Interactions of TANGO and leukocyte integrin CD11c/CD18 regulate the migration of human monocytes

The TANGO gene was originally identified as a new member of the MIA gene family. It codes for a protein of yet unknown function. TANGO revealed a very broad expression pattern in contrast to the highly restricted expression pattern determined for the other family members. The only cells lacking TANGO expression are cells of the hematopoietic system. One of the major differences between mature hematopoietic cells and other tissue cells is the lack of adhesion until these cells leave the bloodstream. In this study, we observed that TANGO expression was induced after adhesion of human monocytic cells to substrate. To understand the mechanism of TANGO function during monocyte adhesion we isolated interacting proteins and found an interaction between TANGO and the leukocyte-specific integrin CD11c. In functional assays, we observed reduced attachment of human monocytic cells to fibrinogen, ICAM-1 and to human microvascular endothelial cells (HMECs) after stimulation with recombinant TANGO protein. Additionally, the migrating capacity of premonocytic cells through fibrinogen or HMECs was increased after stimulation of these cells with recombinant TANGO. Therefore, we suggest that TANGO reduced the attachment to fibrinogen or other cell adhesion molecules. As TANGO does not compete for CD11c ligand binding directly, we hypothesize TANGO function by modulation of integrin activity. Taken together, the results from this study present TANGO as a novel ligand for CD11c, regulating migratory processes of hematopoietic cells.