An isolated, surface-expressed I domain of the integrin alphaLbeta2 is sufficient for strong adhesive function when locked in the open conformation with a disulfide bond.
We introduced disulfide bonds to lock the integrin alphaLbeta2 I domain in predicted open, ligand binding or closed, nonbinding conformations. Transfectants expressing alphaLbeta2 heterodimers containing locked-open but not locked-closed or wild-type I domains constitutively adhered to intercellular adhesion molecule-1 (ICAM-1) substrates. Locking the I domain closed abolished constitutive and activatable adhesion. The isolated locked-open I domain bound as well as the activated alphaLbeta2 heterodimer, and binding was abolished by reduction of the disulfide. Lovastatin, which binds under the conformationally mobile C-terminal alpha-helix of the I domain, inhibited binding to ICAM-1 by alphaLbeta2 with wild-type, but not locked-open I domains. These data establish the importance of conformational change in the alphaL I domain for adhesive function and show that this domain is sufficient for full adhesive activity.
The Center for Blood Research, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
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Shimaoka
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Ferzly
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Oxvig
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Takagi
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Springer
D002448:Cell Adhesion; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D008148:Lovastatin / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011487:Protein Conformation
D004220:Disulfides; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D008148:Lovastatin