Using DNA microarray screening (GeneFilter 211, Research Genetics, Huntsville, AL) of mRNA from primary human umbilical vein endothelial cells (HUVEC), we identified 52 genes with significantly altered expression under shear stress [25 dynes͞cm 2 for 6 or 24 h (1 dyne ؍ 10 N), compared with matched stationary controls]; including several genes not heretofore recognized to be shear stress responsive. We examined mRNA expression of nine genes by Northern blot analysis, which confirmed the results obtained on DNA microarrays. Thirty-two genes were up-regulated (by more than 2-fold), the most enhanced being cytochromes P450 1A1 and 1B1, zinc finger protein EZF͞GKLF, glucocorticoid-induced leucine zipper protein, argininosuccinate synthase, and human prostaglandin transporter. Most dramatically decreased (by more than 2-fold) were connective tissue growth factor, endothelin-1, monocyte chemotactic protein-1, and spermidine͞spermine N1-acetyltransferase. The changes observed suggest several potential mechanisms for increased NO production under shear stress in endothelial cells. During the past 15 years, over 40 genes have been identified as being regulated by shear stress in endothelial cells (1-4). Shear stress responsive genes are involved in cell proliferation, differentiation, maintenance of vascular tone, thrombosis, cellmatrix and cell-cell adhesion, and modulation of the inflammatory͞immune system. The identification of such genes is important not only for developing a fundamental understanding of how endothelial cells work, but also for understanding and treating pathological conditions that are influenced by shear stress, such as thrombosis, restenosis, and atherosclerosis (5, 6).Most of the genes that have been shown to be regulated by shear stress were identified by using traditional techniques such as Northern blot analysis or reverse transcriptase PCR (7-9). The main limitation of these techniques is that only one gene or at best a handful of genes can be studied in one experiment. When multiple genes are studied by using traditional methods, the experiments usually require a reiteration of the detection procedure for each gene. Investigators must therefore be very selective in the genes they choose to study, necessitating a priori information linking the chosen genes to shear stress. Thus, these experiments generally tend to validate or disprove specific hypotheses and do not lead to the discovery of unexpected differentially expressed genes. However, DNA microarray technology allows researchers to study several thousands of genes at one time. In addition to identifying unexpected genes, this technology also has the power to lead to the development of new hypotheses concerning how cells respond to shear stress and identification of coregulated pathways responsive to the mechanical environment of the cell.We used DNA GeneFilter GF211 from Research Genetics (Huntsville, AL; ref. 10), which contains over 4,000 named human genes, to identify genes altered by shear stress in primary human umbilical vein en...
The pregnane X receptor (PXR)/steroid and xenobiotic receptor (SXR) transcriptionally activates cytochrome P4503A4 (CYP3A4) when ligand activated by endobiotics and xenobiotics. We cloned the human PXR gene and analysed the sequence in DNAs of individuals whose CYP3A phenotype was known. The PXR gene spans 35 kb, contains nine exons, and mapped to chromosome 13q11-13. Thirty-eight single nucleotide polymorphisms (SNPs) were identified including six SNPs in the coding region. Three of the coding SNPs are non-synonymous creating new PXR alleles [PXR*2, P27S (79C to T); PXR*3, G36R (106G to A); and PXR*4, R122Q (4321G to A)]. The frequency of PXR*2 was 0.20 in African Americans and was never found in Caucasians. Hepatic expression of CYP3A4 protein was not significantly different between African Americans homozygous for PXR*1 compared to those with one PXR*2 allele. PXR*4 was a rare variant found in only one Caucasian person. Homology modelling suggested that R122Q, (PXR*4) is a direct DNA contact site variation in the third alpha-helix in the DNA binding domain. Compared with PXR*1, and variants PXR*2 and PXR*3, only the variant PXR*4 protein had significantly decreased affinity for the PXR binding sequence in electromobility shift assays and attenuated ligand activation of the CYP3A4 reporter plasmids in transient transfection assays. However, the person heterozygous for PXR*4 is normal for CYP3A4 metabolism phenotype. The relevance of each of the 38 PXR SNPs identified in DNA of individuals whose CYP3A basal and rifampin-inducible CYP3A4 expression was determined in vivo and/or in vitro was demonstrated by univariate statistical analysis. Because ligand activation of PXR and upregulation of a system of drug detoxification genes are major determinants of drug interactions, it will now be useful to extend this work to determine the association of these common PXR SNPs to human variation in induction of other drug detoxification gene targets.
Transgenic pigs were generated that produced human protein C in their milk at up to 1 g/liter. The gene construct was a fusion gene consisting of the cDNA for human protein C inserted into the first exon of the mouse whey acidic protein gene. These results demonstrate that the mouse whey acidic protein gene contains regulatory elements that can direct cDNA expression at high levels in the pig mammary gland. Recombinant human protein C that was produced at about 380 pg/ml per hr in transgenic pig milk possessed anticoagulant activity that was equivalent to that of protein C derived from human plasma. These studies provide evidence that y-carboxylation can occur at high levels in the mammary gland of a pig.
In eukaryotes, coat protein complex II (COPII) proteins are involved in transporting cargo proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. The COPII proteins, Sar1, Sec23/24, and Sec13/31 polymerize into a coat that gathers cargo proteins into a coated vesicle. Structures have been recently solved of individual COPII proteins, COPII proteins in complex with cargo, and higher-order COPII coat assemblies. In this review, we will summarize the latest developments in COPII structure and discuss how these structures shed light on the functional mechanisms of the COPII coat.
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