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Jiang M, Liu R, Liu L, Kot A, Liu X, Xiao W, Jia J, Li Y, Lam KS, Yao W. Identification of osteogenic progenitor cell-targeted peptides that augment bone formation. Nat Commun 2020; 11:4278. [PMID: 32855388 PMCID: PMC7453024 DOI: 10.1038/s41467-020-17417-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 06/16/2020] [Indexed: 12/02/2022] Open
Abstract
Activation and migration of endogenous mesenchymal stromal cells (MSCs) are critical for bone regeneration. Here, we report a combinational peptide screening strategy for rapid discovery of ligands that not only bind strongly to osteogenic progenitor cells (OPCs) but also stimulate osteogenic cell Akt signaling in those OPCs. Two lead compounds are discovered, YLL3 and YLL8, both of which increase osteoprogenitor osteogenic differentiation in vitro. When given to normal or osteopenic mice, the compounds increase mineral apposition rate, bone formation, bone mass, and bone strength, as well as expedite fracture repair through stimulated endogenous osteogenesis. When covalently conjugated to alendronate, YLLs acquire an additional function resulting in a “tri-functional” compound that: (i) binds to OPCs, (ii) targets bone, and (iii) induces “pro-survival” signal. These bone-targeted, osteogenic peptides are well suited for current tissue-specific therapeutic paradigms to augment the endogenous osteogenic cells for bone regeneration and the treatment of bone loss. Activation of osteogenic cells is essential for bone regeneration. Here, the authors screen a peptide library and identify 2 compounds that promote osteogenic progenitor cell differentiation in vitro, and show that they increase bone formation and fracture repair in mice.
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Affiliation(s)
- Min Jiang
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA.,Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Shanghai Institute of Traumatology and Orthopaedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Ruijin 2nd Road, 200025, Shanghai, China
| | - Ruiwu Liu
- Department of Biochemistry and Molecular Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Lixian Liu
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Alexander Kot
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Xueping Liu
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Wenwu Xiao
- Department of Biochemistry and Molecular Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Junjing Jia
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Yuanpei Li
- Department of Biochemistry and Molecular Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Kit S Lam
- Department of Biochemistry and Molecular Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA
| | - Wei Yao
- Center for Musculoskeletal Health, Department of Internal Medicine, The University of California at Davis Medical Center, Sacramento, CA, 95817, USA.
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2
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Capuano A, Fogolari F, Bucciotti F, Spessotto P, Nicolosi PA, Mucignat MT, Cervi M, Esposito G, Colombatti A, Doliana R. The α4β1/EMILIN1 interaction discloses a novel and unique integrin-ligand type of engagement. Matrix Biol 2017; 66:50-66. [PMID: 29037761 DOI: 10.1016/j.matbio.2017.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/06/2017] [Accepted: 10/07/2017] [Indexed: 10/18/2022]
Abstract
EMILIN1, a homo-trimeric adhesive ECM glycoprotein, interacts with the α4β1 integrin through its gC1q domain. Uniquely among the C1q family members, the EMILIN1 gC1q presents only nine-stranded β-sandwich fold and the missing strand is substituted by a disordered 19-residue long segment spanning from Y927 to G945 at the apex of the gC1q domain. This unstructured loop exposes to the solvent the acidic residue E933, which plays a key role in the α4β1 integrin mediated interaction. Here, we experimentally determined that the three E933 residues (one from each monomer) are all required for ligand binding. By docking the NMR structure of the gC1q to a virtual α4β1 crystal structure based on the known structures of α4β7 and α5β1 integrins we built a model of α4β1-gC1q complex where three E933 residues are smoothly forced to coordinate the Mg2+ ion at the βI MIDAS site of the integrin. By bringing the three E933 close in space, the trimeric supramolecular organization of gC1q allows the formation of a proper 3D geometry and suggests a quaternary-structure-dependent mode of interaction. Furthermore, we experimentally identified R904 as a synergistic residue for cell adhesion. Accordingly, the model showed that this residue is able to form potential stabilizing intra-chain salt bridges with residues E928 and E930. This mode of interaction likely accounts for a more stable and durable α4β1-gC1q interaction in comparison with the prototypic CS1 ligand. To our knowledge, this is the first report describing the simultaneous involvement of all the three acidic residues of a trimeric ligand in the formation of a dimeric complex with the integrin βI domain.
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Affiliation(s)
- Alessandra Capuano
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Federico Fogolari
- Department of Computer Science, Mathematics and Physics, University of Udine, Piazzale Kolbe 4, 33100 Udine, Italy
| | - Francesco Bucciotti
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Paola Spessotto
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Pier Andrea Nicolosi
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Maria Teresa Mucignat
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Marta Cervi
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy
| | - Gennaro Esposito
- Department of Computer Science, Mathematics and Physics, University of Udine, Piazzale Kolbe 4, 33100 Udine, Italy; Math&Science Division, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Alfonso Colombatti
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy.
| | - Roberto Doliana
- Department of Translational Research, Molecular Oncology Unit, CRO Aviano, National Cancer Institute, Via Franco Gallini 2, 33081 Aviano, PN, Italy.
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3
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Bhunia D, Saha A, Adak A, Das G, Ghosh S. A dual functional liposome specifically targets melanoma cells through integrin and ephrin receptors. RSC Adv 2016. [DOI: 10.1039/c6ra23864e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A novel bi-functional liposome delivers docetaxel specifically to melanoma cancer cells targeting integrin (α4β1) and ephrin (EphA2) receptors and enhances the efficacy of docetaxel.
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Affiliation(s)
- Debmalya Bhunia
- Organic & Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700032
- India
| | - Abhijit Saha
- Organic & Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700032
- India
| | - Anindyasundar Adak
- Organic & Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700032
- India
| | - Gaurav Das
- Academy of Scientific and Innovative Research (AcSIR)
- Kolkata 700 032
- India
| | - Surajit Ghosh
- Organic & Medicinal Chemistry Division
- CSIR-Indian Institute of Chemical Biology
- Kolkata-700032
- India
- Academy of Scientific and Innovative Research (AcSIR)
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4
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Ham TR, Lee RT, Han S, Haque S, Vodovotz Y, Gu J, Burnett LR, Tomblyn S, Saul JM. Tunable Keratin Hydrogels for Controlled Erosion and Growth Factor Delivery. Biomacromolecules 2015; 17:225-36. [PMID: 26636618 DOI: 10.1021/acs.biomac.5b01328] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Tunable erosion of polymeric materials is an important aspect of tissue engineering for reasons that include cell infiltration, controlled release of therapeutic agents, and ultimately to tissue healing. In general, the biological response to proteinaceous polymeric hydrogels is favorable (e.g., minimal inflammatory response). However, unlike synthetic polymers, achieving tunable erosion with natural materials is a challenge. Keratins are a class of intermediate filament proteins that can be obtained from several sources, including human hair, and have gained increasing levels of use in tissue engineering applications. An important characteristic of keratin proteins is the presence of a large number of cysteine residues. Two classes of keratins with different chemical properties can be obtained by varying the extraction techniques: (1) keratose by oxidative extraction and (2) kerateine by reductive extraction. Cysteine residues of keratose are "capped" by sulfonic acid and are unable to form covalent cross-links upon hydration, whereas cysteine residues of kerateine remain as sulfhydryl groups and spontaneously form covalent disulfide cross-links. Here, we describe a straightforward approach to fabricate keratin hydrogels with tunable rates of erosion by mixing keratose and kerateine. SEM imaging and mechanical testing of freeze-dried materials showed similar pore diameters and compressive moduli, respectively, for each keratose-kerateine mixture formulation (∼1200 kPa for freeze-dried materials and ∼1.5 kPa for hydrogels). However, the elastic modulus (G') determined by rheology varied in proportion with the keratose-kerateine ratios, as did the rate of hydrogel erosion and the release rate of thiol from the hydrogels. The variation in keratose-kerateine ratios also led to tunable control over release rates of recombinant human insulin-like growth factor 1.
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Affiliation(s)
- Trevor R Ham
- Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States.,Department of Biomedical Engineering, University of Akron , Auburn Science and Engineering Center 275, West Tower, Akron, Ohio 44325, United States
| | - Ryan T Lee
- Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States
| | - Sangheon Han
- Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States
| | - Salma Haque
- Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States
| | - Yael Vodovotz
- Department of Food Science and Technology, The Ohio State University , 2015 Fyffe Court, Columbus, Ohio 43210, United States
| | - Junnan Gu
- Department of Food Science and Technology, The Ohio State University , 2015 Fyffe Court, Columbus, Ohio 43210, United States
| | - Luke R Burnett
- KeraNetics, LLC , 200 East First Street, Box 4, Suite 102, Winston-Salem, North Carolina 27101, United States
| | - Seth Tomblyn
- KeraNetics, LLC , 200 East First Street, Box 4, Suite 102, Winston-Salem, North Carolina 27101, United States
| | - Justin M Saul
- Department of Chemical, Paper and Biomedical Engineering, Miami University , 650 East High Street, Oxford, Ohio 45056, United States
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5
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Han S, Ham TR, Haque S, Sparks JL, Saul JM. Alkylation of human hair keratin for tunable hydrogel erosion and drug delivery in tissue engineering applications. Acta Biomater 2015; 23:201-213. [PMID: 25997587 PMCID: PMC4522204 DOI: 10.1016/j.actbio.2015.05.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 05/08/2015] [Accepted: 05/12/2015] [Indexed: 12/11/2022]
Abstract
Polymeric biomaterials that provide a matrix for cell attachment and proliferation while achieving delivery of therapeutic agents are an important component of tissue engineering and regenerative medicine strategies. Keratins are a class of proteins that have received attention for numerous tissue engineering applications because, like other natural polymers, they promote favorable cell interactions and have non-toxic degradation products. Keratins can be extracted from various sources including human hair, and they are characterized by a high percentage of cysteine residues. Thiol groups on reductively extracted keratin (kerateine) form disulfide bonds, providing a more stable cross-linked hydrogel network than oxidatively extracted keratin (keratose) that cannot form disulfide crosslinks. We hypothesized that an iodoacetamide alkylation (or "capping") of cysteine thiol groups on the kerateine form of keratin could be used as a simple method to modulate the levels of disulfide crosslinking in keratin hydrogels, providing tunable rates of gel erosion and therapeutic agent release. After alkylation, the alkylated kerateines still formed hydrogels and the alkylation led to changes in the mechanical and visco-elastic properties of the materials consistent with loss of disulfide crosslinking. The alkylated kerateines did not lead to toxicity in MC3T3-E1 pre-osteoblasts. These cells adhered to keratin at levels comparable to fibronectin and greater than collagen. Alkylated kerateine gels eroded more rapidly than non-alkylated kerateine and this control over erosion led to tunable rates of delivery of rhBMP-2, rhIGF-1, and ciprofloxacin. These results demonstrate that alkylation of kerateine cysteine residues provides a cell-compatible approach to tune rates of hydrogel erosion and therapeutic agent release within the context of a naturally-derived polymeric system.
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Affiliation(s)
- Sangheon Han
- Department of Chemical, Paper and Biomedical Engineering, Miami University, 650 E. High Street, Oxford, OH 45056, USA
| | - Trevor R Ham
- Department of Chemical, Paper and Biomedical Engineering, Miami University, 650 E. High Street, Oxford, OH 45056, USA; Department of Biomedical Engineering, University of Akron, Auburn Science and Engineering Center 275, West Tower, Akron, OH 44325, USA
| | - Salma Haque
- Department of Chemical, Paper and Biomedical Engineering, Miami University, 650 E. High Street, Oxford, OH 45056, USA
| | - Jessica L Sparks
- Department of Chemical, Paper and Biomedical Engineering, Miami University, 650 E. High Street, Oxford, OH 45056, USA
| | - Justin M Saul
- Department of Chemical, Paper and Biomedical Engineering, Miami University, 650 E. High Street, Oxford, OH 45056, USA.
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6
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Hanf KJM, Arndt JW, Chen LL, Jarpe M, Boriack-Sjodin PA, Li Y, van Vlijmen HWT, Pepinsky RB, Simon KJ, Lugovskoy A. Antibody humanization by redesign of complementarity-determining region residues proximate to the acceptor framework. Methods 2013; 65:68-76. [PMID: 23816785 DOI: 10.1016/j.ymeth.2013.06.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 05/29/2013] [Accepted: 06/18/2013] [Indexed: 12/01/2022] Open
Abstract
Antibodies are key components of the adaptive immune system and are well-established protein therapeutic agents. Typically high-affinity antibodies are obtained by immunization of rodent species that need to be humanized to reduce their immunogenicity. The complementarity-determining regions (CDRs) contain the residues in a defined loop structure that confer antigen binding, which must be retained in the humanized antibody. To design a humanized antibody, we graft the mature murine CDRs onto a germline human acceptor framework. Structural defects due to mismatches at the graft interface can be fixed by mutating some framework residues to murine, or by mutating some residues on the CDRs' backside to human or to a de novo designed sequence. The first approach, framework redesign, can yield an antibody with binding better than the CDR graft and one equivalent to the mature murine, and reduced immunogenicity. The second approach, CDR redesign, is presented here as a new approach, yielding an antibody with binding better than the CDR graft, and immunogenicity potentially less than that from framework redesign. Application of both approaches to the humanization of anti-α4 integrin antibody HP1/2 is presented and the concept of the hybrid humanization approach that retains "difficult to match" murine framework amino acids and uses de novo CDR design to minimize murine amino acid content and reduce cell-mediated cytotoxicity liabilities is discussed.
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Affiliation(s)
- Karl J M Hanf
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States.
| | - Joseph W Arndt
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | - Ling Ling Chen
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | - Matthew Jarpe
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | | | - You Li
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | | | - R Blake Pepinsky
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | - Kenneth J Simon
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States
| | - Alexey Lugovskoy
- Biogen Idec, 12 Cambridge Center, Cambridge, MA 02142, United States.
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7
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Li Y, Wu J, Song F, Tang J, Wang SJ, Yu XL, Chen ZN, Jiang JL. Extracellular membrane-proximal domain of HAb18G/CD147 binds to metal ion-dependent adhesion site (MIDAS) motif of integrin β1 to modulate malignant properties of hepatoma cells. J Biol Chem 2011; 287:4759-72. [PMID: 22130661 DOI: 10.1074/jbc.m111.277699] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Several lines of evidence suggest that HAb18G/CD147 interacts with the integrin variants α3β1 and α6β1. However, the mechanism of the interaction remains largely unknown. In this study, mammalian protein-protein interaction trap (MAPPIT), a mammalian two-hybrid method, was used to study the CD147-integrin β1 subunit interaction. CD147 in human hepatocellular carcinoma (HCC) cells was interfered with by small hairpin RNA. Nude mouse xenograft model and metastatic model of HCC were used to detect the role of CD147 in carcinogenesis and metastasis. We found that the extracellular membrane-proximal domain of HAb18G/CD147 (I-type domain) binds at the metal ion-dependent adhesion site in the βA domain of the integrin β1 subunit, and Asp(179) in the I-type domain of HAb18G/CD147 plays an important role in the interaction. The levels of the proteins that act downstream of integrin, including focal adhesion kinase (FAK) and phospho-FAK, were decreased, and the cytoskeletal structures of HCC cells were rearranged bearing the HAb18G/CD147 deletion. Simultaneously, the migration and invasion capacities, secretion of matrix metalloproteinases, colony formation rate in vitro, and tumor growth and metastatic potential in vivo were decreased. These results indicate that the interaction of HAb18G/CD147 extracellular I-type domain with the integrin β1 metal ion-dependent adhesion site motif activates the downstream FAK signaling pathway, subsequently enhancing the malignant properties of HCC cells.
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Affiliation(s)
- Yong Li
- Cell Engineering Research Centre and Department of Cell Biology, State Key Laboratory of Cancer Biology, Fourth Military Medical University, Xi'an 710032, China
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8
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Shimaoka M, Springer TA. Therapeutic antagonists and conformational regulation of integrin function. Nat Rev Drug Discov 2003; 2:703-16. [PMID: 12951577 DOI: 10.1038/nrd1174] [Citation(s) in RCA: 248] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Integrins are a structurally elaborate family of adhesion molecules that transmit signals bi-directionally across the plasma membrane by undergoing large-scale structural rearrangements. By regulating cell-cell and cell-matrix contacts, integrins participate in a wide range of biological processes, including development, tissue repair, angiogenesis, inflammation and haemostasis. From a therapeutic standpoint, integrins are probably the most important class of cell-adhesion receptors. Recent progress in the development of integrin antagonists has resulted in their clinical application and has shed new light on integrin biology. On the basis of their mechanism of action, small-molecule integrin antagonists fall into three different classes. Each of these classes affect the equilibria that relate integrin conformational states, but in different ways.
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Affiliation(s)
- Motomu Shimaoka
- The Center for Blood Research, Department of Anesthesia and Pathology, Harvard Medical School, 200 Longwood, Boston, Massachussets 02115, USA
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9
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Koo GC, Shah K, Ding GJF, Xiao J, Wnek R, Doherty G, Tong XC, Pepinsky RB, Lin KC, Hagmann WK, Kawka D, Singer II. A small molecule very late antigen-4 antagonist can inhibit ovalbumin-induced lung inflammation. Am J Respir Crit Care Med 2003; 167:1400-9. [PMID: 12569079 DOI: 10.1164/rccm.200207-696oc] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A nonpeptidyl small molecule antagonist, compound A, to nonactivated very late antigen-4 (VLA4) was examined in lung inflammation induced by a single dose of ovalbumin challenge. Compound A presented a good pharmacokinetic property, when given intratracheally, and the blood cells from such pharmacokinetic study showed good receptor occupancy of the compound for approximately 8 hours. Compound A was then tested in an ovalbumin-induced airway inflammation model by intranasal or intravenous route of administration. There was a dose-dependent inhibition of eosinophilia in the bronchiolar lavage fluid, when compound A was given intranasally but not when it was given intravenously. For comparison, antibody to VLA4 and another compound, BIO1211, which reacts only with activated VLA4, were examined in this system. Immunohistochemical analyses of the lung tissue substantiated the findings in the bronchiolar lavage fluid. Specific staining of the major basic protein of eosinophils showed peribronchiolar infiltration of eosinophils. Some of these eosinophils were also positive for nitrotyrosine, suggesting activation of eosinophils in the lung interstitium. There was deposition of major basic protein and nitrotyrosine at the base of the perivascular endothelium, indicative of degranulation of eosinophils in the area. After intranasal treatment with compound A, eosinophils in the lungs and their activation products were substantially decreased, documenting its effectiveness in inhibiting lung inflammation.
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Affiliation(s)
- Gloria C Koo
- Merck Research Laboratories, Rahway, NJ 07065, USA.
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10
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Abstract
Circulating lymphocytes normally migrate through extravascular spaces in relatively low numbers as important members of the immunosurveillance process. That is until signals are received by endothelial cells that there is an underlying infection or inflammatory condition. These vascular surface cells in turn overexpress and present ligands to circulating lymphocyte adhesion molecules. Upon encountering this higher density of ligands, lymphocytes, which had been leisurely rolling along the vascular surface, now become more firmly attached, change shape, and migrate through tight junctions to the sites of infection or inflammation. If the initiating events are not resolved and the condition becomes chronic, there can be a sustained extravasation of lymphocytes that can exacerbate the inflammatory condition, which in turn will continue to recruit more inflammatory cells resulting in unwanted tissue destruction. It is for the attenuation of this cycle of sustained inflammatory cell recruitment that very late activating antigen-4 (VLA-4) antagonists are being developed. Most lymphocytes, except neutrophils, express VLA-4 on their surface and they interact with endothelial vascular cell adhesion molecule-1 (VCAM-1). It is this interaction that VLA-4 antagonists are intended to disrupt, thus, putting an end to the cycle of chronic inflammation, which is the hallmark of many diseases. This review will provide an update of VLA-4 antagonists that have appeared since early 2001 and will discuss some of the issues, both positive and negative, that may be encountered in their development.
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Affiliation(s)
- Ginger X Yang
- Merck Research Laboratories, Rahway, New Jersey 07090, USA.
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11
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Abstract
Integrins are alphabeta heterodimeric cell-surface receptors that are vital to the survival and function of nucleated cells. They recognize aspartic-acid- or a glutamic-acid-based sequence motifs in structurally diverse ligands. Integrin recognition of most ligands is divalent cation dependent and conformationally sensitive. In addition to this common property, there is an underlying binding specificity between integrins and ligands for which there has been no structural basis. The recently reported crystal structures of the extracellular segment of an integrin in its unliganded state and in complex with a prototypical Arg-Gly-Asp (RGD) ligand have provided an atomic basis for cation-mediated binding of aspartic-acid-based ligands to integrins. They also serve as a basis for modelling other integrins in complex with larger physiologic ligands. These models provide new insights into the molecular basis for ligand binding specificity in integrins and its regulation by activation-driven tertiary and quaternary changes.
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Affiliation(s)
- M Amin Arnaout
- Renal Unit, Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, and Harvard Medical School, Charlestown, MA 02129, USA.
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12
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Piraino PS, Yednock TA, Freedman SB, Messersmith EK, Pleiss MA, Vandevert C, Thorsett ED, Karlik SJ. Prolonged reversal of chronic experimental allergic encephalomyelitis using a small molecule inhibitor of alpha4 integrin. J Neuroimmunol 2002; 131:147-59. [PMID: 12458046 DOI: 10.1016/s0165-5728(02)00273-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
CNS leukocytic invasion in experimental allergic encephalomyelitis (EAE) depends on alpha4beta1 integrin/vascular cell adhesion molecule-1 (VCAM-1) interactions. A small molecule inhibitor of alpha4beta1 integrin (CT301) was administered to guinea pigs in the chronic phase (>d40) of EAE for 10, 20, 30 or 40 days. CT301 elicited a rapid, significant improvement in the clinical and pathological scores that was maintained throughout the treatment period. A progressive loss of cells in the spinal cord of treated animals confirmed the resolution of inflammation associated with clinical recovery. Therefore, prolonged inhibition of alpha4beta1 integrin caused a sustained reversal of disease pathology in chronic EAE and may be similarly useful in MS.
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Affiliation(s)
- P S Piraino
- Department of Physiology, London Health Sciences Center, University of Western Ontario, London, ON, Canada
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13
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Abstract
The divalent-cation-dependent binding of alphabeta heterodimeric integrins to their ligands regulates most cellular processes. Integrin-ligand interactions are tightly controlled by inside-out activation signals. Ligand-bound integrins in turn transduce outside-in signals typical of other receptors. Precise information of how ligands bind to integrins is restricted to that of a small vWF A-type domain present in some alpha-subunits (alphaA). Both inside-out and outside-in signals elicit tertiary and quaternary changes in integrins, but the precise nature and scope and of these changes are unknown. The recently solved structures of the extracellular segment of integrin alphaVbeta3 in its unliganded and liganded states are generating exciting new insights into the design, wiring, function and regulation of this protein family. The structures reveal a surprising degree of flexibility at defined regions in the structure that is potentially controlled by cations. The quaternary structure of the ligand-binding region bears a striking resemblance to the nucleotide-binding pocket of G-proteins, implying analogous activation and signaling mechanisms. Structural links exist through which ligand-induced tertiary changes may be translated into quaternary changes and vice versa. The structures also raise the tantalizing hypothesis that alphaA is a regulated endogenous integrin ligand, so that no special regulatory features are needed in this integrin. These findings provide the framework for new investigations of structure-activity relationships in integrins, with important implications for targeting these receptors therapeutically [corrected].
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Affiliation(s)
- M Amin Arnaout
- Renal Unit, Leukocyte Biology & Inflammation Program, Structural Biology Program, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA.
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14
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Weinreb PH, Yang WJ, Violette SM, Couture M, Kimball K, Pepinsky RB, Lobb RR, Josiah S. A cell-free electrochemiluminescence assay for measuring beta1-integrin-ligand interactions. Anal Biochem 2002; 306:305-13. [PMID: 12123670 DOI: 10.1006/abio.2002.5723] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have developed a cell-free assay for binding of solubilized beta1 integrins to their physiologically relevant ligands using an electrochemiluminescent detection method. The method utilizes ruthenium-conjugated monoclonal antibodies for detection of either purified integrins or, more conveniently, integrin-expressing cell lysates, which are captured on beads coated with extracellular matrix or vascular ligand proteins. For the interaction of alpha1beta1 integrin with collagen IV, a signal of 10-fold over background was generated with samples containing only 10 ng (0.05 pmol) of integrin. This interaction is cation-dependent and can be inhibited by blocking antibodies to the alpha1 subunit. The method was extended to studies of ligand binding by integrins alpha2beta1, alpha4beta1, alpha5beta1, and alpha6beta1. For each integrin-ligand pair, the specificity of the interaction was verified with neutralizing antibodies against the specific integrin. The specific binding signal correlated with the activating ability of the labeled antibody used for detection, although the ability of divalent cations (Mn2+, Mg2+, Ca2+) to support integrin-ligand binding varied dramatically among the various integrin-ligand pairs. The assay provides a simple method for investigating integrin-ligand interactions without avidity and/or signaling effects which can complicate conventional cell-based assay methods.
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15
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Singh J, van Vlijmen H, Lee WC, Liao Y, Lin KC, Ateeq H, Cuervo J, Zimmerman C, Hammond C, Karpusas M, Palmer R, Chattopadhyay T, Adams SP. 3D QSAR (COMFA) of a series of potent and highly selective VLA-4 antagonists. J Comput Aided Mol Des 2002; 16:201-11. [PMID: 12363218 DOI: 10.1023/a:1020130418084] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The integrin VLA-4 (alpha4,beta1) is involved in the migration of white blood cells to sites of inflammation, and is implicated in the pathology of a variety of diseases including asthma and multiple sclerosis. We report the structure-activity relationships of a series of VLA-4 antagonists that were based upon the integrin-binding sequence of the connecting segment peptide of fibronectin (Leu-Asp-Val), and of VCAM-1 (Ile-Asp-Ser), both natural ligands of VLA-4. We explore variation in the ligand derived peptide portion of these antagonists and also in the novel N-terminal cap, which have discovered through chemical optimization, and which confers high affinity and selectivity. Using the X-ray derived conformation of the Ile-Asp-Ser region of VCAM-1, we rationalize the structure-activity relationships of these antagonists using 3D QSAR (COMFA). The COMFA model was found to be highly predictive with a cross-validated R2CV of 0.7 and a PRESS of 0.49. The robustness of the model was confirmed by testing the influence of various parameters, including grid size, column filtering, as well as the role of orientation of the aligned molecules. Our results suggest that the VCAM-1 structure is useful in generating highly predictive models of our VLA-4 antagonists. The COMFA model coupled with the knowledge that the peptide amides are tolerant to methylation should prove useful in future peptidomimetic design studies.
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16
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Yusuf-Makagiansar H, Anderson ME, Yakovleva TV, Murray JS, Siahaan TJ. Inhibition of LFA-1/ICAM-1 and VLA-4/VCAM-1 as a therapeutic approach to inflammation and autoimmune diseases. Med Res Rev 2002; 22:146-67. [PMID: 11857637 DOI: 10.1002/med.10001] [Citation(s) in RCA: 293] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This review focuses on providing insights into the structural basis and clinical relevance of LFA-1 and VLA-4 inhibition by peptides and small molecules as adhesion-based therapeutic strategies for inflammation and autoimmune diseases. Interactions of cell adhesion molecules (CAM) play central roles in mediating immune and inflammatory responses. Leukocyte function-associated antigen (LFA-1, alpha(L)beta(2), and CD11a/CD18) and very late antigen (VLA-4, alpha(4)beta(1), and CD49d/CD29) are members of integrin-type CAM that are predominantly involved in leukocyte trafficking and extravasation. LFA-1 is exclusively expressed on leukocytes and interacts with its ligands ICAM-1, -2, and -3 to promote a variety of homotypic and heterotypic cell adhesion events required for normal and pathologic functions of the immune systems. VLA-4 is expressed mainly on lymphocyte, monocytes, and eosinophils, but is not found on neutrophils. VLA-4 interacts with its ligands VCAM-1 and fibronectin (FN) CS1 during chronic inflammatory diseases, such as rheumatoid arthritis, asthma, psoriasis, transplant-rejection, and allergy. Blockade of LFA-1 and VLA-4 interactions with their ligands is a potential target for immunosuppression. LFA-1 and VLA-4 antagonists (antibodies, peptides, and small molecules) are being developed for controlling inflammation and autoimmune diseases. The therapeutic intervention of mostly mAb-based has been extensively studied. However, due to the challenging relative efficacy/safety ratio of mAb-based therapy application, especially in terms of systemic administration and immunogenic potential, strategic alternatives in the forms of peptide, peptide mimetic inhibitors, and small molecule non-peptide antagonists are being sought. Linear and cyclic peptides derived from the sequences of LFA-1, ICAM-1, ICAM-2, VCAM-1, and FN C1 have been shown to have inhibitory effects in vitro and in vivo. Finally, understanding the mechanism of LFA-1 and VLA-4 binding to their ligands has become a fundamental basis in developing therapeutic agents for inflammation and autoimmune diseases.
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Affiliation(s)
- Helena Yusuf-Makagiansar
- Department of Pharmaceutical Chemistry, The University of Kansas, Simons Research Laboratory, 2095 Constant Avenue, Lawrence, Kansas 66047, USA
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17
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Humphries MJ. Insights into integrin-ligand binding and activation from the first crystal structure. ARTHRITIS RESEARCH 2002; 4 Suppl 3:S69-78. [PMID: 12110125 PMCID: PMC3240139 DOI: 10.1186/ar563] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2002] [Revised: 02/28/2002] [Accepted: 03/03/2002] [Indexed: 12/31/2022]
Abstract
Integrin receptors transduce bidirectional signals between extracellular adhesion molecules and intracellular cytoskeletal and signalling molecules. The structural basis of integrin signalling is unknown, but the recent publication of the first crystal structure of the extracellular domain of integrin alphaVbeta3 has provided a number of insights. In this review, previous structure-function analyses of integrins that have employed biochemical and molecular biological approaches are placed in the context of the crystal structure, and novel routes to the development of integrin antagonists are discussed.
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Affiliation(s)
- Martin J Humphries
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, UK.
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18
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You TJ, Maxwell DS, Kogan TP, Chen Q, Li J, Kassir J, Holland GW, Dixon RAF. A 3D structure model of integrin alpha 4 beta 1 complex: I. Construction of a homology model of beta 1 and ligand binding analysis. Biophys J 2002; 82:447-57. [PMID: 11751331 PMCID: PMC1302484 DOI: 10.1016/s0006-3495(02)75409-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
It is well established that integrin alpha 4 beta 1 binds to the vascular cell adhesion molecule (VCAM) and fibronectin and plays an important role in signal transduction. Blocking the binding of VCAM to alpha 4 beta 1 is thought to be a way of controlling a number of disease processes. To better understand how various inhibitors might block the interaction of VCAM and fibronectin with alpha 4 beta 1, we began constructing a structure model for the integrin alpha 4 beta 1 complex. As the first step, we have built a homology model of the beta 1 subunit based on the I domain of the integrin CD11B subunit. The model, including a bound Mg(2+) ion, was optimized through a specially designed relaxation scheme involving restrained minimization and dynamics steps. The native ligand VCAM and two highly active small molecules (TBC772 and TBC3486) shown to inhibit binding of CS-1 and VCAM to alpha 4 beta 1 were docked into the active site of the refined model. Results from the binding analysis fit well with a pharmacophore model that was independently derived from active analog studies. A critical examination of residues in the binding site and analysis of docked ligands that are both potent and selective led to the proposal of a mechanism for beta 1/beta 7 ligand binding selectivity.
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Affiliation(s)
- Tony J You
- Department of Medicinal Chemistry and Biophysics, Texas Biotechnology Corporation, Houston, Texas 77030, USA.
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19
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Affiliation(s)
- M J Humphries
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, M13 9PT, UK.
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20
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Chen LL, Whitty A, Scott D, Lee WC, Cornebise M, Adams SP, Petter RC, Lobb RR, Pepinsky RB. Evidence that ligand and metal ion binding to integrin alpha 4beta 1 are regulated through a coupled equilibrium. J Biol Chem 2001; 276:36520-9. [PMID: 11473127 DOI: 10.1074/jbc.m106216200] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have used the highly selective alpha(4)beta(1) inhibitor 2S-[(1-benzenesulfonyl-pyrrolidine-2S-carbonyl)-amino]-4-[4-methyl-2S-(methyl-[2-[4-(3-o-tolyl-ureido)-phenyl]-acetyl]-amino)-pentanoylamino]-butyric acid (BIO7662) as a model ligand to study alpha(4)beta(1) integrin-ligand interactions on Jurkat cells. Binding of [(35)S]BIO7662 to Jurkat cells was dependent on the presence of divalent cations and could be blocked by treatment with an excess of unlabeled inhibitor or with EDTA. K(D) values for the binding of BIO7662 to Mn(2+)-activated alpha(4)beta(1) and to the nonactivated state of the integrin that exists in 1 mm Mg(2+), 1 mm Ca(2+) were <10 pm, indicating that it has a high affinity for both activated and nonactivated integrin. No binding was observed on alpha(4)beta(1) negative cells. Through an analysis of the metal ion dependences of ligand binding, several unexpected findings about alpha(4)beta(1) function were made. First, we observed that Ca(2+) binding to alpha(4)beta(1) was stimulated by the addition of BIO7662. From solution binding studies on purified alpha(4)beta(1), two types of Ca(2+)-binding sites were identified, one dependent upon and the other independent of BIO7662 binding. Second, we observed that the metal ion dependence of ligand binding was affected by the affinity of the ligand for alpha(4)beta(1). ED(50) values for the metal ion dependence of the binding of BIO7762 and the binding of a lower affinity ligand, BIO1211, differed by 2-fold for Mn(2+), 30-fold for Mg(2+), and >1000-fold for Ca(2+). Low Ca(2+) (ED(50) = 5-10 microm) stimulated the binding of BIO7662 to alpha(4)beta(1). The effects of microm Ca(2+) closely resembled the effects of Mn(2+) on alpha(4)beta(1) function. Third, we observed that the rate of BIO7662 binding was dependent on the metal ion concentration and that the ED(50) for the metal ion dependence of BIO7662 binding was affected by the concentration of the BIO7662. These studies point to an even more complex interplay between metal ion and ligand binding than previously appreciated and provide evidence for a three-component coupled equilibrium model for metal ion-dependent binding of ligands to alpha(4)beta(1).
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Affiliation(s)
- L L Chen
- Biogen, Inc., Cambridge, Massachusetts 02142, USA
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21
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Weetall M, Hugo R, Friedman C, Maida S, West S, Wattanasin S, Bouhel R, Weitz-Schmidt G, Lake P. A homogeneous fluorometric assay for measuring cell adhesion to immobilized ligand using V-well microtiter plates. Anal Biochem 2001; 293:277-87. [PMID: 11399044 DOI: 10.1006/abio.2001.5140] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have developed a homogeneous high-capacity assay format for measuring integrin- and selectin-dependent cell binding to immobilized ligand using V-well microtiter plates. 2',7'-Bis(2-carboxyethyl)-5-(and-6)-carboxylfluorescence, acetoxymethylester-labeled cells are added to ligand-coated V-shaped microtiter wells. Bound cells are separated from free cells using centrifugal force to produce shear stress. Nonadherent cells accumulate in the nadir of the well and are measured using a fluorescence plate reader. Antibody or low-molecular-weight inhibitors of either the ligand or the cell surface receptor result in less cell binding, more cells in the pellet, and increased signal. The optimization and validation of the very late antigen-4/vascular cell adhesion molecule-1 assay is described in detail. We demonstrate that this assay can be rapidly adapted to measure other integrin- and selectin-mediated interactions. This assay format has several advantages over conventional assays. The centrifugal process is biologically relevant and eliminates the washing steps to remove nonadherent cells that can cause well-to-well and plate-to-plate variation. Because the assay is robust with a high signal-to-noise ratio and low variability, it is ideally suited for studying multiple parameters of cell adhesion and for high capacity screening.
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Affiliation(s)
- M Weetall
- Novartis Pharmaceuticals, Summit, New Jersey 07901, USA.
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22
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Orozco OE, Walus L, Sah DW, Pepinsky RB, Sanicola M. GFRalpha3 is expressed predominantly in nociceptive sensory neurons. Eur J Neurosci 2001; 13:2177-82. [PMID: 11422460 DOI: 10.1046/j.0953-816x.2001.01596.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Activation of the RET receptor tyrosine kinase by glial-derived neurotrophic factor family members is dependent on a family of coreceptors, GFRalpha1-4. GFRalpha3 preferentially binds the newest member of the glial-derived neurotrophic factor family of ligands, artemin. The major site of GFRalpha3 expression is in the dorsal root ganglion; however, the class of sensory neurons that expresses GFRalpha3 has not been reported previously. Using immunohistochemical methods, we show that the majority of dorsal root ganglion cells that express GFRalpha3 also express vanilloid receptor type 1, peripherin, RET, trkA and calcitonin gene-related peptide. In addition, a significant subpopulation of GFRalpha3-expressing cells also binds the lectin IB4. We demonstrate that GFRalpha3 artemin neurons are immunopositive for markers expected of nociceptors and include a subset of neurons distinct from the GDNF-responsive population. Our results indicate artemin may exert selective effects on pain sensation.
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MESH Headings
- Animals
- Biomarkers
- Calcitonin Gene-Related Peptide/metabolism
- Drosophila Proteins
- Female
- Ganglia, Spinal/cytology
- Ganglia, Spinal/metabolism
- Glial Cell Line-Derived Neurotrophic Factor Receptors
- Immunohistochemistry
- Intermediate Filament Proteins/metabolism
- Lectins/metabolism
- Male
- Membrane Glycoproteins
- Mice
- Mice, Inbred C57BL
- Nerve Tissue Proteins/metabolism
- Neurofilament Proteins/metabolism
- Neurons, Afferent/cytology
- Neurons, Afferent/metabolism
- Nociceptors/cytology
- Nociceptors/metabolism
- Pain/metabolism
- Pain/physiopathology
- Peripherins
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-ret
- Rats
- Rats, Sprague-Dawley
- Receptor Protein-Tyrosine Kinases/metabolism
- Receptor, trkA/metabolism
- Receptors, Cell Surface/metabolism
- Receptors, Drug/metabolism
- Receptors, Nerve Growth Factor
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Affiliation(s)
- O E Orozco
- Biogen, 14 Cambridge Center, Cambridge MA 02142, USA
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23
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Pepinsky RB, Rayhorn P, Day ES, Dergay A, Williams KP, Galdes A, Taylor FR, Boriack-Sjodin PA, Garber EA. Mapping sonic hedgehog-receptor interactions by steric interference. J Biol Chem 2000; 275:10995-1001. [PMID: 10753901 DOI: 10.1074/jbc.275.15.10995] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have defined regions in the Sonic hedgehog (Shh) molecule that are important for Patched (Ptc) receptor binding by targeting selected surface amino acid residues with probes of diverse sizes and shapes and assessing the effects of these modifications on function. Eleven amino acid residues that surround the surface of the protein were chosen for these studies and mutated to cysteine residues. These cysteines were then selectively modified with thiol-specific probes, and the modified proteins were tested for hedgehog receptor binding activity and their ability to induce differentiation of C3H10T1/2 cells into osteoblasts. Based on these analyses, approximately one-third of the Shh surface can be modified without effect on function regardless of the size of the attachment. These sites are located near to where the C terminus protrudes from the surface of the protein. All other sites were sensitive to modification, indicating that the interaction of Shh with its primary receptor Ptc is mediated over a large surface of the Shh protein. For sites Asn-50 and Ser-156, function was lost with the smallest of the probes tested, indicating that these residues are in close proximity to the Ptc-binding site. The epitope for the neutralizing mAb 5E1 mapped to a close but distinct region of the structure. The structure-activity data provide a unique view of the interactions between Shh and Ptc that is not readily attainable by conventional mapping strategies.
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Affiliation(s)
- R B Pepinsky
- Biogen, Inc., Cambridge, Massachusetts 02142, USA
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24
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Gupta S, Li H, Sampson NS. Characterization of fertilin beta-disintegrin binding specificity in sperm-egg adhesion. Bioorg Med Chem 2000; 8:723-9. [PMID: 10819161 DOI: 10.1016/s0968-0896(00)00005-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
An essential step leading to fertilization is the binding of a sperm to the egg plasma membrane. Fertilin beta, a membrane bound protein on the extracellular surface of sperm, partially mediates this binding via the alpha6beta1 integrin. Fertilin beta is a member of the still expanding family of ADAM proteins (a disintegrin and metalloprotease) that are implicated in many cellular functions ranging from neurogenesis to myoblast fusion and cytokine processing. Fertilin beta contains a highly conserved motif (D/E)ECD in the disintegrin domain. This suggests that (D/E)ECD could be the consensus sequence for recognition of disintegrins by alpha6beta1 integrins. Previously, it has been demonstrated that small peptides containing different moieties of this consensus sequence are inhibitors of in vitro fertilization. In the present study, we sought to determine whether a four amino acid peptide sequence with two adjacent acidic residues improved inhibition, and investigated the importance for inhibition of a cysteine versus a cystine. A series of linear and cyclic peptides were synthesized, in which either one or both adjacent acidic residues in the sequence DECD were mutated to their corresponding amides (N or Q). To explore the required oxidation state of the cysteine in the (D/E)ECD sequence, it was protected as a mixed disulfide. Our results indicate that only one acidic residue is required for inhibition of fertilization and a reduced C is required.
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Affiliation(s)
- S Gupta
- Department of Chemistry, State University of New York, Stony Brook 11794-3400, USA
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25
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Chen LL, Whitty A, Lobb RR, Adams SP, Pepinsky RB. Multiple activation states of integrin alpha4beta1 detected through their different affinities for a small molecule ligand. J Biol Chem 1999; 274:13167-75. [PMID: 10224072 DOI: 10.1074/jbc.274.19.13167] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We have used the highly specific alpha4beta1 inhibitor 4-((N'-2-methylphenyl)ureido)-phenylacetyl-leucine-aspartic acid-valine-proline (BIO1211) as a model LDV-containing ligand to study alpha4beta1 integrin-ligand interactions on Jurkat cells under diverse conditions that affect the activation state of alpha4beta1. Observed KD values for BIO1211 binding ranged from a value of 20-40 nM in the non-activated state of the integrin that exists in 1 mM Mg2+, 1 mM Ca2+ to 100 pM in the activated state seen in 2 mM Mn2+ to 18 pM when binding was measured after co-activation by 2 mM Mn2+ plus 10 microgram/ml of the integrin-activating monoclonal antibody TS2/16. The large range in KD values was governed almost exclusively by differences in the dissociation rates of the integrin-BIO1211 complex, which ranged from 0.17 x 10(-4) s-1 to >140 x 10(-4) s-1. Association rate constants varied only slightly under the same conditions, all falling in the narrow range from 0.9 to 2.7 x 10(6) M-1 s-1. The further increase in affinity observed upon co-activation by divalent cations and TS2/16 compared with that observed at saturating concentrations of metal ions or TS2/16 alone indicates that the mechanism by which these factors bring about activation are distinct and identified a previously unrecognized high affinity state on alpha4beta1 that had not been detected by conventional assay methods. Similar changes in affinity were observed when the binding properties of vascular cell adhesion molecule-1 and CS1 to alpha4beta1 were studied, indicating that the different affinity states detected with BIO1211 are an inherent property of the integrin.
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Affiliation(s)
- L L Chen
- Biogen, Inc., Cambridge, Massachusetts 02142, USA
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