Submitted October 10, 2008
Accepted April 27, 2009
-arrestin 2 is required for the induction and strengthening of integrin-mediated leukocyte adhesion during CXCR2-driven extravasation
Raffaella Molteni, Carolina Lage Crespo, Sara Feigelson, Christian Moser, Monica Fabbri, Valentin Grabovsky, Fritz Krombach, Carlo Laudanna, Ronen Alon, and Ruggero Pardi*
San Raffaele University School of Medicine, Milano, Italy
Scientific Institute San Raffaele, Milano, Italy
Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
Walter Brendel Center of Experimental Medicine, Ludwig-Maximilians-Universitat Munchen, Munich, Germany
Division of General Pathology, Department of Pathology, School of Medicine, and the Center for Biomedical Computing (CBMC), University of Verona, Verona, Italy
* Corresponding author; email: pardi.ruggero{at}hsr.it.
Leukocyte extravasation involves interdependent signaling pathways underlying the complex dynamics of firm adhesion, crawling and diapedesis. While signal transduction by agonist-bound chemokine receptors plays a central role in the above responses, it is unclear how it contributes to the sustained and concurrent nature of such responses, given the rapid kinetics of chemokine-induced trimeric G protein coupling and homologous desensitization. Our findings unveil a novel role of 
-arrestins in regulating the activation of signaling pathways underlying discrete integrin-mediated steps in CXCR2-driven leukocyte extravasation. By combining in vivo approaches in -arrestin knockout mice with in vitro studies in engineered cellular models we show that membrane-recruited -arrestin-2 is required for the onset and maintenance of shear stress-resistant leukocyte adhesion mediated by both 1 and 2 integrins. While both -arrestin isoforms are required for rapid KC-induced arrest onto limiting amounts of VCAM-1, adhesion strengthening under shear is selectively dependent on -arrestin 2. The latter synergizes with phospholipase C in promoting activation of Rap1A and B, both of which cooperatively control subsecond adhesion as well as post-arrest adhesion stabilization. Thus, receptor-induced G
i and -arrestins act sequentially and in spatially distinct compartments to promote optimal KC-induced integrin-dependent adhesion during leukocyte extravasation.
