13 research outputs found
HIV-1 Nef Induces Proinflammatory State in Macrophages through Its Acidic Cluster Domain: Involvement of TNF Alpha Receptor Associated Factor 2
Background: HIV-1 Nef is a virulence factor that plays multiple roles during HIV replication. Recently, it has been described that Nef intersects the CD40 signalling in macrophages, leading to modification in the pattern of secreted factors that appear able to recruit, activate and render T lymphocytes susceptible to HIV infection. The engagement of CD40 by CD40L induces the activation of different signalling cascades that require the recruitment of specific tumor necrosis factor receptor-associated factors (i.e. TRAFs). We hypothesized that TRAFs might be involved in the rapid activation of NF-kappa B, MAPKs and IRF-3 that were previously described in Nef-treated macrophages to induce the synthesis and secretion of proinflammatory cytokines, chemokines and IFN beta to activate STAT1, -2 and -3. Methodology/Principal Findings: Searching for possible TRAF binding sites on Nef, we found a TRAF2 consensus binding site in the AQEEEE sequence encompassing the conserved four-glutamate acidic cluster. Here we show that all the signalling effects we observed in Nef treated macrophages depend on the integrity of the acidic cluster. In addition, Nef was able to interact in vitro with TRAF2, but not TRAF6, and this interaction involved the acidic cluster. Finally silencing experiments in THP-1 monocytic cells indicate that both TRAF2 and, surprisingly, TRAF6 are required for the Nef-induced tyrosine phosphorylation of STAT1 and STAT2. Conclusions: Results reported here revealed TRAF2 as a new possible cellular interactor of Nef and highlighted that in monocytes/macrophages this viral protein is able to manipulate both the TRAF/NF-kappa B and TRAF/IRF-3 signalling axes, thereby inducing the synthesis of proinflammatory cytokines and chemokines as well as IFN beta
Structural insight into the membrane targeting domain of the Legionella deAMPylase SidD
AMPylation, the post-translational modification with adenosine monophosphate (AMP), is catalyzed by effector proteins from a variety of pathogens. Legionella pneumophila is thus
far the only known pathogen that, in addition to encoding an AMPylase (SidM/DrrA), also
encodes a deAMPylase, called SidD, that reverses SidM-mediated AMPylation of the vesicle
transport GTPase Rab1. DeAMPylation is catalyzed by the N-terminal phosphatase-like
domain of SidD. Here, we determined the crystal structure of full length SidD including the
uncharacterized C-terminal domain (CTD). A flexible loop rich in aromatic residues within
the CTD was required to target SidD to model membranes in vitro and to the Golgi apparatus
within mammalian cells. Deletion of the loop (??loop) or substitution of its aromatic phenylalanine
residues rendered SidD cytosolic, showing that the hydrophobic loop is the
primary membrane-targeting determinant of SidD. Notably, deletion of the two terminal
alpha helices resulted in a CTD variant incapable of discriminating between membranes of
different composition. Moreover, a L. pneumophila strain producing SidD??loop phenocopied
a L. pneumophila ??sidD strain during growth in mouse macrophages and displayed prolonged
co-localization of AMPylated Rab1 with LCVs, thus revealing that membrane targeting
of SidD via its CTD is a critical prerequisite for its ability to catalyze Rab1 deAMPylation
during L. pneumophila infection
The conserved acidic cluster domain of HIV-1 Nef is required to induces a proinflammatory state in primary macrophages: involvement of TNF alpha Receptor Associated Factor 2
The Choice of Transcatheter Aortic Valve Implementation (TAVI): Do Patient Co-morbidity and Hospital Ownership Type Matter?
In Vitro Strategy to Measure Sterol/Phosphatidylinositol-4-Phosphate Exchange Between Membranes
International audienc