The causative agent of malaria, Plasmodium, replicates inside a membrane-bound parasitophorous vacuole (PV) that shields this intracellular parasite from the cytosol of the host cell1. One common threat for intracellular pathogens is the homeostatic process of autophagy through which cells capture unwanted intracellular material for lysosomal degradation2. During the liver stage of a malaria infection, Plasmodium parasites are targeted by the autophagy machinery of the host cell and the PV membrane (PVM) becomes decorated with several autophagy markers, including LC3 (microtubule-associated protein 1 light chain 3)3,4. Here we show that Plasmodium berghei parasites infecting hepatic cells rely on the PVM transmembrane protein UIS3 to avoid elimination by host cell-mediated autophagy. We found that UIS3 binds host LC3 through a non-canonical interaction with a specialised surface on LC3 where host proteins with essential functions during autophagy also bind. UIS3 acts as a bona fide autophagy inhibitor by competing with host LC3-interacting proteins for LC3 binding. Our work identifies UIS3, one of the most promising candidates for a genetically-attenuated vaccine against malaria5, as a unique and potent mediator of autophagy evasion in Plasmodium. We propose that the protein-protein interaction between UIS3 and host LC3 represents a target for antimalarial drug development.

Gammaherpesviruses subvert eukaryotic signaling pathways to favor latent infections in their cellular reservoirs. To this end, they express proteins that regulate or replace functionally specific signaling proteins of eukaryotic cells. Here we describe a new type of such viral-host interaction that is established through M2, a protein encoded by murine gammaherpesvirus 68. M2 associates with Vav proteins, a family of phosphorylation-dependent Rho/Rac exchange factors that play critical roles in lymphocyte signaling. M2 expression leads to Vav1 hyperphosphorylation and to the subsequent stimulation of its exchange activity towards Rac1, a process mediated by the formation of a trimolecular complex with Src kinases. This heteromolecular complex is coordinated by proline-rich and Src family-dependent phosphorylated regions of M2. Infection of Vavdeficient mice with gammaherpesvirus 68 results in increased long-term levels of latency in germinal center B lymphocytes, corroborating the importance of the M2/Vav cross talk in the process of viral latency. These results reveal a novel strategy used by the murine gammaherpesvirus family to subvert the lymphocyte signaling machinery to its own benefit.The persistence of herpesvirus in the infected organism is dictated by the establishment of latency in particular cell types within the host. In the case of gammaherpesviruses, such as the human pathogens Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), latency occurs by maintenance of the viral genome in the nuclei of infected B lymphocytes. To favor such a process, these viruses have developed a number of strategies aimed at interfering with different aspects of the host cell signaling machinery. For instance, the EBV genome encodes two proteins, latent membrane protein 1 (LMP1) and LMP2, which contribute to the activation of naïve B cells by mimicking the function of two important B-cell surface receptors, the CD40 molecule and the B-cell receptor, respectively (9). The spurious activation of the downstream pathways of those receptors by LMP1 and LMP2 contributes to B-cell activation, differentiation, and the rescue of infected germinal center (GC) B-cell blasts into the memory B-cell pool (36). Similarly, the K1 and K15 proteins encoded by KSHV can alter B-cell signaling by promoting the activation of the NF-B and the nuclear factor of activated T cells. In addition, they interfere with the function of tyrosine kinases and tumor necrosis factor receptor-associated factors (9). It is likely that the viral machinery devoted to the manipulation of the signaling pathways of host cells is not restricted to these examples. Indeed, the genomes of most gammaherpesviruses contain a large number of genes that are not directly linked to viral entry, replication, or morphogenesis (10,15,27,31). The identification of additional herpesvirus proteins controlling the activation, differentiation, and survival of latently infected cells is of particular interest as these proteins constitute key components of ga...

Host colonisation by lymphotropic gammaherpesviruses depends critically on the expansion of viral genomes in germinal centre (GC) B cells. Yet, host and virus molecular mechanisms involved in driving such proliferation remain largely unknown. Here, we show that the ORF73 protein encoded by the murid herpesvirus-4 (MuHV-4) inhibits host nuclear factor-kappa B (NF-jB) transcriptional activity through poly-ubiquitination and subsequent proteasomal-dependent nuclear degradation of the NF-jB family member p65/RelA. The mechanism involves the assembly of an ElonginC/Cullin5/SOCS (suppressors of cytokine signalling)-like complex, mediated by an unconventional viral SOCS-box motif present in ORF73. Functional deletion of this SOCS-box motif ablated NF-jB inhibitory effect of ORF73, suppressed MuHV-4 expansion in GC B cells and prevented MuHV-4 persistent infection in mice. These findings demonstrate that viral inhibition of NF-jB activity in latently infected GC centroblasts is critical for the establishment of a gammaherpesvirus persistent infection, underscoring the physiological importance of proteasomal degradation of RelA/NF-jB as a regulatory mechanism of this signalling pathway.

Latency-associated nuclear antigen (LANA) mediates γ2-herpesvirus genome persistence and regulates transcription. We describe the crystal structure of the murine gammaherpesvirus-68 LANA C-terminal domain at 2.2 Å resolution. The structure reveals an alpha-beta fold that assembles as a dimer, reminiscent of Epstein-Barr virus EBNA1. A predicted DNA binding surface is present and opposite this interface is a positive electrostatic patch. Targeted DNA recognition substitutions eliminated DNA binding, while certain charged patch mutations reduced bromodomain protein, BRD4, binding. Virus containing LANA abolished for DNA binding was incapable of viable latent infection in mice. Virus with mutations at the charged patch periphery exhibited substantial deficiency in expansion of latent infection, while central region substitutions had little effect. This deficiency was independent of BRD4. These results elucidate the LANA DNA binding domain structure and reveal a unique charged region that exerts a critical role in viral latent infection, likely acting through a host cell protein(s).