LrrA, a novel leucine-rich repeat protein involved in cytoskeleton remodeling, is required for multicellular morphogenesis in Dictyostelium discoideum

AbstractCell sorting by differential cell adhesion and movement is a fundamental process in multicellular morphogenesis. We have identified a Dictyostelium discoideum gene encoding a novel protein, LrrA, which composes almost entirely leucine-rich repeats (LRRs) including a putative leucine zipper motif. Transcription of lrrA appeared to be developmentally regulated with robust expression during vegetative growth and early development. lrrA null cells generated by homologous recombination aggregated to form loose mounds, but subsequent morphogenesis was blocked without formation of the apical tip. The cells adhered poorly to a substratum and did not form tight cell–cell agglomerates in suspension; in addition, they were unable to polarize and exhibit chemotactic movement in the submerged aggregation and Dunn chamber chemotaxis assays. Fluorescence-conjugated phalloidin staining revealed that both vegetative and aggregation competent lrrA− cells contained numerous F-actin-enriched microspikes around the periphery of cells. Quantitative analysis of the fluorescence-stained F-actin showed that lrrA− cells exhibited a dramatically increase in F-actin as compared to the wild-type cells. When developed together with wild-type cells, lrrA− cells were unable to move to the apical tip and sorted preferentially to the rear and lower cup regions. These results indicate that LrrA involves in cytoskeleton remodeling, which is needed for normal chemotactic aggregation and efficient cell sorting during multicellular morphogenesis, particularly in the formation of apical tip

Signal transducer and activator of transcription 3 activation up-regulates interleukin-6 autocrine production: a biochemical and genetic study of established cancer cell lines and clinical isolated human cancer cells

<p>Abstract</p> <p>Background</p> <p>Spontaneous interleukin-6 (IL-6) production has been observed in various tumors and implicated in the pathogenesis, progression and drug resistance in cancer. However, the regulation of IL-6 autocrine production in cancer cells is not fully understood. IL-6 is auto-regulated in many types of cell. Two of the three major downstream pathways of IL-6, MEK/extracellular signal-related kinase (Erk) pathway and phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, have been shown to regulate IL-6 expression through the activation of AP-1 and NF-κB. However, it is not clear what the role of Janus kinase (Jak) 2/signal transducer and activator of transcription (Stat) 3 pathway. This study was designed to determine the role of Jak2/Stat3 pathway in the regulation of IL-6 autocrine production in cancer cells.</p> <p>Results</p> <p>Inhibitors of Jak2/Stat3, MEK/Erk and PI3-K/Akt pathways down-regulated IL-6 secretion in the lung adenocarcinoma PC14PE6/AS2 (AS2) cells, which spontaneously secreted IL-6 and possessed constitutively activated Stat3. Transfection with dominant-negative Stat3, Stat3 siRNA, or Stat3 shRNA decreased IL-6 expression in AS2 cells. Conversely, transfection with constitutively-activated Stat3 increased the production of IL-6. In AS2 derived cells, resistance to paclitaxel was positively correlated with Stat3 activation status and the expression of IL-6, which is commonly secreted in drug resistant cancer cells. The pharmacological inhibition of NF-κB, PI3-K/Akt and MEK/Erk and the pharmacological inhibition and genetic inhibition (Stat3 siRNA) of Jak2/Stat3 pathway decreased IL-6 autocrine production in various drug resistant cancer cell lines and similarly decreased IL-6 autocrine production in clinically isolated lung cancer cells.</p> <p>Conclusions</p> <p>This study is the first to directly address the role Stat3 plays on the autocrine production of IL-6, which occurs through a positive-feedback loop. Our biochemical and genetic studies clearly demonstrated that Jak2/Stat3, in combination with other IL-6 downstream pathways, contributed frequently and substantially to IL-6 autocrine production in a broad spectrum of cancer cell lines as well as in clinical cancer samples. Our findings suggest that Stat3 could potentially be regulated to suppress IL-6 autocrine production in cancer cells to inhibit the progression of cancer and reduce drug resistance.</p

Signal transducer and activator of transcription 3 activation up-regulates interleukin-6 autocrine production: a biochemical and genetic study of established cancer cell lines and clinical isolated human cancer cells

<p>Abstract</p> <p>Background</p> <p>Spontaneous interleukin-6 (IL-6) production has been observed in various tumors and implicated in the pathogenesis, progression and drug resistance in cancer. However, the regulation of IL-6 autocrine production in cancer cells is not fully understood. IL-6 is auto-regulated in many types of cell. Two of the three major downstream pathways of IL-6, MEK/extracellular signal-related kinase (Erk) pathway and phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, have been shown to regulate IL-6 expression through the activation of AP-1 and NF-κB. However, it is not clear what the role of Janus kinase (Jak) 2/signal transducer and activator of transcription (Stat) 3 pathway. This study was designed to determine the role of Jak2/Stat3 pathway in the regulation of IL-6 autocrine production in cancer cells.</p> <p>Results</p> <p>Inhibitors of Jak2/Stat3, MEK/Erk and PI3-K/Akt pathways down-regulated IL-6 secretion in the lung adenocarcinoma PC14PE6/AS2 (AS2) cells, which spontaneously secreted IL-6 and possessed constitutively activated Stat3. Transfection with dominant-negative Stat3, Stat3 siRNA, or Stat3 shRNA decreased IL-6 expression in AS2 cells. Conversely, transfection with constitutively-activated Stat3 increased the production of IL-6. In AS2 derived cells, resistance to paclitaxel was positively correlated with Stat3 activation status and the expression of IL-6, which is commonly secreted in drug resistant cancer cells. The pharmacological inhibition of NF-κB, PI3-K/Akt and MEK/Erk and the pharmacological inhibition and genetic inhibition (Stat3 siRNA) of Jak2/Stat3 pathway decreased IL-6 autocrine production in various drug resistant cancer cell lines and similarly decreased IL-6 autocrine production in clinically isolated lung cancer cells.</p> <p>Conclusions</p> <p>This study is the first to directly address the role Stat3 plays on the autocrine production of IL-6, which occurs through a positive-feedback loop. Our biochemical and genetic studies clearly demonstrated that Jak2/Stat3, in combination with other IL-6 downstream pathways, contributed frequently and substantially to IL-6 autocrine production in a broad spectrum of cancer cell lines as well as in clinical cancer samples. Our findings suggest that Stat3 could potentially be regulated to suppress IL-6 autocrine production in cancer cells to inhibit the progression of cancer and reduce drug resistance.</p

The dimer interface of the SARS coronavirus nucleocapsid protein adapts a porcine respiratory and reproductive syndrome virus-like structure

AbstractWe have employed NMR to investigate the structure of SARS coronavirus nucleocapsid protein dimer. We found that the secondary structure of the dimerization domain consists of five α helices and a β-hairpin. The dimer interface consists of a continuous four-stranded β-sheet superposed by two long α helices, reminiscent of that found in the nucleocapsid protein of porcine respiratory and reproductive syndrome virus. Extensive hydrogen bond formation between the two hairpins and hydrophobic interactions between the β-sheet and the α helices render the interface highly stable. Sequence alignment suggests that other coronavirus may share the same structural topology

Nationwide Surveillance of Influenza during the Pandemic (2009–10) and Post-Pandemic (2010–11) Periods in Taiwan

INTRODUCTION: Although WHO declared the world moving into the post-pandemic period on August 10, 2010, influenza A(H1N1) 2009 virus continued to circulate globally. Its impact was expected to continue during the 2010-11 influenza season. This study describes the nationwide surveillance findings of the pandemic and post-pandemic influenza periods in Taiwan and assesses the impact of influenza A(H1N1) 2009 during the post-pandemic period. METHODS: The Influenza Laboratory Surveillance Network consisted of 12 contract laboratories for collecting and testing samples with acute respiratory tract infections. Surveillance of emergency room visits and outpatient department visits for influenza-like illness (ILI) were conducted using the Real-Time Outbreak and Disease Surveillance system and the National Health Insurance program data, respectively. Hospitalized cases with severe complications and deaths were reported to the National Notifiable Disease Surveillance System. RESULTS: During the 2009-10 influenza season, pandemic A(H1N1) 2009 was the predominant circulating strain and caused 44 deaths. However, the 2010-11 influenza season began with A(H3N2) being the predominant circulating strain, changing to A(H1N1) 2009 in December 2010. Emergency room and outpatient department ILI surveillance displayed similar trends. By March 31, 2011, there were 1,751 cases of influenza with severe complications; 50.1% reported underlying diseases. Of the reported cases, 128 deaths were associated with influenza. Among these, 93 (72.6%) were influenza A(H1N1) 2009 and 30 (23.4%) A(H3N2). Compared to the pandemic period, during the immediate post-pandemic period, increased number of hospitalizations and deaths were observed, and the patients were consistently older. CONCLUSIONS: Reemergence of influenza A(H1N1) 2009 during the 2010-11 influenza season had an intense activity with age distribution shift. To further mitigate the impact of future influenza epidemics, Taiwan must continue its multifaceted influenza surveillance systems, remain flexible with antiviral use policies, and revise the vaccine policies to include the population most at risk

Prognostic factors and monomicrobial necrotizing fasciitis: gram-positive versus gram-negative pathogens

<p>Abstract</p> <p>Background</p> <p>Monomicrobial necrotizing fasciitis is rapidly progressive and life-threatening. This study was undertaken to ascertain whether the clinical presentation and outcome for patients with this disease differ for those infected with a gram-positive as compared to gram-negative pathogen.</p> <p>Methods</p> <p>Forty-six patients with monomicrobial necrotizing fasciitis were examined retrospectively from November 2002 to January 2008. All patients received adequate broad-spectrum antibiotic therapy, aggressive resuscitation, prompt radical debridement and adjuvant hyperbaric oxygen therapy. Eleven patients were infected with a gram-positive pathogen (Group 1) and 35 patients with a gram-negative pathogen (Group 2).</p> <p>Results</p> <p>Group 2 was characterized by a higher incidence of hemorrhagic bullae and septic shock, higher APACHE II scores at 24 h post-admission, a higher rate of thrombocytopenia, and a higher prevalence of chronic liver dysfunction. Gouty arthritis was more prevalent in Group 1. For non-survivors, the incidences of chronic liver dysfunction, chronic renal failure and thrombocytopenia were higher in comparison with those for survivors. Lower level of serum albumin was also demonstrated in the non-survivors as compared to those in survivors.</p> <p>Conclusions</p> <p>Pre-existing chronic liver dysfunction, chronic renal failure, thrombocytopenia and hypoalbuminemia, and post-operative dependence on mechanical ventilation represent poor prognostic factors in monomicrobial necrotizing fasciitis. Patients with gram-negative monobacterial necrotizing fasciitis present with more fulminant sepsis.</p