Cytohesin-1 is a dynamic regulator of distinct LFA-1 functions in leukocyte arrest and transmigration triggered by chemokines.
Cytohesin-1 is a regulatory interaction partner of the beta2 integrin alphaLbeta2 (LFA-1) and a guanine exchange factor (GEF) for ADP ribosylation factor (ARF)-GTPases. However, a functional role of cytohesin-1 in leukocyte adhesion to activated endothelium and subsequent transmigration in response to chemokines has not been defined. Overexpression of cytohesin-1 increased LFA-1-dependent arrest of leukocytic cells triggered by chemokines on cytokine-activated endothelium in flow while reducing the fraction of rolling cells. Conversely, a dominant-negative PH domain construct of cytohesin-1 but not a mutant deficient in GEF activity impaired arrest, indicating an involvement of the PH domain while GEF function is not required. Expression of these constructs and a beta2 mutant interrupting the interaction with cytohesin-1 indicated that shape change in flow and transendothelial chemotaxis involve both LFA-1 avidity regulation and GEF activity of cytohesin-1. As a potential downstream target, ARF6 but not ARF1 was identified to participate in chemotaxis. Our data suggest that cytohesin-1 and ARF6 are involved in the dynamic regulation of complex signaling pathways and cytoskeletal remodeling processes governing LFA-1 functions in leukocyte recruitment. Differential effects of cytohesin-1 and ARF6 mutants in our systems reveal that cytohesin-1 with its GEF activity controls both conversion of rolling into firm arrest and transmigration triggered by chemokines, whereas a cyclical activity of ARF6 plays a more important role in diapedesis.
Weber
K S
KS
Institut für Prophylaxe der Kreislaufkrankheiten, Gene Center, Ludwig-Maximilians-Universität, Munich, Germany. cweber@post.klinikum.rwth-aachen.de
Weber
C
C
Ostermann
G
G
Dierks
H
H
Nagel
W
W
Kolanus
W
W
D015815:Cell Adhesion Molecules / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology*; D018925:Chemokines / Q000502:physiology*; D004727:Endothelium / Q000166:cytology; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology; D007962:Leukocytes / Q000166:cytology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology*
D015815:Cell Adhesion Molecules; D018925:Chemokines; D020662:Guanine Nucleotide Exchange Factors; D016169:Lymphocyte Function-Associated Antigen-1; C100723:cytohesin-1; D020558:GTP Phosphohydrolases