Interest toward the human microbiome, particularly gut microbiome has flourished in recent decades owing to the rapidly advancing sequence-based screening and humanized gnotobiotic model in interrogating the dynamic operations of commensal microbiota. Although this field is still at a very preliminary stage, whereby the functional properties of the complex gut microbiome remain less understood, several promising findings have been documented and exhibit great potential toward revolutionizing disease etiology and medical treatments. In this review, the interactions between gut microbiota and the host have been focused on, to provide an overview of the role of gut microbiota and their unique metabolites in conferring host protection against invading pathogen, regulation of diverse host physiological functions including metabolism, development and homeostasis of immunity and the nervous system. We elaborate on how gut microbial imbalance (dysbiosis) may lead to dysfunction of host machineries, thereby contributing to pathogenesis and/or progression toward a broad spectrum of diseases. Some of the most notable diseases namely Clostridium difficile infection (infectious disease), inflammatory bowel disease (intestinal immune-mediated disease), celiac disease (multisystemic autoimmune disorder), obesity (metabolic disease), colorectal cancer, and autism spectrum disorder (neuropsychiatric disorder) have been discussed and delineated along with recent findings. Novel therapies derived from microbiome studies such as fecal microbiota transplantation, probiotic and prebiotics to target associated diseases have been reviewed to introduce the idea of how certain disease symptoms can be ameliorated through dysbiosis correction, thus revealing a new scientific approach toward disease treatment. Toward the end of this review, several research gaps and limitations have been described along with suggested future studies to overcome the current research lacunae. Despite the ongoing debate on whether gut microbiome plays a role in the above-mentioned diseases, we have in this review, gathered evidence showing a potentially far more complex link beyond the unidirectional cause-and-effect relationship between them.

The severe acute respiratory syndrome coronavirus(SARS-CoV) nucleocapsid (N) protein is one of the four structural proteins of the virus and is predicted to be a 46-kDa phosphoprotein. Our in silico analysis predicted N to be heavily phosphorylated at multiple residues. Experimentally, we have shown in this report that the N protein of the SARS-CoV gets serine-phosphorylated by multiple kinases, in both the cytoplasm and the nucleus. The phosphoprotein is stable and localizes in the cytoplasm and coprecipitates with the membrane fraction. Also, using specific inhibitors of phosphorylation and an in vitro phosphorylation assay, we show that the nucleocapsid protein is a substrate of cyclin-dependent kinase (CDK), glycogen synthase kinase, mitogenactivated protein kinase, and casein kinase II. Further, we show that the phosphorylated protein is translocated to the cytoplasm by binding to 14-3-3 (tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein). 14-3-3 proteins are a family of highly conserved, ubiquitously expressed eukaryotic proteins that function primarily as adapters that modulate interactions between components of various cellular signaling and cell cycle regulatory pathways through phosphorylation-dependent protein-protein interactions. Coincidentally, the N protein was also found to downregulate the expression of the theta isoform of 14-3-3 (14-3-3), leading to the accumulation of phosphorylated N protein in the nucleus, in the absence of growth factors. Using short interfering RNA specific to 14-3-3 we have inhibited its expression to show accumulation of phosphorylated N protein in the nucleus. Thus, the data presented here provide a possible mechanism for phosphorylation-dependent nucleocytoplasmic shuttling of the N protein. This 14-3-3-mediated transport of the phosphorylated N protein and its possible implications in interfering with the cellular machinery are discussed.

Three major outbreaks of the coronavirus, a zoonotic virus known to cause respiratory disease, have been reported since 2002, including SARS-CoV, MERS-CoV and the most recent 2019-nCoV, or more recently known as SARS-CoV-2. Bats are known to be the primary animal reservoir for coronaviruses. However, in the past few decades, the virus has been able to mutate and adapt to infect humans, resulting in an animal-to-human species barrier jump. The emergence of a novel coronavirus poses a serious global public health threat and possibly carries the potential of causing a major pandemic outbreak in the naïve human population. The recent outbreak of COVID-19, the disease caused by SARS-CoV-2, in Wuhan, Hubei Province, China has infected over 36.5 million individuals and claimed over one million lives worldwide, as of 8 October 2020. The novel virus is rapidly spreading across China and has been transmitted to 213 other countries/territories across the globe. Researchers have reported that the virus is constantly evolving and spreading through asymptomatic carriers, further suggesting a high global health threat. To this end, current up-to-date information on the coronavirus evolution and SARS-CoV-2 modes of transmission, detection techniques and current control and prevention strategies are summarized in this review.

Deregulation of the cell cycle is a common strategy employed by many DNA and RNA viruses to trap and exploit the host cell machinery toward their own benefit. In many coronaviruses, the nucleocapsid protein (N protein) has been shown to inhibit cell cycle progression although the mechanism behind this is poorly

In March 2003, a novel coronavirus was isolated from patients exhibiting atypical pneumonia, and was subsequently proven to be the causative agent of the disease now referred to as SARS (severe acute respiratory syndrome). The complete genome of the SARS-CoV (SARS coronavirus) has since been sequenced. The SARS-CoV nucleocapsid (SARS-CoV N) protein shares little homology with other members of the coronavirus family. In the present paper, we show that SARS-CoV N is capable of inducing apoptosis of COS-1 monkey kidney cells in the absence of growth factors by down-regulating ERK (extracellular-signal-regulated kinase), up-regulating JNK (c-Jun N-terminal kinase) and p38 MAPK (mitogen-activated protein kinase) pathways, and affecting their downstream effectors. SARS-CoV N expression also down-regulated phospho-Akt and Bcl-2 levels, and activated caspases 3 and 7. However, apoptosis was independent of the p53 and Fas signalling pathways. Furthermore, activation of the p38 MAPK pathway was found to induce actin reorganization in cells devoid of growth factors. At the cytoskeletal level, SARS-CoV N down-regulated FAK (focal adhesion kinase) activity and also down-regulated fibronectin expression. This is the first report showing the ability of the N protein of SARS-CoV to induce apoptosis and actin reorganization in mammalian cells under stressed conditions.

Ever since the discovery of SARS-CoV in the year 2003, numerous researchers around the world have been working relentlessly to understand the biology of this virus. As in other coronaviruses, nucleocapsid (N) is one of the most crucial structural components of the SARS-CoV. Hence major attention has been focused on characterization of this protein. Independent studies conducted by several laboratories have elucidated significant insight into the primary function of this protein, which is to encapsidate the viral genome. In addition, many reports also suggest that this protein interferes with different cellular pathways, thus implying it to be a key regulatory component of the virus too. In the first part of this review, we will discuss these different properties of the N-protein in a consolidated manner. Further, this protein has also been proposed to be an efficient diagnostic tool and a candidate vaccine against the SARS-CoV. Hence, towards the end of this article, we will discuss some recent progress regarding the possible clinically relevant use of the N-protein.

The hepatitis E virus (HEV) is the causative agent of hepatitis E, an acute form of viral hepatitis. The biology and pathogenesis of HEV remain poorly understood. We have used in vitro binding assays to show that the HEV ORF3 protein (pORF3) binds to a number of cellular signal transduction pathway proteins. This includes the protein tyrosine kinases Src, Hck, and Fyn, the p85␣ regulatory subunit of phosphatidylinositol 3-kinase, phospholipase C␥, and the adaptor protein Grb2. A yeast two-hybrid assay was used to further confirm the pORF3-Grb2 interaction. The binding involves a proline-rich region in pORF3 and the src homology 3 (SH3) domains in the cellular proteins. Competition assays and computer-assisted modeling was used to evaluate the binding surfaces and interaction energies of the pORF3⅐SH3 complex. In pORF3-expressing cells, pp60 src was found to associate with an 80-kDa protein, but no activation of the Src kinase was observed in these cells. However, there was increased activity and nuclear localization of ERK in the pORF3-expressing cells. These studies suggest that pORF3 is a viral regulatory protein involved in the modulation of cell signaling. The ORF3 protein of HEV appears to be the first example of a SH3 domain-binding protein encoded by a virus that causes an acute and primarily self-limited infection.Hepatitis E virus (HEV), 1 the causative agent for hepatitis E, is a waterborne pathogen endemic to much of the developing world where it causes rampant sporadic infections and large scale epidemics (1-4). While the infection is self-limited with no associated chronicity, a fraction of the patients progress to fulminant hepatitis (5, 6), the most severe form of acute hepatitis. High mortality rates of 20 -30% reported for HEV infection during pregnancy (7,8) are also the result of fulminant hepatitis. The reasons for this and the mechanisms of viral pathogenesis are not known. The studies on HEV biology and pathogenesis have been severely restricted by the lack of a reliable cell culture system and small animal models of viral infection. We have used subgenomic expression strategies to study the properties and functions of individual HEV gene products toward understanding viral replication and pathogenicity (9 -12).The HEV genome is a ϳ7.5-kilobase polyadenylated, positive-sense RNA that contains three open reading frames (ORFs) designated ORF1, ORF2, and ORF3 (13). The ORF3 of HEV encodes a protein of ϳ13.5 kDa, called pORF3, for which no function has been assigned. When expressed in animal cells, pORF3 is phosphorylated at a single serine residue (Ser 80 ) in its 123-amino acid primary sequence (11). In vitro phosphorylation experiments suggested that pORF3 may be a substrate for the mitogen-activated protein (MAP) kinase, and subcellular fractionation revealed its association with the cytoskeleton (11). Recent results using inhibitors, activators, and dominant negative alleles show that pORF3 is a substrate for the extracellular signal-regulated kinase (ERK) as well as the stressactivated pr...

Severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) caused a severe outbreak in several regions of the world in 2003. The virus is a novel coronavirus isolated from patients exhibiting atypical pneumonia and may have originated from wild animals such as civet cats in southern China. The genome of SARS-CoV is a positive-sense, single-stranded RNA whose sequence is distantly related to all known coronaviruses that infect humans and animals. Like other known coronaviruses, SARS-CoV is an enveloped virus containing three outer structural proteins, namely the membrane (M), envelope (E), and spike (S) proteins. The nucleocapsid (N) protein together with the viral RNA genome presumably form a helical core located within the viral envelope. The SARS-CoV nucleocapsid (N) protein is a 423 amino-acid, predicted phospho-protein of 46 kDa that shares little homology with other members of the coronavirus family. A short serine-rich stretch, and a putative bipartite nuclear localization signal are unique to it, thus suggesting its involvement in many important functions during the viral life cycle. In this report we have cloned the N gene of the SARS coronavirus, and studied its property of self-association to form dimers. We expressed the N protein as a fusion protein in the yeast two-hybrid system to demonstrate self-association and confirmed dimerization of the N protein from mammalian cell lysates by coimmunoprecipitation. Furthermore, via deletion analysis, we have shown that the C-terminal 209 amino-acid region constitutes the interaction domain responsible for self-association of the N protein to form dimers.