DOCK2 is required for chemokine-promoted human T lymphocyte adhesion under shear stress mediated by the integrin alpha4beta1.
The alpha4beta1 integrin is an essential adhesion molecule for recruitment of circulating lymphocytes into lymphoid organs and peripheral sites of inflammation. Chemokines stimulate alpha4beta1 adhesive activity allowing lymphocyte arrest on endothelium and subsequent diapedesis. Activation of the GTPase Rac by the guanine-nucleotide exchange factor Vav1 promoted by CXCL12 controls T lymphocyte adhesion mediated by alpha4beta1. In this study, we investigated the role of DOCK2, a lymphocyte guanine-nucleotide exchange factor also involved in Rac activation, in CXCL12-stimulated human T lymphocyte adhesion mediated by alpha4beta1. Using T cells transfected with DOCK2 mutant forms defective in Rac activation or with DOCK2 small interfering RNA, we demonstrate that DOCK2 is needed for efficient chemokine-stimulated lymphocyte attachment to VCAM-1 under shear stress. Flow chamber, soluble binding, and cell spreading assays identified the strengthening of alpha4beta1-VCAM-1 interaction, involving high affinity alpha4beta1 conformations, as the adhesion step mainly controlled by DOCK2 activity. The comparison of DOCK2 and Vav1 involvement in CXCL12-promoted Rac activation and alpha4beta1-dependent human T cell adhesion indicated a more prominent role of Vav1 than DOCK2. These results suggest that DOCK2-mediated signaling regulates chemokine-stimulated human T lymphocyte alpha4beta1 adhesive activity, and that cooperation with Vav1 might be required to induce sufficient Rac activation for efficient adhesion. In contrast, flow chamber experiments using lymph node and spleen T cells from DOCK2(-/-) mice revealed no significant alterations in CXCL12-promoted adhesion mediated by alpha4beta1, indicating that DOCK2 activity is dispensable for triggering of this adhesion in mouse T cells, and suggesting that Rac activation plays minor roles in this process.
García-Bernal
David
D
Department of Immunology, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
Sotillo-Mallo
Elena
E
Nombela-Arrieta
César
C
Samaniego
Rafael
R
Fukui
Yoshinori
Y
Stein
Jens V
JV
Teixidó
Joaquin
J
D000818:Animals; D002448:Cell Adhesion; D054377:Chemokine CXCL12; D018925:Chemokines / Q000502:physiology; D019743:Chemokines, CXC / Q000502:physiology*; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D006801:Humans; D039041:Integrin alpha4beta1 / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D051567:Proto-Oncogene Proteins c-vav / Q000502:physiology*; D013314:Stress, Mechanical; D013601:T-Lymphocytes / Q000166:cytology*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D018925:Chemokines; D019743:Chemokines, CXC; C515256:Cxcl12 protein, mouse; C402110:DOCK2 protein, human; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D039041:Integrin alpha4beta1; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; D019010:Vascular Cell Adhesion Molecule-1