Receptor functions for the integrin VLA-3: fibronectin, collagen, and laminin binding are differentially influenced by Arg-Gly-Asp peptide and by divalent cations.
The capability of the integrin VLA-3 to function as a receptor for collagen (Coll), laminin (Lm), and fibronectin (Fn) was addressed using both whole cell adhesion assays and ligand affinity columns. Analysis of VLA-3-mediated cell adhesion was facilitated by the use of a small cell lung carcinoma line (NCI-H69), which expresses VLA-3 but few other integrins. While VLA-3 interaction with Fn was often low or undetectable in cells having both VLA-3 and VLA-5, NCI-H69 cells readily attached to Fn in a VLA-3-dependent manner. Both Arg-Gly-Asp (RGD) peptide inhibition studies, and Fn fragment affinity columns suggested that VLA-3, like VLA-5, may bind to the RGD site in human Fn. However, unlike Fn, both Coll and Lm supported VLA-3-mediated adhesion that was not inhibited by RGD peptide, and was totally unaffected by the presence of VLA-5. In addition, VLA-3-mediated binding to Fn was low in the presence of Ca++, but was increased 6.6-fold with Mg++, and 30-fold in the presence of Mn++. In contrast, binding to Coll was increased only 1.2-fold with Mg++, and 1.7-fold in Mn++, as compared to the level seen with Ca++. Together, these experiments indicate that VLA-3 can bind Coll, Lm, and Fn, and also show that (a) VLA-3 can recognize both RGD-dependent and RGD-independent ligands, and (b) different VLA-3 ligands have distinctly dissimilar divalent cation sensitivities.
Elices
M J
MJ
Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Urry
L A
LA
Hemler
M E
ME
D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002413:Cations, Divalent / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D002846:Chromatography, Affinity; D003094:Collagen / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D007797:Laminin / Q000378:metabolism*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002413:Cations, Divalent; D005353:Fibronectins; D016023:Integrins; D007797:Laminin; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid; D003094:Collagen