Structural specializations of α4β7, an integrin that mediates rolling adhesion

Abstract

Electron microscopy and crystallography studies of α4β7 integrin reveal the mechanism by which this atypical integrin enables rolling adhesion prior to integrin activation.

Functional Implications of the Binding Mode of a Human Conformation-Dependent V2 Monoclonal Antibody against HIV

“…Model of integrin binding. Our model of the integrin binding motif in V2 is consistent with a recently published crystal structure of the ␣4␤7 headpiece in complex with an I/LD mimetic, RO0505379 (1,6-dimethyl-2-oxo-4-trifluoromethyl-pyridine) (54). The structure shows that the molecule binds to a cleft between ␣4 and ␤7, with its carboxyl group mimicking an aspartic acid side chain, one oxygen coordinated by a bound metal (Mg 2ϩ ), and the other oxygen coordinated by the backbone of Y143 of ␤7 (Fig.…”

Functional Implications of the Binding Mode of a Human Conformation-Dependent V2 Monoclonal Antibody against HIV

“…Model of integrin binding. Our model of the integrin binding motif in V2 is consistent with a recently published crystal structure of the ␣4␤7 headpiece in complex with an I/LD mimetic, RO0505379 (1,6-dimethyl-2-oxo-4-trifluoromethyl-pyridine) (54). The structure shows that the molecule binds to a cleft between ␣4 and ␤7, with its carboxyl group mimicking an aspartic acid side chain, one oxygen coordinated by a bound metal (Mg 2ϩ ), and the other oxygen coordinated by the backbone of Y143 of ␤7 (Fig.…”

Conformational landscape of integrin α4β1 and its recognition of VCAM and conformation-stabilizing small molecules

“…Thus, α4β1 is less bent than previously reported structures of ligand-free integrins [19][20][21] . We did not detect appreciable particle subsets in either 2D or 3D classifications exhibiting separated legs, as observed in extended-closed integrins, or with an open headpiece, in agreement with negative-stain EM of integrin ectodomains 12,18 . These results suggest that full-length α4β1 reconstituted in detergent micelles is stable in its less-bent, closed conformation in physiological Ca 2+ and Mg 2+ concentrations, consistent with cell-based measurements showing that unliganded α4β1 is predominantly bent-closed (98.5%) and only rarely adopts extended-closed (0.4%)…”

“…The phenylalanine sidechain forms an amide-π stacking interaction with a β1 backbone amide. Similar backbone amide-π stacking is also found in other crystal structures with phenylalanine-based integrin inhibitors, including RO0505376 bound to α4β7 and tirofiban bound to αIIbβ3 12,51 .…”

Small Molecule Agonist of Very Late Antigen-4 (VLA-4) Integrin Induces Progenitor Cell Adhesion

“…10A). The model predicts that THI0019 bridges both the ␣ and ␤ subunits, which is consistent with previous x-ray structures of integrins co-crystallized with small molecules (10,38). Unlike most antagonists, however, there was no interaction with the MIDAS site in the ␤ subunit, which is consistent with the LIBS antibody results.…”

Functional Implications of the Binding Mode of a Human Conformation-Dependent V2 Monoclonal Antibody against HIV

“…Model of integrin binding. Our model of the integrin binding motif in V2 is consistent with a recently published crystal structure of the ␣4␤7 headpiece in complex with an I/LD mimetic, RO0505379 (1,6-dimethyl-2-oxo-4-trifluoromethyl-pyridine) (54). The structure shows that the molecule binds to a cleft between ␣4 and ␤7, with its carboxyl group mimicking an aspartic acid side chain, one oxygen coordinated by a bound metal (Mg 2ϩ ), and the other oxygen coordinated by the backbone of Y143 of ␤7 (Fig.…”

Conformational landscape of integrin α4β1 and its recognition of VCAM and conformation-stabilizing small molecules

“…Thus, α4β1 is less bent than previously reported structures of ligand-free integrins [19][20][21] . We did not detect appreciable particle subsets in either 2D or 3D classifications exhibiting separated legs, as observed in extended-closed integrins, or with an open headpiece, in agreement with negative-stain EM of integrin ectodomains 12,18 . These results suggest that full-length α4β1 reconstituted in detergent micelles is stable in its less-bent, closed conformation in physiological Ca 2+ and Mg 2+ concentrations, consistent with cell-based measurements showing that unliganded α4β1 is predominantly bent-closed (98.5%) and only rarely adopts extended-closed (0.4%)…”

“…The phenylalanine sidechain forms an amide-π stacking interaction with a β1 backbone amide. Similar backbone amide-π stacking is also found in other crystal structures with phenylalanine-based integrin inhibitors, including RO0505376 bound to α4β7 and tirofiban bound to αIIbβ3 12,51 .…”

Small Molecule Agonist of Very Late Antigen-4 (VLA-4) Integrin Induces Progenitor Cell Adhesion

“…10A). The model predicts that THI0019 bridges both the ␣ and ␤ subunits, which is consistent with previous x-ray structures of integrins co-crystallized with small molecules (10,38). Unlike most antagonists, however, there was no interaction with the MIDAS site in the ␤ subunit, which is consistent with the LIBS antibody results.…”

Functional Implications of the Binding Mode of a Human Conformation-Dependent V2 Monoclonal Antibody against HIV

“…Model of integrin binding. Our model of the integrin binding motif in V2 is consistent with a recently published crystal structure of the ␣4␤7 headpiece in complex with an I/LD mimetic, RO0505379 (1,6-dimethyl-2-oxo-4-trifluoromethyl-pyridine) (54). The structure shows that the molecule binds to a cleft between ␣4 and ␤7, with its carboxyl group mimicking an aspartic acid side chain, one oxygen coordinated by a bound metal (Mg 2ϩ ), and the other oxygen coordinated by the backbone of Y143 of ␤7 (Fig.…”

Conformational landscape of integrin α4β1 and its recognition of VCAM and conformation-stabilizing small molecules

“…Thus, α4β1 is less bent than previously reported structures of ligand-free integrins [19][20][21] . We did not detect appreciable particle subsets in either 2D or 3D classifications exhibiting separated legs, as observed in extended-closed integrins, or with an open headpiece, in agreement with negative-stain EM of integrin ectodomains 12,18 . These results suggest that full-length α4β1 reconstituted in detergent micelles is stable in its less-bent, closed conformation in physiological Ca 2+ and Mg 2+ concentrations, consistent with cell-based measurements showing that unliganded α4β1 is predominantly bent-closed (98.5%) and only rarely adopts extended-closed (0.4%)…”

“…The phenylalanine sidechain forms an amide-π stacking interaction with a β1 backbone amide. Similar backbone amide-π stacking is also found in other crystal structures with phenylalanine-based integrin inhibitors, including RO0505376 bound to α4β7 and tirofiban bound to αIIbβ3 12,51 .…”

Small Molecule Agonist of Very Late Antigen-4 (VLA-4) Integrin Induces Progenitor Cell Adhesion

“…10A). The model predicts that THI0019 bridges both the ␣ and ␤ subunits, which is consistent with previous x-ray structures of integrins co-crystallized with small molecules (10,38). Unlike most antagonists, however, there was no interaction with the MIDAS site in the ␤ subunit, which is consistent with the LIBS antibody results.…”