Blog

Significance was assessed by a Mann-Whitney test (*,P< 0.05). The presence of CXCL12 strongly induced Jurkat migration, with 20% of the cells crossing the membrane in 2 h (Fig.5A). proteins, induces morphological changes. We also used an innovative imaging system to immobilize and visualize living individual cells in suspension. When combined with confocal axial tomography, this technique greatly enhances three-dimensional optical resolution. With this technique, we confirmed the induction of long filopodium-like structures in unfixed Nef-expressing lymphocytes. The cytoskeleton reorganization induced by Nef is usually associated with an important impairment of cell movements. The adhesion and spreading of infected cells to fibronectin, their spontaneous motility, and their migration toward chemokines (CXCL12, CCL3, and CCL19) were all significantly decreased. Therefore, Nef induces complex effects around the lymphocyte actin cytoskeleton and cellular morphology, which likely impacts the capacity of infected cells to circulate and to encounter and communicate with bystander cells. Human immunodeficiency virus type 1 (HIV-1) mostly replicates in T-cell areas of secondary lymphoid organs (SLOs) and induces pathological changes in their architecture. Such changes are likely due to a combination of events, including destruction of T cells, chronic immune activation, and alteration of T-cell motility toward and inside the SLOs (27,37,50,53). Indeed, to fulfill their immune surveillance role, T cells constantly circulate in and out of blood, lymph nodes (LNs), and tissues (60). Lymphocyte recruitment from the bloodstream into LNs depends on three distinct processes, i.e., attachment to high endothelial venules (HEVs), extravasation, and cell migration (10,60). Adhesion to the endothelium and extracellular matrix (ECM) is usually a crucial step, regulated in part by 1 integrins, 41 (VLA-4) and 51, that bind VCAM-1 and/or fibronectin (56). Chemokines and their Gi-protein-coupled receptors are key regulators of lymphocyte trafficking (32). For instance, CCL19 and CCL21 are constitutively produced by HEVs and by fibroblastic reticular cells of T-cell areas of LNs (21,28,29). These two chemokines share the receptor CCR7, expressed (4R,5S)-nutlin carboxylic acid by nave T cells and a fraction of memory T cells (47). They play a major role in lymphocyte homing to LNs, in steady state as well as under conditions of inflammation, and may control T-cell positioning within defined functional compartments Rabbit Polyclonal to RBM26 (1,17,18,47). CXCR4 and its ligand CXCL12/SDF-1 (4R,5S)-nutlin carboxylic acid also contribute to T-cell entry into LNs (5,23,40). In addition, effector and memory T cells express a broad range of receptors binding inflammatory chemokines, such as the CCR5 ligands CCL3 (MIP1), CCL4 (MIP1), and CCL5 (Rantes). Efficient accomplishment of lymphocyte migration and immune functions requires tight regulation of the cellular cytoskeleton (59). This is mediated by the small GTPases of (4R,5S)-nutlin carboxylic acid the Rho subfamily, such as Rho, Rac, and Cdc42 (11,58). They activate specific actin filament assembly factors to generate sheet-like protrusive structures (such as lamellipodia and ruffles) and finger-like protrusions (such as filopodia and microvilli) (6). These structures have different functions. Lamellipodia and ruffles are formed during crawling cell motility and spreading. Filopodia protrude from the leading edges of many motile cells. They appear to perform sensory and exploratory functions to steer cells, depending on cues from the environment (42). Moreover, filopodia, or other thin structures called tunneling nanotubes, have been shown to form intercellular bridges, allowing viruses to spread through remote contacts between infected cells and targets (44,48,49,52). HIV-1 hijacks cytoskeleton dynamics in order to ensure viral entry and transport within and egress from target cells (34; reviewed in reference13). In particular, the viral protein Nef modifies actin remodeling in various cell systems. In T cells, Nef alters actin rearrangements brought on by activation of T-cell (TCR) or chemokine receptors (22,54). Nef inhibits immunological synapse formation, a dynamic process involving rapid actin modifications (57). Nef also affects plasma membrane plasticity, inducing secretion of microvesicle clusters (33). In macrophages, Nef induces the extension of long intercellular conduits allowing its own transfer to B cells (61). A number of studies have reported that Nef affects T-cell chemotaxis (generally to CXCL12) through the modulation of Rho-GTPase-regulated signaling pathways (7,24,39,54). Migration studies have generally been performed.