Different mechanisms regulate lysophosphatidic acid (LPA)-dependent versus phorbol ester-dependent internalization of the LPA1 receptor

Lysophosphatidic acid (LPA) stimulates cells by activation of five G-protein-coupled receptors, termed LPA 1-5. The LPA 1 receptor is the most widely expressed and is a major regulator of cell migration. In this study, we show that phorbol ester (PMA)-induced internalization of the LPA(1) receptor requires clathrin AP-2 complexes, protein kinase C, and a distal dileucine motif (amino acids 352 and 353) in the cytoplasmic tail but not beta-arrestin. Agonist-dependent internalization of LPA 1, however, requires a cluster of serine residues (amino acids 341-347) located proximal to the dileucine motif, beta-arrestin, and to a lesser extent clathrin AP-2. The serine cluster of LPA 1 is required for beta-arrestin2-GFP translocation to the plasma membrane and signal desensitization. In contrast, the dileucine motif (IL) is required for both basal and PMA-induced internalization. Evidence for the beta-arrestin independence of PMA-induced internalization of LPA 1 comes from the observations that beta-arrestin2-GFP is not recruited to the plasma membrane upon PMA treatment and that LPA 1 is readily internalized in beta-arrestin1/2 knock-out mouse embryonic fibroblasts. These results indicate that distinct molecular mechanisms regulate agonist-dependent and PMA-dependent internalization of the LPA 1 receptor.     

Characterization of Flagellum Gene Families of Methanogenic Archaea and Localization of Novel Flagellum Accessory Proteins

Archaeal flagella are unique motility structures, and the absence of bacterial structural motility genes in the complete genome sequences of flagellated archaeal species suggests that archaeal flagellar biogenesis is likely mediated by novel components. In this study, a conserved flagellar gene family from each of Methanococcus voltae, Methanococcus maripaludis, Methanococcus thermolithotrophicus, and Methanococcus jannaschii has been characterized. These species possess multiple flagellin genes followed immediately by eight known and supposed flagellar accessory genes, flaCDEFGHIJ. Sequence analyses identified a conserved Walker box A motif in the putative nucleotide binding proteins FlaH and FlaI that may be involved in energy production for flagellin secretion or assembly. Northern blotting studies demonstrated that all the species have abundant polycistronic mRNAs corresponding to some of the structural flagellin genes, and in some cases several flagellar accessory genes were shown to be cotranscribed with the flagellin genes. Cloned flagellar accessory genes of M. voltae were successfully overexpressed as His-tagged proteins in Escherichia coli. These recombinant flagellar accessory proteins were affinity purified and used as antigens to raise polyclonal antibodies for localization studies. Immunoblotting of fractionated M. voltae cells demonstrated that FlaC, FlaD, FlaE, FlaH, and FlaI are all present in the cell as membrane-associated proteins but are not major components of isolated flagellar filaments. Interestingly, flaD was found to encode two proteins, each translated from a separate ribosome binding site. These protein expression data indicate for the first time that the putative flagellar accessory genes of M. voltae, and likely those of other archaeal species, do encode proteins that can be detected in the cell.     

Association of Adenovirus Infection with Human Obesity

DHURANDHAR, NIKHIL V, PUSHPA R KULKARNI, SHARAD M AJINKYA, ABHAYA A SHERIKAR, RICHARD L ATKINSON. Association of adenovirus infection with human obesity. We previously reported that chickens infected with the avian adenovirus SMAM-1 developed a unique syndrome characterized by excessive intra-abdominal fat deposition accompanied by paradoxically low serum cholesterol and triglyceride levels. There have been no previous reports of avian adenoviruses infecting humans. We screened the serum of 52 humans with obesity in Bombay, India, for antibodies against SMAM-1 virus using the agar gel precipitation test (AGPT) method. Bodyweights and serum cholesterol and triglyceride levels were compared in SMAM-1-positive (P-AGPT) and SMAM-1-negative (N-AGPT) groups. Ten subjects were positive for antibodies to SMAM-1, and 42 subjects did not have antibodies. The P-AGPT group had a significantly higher bodyweight (p<0.02) and body mass index (p<0.001) (95.1 ± 2.1 kg and 35.3 ± 1.5 kg/m², respectively) compared with the N-AGPT group (80.1 ± 0.6 kg and 30.7 ± 0.6 kg/m², respectively). Also, the P-AGPT group had significantly lower serum cholesterol (p<0.02) and triglyceride (p<0.001) values (4.65 mmol/L and 1.45 mmol/L, respectively) compared with the N-AGPT group (5.51 mmol/L and 2.44 mmol/L, respectively). Two subjects positive for SMAM-1 antibodies had antibodies against each others' serum, suggesting the presence of antigens in one or both. When these two serum samples were inoculated into chicken embryos, macroscopic lesions compatible with SMAM-1 infection developed. The inoculation of serum from N-AGPT subjects did not produce such lesions. The presence of increased obesity, antibodies to SMAM-1, reduced levels of blood lipids, and viremia that produces a typical infection in chicken embryos suggests that SMAM-1, or a serologically similar human virus, may be involved in the cause of obesity in some humans.     

Multimodal approach to explore the pathogenicity of BARD1, ARG 658 CYS,and ILE 738 VAL mutants

BARD1–BRCA1 complex plays an important role in DNA damage repair, apoptosis, chromatin remodeling, and other important processes required for cell survival. BRCA1 and BARD1 heterodimer possess E3 ligase activity and is involved in genome maintenance, by functioning in surveillance for DNA damage, thereby regulating multiple pathways including tumor suppression. BRCT domains are evolutionary conserved domains present in different proteins such as BRCA1, BARD1, XRCC, and MDC1 regulating damage response and cell-cycle control through protein–protein interactions. Nonetheless, the role of BARD1BRCT in the recruitment of DNA repair mechanism and structural integrity with BRCA1 complex is still implicit. To explicate the role of BARD1BRCT in the DNA repair mechanism, in silico, in vitro, and biophysical approach were applied to characterize BARD1 BRCT wild-type and Arg658Cys and Ile738Val mutants. However, no drastic secondary and tertiary structural changes in the mutant proteins were observed. Thermal and chemical denaturation studies revealed that mutants Arg658Cys and Ile738Val have a decrease in T_m and ?G than the wild type. In silico studies of BARD1 BRCT (568-777) and mutant protein indicate loss in structural compactness on the Ile738Val mutant. Comparative studies of wild-type and mutants will thus be helpful in understanding the basic role of BARD1BRCT in DNA damage repair.     

Stress enhanced calcium kinetics in a neuron

Accurate modeling of the mechanobiological response of a Traumatic Brain Injury is beneficial toward its effective clinical examination, treatment and prevention. Here, we present a stress history-dependent non-spatial kinetic model to predict the microscale phenomena of secondary insults due to accumulation of excess calcium ions (Ca\(^{2+}\)) induced by the macroscale primary injuries. The model is able to capture the experimentally observed increase and subsequent partial recovery of intracellular Ca\(^{2+}\) concentration in response to various types of mechanical impulses. We further establish the accuracy of the model by comparing our predictions with key experimental observations.     

Variation in the group B Streptococcus CsrRS regulon and effects on pathogenicity

CsrRS (or CovRS) is a two-component regulatory system that controls expression of multiple virulence factors in the important human pathogen group B Streptococcus (GBS). We now report global gene expression studies in GBS strains 2603V/R and 515 and their isogenic csrR and csrS mutants. Together with data reported previously for strain NEM316, the results reveal a conserved 39-gene CsrRS regulon. In vitro phosphorylation-dependent binding of recombinant CsrR to promoter regions of both positively and negatively regulated genes suggests that direct binding of CsrR can mediate activation as well as repression of target gene expression. Distinct patterns of gene regulation in csrR versus csrS mutants in strain 2603V/R compared to 515 were associated with different hierarchies of relative virulence of wild-type, csrR, and csrS mutants in murine models of systemic infection and septic arthritis. We conclude that CsrRS regulates a core group of genes including important virulence factors in diverse strains of GBS but also displays marked variability in the repertoire of regulated genes and in the relative effects of CsrS signaling on CsrR-mediated gene regulation. Such variation is likely to play an important role in strain-specific adaptation of GBS to particular host environments and pathogenic potential in susceptible hosts.     

Reliability of international normalised ratios from two point of care test systems: comparison with conventional methods

Objective To find out how accurately two point of care test systems—CoaguChek Mini and TAS PT-NC (RapidPointCoag)—display international normalised ratios (INRs).Design Comparison of the INRs from the two systems with a “true” INR on a conventional manual test from the same sample of blood.Setting 10 European Concerted Action on Anticoagulation centres.Participants 600 patients on long term dosage of warfarin.Main outcome measures Comparable results between the different methods.Results The mean displayed INR differed by 21.3% between the two point of care test monitoring systems. The INR on one system was 15.2% higher, on average, than the true INR, but on the other system the INR was 7.1% lower. The percentage difference between the mean displayed INR and the true INR at individual centres varied considerably with both systems.Conclusions Improved international sensitivity index calibration of point of care test monitors by their manufacturers is needed, and better methods of quality control of individual instruments by their users are also needed.     

Role of cyclooxygenase-2 functional gene polymorphisms in Helicobacter pylori induced gastritis and gastric atrophy

In India, the role of host genetic factors is poorly studied for Helicobacter pylori associated diseases. Therefore, we evaluated the association of functionally relevant COX-2 gene polymorphisms (-765 G>C and +8473 T>C) in gastritis and precancerous lesions susceptibility. After upper GI endoscopy, 130 rapid urease test positive patients with non-ulcer dyspepsia, also showed positivity for H. pylori using modified Geimsa staining and anti-CagA IgG serology were included. All patients and 260 asymptomatic controls were genotyped for COX-2 variations using PCR-RFLP. COX-2 -765 (GC+CC) genotypes, -765 C allele, +8473 CC genotype, +8473 (TC+CC) genotypes, +8473 C allele, and variant haplotypes imparted high risk for gastritis (P = 0.036, OR = 1.82; P = 0.007, 1.92; P = 0.025, OR = 2.13; P = 0.017, OR = 1.80; P = 0.017, OR = 1.45; P = 0.010, OR = 2.40; P = 0.023, OR = 1.50 and P = 0.012, OR = 2.20 folds, respectively). In contrast, COX-2 -765 C allele carriers had low risk for lymphocyte (P = 0.020, OR = 0.35), plasma cell infiltrations (P = 0.016, OR = 0.33), and gastric atrophy (GA) development (P = 0.019, OR = 0.35). In conclusion, COX-2 variant allele/genotype/haplotype carriers may be at high risk for gastritis. However, COX-2 -765 C allele carriers may be at low risk for GA development.     

Mutagenic inverted repeat assisted genome engineering (MIRAGE)

Here we describe a one-step method to create precise modifications in the genome of Saccharomyces cerevisiae as a tool for synthetic biology, metabolic engineering, systems biology and genetic studies. Through homologous recombination, a mutagenesis cassette containing an inverted repeat of selection marker(s) is integrated into the genome. Due to its inherent instability in genomic DNA, the inverted repeat catalyzes spontaneous self-excision, resulting in precise genome modification. Since this excision occurs at very high frequencies, selection for the integration event can be followed immediately by counterselection, without the need for growth in permissive conditions. This is the first time a truly one-step method has been described for genome modification in any organism.