Galectin-8 binding to integrins inhibits cell adhesion and induces apoptosis.
The interaction of cells with the extracellular matrix regulates cell adhesion, motility, growth, survival and differentiation through integrin-mediated signal transduction. Here we demonstrate that galectin-8, a secreted mammalian (beta)-galactoside binding protein, inhibits adhesion of human carcinoma (1299) cells to plates coated with integrin ligands, and induces cell apoptosis. Pretreatment of the cells with Mn(2+), which increases the affinity of integrins for their ligands, abolished the inhibitory effects of galectin-8. The inhibitory effects of galectin-8 were specific and were not mimicked by plant lectins or other galectins (galectin-1 and galectin-3). In accordance with its anti-adhesive effects, transfection of galectin-8 cDNA into 1299 cells significantly reduced (by 75%) colony formation, when compared to the number of colonies formed by cells transfected with an empty vector. Affinity chromatography over immobilized galectin-8 indicated that few membrane proteins interacted with galectin-8 in a sugar-dependent manner. Microsequencing and western immunoblotting revealed that (alpha)(3)(beta)(1 )integrin derived from 1299 as well as other cells (e.g. HeLa and human endothelial cells) is a major galectin-8 binding-protein. Furthermore, immunoprecipitation and immunohistochemical studies suggested that endogenous galectin-8, secreted from 1299 cells, forms complexes with (alpha)(3)(beta)(1) integrins expressed on the surface of 1299 cells. Galectin-8 also interacts with other members of the integrin family, like (alpha)(6)(beta)(1 )integrins. In contrast, galectin-8 only minimally interacts with (alpha)(4 )or (beta)(3 )integrins. We propose that galectin-8 is an integrin binding-protein that interacts to a different extent with several, but not all members of the integrin family. Binding of galectin-8 modulates integrin interactions with the extracellular matrix and thus regulates cell adhesion and cell survival.
Hadari
Y R
YR
Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel. lizick@weizmann. weizmann.ac.il
Arbel-Goren
R
R
Levy
Y
Y
Amsterdam
A
A
Alon
R
R
Zakut
R
R
Zick
Y
Y
D017209:Apoptosis / Q000502:physiology*; D001665:Binding Sites / Q000502:physiology*; D050260:Carbohydrate Metabolism; D002448:Cell Adhesion / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism; D037161:Galectins; D006131:Growth Inhibitors / Q000378:metabolism; D039201:Integrin alpha3beta1; D016023:Integrins / Q000378:metabolism*; D037102:Lectins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D037161:Galectins; D006131:Growth Inhibitors; D039201:Integrin alpha3beta1; D016023:Integrins; C091991:LGALS8 protein, human; D037102:Lectins; D011994:Recombinant Proteins