Direct interactions of phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) with inwardly rectifying potassium channels are stronger with channels rendered constitutively active by binding to PtdIns(4,5)P2, such as IRK1, than with G-protein-gated channels (GIRKs). As a result, PtdIns(4,5)P2 alone can activate IRK1 but not GIRKs, which require extra gating molecules such as the beta gamma subunits of G proteins or sodium ions. Here we identify two conserved residues near the inner-membrane interface of these channels that are critical in interactions with PtdIns(4,5)P2. Between these two arginines, a conservative change of isoleucine residue 229 in GIRK4 to the corresponding leucine found in IRK1 strengthens GIRK4-PtdIns(4,5)P2 interactions, eliminating the need for extra gating molecules. A negatively charged GIRK4 residue, two positions away from the most strongly interacting arginine, mediates stimulation of channel activity by sodium by strengthening channel-PtdIns(4,5)P2 interactions. Our results provide a mechanistic framework for understanding how distinct gating mechanisms of inwardly rectifying potassium channels allow these channels to subserve their physiological roles.

We have previously shown that miR-486-5p is one of the most downregulated micro RNAs in lung cancer. The objective of the study was to investigate the role of miR-486-5p in the progression and metastasis of non-small-cell lung cancer (NSCLC). We evaluated miR-486-5p expression status on 76 frozen and 33 formalin-fixed paraffin-embedded tissues of NSCLC by quantitative reverse transcriptase PCR to determine its clinicopathologic significance. We then performed function analysis of miR-486-5p to determine its potential roles on cancer cell migration and invasion in vitro and metastasis in vivo. We also investigated the target genes of miR-486-5p in lung tumorigenesis. miR-486-5p expression level was significantly lower in lung tumors compared with their corresponding normal tissues (P<0.0001), and associated with stage (P =0.0001) and lymph node metastasis of NSCLC (P = 0.0019). Forced expression of miR-486-5p inhibited NSCLC cell migration and invasion in vitro and metastasis in mice by inhibiting cell proliferation. Furthermore, ectopic expression of miR-486-5p in cancer cells reduced ARHGAP5 expression level, whereas miR-486-5p silencing increased its expression. Luciferase assay demonstrated that miR-486-5p could directly bind to the 3′-untranslated region of ARHGAP5. The expression level of miR-486-5p was inversely correlated with that of ARHGAP5 in lung tumor tissues (P =0.0156). Reduced expression of ARHGAP5 considerably inhibited lung cancer cell migration and invasion, resembling that of miR-486-5p overexpression. miR-486-5p may act as a tumor-suppressor contributing to the progression and metastasis of NSCLC by targeting ARHGAP5. miR-486-5p would provide potential diagnostic and therapeutic targets for the disease.

BackgroundThe effect of corticosteroids on influenza A(H1N1)pdm09 viral pneumonia patients remains controversial, and the impact of dosage has never been studied.MethodsUsing data of hospitalized adolescent and adult patients with influenza A(H1N1)pdm09 viral pneumonia, prospectively collected from 407 hospitals in mainland China, the effects of low‐to‐moderate‐dose (25‐150 mg d−1) and high‐dose (>150 mg d−1) corticosteroids on 30‐day mortality, 60‐day mortality, and nosocomial infection were assessed with multivariate Cox regression and propensity score‐matched case–control analysis.ResultsIn total, 2141 patients (median age: 34 years; morality rate: 15.9%) were included. Among them, 1160 (54.2%) had PaO2/FiO2<300 mm Hg on admission, and 1055 (49.3%) received corticosteroids therapy. Corticosteroids, without consideration of dose, did not influence either 30‐day or 60‐day mortality. Further analysis revealed that, as compared with the no‐corticosteroid group, low‐to‐moderate‐dose corticosteroids were related to reduced 30‐day mortality (adjusted hazard ratio [aHR] 0.64 [95% CI 0.43‐0.96, P=.033]). In the subgroup analysis among patients with PaO2/FiO2<300 mm Hg, low‐to‐moderate‐dose corticosteroid treatment significantly reduced both 30‐day mortality (aHR 0.49 [95% CI 0.32‐0.77]) and 60‐day mortality (aHR 0.51 [95% CI 0.33‐0.78]), while high‐dose corticosteroid therapy yielded no difference. For patients with PaO2/FiO2 ≥300 mm Hg, corticosteroids (irrespective of dose) showed no benefit and even increased 60‐day mortality (aHR 3.02 [95% CI 1.06‐8.58]). Results were similar in the propensity model analysis.ConclusionsLow‐to‐moderate‐dose corticosteroids might reduce mortality of influenza A(H1N1)pdm09 viral pneumonia patients with PaO2/FiO2<300 mm Hg. Mild patients with PaO2/FiO2 ≥300 mm Hg could not benefit from corticosteroid therapy.

G protein-sensitive inwardly rectifying potassium (GIRK) channels are activated through direct interactions of their cytoplasmic N- and C-terminal domains with the beta gamma subunits of G proteins. By using a combination of biochemical and electrophysiological approaches, we identified minimal N- and C-terminal G beta gamma -binding domains responsible for stimulation of GIRK4 channel activity. Within these domains one N-terminal residue, His-64, and one C-terminal residue, Leu-268, proved critical for G beta gamma-mediated GIRK4 activity. Moreover, mutations at these GIRK4 sites reduced significantly binding of the channel domains to G beta gamma . The corresponding residues in GIRK1 also showed a critical involvement in G beta gamma sensitivity. In GIRK4/GIRK1 heteromers the GIRK4 His-64 and Leu-268 residues showed greater contributions to G beta zeta sensitivity than did the corresponding GIRK1 His-57 and Leu-262 residues. These results identify functionally important channel interaction sites with the beta gamma subunits of G proteins, critical for channel activity.

BackgroundThere is limited data on the clinical outcome of patients with pandemic H1N1 (pH1N1) pneumonia who received oseltamivir treatment, especially when the treatment was administered more than 48 hours after symptom onset.MethodsDuring the pandemic in 2009, a cohort of pH1N1 influenza pneumonia was built in China, and their clinical information was collected systematically, and analyzed with Cox models.Results920 adults and 541 children with pneumonia who didn't receive corticosteroids were analyzed. In-hospital mortality was higher in adults who did not receive antiviral therapy (18.2%) than those with who received oseltamivir ≤ 2days (2.9%), between 2–5 days (4.6%) and >5 days after illness onset (4.9%), p<0.01. A similar trend was observed in pediatric patients. Cox regression showed that at 60 days after symptoms onset, 11 patients (10.8%) who did not receive antivirals died versus 4 (1.8%), 18 (3.3%), and 23 (3.7%) patients whose oseltamivir treatment was started ≤ 2days, between 2–5days, and >5 days, respectively. For males patients, aged ≥ 14 years and baseline PaO2/FiO2<200, oseltamivir administration reduced the mortality risk by 92.1%, 88% and 83.5%, respectively. Higher doses of oseltamivir (>3.8 mg/kg/d) did not improve clinical outcome (mortality, higher dose 2.5% vs standard dose 2.8%, p>0.05).ConclusionsAntiviral therapy might reduce mortality of patients with pH1N1 pneumonia, even when initiated more than 48 hours after onset of illness. Greater protective effects might be in males, patients aged 14–60 years, and patients with PaO2/FiO2<200.