DC mobilization from peripheral tissues relies on pattern Selleck Dabrafenib recognition receptor signalling to promote DC maturation. Accordingly, MV acts as DC-SIGN and TLR2 agonist 7, 9 and induces phenotypic maturation (including upregulation of MHC and co-stimulatory molecules and cytokine release), morphodynamic changes and enhanced motility of infected DC on fibronectin (FN) supports 10. In contrast, CCR5/CCR7 switching, MHCII upregulation, and IL-12 production are less efficiently induced by MV as compared to other maturation stimuli 11, 12. These differences do, however, not explain the inability of MV-infected DC (MV-DC) to promote T-cell expansion in vitro 12–14. Rather, ligation of an
as yet unknown surface receptor by the MV glycoprotein (gp) complex (displayed on the surface of MV-DC) interferes with TCR-stimulated activation of the phosphatidylinositol-3(PI3)/Akt kinase pathway. This efficiently abrogates
activation of downstream effectors essential for actin cytoskeletal reorganization and cell cycle entry (reviewed in 15–17). MV contact induced activation of sphingomyelinases in T cells which accounts for its interference with cytoskeletal dynamics 18, yet molecules and mechanisms actively conferring IS instability to MV-DC/T-cell conjugates are poorly characterized. The mature IS segregates molecules involved in peptide recognition and TCR signalling from surrounding molecules also including those involved in stabilization and adhesion. It is an area of highly active cytoskeletal rearrangement, which essentially controls centripetal movement of TCR Torin 1 microclusters, but also receptor segregation including that of integrins, which regulate both TCR microcluster Carbohydrate confinement and stability of the DC/T-cell conjugate (for a recent review 19). Initially described as guidance factors regulating axonal path-finding during neuronal development, the general ability of semaphorins (SEMAs) to act as adhesion/repulsion cues
has meanwhile highlighted the importance of these molecules in diverse physiological functions also including vascular growth, cell migration, and immune cell regulation 20–23. SEMAs share a common “SEMA” domain and are divided into eight subclasses, and those expressed in vertebrates are membrane associated (class IV-VII) or secreted (class III, SEMA3 species). Class VIII summarizes virally encoded, secreted SEMAs with similarity to SEMA7A, and modulate immune activation by acting on monocytes 21, 24, 25. Most membrane-resident SEMAs use members of the plexin family for binding and signalling, while most SEMA3 molecules require neuropilins (NP-1 or -2) as obligate binding receptors for initiating cellular responses through plexins. In addition to using these receptors, certain SEMAs (SEMA7A and SEMA4A and 4D) also signal to their immune effector cells by interaction with integrins, CD72, or TIM-2 23, 26.