A mutation in the integrin α_IIb subunit that selectively inhibits α_IIbβ₃ receptor function

Summary

The α_IIband α_vintegrins have been shown to play a significant role in a variety of disease processes. α_IIbβ₃is a platelet-specific fibrinogen receptor that is critical for thrombosis and hemo-stasis. Determination of the basis of ligand recognition by α_IIbβ₃is essential for modulation of platelet function. To identify α_IIbresidues involved in α_IIbβ₃ligand binding function, cells expressing a constitutively active variant of α_IIbβ₃were randomly mutagenized and selected for loss of α_IIbβ₃ligand binding function. One mutant isolated in this manner contained a single amino acid substitution at position 96 in α_IIb(Ser96→Leu). Cells expressing this α_IIbmutant did not bind the ligand mimetic antibody PAC1 or adhere to fibrinogen. In addition, the mutant receptor did not bind to an RGD affinity matrix. Substitution of conserved serine residues at position 1 in β strand A of all seven repeats of α_IIbsimilarly inhibited ligand binding to α_IIbβ₃. α_IIbS96 maps to the central cavity of the β–propeller fold of the α_IIbsubunit immediately adjacent to a structurally important sequence at the center of the α and β subunit interface. In contrast, substitution of the analogous residues in α_vor α₄did not disrupt the ligand binding function of α_vβ₃or α₄β₁. These data support a potential unique structural or mechanistic role for this residue in α_IIbβ₃receptor function.

Keywords

α_IIbβ₃ - platelets - mutagenesis - flow cytometry

• References

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