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Dimerization and the effectiveness of ICAM-1 in mediating LFA-l-dependent adhesion
被引:59
作者:
Jun, CD
Shimaoka, M
Carman, CV
Takagi, J
Springer, TA
机构:
[1] Harvard Univ, Sch Med, Ctr Blood Res, Boston, MA 02115 USA
[2] Harvard Univ, Sch Med, Dept Pathol, Boston, MA 02115 USA
来源:
关键词:
D O I:
10.1073/pnas.121186998
中图分类号:
O [数理科学和化学];
P [天文学、地球科学];
Q [生物科学];
N [自然科学总论];
学科分类号:
07 ;
0710 ;
09 ;
摘要:
Dimeric intercellular adhesion molecule-1 (ICAM-1) binds more efficiently to lymphocyte function-associated antigen-1 (LFA-1) than monomeric ICAM-1. However, it is unknown whether dimerization enhances binding simply by providing two ligand-binding sites and thereby increasing avidity, or whether it serves to generate a single "fully competent" LFA-1-binding surface. Domain 1 of ICAM-1 contains both the binding site for LFA-1, centered on residue E34, and a homodimerization interface. Whether the LFA-1-binding site extends across the homodimerization interface has not been tested. To address this question, we constructed four different heterodimeric soluble forms of ICAM-1 joined at the C terminus via an cu-helical coiled coil (ACID-BASE). These heterodimeric ICAM-1 constructs include, (i) E34/E34 (two intact LFA-1-binding sites), (ii) E34/K34 tone disrupted LFA-1-binding site), (iii) E34/Delta D1-2 (one deleted LFA-1-binding site), and (iv) K34/K34 (two disrupted LFA-1-binding sites). Cells bearing activated LFA-1 bound similarly to surfaces coated with either E34/K34 or E34/Delta D1-2 and with an approximate to2-fold reduction in efficiency compared with E34/E34, suggesting that D1 dimerization. which is precluded in E34/Delta D1-D2. is not necessary for optimal LFA-1 binding. Furthermore, BIAcore (BIAcore, Piscataway, NJ) affinity measurements revealed that soluble open LFA-1 I domain bound to immobilized soluble ICAM-1, E34/E34. E34/K34, and E34/Delta D1-D2 with nearly identical affinities. These studies demonstrate that a single ICAM-1 monomer, not dimeric ICAM-1, represents the complete, "fully competent" LFA-1-binding surface.
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页码:6830 / 6835
页数:6
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