Abstract
It was previously shown that mutations of integrin alpha4 chain sites, within putative EF-hand-type divalent cation-binding domains, each caused a marked reduction in alpha4beta1-dependent cell adhesion. Some reports have suggested that alpha-chain "EF-hand" sites may interact directly with ligands. However, we show here that mutations of three different alpha4 "EF-hand" sites each had no effect on binding of soluble monovalent or bivalent vascular cell adhesion molecule 1 whether measured indirectly or directly. Furthermore, these mutations had minimal effect on alpha4beta1-dependent cell tethering to vascular cell adhesion molecule 1 under shear. However, EF-hand mutants did show severe impairments in cellular resistance to detachment under shear flow. Thus, mutation of integrin alpha4 "EF-hand-like" sites may impair 1) static cell adhesion and 2) adhesion strengthening under shear flow by a mechanism that does not involve alterations of initial ligand binding.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Amino Acid Substitution / genetics
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Antigens, CD / chemistry*
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Antigens, CD / genetics
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Antigens, CD / metabolism*
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Binding Sites
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Cations, Divalent / metabolism
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Cations, Divalent / pharmacology
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Cell Adhesion / drug effects
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EF Hand Motifs
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Fibronectins / chemistry
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Fibronectins / metabolism
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Humans
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Immunoglobulin G / metabolism
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Integrin alpha4
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Integrin alpha4beta1
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Integrins / chemistry
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Integrins / genetics
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Integrins / metabolism
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K562 Cells
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Ligands
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Manganese / metabolism
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Manganese / pharmacology
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Mutation / genetics
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Peptide Fragments / chemistry
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Peptide Fragments / metabolism
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Protein Binding / drug effects
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Receptors, Lymphocyte Homing / chemistry
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Receptors, Lymphocyte Homing / genetics
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Receptors, Lymphocyte Homing / metabolism
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Solubility
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Transfection
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Vascular Cell Adhesion Molecule-1 / chemistry
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Vascular Cell Adhesion Molecule-1 / metabolism
Substances
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Antigens, CD
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Cations, Divalent
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Fibronectins
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Immunoglobulin G
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Integrin alpha4beta1
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Integrins
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Ligands
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Peptide Fragments
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Receptors, Lymphocyte Homing
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Recombinant Fusion Proteins
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Vascular Cell Adhesion Molecule-1
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Integrin alpha4
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Manganese