BRCA1-regulated nuclear innate sensing of Herpesviral genome by IFI16 and IFI16’s acetylation is critical for its cytoplasmic trafficking and induction of innate responses: DOI: 10.14800/ics.1076

Sensing of invading DNA virus genomes appear to be triggered by a number of host cell DNA sensors depending on their subcellular localization which stimulate innate anti-viral responses such as the activation of type-I interferons (IFNs) and/or inflammasomes resulting in the  production of inflammatory IL-1? and IL-18 cytokines. With growing understanding of diverse identities whether these proteins function alone or  with other host cell molecules and the post-translational modifications affecting their functions are under intense investigations. Nuclear resident IFI16 have been shown to sense the episomal DNA genomes of herpes viruses resulting in the induction of IFI16-inflammasome and/or interferon responses. Here, we highlight our recent finding regarding the role of cellular  BRCA1, a transcription factor and DNA damage response protein, forming a distinct complex with IFI16 to regulate the nuclear innate sensing of herpes viral DNA and subsequent IFI16-ASC-procaspase-1 inflammasome complex formation and distribution to the cytoplasm leading into caspase-1 and IL-1? production. BRCA1 is also responsible for the cytoplasmic IFI16-STING signalosome activation and induction of IFN-? during de novo KSHV and HSV-1 infection. Our concurrent studies have also revealed that the histone acetyl transferase p300 mediated acetylation of nuclear IFI16 is a dynamic post-genome recognition event responsible for Ran dependent nuclear to cytoplasmic trafficking of IFI16 during herpesvirus infection. This post-translational modification is essential for IFI16-ASC interaction and inflammasome activation as well as for the association with STING in the cytoplasm resulting in IRF-3 phosphorylation, nuclear pIRF-3 localization and interferon-? production. Collectively, these comprehensive studies highlight that BRCA1 plays a hitherto unidentified immunomodulatory role to facilitate the anti-viral functions of IFI16 and acetylation of nuclear IFI16 is a necessary post-translational modification for innate responses during herpesvirus infection. These studies open up a new understanding of virus-host interplay, viral genome sensing and host innate anti-viral defense mechanisms

BRCA1-regulated nuclear innate sensing of Herpesviral genome by IFI16 and IFI16’s acetylation is critical for its cytoplasmic trafficking and induction of innate responses

Sensing of invading DNA virus genomes appear to be triggered by a number of host cell DNA sensors depending on their subcellular localization which stimulate innate anti-viral responses such as the activation of type-I interferons (IFNs) and/or inflammasomes resulting in the  production of inflammatory IL-1β and IL-18 cytokines. With growing understanding of diverse identities whether these proteins function alone or  with other host cell molecules and the post-translational modifications affecting their functions are under intense investigations. Nuclear resident IFI16 have been shown to sense the episomal DNA genomes of herpes viruses resulting in the induction of IFI16-inflammasome and/or interferon responses. Here, we highlight our recent finding regarding the role of cellular  BRCA1, a transcription factor and DNA damage response protein, forming a distinct complex with IFI16 to regulate the nuclear innate sensing of herpes viral DNA and subsequent IFI16-ASC-procaspase-1 inflammasome complex formation and distribution to the cytoplasm leading into caspase-1 and IL-1β production. BRCA1 is also responsible for the cytoplasmic IFI16-STING signalosome activation and induction of IFN-β during de novo KSHV and HSV-1 infection. Our concurrent studies have also revealed that the histone acetyl transferase p300 mediated acetylation of nuclear IFI16 is a dynamic post-genome recognition event responsible for Ran dependent nuclear to cytoplasmic trafficking of IFI16 during herpesvirus infection. This post-translational modification is essential for IFI16-ASC interaction and inflammasome activation as well as for the association with STING in the cytoplasm resulting in IRF-3 phosphorylation, nuclear pIRF-3 localization and interferon-β production. Collectively, these comprehensive studies highlight that BRCA1 plays a hitherto unidentified immunomodulatory role to facilitate the anti-viral functions of IFI16 and acetylation of nuclear IFI16 is a necessary post-translational modification for innate responses during herpesvirus infection. These studies open up a new understanding of virus-host interplay, viral genome sensing and host innate anti-viral defense mechanisms

The molecular chaperone heat shock protein-90 positively regulates rotavirus infection

AbstractRotaviruses are the major cause of severe dehydrating gastroenteritis in children worldwide. In this study, we report a positive role of cellular chaperone Hsp90 during rotavirus infection. A highly specific Hsp90 inhibitor, 17-allylamono-demethoxygeldanamycin (17-AAG) was used to delineate the functional role of Hsp90. In MA104 cells treated with 17-AAG after viral adsorption, replication of simian (SA11) or human (KU) strains was attenuated as assessed by quantitating both plaque forming units and expression of viral genes. Phosphorylation of Akt and NFκB observed 2–4 hpi with SA11, was strongly inhibited in the presence of 17-AAG. Direct Hsp90–Akt interaction in virus infected cells was also reduced in the presence of 17-AAG. Anti-rotaviral effects of 17-AAG were due to inhibition of activation of Akt that was confirmed since, PI3K/Akt inhibitors attenuated rotavirus growth significantly. Thus, Hsp90 regulates rotavirus by modulating cellular signaling proteins. The results highlight the importance of cellular proteins during rotavirus infection and the possibility of targeting cellular chaperones for developing new anti-rotaviral strategies

Science with the Daksha High Energy Transients Mission

We present the science case for the proposed Daksha high energy transients mission. Daksha will comprise of two satellites covering the entire sky from 1~keV to $>1$~MeV. The primary objectives of the mission are to discover and characterize electromagnetic counterparts to gravitational wave source; and to study Gamma Ray Bursts (GRBs). Daksha is a versatile all-sky monitor that can address a wide variety of science cases. With its broadband spectral response, high sensitivity, and continuous all-sky coverage, it will discover fainter and rarer sources than any other existing or proposed mission. Daksha can make key strides in GRB research with polarization studies, prompt soft spectroscopy, and fine time-resolved spectral studies. Daksha will provide continuous monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy counterparts to Fast Radio Bursts. Using Earth occultation to measure source fluxes, the two satellites together will obtain daily flux measurements of bright hard X-ray sources including active galactic nuclei, X-ray binaries, and slow transients like Novae. Correlation studies between the two satellites can be used to probe primordial black holes through lensing. Daksha will have a set of detectors continuously pointing towards the Sun, providing excellent hard X-ray monitoring data. Closer to home, the high sensitivity and time resolution of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray Flashes.Comment: 19 pages, 7 figures. Submitted to ApJ. More details about the mission at https://www.dakshasat.in

Interaction of KSHV with Host Cell Surface Receptors and Cell Entry

Virus entry is a complex process characterized by a sequence of events. Since the discovery of KSHV in 1994, tremendous progress has been made in our understanding of KSHV entry into its in vitro target cells. KSHV entry is a complex multistep process involving viral envelope glycoproteins and several cell surface molecules that is utilized by KSHV for its attachment and entry. KSHV has a broad cell tropism and the attachment and receptor engagement on target cells have an important role in determining the cell type-specific mode of entry. KSHV utilizes heparan sulfate, integrins and EphrinA2 molecules as receptors which results in the activation of host cell pre-existing signal pathways that facilitate the subsequent cascade of events resulting in the rapid entry of virus particles, trafficking towards the nucleus followed by viral and host gene expression. KSHV enters human fibroblast cells by dynamin dependant clathrin mediated endocytosis and by dynamin independent macropinocytosis in dermal endothelial cells. Once internalized into endosomes, fusion of the viral envelope with the endosomal membranes in an acidification dependent manner results in the release of capsids which subsequently reaches the nuclear pore vicinity leading to the delivery of viral DNA into the nucleus. In this review, we discuss the principal mechanisms that enable KSHV to interact with the host cell surface receptors as well as the mechanisms that are required to modulate cell signaling machinery for a successful entry

Interactions between Exosomes from Breast Cancer Cells and Primary Mammary Epithelial Cells Leads to Generation of Reactive Oxygen Species Which Induce DNA Damage Response, Stabilization of p53 and Autophagy in Epithelial Cells

<div><p>Exosomes are nanovesicles originating from multivesicular bodies and are released by all cell types. They contain proteins, lipids, microRNAs, mRNAs and DNA fragments, which act as mediators of intercellular communications by inducing phenotypic changes in recipient cells. Tumor-derived exosomes have been shown to play critical roles in different stages of tumor development and metastasis of almost all types of cancer. One of the ways by which exosomes affect tumorigenesis is to manipulate the tumor microenvironments to create tumor permissive “niches”. Whether breast cancer cell secreted exosomes manipulate epithelial cells of the mammary duct to facilitate tumor development is not known. To address whether and how breast cancer cell secreted exosomes manipulate ductal epithelial cells we studied the interactions between exosomes isolated from conditioned media of 3 different breast cancer cell lines (MDA-MB-231, T47DA18 and MCF7), representing three different types of breast carcinomas, and normal human primary mammary epithelial cells (HMECs). Our studies show that exosomes released by breast cancer cell lines are taken up by HMECs, resulting in the induction of reactive oxygen species (ROS) and autophagy. Inhibition of ROS by N-acetyl-L-cysteine (NAC) led to abrogation of autophagy. HMEC-exosome interactions also induced the phosphorylation of ATM, H2AX and Chk1 indicating the induction of DNA damage repair (DDR) responses. Under these conditions, phosphorylation of p53 at serine 15 was also observed. Both DDR responses and phosphorylation of p53 induced by HMEC-exosome interactions were also inhibited by NAC. Furthermore, exosome induced autophagic HMECs were found to release breast cancer cell growth promoting factors. Taken together, our results suggest novel mechanisms by which breast cancer cell secreted exosomes manipulate HMECs to create a tumor permissive microenvironment.</p></div

Detection of phosphorylation of p53 in HMECs incubated with exosomes and its abrogation by NAC.

<p>(A) Western blotting for detection of phosphorylation of p53 at serine 15 (pp53 S15) in HMECs incubated with exosomes from MDA-MB-231 cells for up to 3 h. Equal protein concentrations of cellular lysates were analyzed by western blots for pp53 S15 and total levels of p53. β- actin was used as an equal loading control. (B) Western blot analysis for pp53 S15 in cellular lysates of HMECs untreated and those treated with exosomes from 3 different breast cancer cell lines, MDA-MB-231, T47DA18 and MCF7 respectively for 24 h. β- actin was used as an equal loading control. (C) Western blot analysis for pp53 S15 in cellular lysates of HMECs untreated, treated with NAC alone, treated with NAC and incubated with exosomes, in untreated but incubated with exosomes from MDA-MB-231 cells for 3 h. Tubulin was used as an equal loading control.</p

CIB1 synergizes with EphrinA2 to regulate Kaposi's sarcoma-associated herpesvirus macropinocytic entry in human microvascular dermal endothelial cells.

KSHV envelope glycoproteins interact with cell surface heparan sulfate and integrins, and activate FAK, Src, PI3-K, c-Cbl, and Rho-GTPase signal molecules in human microvascular dermal endothelial (HMVEC-d) cells. c-Cbl mediates the translocation of virus bound α3β1 and αVβ3 integrins into lipid rafts (LRs), where KSHV interacts and activates EphrinA2 (EphA2). EphA2 associates with c-Cbl-myosin IIA and augmented KSHV-induced Src and PI3-K signals in LRs, leading to bleb formation and macropinocytosis of KSHV. To identify the factor(s) coordinating the EphA2-signal complex, the role of CIB1 (calcium and integrin binding protein-1) associated with integrin signaling was analyzed. CIB1 knockdown did not affect KSHV binding to HMVEC-d cells but significantly reduced its entry and gene expression. In contrast, CIB1 overexpression increased KSHV entry in 293 cells. Single virus particle infection and trafficking during HMVEC-d cell entry was examined by utilizing DiI (envelope) and BrdU (viral DNA) labeled virus. CIB1 was associated with KSHV in membrane blebs and in Rab5 positive macropinocytic vesicles. CIB1 knockdown abrogated virus induced blebs, macropinocytosis and virus association with the Rab5 macropinosome. Infection increased the association of CIB1 with LRs, and CIB1 was associated with EphA2 and KSHV entry associated signal molecules such as Src, PI3-K, and c-Cbl. CIB1 knockdown significantly reduced the infection induced EphA2, Src and Erk1/2 activation. Mass spectrometry revealed the simultaneous association of CIB1 and EphA2 with the actin cytoskeleton modulating myosin IIA and alpha-actinin 4 molecules, and CIB1 knockdown reduced EphA2's association with myosin IIA and alpha-actinin 4. Collectively, these studies revealed for the first time that CIB1 plays a role in virus entry and macropinocytosis, and suggested that KSHV utilizes CIB1 as one of the key molecule(s) to coordinate and sustain the EphA2 mediated signaling involved in its entry, and CIB1 is an attractive therapeutic target to block KSHV infection