Cytohesin-1 regulates beta-2 integrin-mediated adhesion through both ARF-GEF function and interaction with LFA-1.
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.
Geiger
C
C
Laboratorium für Molekulare Biologie, Genzentrum der Universität München, Germany.
Nagel
W
W
Boehm
T
T
van Kooyk
Y
Y
Figdor
C G
CG
Kremmer
E
E
Hogg
N
N
Zeitlmann
L
L
Dierks
H
H
Weber
K S
KS
Kolanus
W
W
D020727:ADP-Ribosylation Factors / Q000502:physiology*; D000818:Animals; D018821:CD18 Antigens / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000502:physiology*; D048429:Cell Size; D000939:Epitopes / Q000737:chemistry; D020662:Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology*; D046911:Macromolecular Substances; D051379:Mice; D008958:Models, Molecular; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology*; D020798:Two-Hybrid System Techniques
D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D000939:Epitopes; D020662:Guanine Nucleotide Exchange Factors; D016169:Lymphocyte Function-Associated Antigen-1; D046911:Macromolecular Substances; D011993:Recombinant Fusion Proteins; C100723:cytohesin-1; D018799:Intercellular Adhesion Molecule-1; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020727:ADP-Ribosylation Factors