The transpeptidase PbpA and non-canonical transglycosylase RodA of Mycobacterium tuberculosis play important roles in regulating bacterial cell lengths

The cell wall of Mycobacterium tuberculosis (Mtb) is a complex structure that protects the pathogen in hostile environments. Peptidoglycan (PG), which helps determine the morphology of the cell envelope, undergoes substantial remodeling under stress. This meshwork of linear chains of sugars, crosslinked through attached peptides, is generated through the sequential action of enzymes termed transglycosylases and transpeptidases. The Mtb genome encodes two classical transglycosylases and four transpeptidases, the functions of which are not fully elucidated. Here, we present work on the yet uncharacterized transpeptidase PbpA and a non-classical transglycosylase RodA. We elucidate their roles in regulating in vitro growth and in vivo survival of pathogenic mycobacteria. We find that RodA and PbpA are required for regulating cell length, but do not affect mycobacterial growth. Biochemical analyses show PbpA to be a classical transpeptidase, while RodA is identified to be a member of an emerging class of non-canonical transglycosylases. Phosphorylation of RodA at T463 modulates its biological function. In a guinea pig infection model, RodA and PbpA are found to be required for both, bacterial survival as well as formation of granuloma structures, thus underscoring the importance of these proteins in mediating mycobacterial virulence in the host. Our results emphasize the fact that while redundant enzymes likely compensate for the absence of RodA or PbpA during in vitro growth, the two proteins play critical roles for the survival of the pathogen inside its host

Protein kinase B (PknB) of Mycobacterium tuberculosisIs essential for growth of the pathogenin vitroas well as for survival within the host

The Mycobacterium tuberculosis protein kinase B (PknB) comprises an intracellular kinase domain, connected through a transmembrane domain to an extracellular region that contains four PASTA domains. The present study describes the comprehensive analysis of different domains of PknB in the context of viability in avirulent and virulent mycobacteria. We find stringent regulation of PknB expression necessary for cell survival, with depletion or overexpression of PknB leading to cell death. Although PknB-mediated kinase activity is essential for cell survival, active kinase lacking the transmembrane or extracellular domain fails to complement conditional mutants not expressing PknB. By creating chimeric kinases, we find that the intracellular kinase domain has unique functions in the virulent strain, which cannot be substituted by other kinases. Interestingly, we find that although the presence of the C-terminal PASTA domain is dispensable in the avirulent M. smegmatis, all four PASTA domains are essential in M. tuberculosis. The differential behavior of PknB vis-a-vis the number of essential PASTA domains and the specificity of kinase domain functions suggest that PknB-mediated growth and signaling events differ in virulent compared with avirulent mycobacteria. Mouse infection studies performed to determine the role of PknB in mediating pathogen survival in the host demonstrate that PknB is not only critical for growth of the pathogen in vitro but is also essential for the survival of the pathogen in the host

Protein kinase A (PknA) of Mycobacterium tuberculosis is independently activated and is critical for growth in vitro and survival of the pathogen in the host

The essential mycobacterial protein kinases PknA and PknB play crucial roles in modulating cell shape and division. However, the precise in vivo functional aspects of PknA have not been investigated. This study aims to dissect the role of PknA in mediating cell survival in vitro as well as in vivo. We observed aberrant cell shape and severe growth defects when PknA was depleted. Using the mouse infection model, we observe that PknA is essential for survival of the pathogen in the host. Complementation studies affirm the importance of the kinase, juxtamembrane and transmembrane domains of PknA. Surprisingly, the extracytoplasmic domain is dispensable for cell growth and survival in vitro. We find that phosphorylation of the activation loop at Thr172 of PknA is critical for bacterial growth. PknB has been previously suggested to be the receptor kinase, which activates multiple kinases, including PknA, by trans-phosphorylating their activation loop residues. Using phospho-specific PknA antibodies and conditional pknB mutant, we find that PknA autophosphorylates its activation loop independent of PknB. Fluorescently tagged PknA and PknB show distinctive distribution patterns within the cell, suggesting that although both kinases are known to modulate cell shape and division, their modes of action are likely to be different. This is supported by our findings that expression of kinase-dead PknA versus kinase-dead PknB in mycobacterial cells leads to different cellular phenotypes. Data indicate that although PknA and PknB are expressed as part of the same operon, they appear to be regulating cellular processes through divergent signaling pathways

Minimal hepatic encephalopathy: consensus statement of a working party of the Indian National Association for study of the liver

Hepatic encephalopathy (HE) is a major complication that develops in some form and at some stage in a majority of patients with liver cirrhosis. Overt HE occurs in approximately 30-45% of cirrhotic patients. Minimal HE (MHE), the mildest form of HE, is characterized by subtle motor and cognitive deficits and impairs health-related quality of life. The Indian National Association for Study of the Liver (INASL) set up a Working Party on MHE in 2008 with a mandate to develop consensus guidelines on various aspects of MHE relevant to clinical practice. Questions related to the definition of MHE, its prevalence, diagnosis, clinical characteristics, pathogenesis, natural history and treatment were addressed by the members of the Working Party

Severity of Hepatitis C Virus (Genotype-3) Infection Positively Correlates with Circulating MicroRNA-122 in Patients Sera

Introduction. Hepatitis C virus (genotype-3) causes acute and chronic hepatitis infection predomination in India. The infectious phase of the virus requires various host factors for its survival and subsequent viral particle production. Small RNA molecules like microRNA-122 (miR-122) are one such factor mostly present in the liver and play a supportive role in viral replication. Objective. In this study, diagnostic potential of miR-122 is evaluated in the sera of chronic hepatitis C patients. Methods. miRNAs were isolated from the sera samples of patients as well as controls and miR-122 expression was quantified by real-time PCR. Results. A significant augmentation was observed in the level of circulating miR-122 (median level, 0.66 versus 0.29, P=0.001) in patients compared to controls with ROC value of 0.929±0.034 (P<0.001). Interestingly, miR-122 level also depicted a significant positive correlation with serum ALT (r=0.53), AST (r=0.44), and viral load (r=0.52). Conclusion. The study thus unveiled the role of miR-122 as a plausible diagnostic biomarker during HCV genotype-3 infection in India

Acute Liver Failure Due to Etodolac, a Selective Cycloxygenase- 2 (COX -2) Inhibitor Non-Steroidal Anti-Inflammatory Drug Established by RUCAM-Based Causality Assessment

Drug induced liver injury is a common cause of acute liver failure (ALF). While most of these cases are due to dose dependent hepa-totoxicity with acetaminophen, idiosyncratic drug-induced liver injury (DILI) is responsible for about 15% cases of ALF. Antibiotics are the most common cause of idiosyncratic DILI as well as DILI induced ALF. Etodolac is a selective cycloxygenase- 2 (COX -2) inhibitor non-steroidal anti-inflammatory drug used as an analgesic and anti-inflammatory in musculoskeletal diseases. Severe liver impairment is extremely rare. Till date, only 3 cases of ALF related to etodolac have been reported in the literature. Here we report two cases with a unique presentation of ALF occurring due to DILI caused by etodolac, as diagnosed by Roussel Uclaf Causality Assessment Method (RUCAM)

Development of a New Generation of Vectors for Gene Expression, Gene Replacement, and Protein-Protein Interaction Studies in Mycobacteria

Escherichia coli-mycobacterium shuttle vectors are important tools for gene expression and gene replacement in mycobacteria. However, most of the currently available vectors are limited in their use because of the lack of extended multiple cloning sites (MCSs) and convenience of appending an epitope tag(s) to the cloned open reading frames (ORFs). Here we report a new series of vectors that allow for the constitutive and regulatable expression of proteins, appended with peptide tag sequences at their N and C termini, respectively. The applicability of these vectors is demonstrated by the constitutive and induced expression of the Mycobacterium tuberculosis pknK gene, coding for protein kinase K, a serine-threonine protein kinase. Furthermore, a suicide plasmid with expanded MCS for creating gene replacements, a plasmid for chromosomal integrations at the commonly used L5 attB site, and a hypoxia-responsive vector, for expression of a gene(s) under hypoxic conditions that mimic latency, have also been created. Additionally, we have created a vector for the coexpression of two proteins controlled by two independent promoters, with each protein being in fusion with a different tag. The shuttle vectors developed in the present study are excellent tools for the analysis of gene function in mycobacteria and are a valuable addition to the existing repertoire of vectors for mycobacterial research

Effect of lowering HBV DNA levels by initial antiviral therapy before adding immunomodulator on treatment of chronic hepatitis B

Background: Lower hepatitis B virus DNA (HBV DNA) levels are associated with better responses in chronic hepatitis B (CHB). It is unclear whether an initial phase of antiviral treatment to lower HBV DNA levels before adding immunomodulator therapy is more effective than the strategy of using immunomodulators from the beginning. Aim: The aim of the study was to compare the efficacy of lamivudine followed by pegylated-interferon (peg-IFN) therapy with placebo followed by peg-IFN therapy in HBeAg-positive CHB patients. Patients and Methods: Sixty-three treatment-naive HBeAg-positive patients with histologically proven CHB and alanine aminotransferase (ALT) &gt; 1.2 &#215; upper limit of normal (ULN) received placebo for 4 wk followed by peg-IFN 1.0 mug/kg/wk for next 24 wk (group A, N = 27; age 32 &#177; 11 yr; M:F = 25:2) or lamivudine 100 mg per day for 4 wk followed by peg-IFN 1.0 mug/kg/wk for next 24 wk (group B, N = 36; age 32.5 &#177; 10.5 yr; M:F = 31:5). Patients were followed for next 24 wk after completion of treatment. Biochemical and virologic responses were assessed at weeks 4, 28, and 52 and analysis was done on intention-to-treat basis. RESULTS: At wk 4, mean &#177; SD of log change in DNA from baseline was 0.2594 &#177; 1.7873 in group A and 1.2186 &#177; 1.6347 in group B, respectively (P = 0.032). At week 28, undetectable HBV DNA was seen in eight (29.6%) and 16 (44.4%) patients in groups A and B, respectively (P= 0.298). At week 28, HBeAg loss occurred in eight (29.6%) in group A and 15 (41.7%) in group B (P = 0.43). Six months posttherapy, at week 52, undetectable HBV DNA was seen in four (14.8%) and 18 (50%) in groups A and B, respectively (P = 0.028) and HBeAg loss was maintained in four (14.8%) and 14 (38.9%) (P = 0.05) patients. Normal ALT was seen in five (18.5%) and 10 (27.8%) at week 28 (P = 0.552) and five (18.5%) and 13 (36.1%) at week 52 (P = 0.159) in groups A and B, respectively. There was a significant correlation among achievement of HBeAg loss, anti-HBe appearance, and undetectable HBV DNA levels at week 28 (P = 0.008) and 52 (P &lt; 0.001) and HBV DNA levels at week 4. Conclusions: The strategy of using an antiviral initially to decrease HBV DNA levels before adding an immunomodulatory agent leads to improved sustained virological response as compared with using immunomodulator from the start