure of the N-terminal domain of human pIgR, which binds dIgA in the absence of other pIgR domains with an equilibrium dissociation constant of 300 nM. The structure of pIgR domain 1 reveals a folding topology similar to immunoglobulin variable domains, but with differences in the counterparts of the complementarity determining regions (CDRs), including a helical turn in CDR1 and a CDR3 loop that points away from the other CDRs. The unusual CDR3 loop position prevents dimerization analogous to the pairing of antibody variable heavy and variable light domains. The pIgR domain 1 structure allows interpretation of previous mutagenesis results and structure-based comparisons between pIgR and other IgA receptors.
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Affiliation(s)
- Agnes E Hamburger
- Division of Biology 114-96, California Institute of Technology, Pasadena, CA 91125, USA
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Tellinghuisen TL, Hamburger AE, Fisher BR, Ostendorp R, Kuhn RJ. In vitro assembly of alphavirus cores by using nucleocapsid protein expressed in Escherichia coli. J Virol 1999; 73:5309-19. [PMID: 10364277 PMCID: PMC112586 DOI: 10.1128/jvi.73.7.5309-5319.1999] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of the alphavirus virion is a multistep event requiring the assembly of the nucleocapsid core in the cytoplasm and the maturation of the glycoproteins in the endoplasmic reticulum and the Golgi apparatus. These components associate during the budding process to produce the mature virion. The nucleocapsid proteins of Sindbis virus and Ross River virus have been produced in a T7-based Escherichia coli expression system and purified. In the presence of single-stranded but not double-stranded nucleic acid, the proteins oligomerize in vitro into core-like particles which resemble the native viral nucleocapsid cores. Despite their similarities, Sindbis virus and Ross River virus capsid proteins do not form mixed core-like particles. Truncated forms of the Sindbis capsid protein were used to establish amino acid requirements for assembly. A capsid protein starting at residue 19 [CP(19-264)] was fully competent for in vitro assembly, whereas proteins with further N-terminal truncations could not support assembly. However, a capsid protein starting at residue 32 or 81 was able to incorporate into particles in the presence of CP(19-264) or could inhibit assembly if its molar ratio relative to CP(19-264) was greater than 1:1. This system provides a basis for the molecular dissection of alphavirus core assembly.
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Affiliation(s)
- T L Tellinghuisen
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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