Method for enhancing solubility of the expressed recombinant proteins in Escherichia coli

The production of correctly folded protein in Escherichia coli is often challenging because of aggregation of the overexpressed protein into inclusion bodies. Although a number of general and protein-specific techniques are available, their effectiveness varies widely. We report a novel method for enhancing the solubility of overexpressed proteins. Presence of a dipeptide, glycylglycine, in the range of 100 mM to 1 M in the medium was found to significantly enhance the solubility (up to 170-fold) of the expressed proteins. The method has been validated using mycobacterial proteins, resulting in improved solubilization, which were otherwise difficult to express as soluble proteins in E. coli. This method can also be used to enhance the solubility of other heterologous recombinant proteins expressed in a bacterial system.     

Selective down-regulation of angiotensin II receptor type 1A signaling by protein tyrosine phosphatase SHP-2 in vascular smooth muscle cells

The heptahelical AT(1) G-protein-coupled receptor lacks inherent tyrosine kinase activity. Angiotensin II binding to AT(1) nevertheless activates several tyrosine kinases and stimulates both tyrosine phosphorylation and phosphatase activity of the SHP-2 tyrosine phosphatase in vascular smooth muscle cells. Since a balance between tyrosine kinase and tyrosine phosphatase activities is essential in angiotensin II signaling, we investigated the role of SHP-2 in modulating tyrosine kinase signaling pathways by stably transfecting vascular smooth muscle cells with expression vectors encoding wild-type SHP-2 protein or a catalytically inactive SHP-2 mutant. Our data indicate that SHP-2 is an efficient negative regulator of angiotensin II signaling. SHP-2 inhibited c-Src catalytic activity by dephosphorylating a positive regulatory tyrosine 418 within the Src kinase domain. Importantly, SHP-2 expression also abrogated angiotensin II-induced activation of ERK, whereas expression of catalytically inactive SHP-2 caused sustained ERK activation. Thus, SHP-2 likely regulates angiotensin II-induced MAP kinase signaling by inactivating c-Src. These SHP-2 effects were specific for a subset of angiotensin II signaling pathways, since SHP-2 overexpression failed to influence Jak2 tyrosine phosphorylation or Fyn catalytic activity. These data show SHP-2 represents a critical negative regulator of angiotensin II signaling, and further demonstrate a new function for this phosphatase in vascular smooth muscle cells.     

Cytoskeletal remodeling in vascular smooth muscle cells in response to angiotensin II-induced activation of the SHP-2 tyrosine phosphatase

Angiotensin II is an octapeptide that regulates diverse cellular responses including the actin cytoskeletal organization. In this study, stable cell lines overexpressing wild-type or catalytically inactive SHP-2 were employed to elucidate the signaling pathway utilized by the SHP-2 tyrosine phosphatase that mediates an angiotensin II-induced reorganization of the actin cytoskeleton in vascular smooth muscle cells (VSMC). The expression of wild-type SHP-2 prevented an angiotensin II dependent increase in stress fiber formation. In contrast, the catalytically inactive mutant SHP-2 increased stress fiber formation. Additional observations further established that SHP-2 regulates the reorganization of the actin cytoskeleton through RhoA- and Vav2-dependent signaling pathways. The expression of wild-type SHP-2 caused a dephosphorylation of several focal adhesion associated proteins including paxillin, p130Cas, and tensin in VSMC. This dephosphorylation of focal adhesion associated proteins was accompanied by significantly decreased numbers of focal adhesions within cells. These results demonstrate a unique role for SHP-2 in the regulation of the cellular architecture of VSMC, suggesting the possibility that this phosphatase might be instrumental in vascular remodeling.     

Soil-transmitted helminths in relation to hemoglobin status among school children of the Kashmir Valley

Soil-transmitted helminths (STHs) remain a major threat to the health of children throughout the world, mostly in developing nations. The aim of the present study was to determine any relationship between STHs and hemoglobin status in school children of Kashmir Valley (India). Stool and blood samples were collected from 382 male and female school children in the age group of 5-15 yr from all 6 school districts of the Kashmir Valley. Finger-prick blood samples were used to collect the hemoglobin, which was then measured on-site by Sahli's acid hematin method; stool samples were processed using both simple smear and zinc sulphate concentration methods. Of the 382 children surveyed, 299 (78.27%) were infected with Ascaris lumbricoides, Trichuris trichiura, or both. Children infected by STHs were found to have lower mean values of hemoglobin than uninfected children. The present study reveals that STHs are abundant among school children of Kashmir Valley, creating a negative effect on the hemoglobin values and indicating the necessity of implementing control measures.     

LUBAC assembles a ubiquitin signaling platform at mitochondria for signal amplification and transport of NF‐κB to the nucleus

Mitochondria are increasingly recognized as cellular hubs to orchestrate signaling pathways that regulate metabolism, redox homeostasis, and cell fate decisions. Recent research revealed a role of mitochondria also in innate immune signaling; however, the mechanisms of how mitochondria affect signal transduction are poorly understood. Here, we show that the NF‐κB pathway activated by TNF employs mitochondria as a platform for signal amplification and shuttling of activated NF‐κB to the nucleus. TNF treatment induces the recruitment of HOIP, the catalytic component of the linear ubiquitin chain assembly complex (LUBAC), and its substrate NEMO to the outer mitochondrial membrane, where M1‐ and K63‐linked ubiquitin chains are generated. NF‐κB is locally activated and transported to the nucleus by mitochondria, leading to an increase in mitochondria‐nucleus contact sites in a HOIP‐dependent manner. Notably, TNF‐induced stabilization of the mitochondrial kinase PINK1 furthermore contributes to signal amplification by antagonizing the M1‐ubiquitin‐specific deubiquitinase OTULIN. Overall, our study reveals a role for mitochondria in amplifying TNF‐mediated NF‐κB activation, both serving as a signaling platform, as well as a transport mode for activated NF‐κB to the nuclear.     

Aberrant promoter methylation and reduced expression of p16 gene in esophageal squamous cell carcinoma from Kashmir valley: a high-risk area

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent cancer in Jammu and Kashmir region of India and has multi-factorial etiology involving dietary habits, genetic factors, and gene environmental interactions. Inactivation of the p16 gene expression by aberrant promoter methylation plays an important role in the progression of esophageal carcinoma. In the present investigation, we have studied the role of p16 promoter methylation in 69 histopathologically confirmed ESCC tissues and compared it with corresponding normal adjacent tissues for DNA methylation in the CpG island in the p16 promoter region by methylation-specific polymerase chain reaction (MSP) and p16 protein expression by immunoblotting. The results showed loss of p16 expression in 67% (46/69) of tumor tissues compared to only 3% in control tissues (2/69). Promoter methylation was observed in 52% (36/69) of tumor tissues and it gradually increased with the increasing severity of histological grades of the cancer (P = 0.0001). Loss of p16 expression with promoter methylation was observed in 26 of 36 cases (72%). Analysis of patients dietary habits revealed a strong association between promoter methylation and high consumption of hot salted tea (P < 0.05) which is a most favourite drink commonly consumed by Kashmiri people.     

Comparative proteomics analysis of sarcosine insoluble outer membrane proteins from clarithromycin resistant and sensitive strains of Helicobacter pylori

Helicobacter pylori causes disease manifestations in humans including chronic gastric and peptic ulcers, gastric cancer, and lymphoid tissue lymphoma. Increasing rates of H. pylori clarithromycin resistance has led to higher rates of disease development. Because antibiotic resistance involves modifications of outer membrane proteins (OMP) in other Gram-negative bacteria, this study focuses on identification of H. pylori OMP’s using comparative proteomic analyses of clarithromycin-susceptible and -resistant H. pylori strains. Comparative proteomics analyses of isolated sarcosine-insoluble OMP fractions from clarithromycin-susceptible and -resistant H. pylori strains were performed by 1) one dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein separation and 2) in-gel digestion of the isolated proteins and mass spectrometry analysis by Matrix Assisted Laser Desorption Ionization-tandem mass spectrometry. Iron-regulated membrane protein, UreaseB, EF-Tu, and putative OMP were down-regulated; HopT (BabB) transmembrane protein, HofC, and OMP31 were up-regulated in clarithromycin-resistant H. pylori. Western blotting and real time PCR, respectively, validated UreaseB subunit and EF-Tu changes at the protein level, and mRNA expression of HofC and HopT. This limited proteomic study provides evidence that alteration of the outer membrane proteins’ profile may be a novel mechanism involved in clarithromycin resistance in H. pylori.