The movement of leukocytes from the blood into peripheral tissues is a central feature of immune surveillance, but also contributes to the pathogenesis of inflammatory and autoimmune diseases. Integrins are a family of adhesion and signaling molecules made up of paired alpha and beta subunits, and the integrin alpha4beta1 plays a prominent role in the trafficking of mononuclear leukocytes. We have previously described the direct interaction of the signaling adaptor molecule paxillin with the cytoplasmic domain of the alpha4 integrin subunit. This interaction is critical for alpha4beta1 integrin dependent cell adhesion under shear flow conditions as it provides a needed connection to the actin cytoskeleton. Furthermore, the alpha4-paxillin interaction is required for effective alpha4beta1 dependent leukocyte migration and does so through the temporal and spatial regulation of the small GTPase Rac. These findings make the alpha4-paxillin interaction a potentially attractive therapeutic target in controlling leukocyte trafficking.
Protein Binding ; Paxillin/*metabolism/physiology ; Models, Biological ; Leukocytes/cytology/*metabolism ; Integrin alpha4beta1/metabolism/physiology ; Integrin alpha4/*metabolism/physiology ; Humans ; Cell Movement/*physiology ; Cell Adhesion/physiology

OBJECTIVETo investigate the biological behavior of stromal cell-derived factor-1 (SDF-1) on multiple myeloma (MM) cell migration and adhesion and it related signaling pathways.

METHODSExpression of adhesion molecules on MM cells of RPMI8226, XG-1 and XG-7 cells was analysed by flow cytometry, the influence of SDF-1 on CD29 and CD49e distribution by immunofluorescence, the effect of SDF-1 on chemotaxis of MM cells by transwell assay. Activation of phosphoinositide-3 kinase (PI3K) in MM cells treated with SDF-1 and by immunoblotting.

RESULTS3 strains of MM cell line expressed many adhesion molecule. RPMI8226, XG-7 cells were all high level of expression of CD29 (> 70%). XG-1, XG-7 cells were all high level of expression of CD44 (> 80%), and XG-7 cells was of CD49d (> 90%). In all of 3 strains, the levels of expression of CD49e were low (< 30%). SDF-1 could not upregulate their expression, but could trigger the establishment of polarized morphology of MM cells and the redistribution of CD29 and CD49e. SDF-1 promoted MM cells adhesion to endothelial cells, stimulated phosphorylation of P85 subunit of PI3K in MM cells and induced MM cells migration, which were inhibited by G protein inhibitor PTX and PI3K inhibitor wortmannin.

CONCLUSIONSDF-1 can promote MM cell adhesion to endothelial cells, trigger establishment of a polarized morphology of MM cells and redistribution of adhesion molecules and induce MM cells migration via PI3K signaling pathway.

Blotting, Western ; Cell Adhesion ; drug effects ; physiology ; Cell Adhesion Molecules ; metabolism ; Cell Line, Tumor ; Cell Movement ; drug effects ; physiology ; Chemokine CXCL12 ; pharmacology ; physiology ; Enzyme Activation ; drug effects ; Flow Cytometry ; Fluorescent Antibody Technique ; Humans ; Integrin alpha4 ; metabolism ; Integrin alpha5 ; metabolism ; Integrin beta1 ; metabolism ; Multiple Myeloma ; metabolism ; pathology ; physiopathology ; Phosphatidylinositol 3-Kinases ; metabolism ; Signal Transduction ; drug effects ; physiology

Homing-associated cell adhesion molecules (H-CAM) on the CD34+ cells play an important role for the engraftment process following hematopoietic stem cell transplantation (HSCT). However, it seems that not only CD34+ cells but also other nucleated cells (NCs) with H-CAM could be implicated in the engraftment process and the proliferation of hematopoietic stem cells. We investigated the differences of HCAM and cell cycle status on the NCs in cord blood (CB), bone marrow (BM), and mobilized peripheral blood (PB). The proportions of CXCR4+ cells within the NC populations were greater in CB than in PB or BM (p=0.0493), although the proportions of CXCR4+, CD44+, and CD49d+ cells within the CB CD34+ cell populations were same within BM or PB. A lower proportion of CD34+CD49d+ cells within the CD34+ cell populations was more noted in CB than in PB or BM (p=0.0085). There were no differences in cell cycle status between CB and BM or PB. Our results suggest that the migrating potential of CB would be enhanced with increased CXCR4 expression on the NCs, but the adhesion potential of CB CD34+ cells would be less than that of PB and BM. These findings may help explain why the lower cell dose is required and engraftment is delayed in cord blood stem cell transplantation.
Antigens, CD34/metabolism ; Antigens, CD44/*metabolism ; Bone Marrow Cells/*metabolism ; Cell Adhesion Molecules/*metabolism ; Cell Cycle/*physiology ; Cell Proliferation ; Cell Separation ; Fetal Blood/*cytology ; Flow Cytometry ; Hematopoietic Stem Cell Transplantation ; Hematopoietic Stem Cells/*metabolism ; Humans ; Integrin alpha4/metabolism ; Receptors, CXCR4/metabolism ; Research Support, Non-U.S. Gov't