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Jun Wang Yan Guo Baocheng Wang Jingwang Bi Kainan Li Xiuju Liang Huili Chu Huihui Jiang 《Molecular biology reports》2012,39(12):11153-11165
The use of lymphatic microvessel density (LVD) and pro-lymphangiogenic mediators as prognostic factors for survival in breast cancer remains controversial. We searched the electronic databases PubMed and EMBASE without language restrictions for relevant literature to aggregate the survival results. To be eligible, every study had to include the assessment of the LVD or the expression of vascular endothelial growth factor (VEGF)-C or -D in patients with breast cancer and provide a survival comparison, including disease-free survival (DFS) or overall survival (OS), according to the LVD, VEGF-C or VEGF-D status. Across all studies, 56.64?% of patients were considered to have a VEGF-C-positive tumor, and 65.54?% of patients had VEGF-D-positive tumors. High LVD had an unfavorable impact on DFS, with a pooled hazard ratio (HR) of 2.222 (95?% CI 1.579–3.126) and an OS with a HR of 2.493 (95?% CI 1.183–5.25). According to the different lymphatic makers, the subgroup HR in the D2-40 studies was 2.431 (95?%?CI 1.622–3.644) for DFS and 4.085 (95?% CI 1.896–8.799) for OS. VEGF-C overexpression, as assessed by immunochemistry, was a prognostic factor for decreased DFS (HR 2.164; 95?% CI 1.256–3.729) and for decreased OS (HR 2.613; 95?% CI 1.637–4.170). VEGF-D overexpression was a significant although weak prognostic factor for DFS only when assessed by immunochemistry, with a HR of 2.108 (95?% CI 1.014–4.384). Our meta-analysis demonstrated that LVD, VEGF-C and VEGF-D could predict poor prognosis in patients with breast cancer. However, standardization of the assessment of LVD and for the expression of lymphangiogenesis factors is needed. 相似文献
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Ge H Tollner TL Hu Z Dai M Li X Guan H Shan D Zhang X Lv J Huang C Dong Q 《Molecular reproduction and development》2012,79(6):392-401
Mitochondrial metabolic capacity and DNA replication have both been shown to affect oocyte quality, but it is unclear which one is more critical. In this study, immature oocytes were treated with FCCP or ddC to independently inhibit the respective mitochondrial metabolic capacity or DNA replication of oocytes during in vitro maturation. To differentiate their roles, we evaluated various parameters related to oocyte maturation (germinal vesicle break down and nuclear maturation), quality (spindle formation, chromosome alignment, and mitochondrial distribution pattern), fertilization capability, and subsequent embryo developmental competence (blastocyst formation and cell number of blastocyst). Inhibition of mitochondrial metabolic capacity with FCCP resulted in a reduced percent of oocytes with nuclear maturation; normal spindle formation and chromosome alignment; evenly distributed mitochondria; and an ability to form blastocysts. Inhibition of mtDNA replication with ddC has no detectable effect on oocyte maturation and mitochondrial distribution, although high-dose ddC increased the percent of oocytes showing abnormal spindle formation and chromosome alignment. ddC did, however, reduce blastocyst formation significantly. Neither FCCP nor ddC exposure had an effect on the rate of fertilization. These findings suggest that the effects associated with lower mitochondrial DNA copy number do not coincide with the effects seen with reduced mitochondrial metabolic activity in oocytes. Inhibiting mitochondrial metabolic activity during oocyte maturation has a negative impact on oocyte maturation and subsequent embryo developmental competence. A reduction in mitochondrial DNA copy number, on the other hand, mainly affects embryonic development potential, but has little effect on oocyte maturation and in vitro fertilization. 相似文献
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Bryk R Gold B Venugopal A Singh J Samy R Pupek K Cao H Popescu C Gurney M Hotha S Cherian J Rhee K Ly L Converse PJ Ehrt S Vandal O Jiang X Schneider J Lin G Nathan C 《Cell host & microbe》2008,3(3):137-145
Antibiotics are typically more effective against replicating rather than nonreplicating bacteria. However, a major need in global health is to eradicate persistent or nonreplicating subpopulations of bacteria such as Mycobacterium tuberculosis (Mtb). Hence, identifying chemical inhibitors that selectively kill bacteria that are not replicating is of practical importance. To address this, we screened for inhibitors of dihydrolipoamide acyltransferase (DlaT), an enzyme required by Mtb to cause tuberculosis in guinea pigs and used by the bacterium to resist nitric oxide-derived reactive nitrogen intermediates, a stress encountered in the host. Chemical screening for inhibitors of Mtb DlaT identified select rhodanines as compounds that almost exclusively kill nonreplicating mycobacteria in synergy with products of host immunity, such as nitric oxide and hypoxia, and are effective on bacteria within macrophages, a cellular reservoir for latent Mtb. Compounds that kill nonreplicating pathogens in cooperation with host immunity could complement the conventional chemotherapy of infectious disease. 相似文献
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Carbonic anhydrase II (CAII) binds to and regulates transport by the NHE1 isoform of the mammalian Na(+)/H(+) exchanger. We localized and characterized the CAII binding region on the C-terminal tail of the Na(+)/H(+) exchanger. CAII did not bind to acidic sequences in NHE1 that were similar to the CAII binding site of bicarbonate transporters. Instead, by expressing a variety of fusion proteins of the C-terminal region of the Na(+)/H(+) exchanger, we demonstrated that CAII binds to the penultimate group of 13 amino acids of the cytoplasmic tail. Within this region, site-specific mutagenesis demonstrated that amino acids S796 and D797 form part of a novel CAII binding site. Phosphorylation of the C-terminal 26 amino acids by heart cell extracts did not alter CAII binding to this region, but phosphorylation greatly increased CAII binding to a protein containing the C-terminal 182 amino acids of NHE1. This suggested that an upstream region of the cytoplasmic tail acts as an inhibitor of CAII binding to the penultimate group of 13 amino acids. The results demonstrate that a novel phosphorylation-regulated CAII binding site exists in distal amino acids of the NHE1 tail. 相似文献
18.
Mycobacterium tuberculosis expresses methionine sulphoxide reductases A and B that protect from killing by nitrite and hypochlorite 总被引:1,自引:0,他引:1
Warren L. Lee Benjamin Gold Crystal Darby Nathan Brot Xiuju Jiang Luiz Pedro S. de Carvalho Daniel Wellner Gregory St. John William R. Jacobs Jr Carl Nathan 《Molecular microbiology》2009,71(3):583-593
Methionine sulphoxide reductases (Msr) reduce methionine sulphoxide to methionine and protect bacteria against reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI). Many organisms express both MsrA, active against methionine-( S )-sulphoxide, and MsrB, active against methionine-( R )-sulphoxide. Mycobacterium tuberculosis (Mtb) expresses MsrA, which protects Δ msrA-Escherichia coli from ROI and RNI. However, the function of MsrA in Mtb has not been defined, and it is unknown whether Mtb expresses MsrB. We identified MsrB as the protein encoded by Rv2674 in Mtb and confirmed the distinct stereospecificities of recombinant Mtb MsrA and MsrB. We generated strains of Mtb deficient in MsrA, MsrB or both and complemented the mutants. Lysates of singly deficient strains displayed half as much Msr activity as wild type against N -acetyl methionine sulphoxide. However, in contrast to other bacteria, single mutants were no more vulnerable than wild type to killing by ROI/RNI. Only Mtb lacking both MsrA and MsrB was more readily killed by nitrite or hypochlorite. Thus, MsrA and MsrB contribute to the enzymatic defences of Mtb against ROI and RNI. 相似文献
19.
Brian L. Lee Xiuju Li Yongsheng Liu Brian D. Sykes Larry Fliegel 《The Journal of biological chemistry》2009,284(17):11546-11556
The Na+/H+ exchanger isoform 1 is a ubiquitously
expressed integral membrane protein that regulates intracellular pH in mammals
by extruding an intracellular H+ in exchange for one extracellular
Na+. We characterized structural and functional aspects of the
critical transmembrane (TM) segment XI (residues 449-470) by using cysteine
scanning mutagenesis and high resolution NMR. Each residue of TM XI was
mutated to cysteine in the background of the cysteine-less protein and the
sensitivity to water-soluble sulfhydryl reactive compounds MTSET
((2-(trimethylammonium) ethyl)methanethiosulfonate) and MTSES
((2-sulfonatoethyl) methanethiosulfonate) was determined for those residues
with at least moderate activity remaining. Of the residues tested, only
proteins with mutations L457C, I461C, and L465C were inhibited by MTSET. The
activity of the L465C mutant was almost completely eliminated, whereas that of
the L457C and I461C mutants was partially affected. The structure of a peptide
representing TM XI (residues Lys447-Lys472) was
determined using high resolution NMR spectroscopy in dodecylphosphocholine
micelles. The structure consisted of helical regions between
Asp447-Tyr454 and Phe460-Lys471 at
the N and C termini of the peptide, respectively, connected by a region with
poorly defined, irregular structure consisting of residues
Gly455-Gly459. TM XI of NHE1 had a structural similarity
to TM XI of the Escherichia coli Na+/H+
exchanger NhaA. The results suggest that TM XI is a discontinuous helix, with
residue Leu465 contributing to the pore.The mammalian Na+/H+ exchanger isoform 1
(NHE1)4 is a
ubiquitous integral membrane protein that regulates intracellular pH. It
mediates removal of a single intracellular proton in exchange for an
extracellular sodium ion (1).
NHE1 has many functions aside from protection of cells from intracellular
acidification (2). It promotes
cell growth and differentiation
(3), regulates sodium fluxes
and cell volume after challenge by osmotic shrinkage
(4), and has been demonstrated
to be involved in modulating cell motility
(5). In addition its activity
is important in invasiveness of neoplastic breast cancer cells
(6). NHE1 also plays critical
roles in heart disease. It has a contributing role in heart hypertrophy and in
the damage that occurs during ischemia and reperfusion. Inhibition of NHE1
with Na+/H+ exchanger inhibitors protects the myocardium
during various disease states
(7-10).NHE1 is composed of two general regions, an N-terminal membrane domain of
∼500 amino acids and a C-terminal regulatory domain of ∼315 amino
acids (1,
8). The membrane domain is
responsible for ion movement and an analysis of topology by cysteine scanning
accessibility suggested it has 3 membrane-associated segments and 12 integral
transmembrane segments (11)
(Fig. 1A). The
mechanism of transport of the membrane domain is of great interest both from a
scientific viewpoint and in the design of improved NHE1 inhibitors that may be
necessary for clinical use (1).
In this regard, we have recently characterized the functionally important
residues and the structure of both TM IV and TM VII. Prolines 167 and 168 of
TM IV were critical to NHE1 function
(12) and cysteine-scanning
mutagenesis was used to show that Phe161 is a pore lining residue
critical to transport. Analysis of the structure of TM IV showed that TM IV is
composed of one region of β-turns, an extended middle region including
Pro167-Pro168, and a helical region
(13). TM VII was much more
typical of a transmembrane helix although it was interrupted with a break in
the helix at the functionally critical residues
Gly261-Glu262
(14).Open in a separate windowFIGURE 1.Models of the Na+/H+ exchanger.
A, simplified topological model of the transmembrane domain of the
NHE1 isoform of the Na+/H+ exchanger as described
earlier (11). EL,
extracellular loop; IL, intracellular loop. B, model of amino acids
present in TM XI.Another important TM segment of the Na+/H+ exchanger
is TM XI (Fig. 1B).
Several different lines of evidence have suggested that it is critical to NHE1
function. A recent study generated chimeras of NHE1 from various species and
found that a region including TM XI was important in determining NHE1
inhibitor sensitivity (15).
More specifically, mutagenesis of several amino acids of TM XI has shown that
it is likely involved in either ion transport or proper targeting to the
plasma membrane. Two mutants in TM XI, Y454C and R458C, are retained in the
endoplasmic reticulum (16). In
addition, mutation of Gly455 and Gly456 in TM XI shift
the pHi dependence of the exchanger to the alkaline side,
whereas mutation of Arg440 in intracellular loop 5 at the
N-terminal end of TM XI shifts the pHi dependence to make
it more acidic (17,
18). Also, the structure of
the bacterial Na+/H+ exchanger NhaA has been elucidated.
Both TM IV and TM XI play a critical role forming an assembly that cross, with
each being a helix, an extended polypeptide and a short helix
(19). We found that TM IV of
NHE1 has a similar structure and function to that of TM IV of NhaA
(2,
13), leaving open the
possibility that TM XI of NHE1 is also similar in structure and function to TM
XI of NhaA.For these reasons, we undertook a systematic examination of the structural
and functional aspects of TM XI of the NHE1 isoform of the
Na+/H+ exchanger. The sequence of human TM XI of NHE1 is
449QFIIAYGGLRGAIAFSLGYLLD470. In this study we use
cysteine scanning mutagenesis and site-specific mutagenesis to identify and
characterize critical pore lining residues of the protein. We also use nuclear
magnetic resonance (NMR) spectroscopy to characterize the structure of a
synthetic peptide representing TM XI in dodecylphosphocholine (DPC) micelles.
Evidence has suggested that TM segments of membrane proteins possess all the
structural information required to form their higher order structures in their
amino acid sequence (20). This
has been demonstrated in earlier studies on membrane protein segments such as
the cystic fibrosis transmembrane conductance regulator
(21), a fungal
G-protein-coupled receptor
(22), bacteriorhodopsin
(23,
24), and rhodopsin
(25), where it was shown that
isolated TM segments from membrane proteins had structures in good agreement
with the segments of the entire protein. Also, the use of DPC micelles has
been shown to be an excellent membrane mimetic environment for these studies
(26,
27). Our study identifies
Leu465 as contributing to the pore of the protein and shows that
the structure of TM XI consists of two helices corresponding to
Asp447-Tyr454 and Phe460-Lys471 at
the N and C termini, respectively, connected by a flexible region at residues
455-459. The structure of TM XI was similar to the x-ray structure of TM XI of
NhaA. 相似文献
20.
Yonglei Liu Xianrang Song Xingwu Wang Ling Wei Xiuju Liu Shuanghu Yuan Liyan Lv 《Journal of cellular biochemistry》2010,111(3):554-563
Hypoxia plays an important role in the development of solid tumors and is associated with their therapeutic resistance. There exist three major forms of hypoxia: acute, chronic, and intermittent hypoxia. Previous studies have shown that cancer cells could behave in the form of adaptation to hypoxia in tumor growth, which could result in their biological changes and determine their responses to the therapies. To investigate the tumor cells' adaptation to hypoxia, we recreated two models using two lung cancer cell lines in the presence of intermittent hypoxia, which is characterized by changes in oxygen pressure within the disorganized vascular network. We investigated biological behaviors such as cell cycle, proliferation, radiation sensitivity, apoptosis and migration, hypoxia signal pathway in the lung cancer cells treated with chronic intermittent hypoxia, as well as the role of hypoxia inducible factor 1 there, hypoxia‐inducible genes analyzed by real‐time RT‐PCR chip in H446 cells treated with the model. The results indicated the changes of some hypoxia target gene expressions of those induced by hypoxia, some of which were confirmed by real‐time RT‐PCR. The cells mediated by irradiation induced resistance to radiation and apoptosis and increased metastasis in lung cancer cells. It was found that such changes were related to hypoxia inducible factor 1, alpha subunit (HIF‐1α). J. Cell. Biochem. 111: 554–563, 2010. © 2010 Wiley‐Liss, Inc. 相似文献