Leukotactin-1-induced ERK activation is mediated via Gi/Go protein/PLC/PKC delta/Ras cascades in HOS cells

Recently cloned leukotactin-1 (Lkn-1) that belongs to CC chemokine family has not been characterized. To understand the intracellular events following Lkn-1 binding to CCR1, we investigated the activities of signaling molecules in response to Lkn-1 in human osteogenic sarcoma cells expressing CCR1. Lkn-1-stimulated cells showed elevated phosphorylation of extracellular signal-related kinases (ERK1/2) with a distinct time course. ERK activation was peaked in 30 min and 12 h showing biphasic activation of ERK. Pertussis toxin, an inhibitor of G(i)/G(o) protein, and phospholipase C (PLC) inhibitor blocked Lkn-1-induced activation of ERK. Protein kinase C delta (PKC delta) specific inhibitor rottlerin inhibited ERK activation in Lkn-1-stimulated cells. The activities of PLC and PKC delta were also enhanced by Lkn-1 stimulation. Dominant negative Ras inhibited activation of ERK. Immediate early response genes such as c-fos and c-myc were induced by Lkn-1 stimulation. Lkn-1 affected the cell cycle progression by cyclin D(3) induction. These results suggest that Lkn-1 activates the ERK pathway by transducing the signal through G(i)/G(o) protein, PLC, PKC delta and Ras, and it may play a role for cell proliferation, differentiation, and regulation of gene expression for other cellular processes.     

Electrically conductive bacterial cellulose by incorporation of carbon nanotubes

Electrically conducting polymeric membranes were prepared by incorporating multiwalled carbon nanotubes (MWCNTs) into bacterial cellulose pellicles produced by Gluconacetobacter xylinum. The MWCNTs were dispersed in a surfactant (cationic cetyl trimethylammonium bromide) solution, and cellulose pellicles were dipped into the solution for 6, 12, and 24 h. The surfactants were then extracted in pure water and dried. Electron microscopy showed that the individual MWCNTs were strongly adhered to the surface and the inside of the cellulose pellicle. The conductivity of the MWCNTs-incorporated cellulose pellicle, as measured by a four-probe at room temperature, was 1.4 x 10(-1) S/cm, based on the total cross-sectional area (approximately 9.6 wt % of MWCNTs). This suggests that the MWCNTs were incorporated uniformly and densely into the pellicles.     

An efficient translational termination of human erythropoietin in Escherichia coli by altering the base following the stop codon

Each of the four nucleotides (A, C, G and T) was introduced as the base following the stop codon to investigate the effect of this fourth base on translational termination efficiency during the heterologous expression of human erythropoietin (hEPO) in E. coli. The efficiency of peptide chain termination in E. coli was markedly dependent on the fourth base. The choice of the fourth base was crucial to prevent the expression of undesirable proteins due to the translational infidelity such as frameshifting and stop codon read-through, and translational termination efficiency could be improved with adenosine as the fourth base.     

Alteration of mitochondrial DNA sequence and copy number in nasal polyp tissue

This study was designed to investigate the possibility that mtDNA mutations might arise in inflammatory or chronically damaged nasal polyp tissue from 23 patients. Thirteen patients (57%) displayed nasal polyp tissue-specific mtDNA mutations in the hypervariable segment of the control region and cytochrome b gene, which were not found in the corresponding blood cells and/or adjacent normal tissue. Nasal polyp tissue-specific length heteroplasmic mutations were also detected in nucleotide position (np) 303–315 homopolymeric poly C track (39%), np 514–523 CA repeats (17%) and np 16184–16193 poly C track (30%). The average mtDNA copy number was about three times higher in nasal polyp tissue than in the corresponding peripheral blood cells and adjacent non-polyp tissues. The level of reactive oxygen species (ROS) was significantly higher in the nasal polyp tissues compared to those from the corresponding samples. High level of ROS in nasal polyp tissue may contribute to development of mtDNA mutations, which may play a crucial role in the vicious cycle of pathophysiology of nasal polyps.