Integrin-independent role of CalDAG-GEFI in neutrophil chemotaxis.
Chemotaxis and integrin activation are essential processes for neutrophil transmigration in response to injury. CalDAG-GEFI plays a key role in the activation of beta1, beta2, and beta3 integrins in platelets and neutrophils by exchanging a GDP for a GTP on Rap1. Here, we explored the role of CalDAG-GEFI and Rap1b in integrin-independent neutrophil chemotaxis. In a transwell assay, CalDAG-GEFI-/- neutrophils had a 46% reduction in transmigration compared with WT in response to a low concentration of LTB4. Visualization of migrating neutrophils in the presence of 10 mM EDTA revealed that CalDAG-GEFI-/- neutrophils had abnormal chemotactic behavior compared with WT neutrophils, including reduced speed and directionality. Interestingly, Rap1b-/- neutrophils had a similar phenotype in this assay, suggesting that CalDAG-GEFI may be acting through Rap1b. We investigated whether the deficit in integrin-independent chemotaxis in CalDAG-GEFI-/- neutrophils could be explained by defective cytoskeleton rearrangement. Indeed, we found that CalDAG-GEFI-/- neutrophils had reduced formation of F-actin pseudopodia after LTB4 stimulation, suggesting that they have a defect in polarization. Overall, our studies show that CalDAG-GEFI helps regulate neutrophil chemotaxis, independent of its established role in integrin activation, through a mechanism that involves actin cytoskeleton and cellular polarization.
Carbo
Carla
C
Immune Disease Institute, Program in Cellular and Molecular Medicine, Department of Laboratory Medicine, Children's Hospital, and Department of Pathology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115, USA.
Duerschmied
Daniel
D
Goerge
Tobias
T
Hattori
Hidenori
H
Sakai
Jiro
J
Cifuni
Stephen M
SM
White
Gilbert C
GC
Chrzanowska-Wodnicka
Magdalena
M
Luo
Hongbo R
HR
Wagner
Denisa D
DD
D000199:Actins; D000818:Animals; D016764:Cell Polarity; D002634:Chemotaxis, Leukocyte; D003599:Cytoskeleton / Q000473:pathology; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D016023:Integrins / Q000378:metabolism*; D007975:Leukotriene B4 / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000502:physiology*; D020827:rap1 GTP-Binding Proteins / Q000502:physiology
D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; D016023:Integrins; C485927:Rasgrp2 protein, mouse; D007975:Leukotriene B4; D020827:rap1 GTP-Binding Proteins