Integrin-independent role of CalDAG-GEFI in neutrophil chemotaxis

J Leukoc Biol. 2010 Aug;88(2):313-9. doi: 10.1189/jlb.0110049. Epub 2010 Apr 22.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins
  • Animals
  • Cell Polarity
  • Chemotaxis, Leukocyte*
  • Cytoskeleton / pathology
  • Guanine Nucleotide Exchange Factors / physiology*
  • Integrins / metabolism*
  • Leukotriene B4 / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • Neutrophils / physiology*
  • rap1 GTP-Binding Proteins / physiology


  • Actins
  • Guanine Nucleotide Exchange Factors
  • Integrins
  • Rasgrp2 protein, mouse
  • Leukotriene B4
  • rap1 GTP-Binding Proteins