Characterization of a tight molecular complex between integrin alpha 6 beta 4 and laminin-5 extracellular matrix.
In many adult epithelia, e.g., epidermis or intestine, adhesion of epithelial cells to basement membrane requires the integrin alpha6 beta4 and laminin-5 (Ln-5). In the absence of one or the other, extensive blistering and exfoliation occur. While alpha6 beta4 was reported to be a receptor for Ln-5, this interaction is poorly understood. We characterize complexes between alpha6 beta4 and Ln-5 in cell-free preparations of extracellular matrix (ECM) from the epithelial cell line, 804G. By microsequencing, Ln-5 and alpha6 beta4 were the major proteins in this ECM and were likely engaged in receptor/ligand complexes because, by immunofluorescence, alpha6 beta4 was colocalized with Ln-5 both in cell monolayers and in cell-free ECM preparations, but they disappeared after preincubation of the monolayers with alpha6 beta4 or Ln-5 function-blocking antibodies. The alpha6 beta4/Ln-5 complexes were resistant to dissociation by extreme pH, urea, chaotropes, eDTA, non-ionic detergents, and b-mercaptoethanol. They were only dissociated by strong anionic detergents, e.g., 1% SDS, suggesting receptor/ligand interactions based on high affinity or avidity. We propose that these alpha6 beta4/Ln-5 complexes may provide links between plasma membrane and basement membrane that resist mechanical stress and support epithelial integrity.
Falk-Marzillier
J
J
Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California, 92037, USA.
Domanico
S Z
SZ
Pelletier
A
A
Mullen
L
L
Quaranta
V
V
D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000378:metabolism; D000954:Antigens, Surface / Q000737:chemistry* / Q000378:metabolism; D002277:Carcinoma; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism; D002474:Cell-Free System; D005109:Extracellular Matrix / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D039161:Integrin alpha6beta4; D016023:Integrins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D051381:Rats; D017474:Receptors, Laminin / Q000032:analysis / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms; D000097794:Kalinin
D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D039161:Integrin alpha6beta4; D016023:Integrins; D008024:Ligands; D046911:Macromolecular Substances; D017474:Receptors, Laminin; D000097794:Kalinin