Japanese encephalitis virus replication is negatively regulated by autophagy and occurs on LC3-I- and EDEM1-containing membranes

Autophagy is a lysosomal degradative pathway that has diverse physiological functions and plays crucial roles in several viral infections. Here we examine the role of autophagy in the life cycle of JEV, a neurotropic flavivirus. JEV infection leads to induction of autophagy in several cell types. JEV replication was significantly enhanced in neuronal cells where autophagy was rendered dysfunctional by ATG7 depletion, and in Atg5-deficient mouse embryonic fibroblasts (MEFs), resulting in higher viral titers. Autophagy was functional during early stages of infection however it becomes dysfunctional as infection progressed resulting in accumulation of misfolded proteins. Autophagy-deficient cells were highly susceptible to virus-induced cell death. We also observed JEV replication complexes that are marked by nonstructural protein 1 (NS1) and dsRNA colocalized with endogenous LC3 but not with GFP-LC3. Colocalization of NS1 and LC3 was also observed in Atg5 deficient MEFs, which contain only the nonlipidated form of LC3. Viral replication complexes furthermore show association with a marker of the ER-associated degradation (ERAD) pathway, EDEM1 (ER degradation enhancer, mannosidase α-like 1). Our data suggest that virus replication occurs on ERAD-derived EDEM1 and LC3-I-positive structures referred to as EDEMosomes. While silencing of ERAD regulators EDEM1 and SEL1L suppressed JEV replication, LC3 depletion exerted a profound inhibition with significantly reduced RNA levels and virus titers. Our study suggests that while autophagy is primarily antiviral for JEV and might have implications for disease progression and pathogenesis of JEV, nonlipidated LC3 plays an important autophagy independent function in the virus life cycle.     

First parturition of tigers in a semi-arid habitat,western India

Long-term data of large felids is important to understand their reproductive biology and behavior for effective conservation planning. We used camera trap data and direct sightings from 2005 to 2013 to estimate the age of the first parturition of Bengal tigers (Panthera tigris) in a semi-arid habitat in India. We monitored 11 females in the Ranthambhore Tiger Reserve (RTR) from when they were 2–6 months old. The mean age at first reproduction (impregnation leading to cubs) was 51.3?±?(SE) 4.5 months. The tiger population in RTR is an important source population and genetic pool in the western most distribution of tiger. Thus, continuous monitoring of tiger populations is important to develop an understanding of reproductive biology.     

The deubiquitinase activity of A20 is dispensable for NF‐κB signaling

A20 has been suggested to limit NF‐κB activation by removing regulatory ubiquitin chains from ubiquitinated substrates. A20 is a ubiquitin‐editing enzyme that removes K63‐linked ubiquitin chains from adaptor proteins, such as RIP1, and then conjugates them to K48‐linked polyubiquitin chains to trigger proteasomal degradation. To determine the role of the deubiquitinase function of A20 in downregulating NF‐κB signaling, we have generated a knock‐in mouse that lacks the deubiquitinase function of A20 (A20‐OTU mice). These mice are normal and have no signs of inflammation, have normal proportions of B, T, dendritic, and myeloid cells, respond normally to LPS and TNF, and undergo normal NF‐κB activation. Our results thus indicate that the deubiquitinase activity of A20 is dispensable for normal NF‐κB signaling.     

Mouse Hepatitis Virus Infection Upregulates Genes Involved in Innate Immune Responses

Neurotropic recombinant strain of Mouse Hepatitis Virus, RSA59, induces meningo-encephalitis, myelitis and demyelination following intracranial inoculation. RSA59 induced neuropathology is partially caused by activation of CNS resident microglia, as demonstrated by changes in cellular morphology and increased expression of a microglia/macrophage specific calcium ion binding factor, Iba1. Affymetrix Microarray analysis for mRNA expression data reveals expression of inflammatory mediators that are known to be released by activated microglia. Microglia-specific cell surface molecules, including CD11b, CD74, CD52 and CD68, are significantly upregulated in contrast to CD4, CD8 and CD19. Protein analysis of spinal cord extracts taken from mice 6 days post-inoculation, the time of peak inflammation, reveals robust expression of IFN-γ, IL-12 and mKC. Data suggest that activated microglia and inflammatory mediators contribute to a local CNS microenvironment that regulates viral replication and IFN-γ production during the acute phase of infection, which in turn can cause phagolysosome maturation and phagocytosis of the myelin sheath, leading to demyelination.     

Dracunculiasis in South Indian bonnet monkey

Dracunculiasis, popularly known as Guinea worm disease, has been eradicated from Tamil Nadu, India, and there have been no indigenous cases reported since 1981. This report describes a female bonnet monkey with dracunculiasis. She presented with fever and a blister in left hind limb. The blister ruptured on exposure to water and a 7-cm-long worm was extruded. The worm died before it could be histologically examined. The diagnosis was based on the typical clinical course, which was pathognomonic of dracunculiasis. Review of literature did not reveal any previous report of dracunculiasis in South Indian bonnet monkeys (Macaca radiata). This paper raises the question whether wild monkeys might act as reservoirs of human infection and cause resurgence of the disease in South India. Animal experiments were approved by the ethical committee of our institute and animal maintenance was according to the recommendations of the Canadian Council for Experimental Animal Care and the Laboratory Animal Science Association of India.     

Size regulation of multiple organelles competing for a limiting subunit pool

How cells regulate the size of intracellular structures and organelles is a longstanding question. Recent experiments suggest that size control of intracellular structures is achieved through the depletion of a limiting subunit pool in the cytoplasm. While the limiting pool model ensures organelle-to-cell size scaling, it does not provide a mechanism for robust size control of multiple co-existing structures. Here we develop a generalized theory for size-dependent growth of intracellular structures to demonstrate that robust size control of multiple intracellular structures, competing for a limiting subunit pool, is achieved via a negative feedback between the growth rate and the size of the individual structure. This design principle captures size maintenance of a wide variety of subcellular structures, from cytoskeletal filaments to three-dimensional organelles. We identify the feedback motifs for structure size regulation based on known molecular processes, and compare our theory to existing models of size regulation in biological assemblies. Furthermore, we show that positive feedback between structure size and growth rate can lead to bistable size distribution and spontaneous size selection.