The LG1-3 tandem of laminin alpha5 harbors the binding sites of Lutheran/basal cell adhesion molecule and alpha3beta1/alpha6beta1 integrins.
The laminin-type globular (LG) domains of laminin alpha chains have been implicated in various cellular interactions that are mediated through receptors such as integrins, alpha-dystroglycan, syndecans, and the Lutheran blood group glycoprotein (Lu). Lu, an Ig superfamily transmembrane receptor specific for laminin alpha5, is also known as basal cell adhesion molecule (B-CAM). Although Lu/B-CAM binds to the LG domain of laminin alpha5, the binding site has not been precisely defined. To better delineate this binding site, we produced a series of recombinant laminin trimers containing modified alpha chains, such that all or part of alpha5LG was replaced with analogous segments of human laminin alpha1LG. In solid phase binding assays using a soluble Lu (Lu-Fc) composed of the Lu extracellular domain and human IgG1 Fc, we found that Lu bound to Mr5G3, a recombinant laminin containing alpha5 domains LN through LG3 fused to human laminin alpha1LG4-5. However, Lu/B-CAM did not bind other recombinant laminins containing alpha5LG3 unless alpha5LG1-2 was also present. A recombinant alpha5LG1-3 tandem lacking the laminin coiled coil (LCC) domain did not reproduce the activity of Lu/B-CAM binding. Therefore, proper structure of the alpha5LG1-3 tandem with the LCC domain was essential for the binding of Lu/B-CAM to laminin alpha5. Our results also suggest that the binding site for Lu/B-CAM on laminin alpha5 may overlap with that of integrins alpha3beta1 and alpha6beta1.
Kikkawa
Yamato
Y
Renal Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA. kikkawa@ps.toyaku.ac.jp
Sasaki
Takako
T
Nguyen
Mai Tuyet
MT
Nomizu
Motoyoshi
M
Mitaka
Toshihiro
T
Miner
Jeffrey H
JH
D001665:Binding Sites / Q000235:genetics; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D039201:Integrin alpha3beta1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D039121:Integrin alpha6beta1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020014:K562 Cells; D007797:Laminin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008188:Lutheran Blood-Group System; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
C090228:BCAM protein, human; D015815:Cell Adhesion Molecules; D039201:Integrin alpha3beta1; D039121:Integrin alpha6beta1; D007797:Laminin; D008188:Lutheran Blood-Group System; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; C097043:laminin alpha5