RESUMEN
Exosomes are extracellular vesicles (EVs) that play a role in intercellular communication. Stimulation of dendritic cells by the HIV-1 virus triggers their release. HIV-1 binds to dendritic cells via dendritic cell immunoreceptor (DCIR). This study shows that inhibiting the binding to DCIR significantly decreases exosome release by HIV-1-pulsed dendritic cells. In addition, exosome release from Raji-CD4 expressing DCIR cells stimulated by anti-DCIR or HIV-1 is decreased when the immunoreceptor tyrosine-based inhibition motif (ITIM) signaling motif of DCIR is mutated. Unlike the EVs released from Raji-CD4-DCIR cells after antibody stimulation, those released from HIV-1-infected cells contain the pro-apoptotic protein DAP-3. Furthermore, EVs from HIV-1 pulsed dendritic cells increase spontaneous apoptosis in uninfected CD4 T lymphocytes while they decrease it in neutrophils. This study describes for the first time that DCIR plays a role in the release of exosomes strengthening the importance of this receptor and EVs/exosomes in HIV-1 pathogenesis.
Asunto(s)
Células Dendríticas/inmunología , Células Dendríticas/virología , Exosomas/metabolismo , VIH-1/fisiología , Receptores Inmunológicos/metabolismo , Células Cultivadas , Células Dendríticas/metabolismo , VIH-1/inmunología , Humanos , Acoplamiento ViralRESUMEN
S100A8/A9 (calprotectin) and S100A12 proinflammatory mediators are found at inflammatory sites and in the serum of patients with inflammatory or autoimmune diseases. These cytoplasmic proteins are secreted by neutrophils at sites of inflammation via alternative secretion pathways of which little is known. This study examined the nature of the stimuli leading to S100A8/A9 and S100A12 secretion as well as the mechanism involved in this alternative secretion pathway. Chemotactic agents, cytokines, and particulate molecules were used to stimulate human neutrophils. MSU crystals, PMA, and H2O2 induced the release of S100A8, S100A9, and S100A12 homodimers, as well as S100A8/A9 heterodimer. High concentrations of S100A8/A9 and S100A12 were secreted in response to nanoparticles like MSU, silica, TiO2, fullerene, and single-wall carbon nanotubes as well as in response to microbe-derived molecules, such as zymosan or HKCA. However, neutrophils exposed to the chemotactic factors fMLP failed to secrete S100A8/A9 or S100A12. Secretion of S100A8/A9 was dependent on the production of reactive oxygen species and required K(+) exchanges through the ATP-sensitive K(+) channel. Altogether, these findings suggest that S100A12 and S100A8/A9 are secreted independently either via distinct mechanisms of secretion or following the activation of different signal transduction pathways.