Potentiation of the ligand-binding activity of integrin alpha3beta1 via association with tetraspanin CD151.
CD151, one of the tetraspanins, forms a stable complex with integrin alpha3beta1, the major laminin receptor on the cell surface. We found that 8C3, an anti-CD151 mAb obtained by screening for reactivity with integrin alpha3beta1-CD151 complexes, was capable of dissociating CD151 from integrin alpha3beta1, thereby allowing us to deplete CD151 from purified integrin alpha3beta1-CD151 complexes. The CD151-free integrin alpha3beta1 thus obtained showed a significant reduction in its ability to bind to laminin-10/11, a high-affinity ligand for integrin alpha3beta1, with a concomitant reduction in its reactivity with mAb AG89, which recognizes activated beta1-containing integrins. These results raised the possibility that the association of integrin alpha3beta1 with CD151 potentiates the ligand-binding activity of the integrin through sustaining its activated conformation. In support of this possibility, the ligand-binding activity was restored when CD151-free integrin alpha3beta1 was reassociated with purified CD151. 8C3-induced dissociation of CD151 from integrin alpha3beta1 was also demonstrated on the surface of living cells by fluorescent resonance energy transfer imaging, accompanied by a concomitant reduction in the cell adhesion to laminin-10/11-coated substrates. CD151 knock-down by RNA interference also resulted in a reduction in the adhesive activity of the cells. Taken together, these results indicate that CD151 association modulates the ligand-binding activity of integrin alpha3beta1 through stabilizing its activated conformation not only with purified proteins but also in a physiological context.
Nishiuchi
Ryoko
R
Institute for Protein Research and Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan.
Sanzen
Noriko
N
Nada
Shigeyuki
S
Sumida
Yasuhiro
Y
Wada
Yoshinao
Y
Okada
Masato
M
Takagi
Junichi
J
Hasegawa
Hitoshi
H
Sekiguchi
Kiyotoshi
K
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019556:COS Cells; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D039201:Integrin alpha3beta1 / Q000302:isolation & purification / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism; D008024:Ligands; D046912:Multiprotein Complexes; D010920:Placenta / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D034622:RNA Interference; D060185:Tetraspanin 24
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C554715:CD151 protein, human; D039201:Integrin alpha3beta1; D007797:Laminin; D008024:Ligands; D046912:Multiprotein Complexes; D060185:Tetraspanin 24