Cadherin interaction probed by atomic force microscopy.
Single molecule atomic force microscopy was used to characterize structure, binding strength (unbinding force), and binding kinetics of a classical cadherin, vascular endothelial (VE)-cadherin, secreted by transfected Chinese hamster ovary cells as cis-dimerized full-length external domain fused to Fc-portion of human IgG. In physiological buffer, the external domain of VE-cadherin dimers is a approximately 20-nm-long rod-shaped molecule that collapses and dissociates into monomers (V-shaped structures) in the absence of Ca(2+). Trans-interaction of dimers is a low-affinity reaction (K(D) = 10(-3)-10(-5) M, k(off) = 1.8 s(-1), k(on) = 10(3)-10(5) M(-1) x s(-1)) with relatively low unbinding force (35-55 pN at retrace velocities of 200-4,000 nm x s(-1)). Higher order unbinding forces, that increase with interaction time, indicate association of cadherins into complexes with cumulative binding strength. These observations favor a model by which the inherently weak unit binding strength and affinity of cadherin trans-interaction requires clustering and cytoskeletal immobilization for amplification. Binding is regulated by low-affinity Ca(2+) binding sites (K(D) = 1.15 mM) with high cooperativity (Hill coefficient of 5.04). Local changes of free extracellular Ca(2+) in the narrow intercellular space may be of physiological importance to facilitate rapid remodeling of intercellular adhesion and communication.
Baumgartner
W
W
Institute of Anatomy, University of Würzburg, Koellikerstrasse 6, D-97070 Würzburg, Germany.
Hinterdorfer
P
P
Ness
W
W
Raab
A
A
Vestweber
D
D
Schindler
H
H
Drenckhahn
D
D
D000818:Animals; D016466:CHO Cells; D015820:Cadherins / Q000378:metabolism*; D002448:Cell Adhesion; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology; D006801:Humans; D018625:Microscopy, Atomic Force; D015335:Molecular Probes; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism
D015820:Cadherins; D015335:Molecular Probes; D011994:Recombinant Proteins