Biomedical subjects

Huamin Zhou

Publications and source records attributed to Huamin Zhou.

6 recordsLinked to original sources

PubMed2006

C.I. Reactive Black 5 decolorization by combined sonolysis and ozonation.

Decolorization of the azo dye C.I. Reactive Black 5 (RB5) in solution by a combination of sonolysis and ozonation was investigated. The results showed that the optimum pH for the reaction was 11.0, and both lower and higher pH decreased the decolorization rate. Increasing the initial concentration of RB5 led to a decreasing decolorization rate. Under the experimental conditions, the decolorization rate increased with an increase in temperature. The decolorization of RB5 followed pseudo-first-order reaction kinetics. Based on the decolorization rate constants obtained at different temperatures within the range 287-338K and the Arrhenius equation, the apparent activation energy (E(a)) was calculated to be 11.2kJmol(-1). This indicated that the reaction has little dependence on temperature. The color decay was considerably faster than the decrease in total organic carbon (TOC), which was attributed to the ease of chromophore destruction. Hence the efficiency of decolorization was 84% compared with 4% of TOC removal after 5min reaction. Additionally, muconic acid, (2Z)-pent-2-enedioic acid and maleic acid were identified as main oxidation products by gas chromatography coupled with mass spectrometry (GC-MS) after 150min of reaction.

Journal Article↗

PubMed2006

Nod1-dependent control of tumor growth.

Nod1, a cytosolic protein that senses meso-diaminopimelic acid-containing ligands derived from peptidoglycan, plays a role in host responses to invasive bacteria. Here we describe a function for Nod1, whereby it controls tumor formation. Cell lines derived from the human breast cancer epithelial cell line MCF-7 were used in a severe combined immune deficiency (SCID) mouse xenograft model to characterize a pathway linking Nod1 to the growth of estrogen-sensitive tumors. In MCF-7 cells, the absence of Nod1 correlates with tumor growth, an increased sensitivity to estrogen-induced cell proliferation, and a failure to undergo Nod1-dependent apoptosis. Conversely, overexpression of Nod1 in MCF-7 cells results in inhibition of estrogen-dependent tumor growth and reduction of estrogen-induced proliferative responses in vitro.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Determinants that control the specific interactions between TAB1 and p38alpha.

Previous studies have revealed that transforming growth factor-beta-activated protein kinase 1 (TAB1) interacts with p38alpha and induces p38alpha autophosphorylation. Here, we examine the sequence requirements in TAB1 and p38alpha that drive their interaction. Deletion and point mutations in TAB1 reveal that a proline residue in the C terminus of TAB1 (Pro412) is necessary for its interaction with p38alpha. Furthermore, a cryptic D-domain-like docking site was identified adjacent to the N terminus of Pro412, putting Pro412 in the phi(B)+3 position of the docking site. Through mutational analysis, we found that the previously identified hydrophobic docking groove in p38alpha is involved in this interaction, whereas the CD domain and ED domain are not. Furthermore, chimeric analysis with p38beta (which does not bind to TAB1) revealed a previously unidentified locus of p38alpha comprising Thr218 and Ile275 that is essential for specific binding of p38alpha to TAB1. Converting either of these residues to the corresponding amino acid of p38beta abolishes p38alpha interaction with TAB1. These p38alpha mutants still can be fully activated by p38alpha upstream activating kinase mitogen-activated protein kinase kinase 6, but their basal activity and activation in response to some extracellular stimuli are reduced. Adjacent to Thr218 and Ile275 is a site where large conformational changes occur in the presence of docking-site peptides derived from p38alpha substrates and activators. This suggests that TAB1-induced autophosphorylation of p38alpha results from conformational changes that are similar but unique to those seen in p38alpha interactions with its substrates and activating kinases.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Frequency and distribution of AP-1 sites in the human genome.

The AP-1-binding sequences are promoter/enhancer elements that play an essential role in the induction of many genes in mammalian cells; however, the number of genes containing AP-1 sites remains unknown. In order to better address the overall effect of AP-1 on expression of genes encoded by the entire genome, a genome-wide analysis of the frequency and distribution of AP-1 sites would be useful; yet to date, no such analysis of AP-1 sites or any other promoter/enhancer elements has been performed. We present here our study of the consensus AP-1 site and two single-bp variants showing that the frequency of AP-1 sites in promoter regions is significantly lower than their average rate of occurrence in the whole genomic sequence, as well as the frequency of a random heptanucleotide suggesting that nature has selected for a decrease in the frequency of AP-1 sites in the regulatory regions of genes. In addition, genes containing multiple AP-1 sites are more prevalent than those containing only one copy of an AP-1 site, which again may have evolved to allow for greater signal amplification or integration in the regulation of AP-1 target genes. However, the number of AP-1-regulated genes identified in various studies is far smaller than the number of genes containing potential AP-1 sites, indicating that not all AP-1 sites are activated in a given cell under a given condition, and is consistent with the prediction by others that cellular context determines which AP-1 sites are targeted by AP-1.

Chromosomes, Human↗

PubMed2005

Distinct roles of basal steady-state and induced H-ferritin in tumor necrosis factor-induced death in L929 cells.

Tumor necrosis factor (TNF) alpha is a cytokine capable of inducing caspase-dependent (apoptotic) cell death in some cells and caspase-independent (necrosis-like) cell death in others. Here, using a mutagenesis screen for genes critical in TNF-induced death in L929 cells, we have found that H-ferritin deficiency is responsible for TNF resistance in a mutant line and that, upon treatment with TNF, this line fails to elevate levels of labile iron pool (LIP), critical for TNF-induced reactive oxygen species (ROS) production and ROS-dependent cell death. Since we found that TNF-induced LIP in L929 cells is primarily furnished by intracellular storage iron, the lesser induction of LIP in H-ferritin-deficient cells results from a reduction of intracellular iron storage caused by less H-ferritin. Different from some other cell lines, the H-ferritin gene in L929 cells is not TNF inducible; however, when H-ferritin is expressed in L929 cells under a TNF-inducible system, the TNF-induced LIP and subsequent ROS production and cell death were all prevented. Thus, LIP is a common denominator of ferritin both in the enhancement of cell death by basal steady-state H-ferritin and in protection against cell death by induced H-ferritin, thereby acting as a key determinant of TNF-induced cell death.

Animals↗

PubMed2004

Beta-actin is required for mitochondria clustering and ROS generation in TNF-induced, caspase-independent cell death.

Tumor necrosis factor (TNF)-alpha induces caspase-independent cell death in the fibrosarcoma cell line L929. This cell death has a necrotic phenotype and is dependent on production of reactive oxygen species (ROS) in the mitochondria. To identify genes involved in this TNF-induced, ROS-dependent cell death pathway, we utilized retrovirus insertion-mediated random mutagenesis to generate TNF-resistant L929 cell lines and we subsequently identified genes whose mutations are responsible for the TNF-resistant phenotype. In one such resistant line, beta-actin was disrupted by viral insertion, and subsequent reconstitution of beta-actin expression levels in the mutant line Actin(mut) restored its sensitivity to TNF. Resistance to TNF in Actin(mut) cells is signal specific since the sensitivity to other death stimuli is either unchanged or even increased. Comparable NF-kappaB activation and p38 phosphorylation in TNF-treated wild-type and Actin(mut) cells also indicates that reduced expression of actin only selectively blocked some of the TNF-induced cellular changes. Actin cleavage involved in apoptosis does not occur in TNF-treated L929 cell death, as in HeLa cells. Consistent over-expression of a caspase-cleaved product, a 15 kDa actin fragment, had no effect on TNF-induced necrosis of L929 cell. By contrast, TNF-induced mitochondria clustering and ROS production were dramatically reduced in Actin(mut) cells, indicating that actin-deficiency-mediated TNF resistance is most likely due to impaired mitochondrial responses to TNF stimulation. Our findings suggest that a full complement of actin is required for transduction of a cell death signal to mitochondria in TNF-treated L929 cells.

Actins↗