Crystal structure of the tegument protein UL82 (pp71) from human cytomegalovirus.

Human cytomegalovirus (HCMV) is an opportunistic pathogen that infects a majority of the world population. It may cause severe disease in immunocompromised people and lead to pregnancy loss or grave disabilities of the fetus upon congenital infection. For effective replication and lifelong persistence in its host, HCMV relies on diverse functions of its tegument protein UL82, also known as pp71. Up to now, little is known about the molecular mechanisms underlying the multiple functions of this crucial viral protein. Here, we describe the X-ray structure of full-length UL82 to a resolution of 2.7 Å. A single polypeptide chain of 559 amino acids mainly folds into three ß-barrels. We show that UL82 forms a dimer in the crystal as well as in solution. We identify point mutations that disturb the dimerization interface and show that the mutant protein is monomeric in solution and upon expression in human cells. On the basis of the three-dimensional structure, we identify structural homologs of UL82 from other herpesviruses and analyze whether their functions are preserved in UL82. We demonstrate that UL82, despite its structural homology to viral deoxyuridinetriphosphatases (dUTPases), does not possess dUTPase activity. Prompted by the structural homology of UL82 to the ORF10 protein of murine herpesvirus 68 (MHV68), which is known to interact with the RNA export factor ribonucleic acid export 1 (Rae1), we performed coimmunoprecipitations and demonstrated that UL82 indeed interacts with Rae1. This suggests that HCMV UL82 may play a role in mRNA export from the nucleus similar to ORF10 encoded by the gammaherpesviruses MHV68.

Correction: Salmonella escapes adaptive immune response via SIRT2 mediated modulation of innate immune response in dendritic cells.

[This corrects the article DOI: 10.1371/journal.ppat.1007437.].

Salmonella escapes adaptive immune response via SIRT2 mediated modulation of innate immune response in dendritic cells.

Salmonella being a successful pathogen, employs a plethora of immune evasion mechanisms. This contributes to pathogenesis, persistence and also limits the efficacy of available treatment. All these contributing factors call upon for new drug targets against Salmonella. For the first time, we have demonstrated that Salmonella upregulates sirtuin 2 (SIRT2), an NAD+ dependent deacetylase in dendritic cells (DC). SIRT2 upregulation results in translocation of NFκB p65 to the nucleus. This further upregulates NOS2 transcription and nitric oxide (NO) production. NO subsequently shows antibacterial activity and suppresses T cell proliferation. NOS2 mediated effect of SIRT2 is further validated by the absence of effect of SIRT2 inhibition in NOS2-/- mice. Inhibition of SIRT2 increases intracellular survival of the pathogen and enhances antigen presentation in vitro. However, in vivo SIRT2 inhibition shows lower bacterial organ burden and reduced tissue damage. SIRT2 knockout mice also demonstrate reduced bacterial organ burden compared to wild-type mice. Collectively, our results prove the role of SIRT2 in Salmonella pathogenesis and the mechanism of action. This can aid in designing of host-targeted therapeutics directed towards inhibition of SIRT2.

Erythrocyte Membrane Bound ATPase and Antioxidant Enzyme Changes Associated with Vascular Calcification is Reduced by Sodium Thiosulfate.

Sodium thiosulfate (STS), a cyanide antidote has been reported to possess antioxidant and calcium chelation effects, useful for the treatment of renal failure due to vascular calcification and urolithiasis. The present study investigated the in vivo modulatory effects of STS on erythrocyte calcium, phosphorous levels, lipid peroxidation, antioxidant enzyme and membrane ATPase activities (Ca2+, Na+K+, Mg2+ and 5'' nucleotidase) in an adenine induced model of vascular calcification in rats. Adenine (0.75%) was supplemented through the diet for 28 days, which resulted in significantly (P < 0.05) increased circulating calcium and phosphorous product and oxidative stress within the RBCs, as measured from lipid peroxidation and reduced antioxidant enzymes. The membrane ATPase activities were altered (increased Ca2+, Na+K+ ATPase and decreased Mg+ ATPase, 5' nucleotidase) compared to the rats fed on normal diet. STS (400 mg/kg) given orally was effective in establishing a normalcy in the RBC alterations. This effect was more pronounced, when STS was given from day 28 to day 49 after induction of calcification, instead of day 0 to day 28. These findings may benefit to evaluate the effectiveness of STS therapy in patients with chronic renal failure associated with increased circulating calcium and phosphorous product that leads to stiffening of vascular smooth muscles of aorta, due to calcium deposition.