Mechanisms of receptor binding and cellular activation by the epidermal growth factor ligand family
Mechanisms of receptor binding and cellular activation by the epidermal growth factor ligand family
In order to aid rational design of novel therapeutic strategies, the molecular process of ligand induced EGFR activation have been investigated. Although ligand binding to the EGFR is known to induce the formation of active homo- and heterodimeric receptors, the precise molecular mechanisms involved in these processes have not been elucidated. This study has focused on two of the EGFR ligands, epidermal growth factor (EGF) and transforming growth factor α (TGFα), which appear to bind to the EGFR in a non identical fashion, even though they display the same affinity. Furthermore, quantitative and qualitative differences in their biological activities have been observed in some cell systems. Thus, the basis for their differential receptor recognition was examined by targeting regions of low homology, and performing quantitative structure-activity relationships.
The 'hinge' residue lying between the fourth and fifth cysteins, shows a low degree of sequence identity between the EGFR ligands, but despite this EGF demonstrates a requirement for a hydrogen bond donor side chain functionality at the 'hinge', whilst this residue in TGFα is hydrophobic in character. The importance of this difference was explored using recombinant mutants comprising conservative or non conservative substitutions to the native TGFα 'hinge', and the specific side chain requirements for this residue in TGFα were defined. In contrast to EGF, hydrogen bond donor 'hinge' mutants were poorly tolerated, exhibiting reduced EGFR binding affinities and parallel decreases in their mitogenic potency. However, conservative hydrophobic TGFα 'hinge' substitutions maintained the receptor binding affinity and biological activity of the ligand. Furthermore, studies with the 'hinge' mutants and native EGFR ligands showed that the chicken EGFR, which binds TGFα with 100x greater affinity than EGF, also exhibited preferences for hydrophobic 'hinge' residues. These studies suggest that the 'hinge' residue is a ligand specific epitope which distinguishes binding of TGFα from that of EGF.
University of Southampton
Puddicombe, Sarah Margaret
1998
Puddicombe, Sarah Margaret
Puddicombe, Sarah Margaret
(1998)
Mechanisms of receptor binding and cellular activation by the epidermal growth factor ligand family.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In order to aid rational design of novel therapeutic strategies, the molecular process of ligand induced EGFR activation have been investigated. Although ligand binding to the EGFR is known to induce the formation of active homo- and heterodimeric receptors, the precise molecular mechanisms involved in these processes have not been elucidated. This study has focused on two of the EGFR ligands, epidermal growth factor (EGF) and transforming growth factor α (TGFα), which appear to bind to the EGFR in a non identical fashion, even though they display the same affinity. Furthermore, quantitative and qualitative differences in their biological activities have been observed in some cell systems. Thus, the basis for their differential receptor recognition was examined by targeting regions of low homology, and performing quantitative structure-activity relationships.
The 'hinge' residue lying between the fourth and fifth cysteins, shows a low degree of sequence identity between the EGFR ligands, but despite this EGF demonstrates a requirement for a hydrogen bond donor side chain functionality at the 'hinge', whilst this residue in TGFα is hydrophobic in character. The importance of this difference was explored using recombinant mutants comprising conservative or non conservative substitutions to the native TGFα 'hinge', and the specific side chain requirements for this residue in TGFα were defined. In contrast to EGF, hydrogen bond donor 'hinge' mutants were poorly tolerated, exhibiting reduced EGFR binding affinities and parallel decreases in their mitogenic potency. However, conservative hydrophobic TGFα 'hinge' substitutions maintained the receptor binding affinity and biological activity of the ligand. Furthermore, studies with the 'hinge' mutants and native EGFR ligands showed that the chicken EGFR, which binds TGFα with 100x greater affinity than EGF, also exhibited preferences for hydrophobic 'hinge' residues. These studies suggest that the 'hinge' residue is a ligand specific epitope which distinguishes binding of TGFα from that of EGF.
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Published date: 1998
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Local EPrints ID: 463280
URI: http://eprints.soton.ac.uk/id/eprint/463280
PURE UUID: dad67a25-e919-49d9-ae9a-d7892e9ff778
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Date deposited: 04 Jul 2022 20:48
Last modified: 04 Jul 2022 20:48
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Author:
Sarah Margaret Puddicombe
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