Abstract
Intracellular signaling pathways, which regulate the interactions of integrins with their ligands, affect a wide variety of biological functions. Here we provide evidence of how cytohesin-1, an integrin-binding protein and guanine-nucleotide exchange factor (GEF) for ARF GTPases, regulates cell adhesion. Mutational analyses of the beta-2 cytoplasmic domain revealed that the adhesive function of LFA-1 depends on its interaction with cytohesin-1, unless the integrin is activated by exogenous divalent cations. Secondly, cytohesin-1 induces expression of an extracellular activation epitope of LFA-1, and the exchange factor function is not essential for this activity. In contrast, LFA-1-mediated cell adhesion and spreading on intercellular cell adhesion molecule 1 is strongly inhibited by a cytohesin-1 mutant, which fails to catalyze ARF GDP-GTP exchange in vitro. Thus, cytohesin-1 is involved in the activation of LFA-1, most probably through direct interaction with the integrin, and induces cell spreading by its ARF-GEF activity. We therefore propose that both direct regulation of the integrin and concomitant changes in the membrane topology of adherent T cells are modulated by dissectable functions of cytohesin-1.
Original language | English |
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Pages (from-to) | 2525-36 |
Number of pages | 12 |
Journal | EMBO Journal |
Volume | 19 |
Issue number | 11 |
DOIs | |
Publication status | Published - 1 Jun 2000 |
Keywords
- ADP-Ribosylation Factors/physiology
- Animals
- CD18 Antigens/physiology
- Cell Adhesion Molecules/genetics
- Cell Adhesion/physiology
- Cell Size
- Epitopes/chemistry
- Guanine Nucleotide Exchange Factors
- Guanosine Diphosphate/metabolism
- Guanosine Triphosphate/metabolism
- HeLa Cells
- Humans
- Intercellular Adhesion Molecule-1/physiology
- Lymphocyte Function-Associated Antigen-1/physiology
- Macromolecular Substances
- Mice
- Models, Molecular
- Rats
- Recombinant Fusion Proteins/physiology
- T-Lymphocytes/cytology
- Two-Hybrid System Techniques