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An isolated, surface-expressed I domain of the integrin alphaLbeta2 is sufficient for strong adhesive function when

C Lu1, M Shimaoka, M Ferzly

  • 1The Center for Blood Research, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.

Proceedings of the National Academy of Sciences of the United States of America
|February 28, 2001
PubMed

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.

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