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141.
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143.
Li-Ying Liou Kevin B. Walsh Arineh R. Vartanian Daniel Beltran-Valero de Bernabe Megan Welch Kevin P. Campbell Michael B. A. Oldstone Stefan Kunz 《PloS one》2010,5(3)
Background
Alpha-dystroglycan (α-DG) is a cell surface receptor providing a molecular link between the extracellular matrix (ECM) and the actin-based cytoskeleton. During its biosynthesis, α-DG undergoes specific and unusual O-glycosylation crucial for its function as a high-affinity cellular receptor for ECM proteins.Methodology/Principal Findings
We report that expression of functionally glycosylated α-DG during thymic development is tightly regulated in developing T cells and largely confined to CD4−CD8− double negative (DN) thymocytes. Ablation of DG in T cells had no effect on proliferation, migration or effector function but did reduce the size of the thymus due to a significant loss in absolute numbers of thymocytes. While numbers of DN thymocytes appeared normal, a marked reduction in CD4+CD8+ double positive (DP) thymocytes occurred. In the periphery mature naïve T cells deficient in DG showed both normal proliferation in response to allogeneic cells and normal migration, effector and memory T cell function when tested in acute infection of mice with either lymphocytic choriomeningitis virus (LCMV) or influenza virus.Conclusions/Significance
Our study demonstrates that DG function is modulated by glycosylation during T cell development in vivo and that DG is essential for normal development and differentiation of T cells. 相似文献144.
Hong CJ Tsai PJ Cheng CY Chou CK Jheng HF Chuang YC Yang CN Lin YT Hsu CW Cheng IH Chen SY Tsai SJ Liou YJ Tsai YS 《PloS one》2010,5(12):e15333
Background
Obesity is a multifactorial disease that arises from complex interactions between genetic predisposition and environmental factors. Leptin is central to the regulation of energy metabolism and control of body weight in mammals.Methodology/Principal Findings
To better recapitulate the complexity of human obesity syndrome, we applied N-ethyl-N-nitrosourea (ENU) mutagenesis in combination with a set of metabolic assays in screening mice for obesity. Mapping revealed linkage to the chromosome 6 within a region containing mouse Leptin gene. Sequencing on the candidate genes identified a novel T-to-A mutation in the third exon of Leptin gene, which translates to a V145E amino acid exchange in the leptin propeptide. Homozygous Leptin145E/145E mutant mice exhibited morbid obesity, accompanied by adipose hypertrophy, energy imbalance, and liver steatosis. This was further associated with severe insulin resistance, hyperinsulinemia, dyslipidemia, and hyperleptinemia, characteristics of human obesity syndrome. Hypothalamic leptin actions in inhibition of orexigenic peptides NPY and AgRP and induction of SOCS1 and SOCS3 were attenuated in Leptin145E/145E mice. Administration of exogenous wild-type leptin attenuated hyperphagia and body weight increase in Leptin145E/145E mice. However, mutant V145E leptin coimmunoprecipitated with leptin receptor, suggesting that the V145E mutation does not affect the binding of leptin to its receptor. Molecular modeling predicted that the mutated residue would form hydrogen bond with the adjacent residues, potentially affecting the structure and formation of an active complex with leptin receptor within that region.Conclusions/Significance
Thus, our evolutionary, structural, and in vivo metabolic information suggests the residue 145 as of special function significance. The mouse model harboring leptin V145E mutation will provide new information on the current understanding of leptin biology and novel mouse model for the study of human obesity syndrome. 相似文献145.
This study is to improve the digestion pattern of miniprepped plasmid analyzed on gel. Frequently, some ambiguous DNA bands, which are suspected to be denatured DNA molecules, appear during electrophoresis of enzyme digested miniprepped plasmids. By employing Southern hybridization of two identical gels, one had been treated with denaturation-neutralization step and another without such treatment, we confirmed that many of these ambiguous DNA bands were single-stranded (SS) DNA molecules. The presence of SS DNA was due to the use of excess amount of NaOH during plasmid DNA purification with the conventional alkaline lysis method. We, therefore, modified the procedure and recommend that a half amount of NaOH (0.1N instead of 0.2N) should be used when isolating small quantity of plasmid DNA with the method. 相似文献
146.
147.
Milko E. van der Boom Shyh-Yeon Liou Yehoshoa Ben-David 《Inorganica chimica acta》2004,357(13):4015-4023
Reaction of NiI2 with the PCP-ligand {1-Et-2,6-(CH2PiPr2)2-C6H3} (1) results in selective activation of the strong sp2-sp3 aryl-ethyl bond to afford the aryl-nickel complex [Ni{2,6-(CH2PiPr2)2-C6H3}I] (2), whereas reaction of NiI2 with {1,3,5-(CH3)3-2,6-(CH2PiPr2)2-C6H} (4) leads to the formation of the benzylic complex [Ni{1-CH2-2,6-(CH2PiPr2)2-3,5-(CH3)2-C6H}I] (5) by selective C-H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-(CH2PiPr2)2-3,5-(CH3)2-C6H}I] (6) by activation of the sp2-sp3 C-C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI2 with {1,3-(CH2PiPr2)2-C6H4} (3) and {1,3-(CH3)2-4,6-(CH2PiPr2)2-C6H2} (7), respectively, lacking the aryl-alkyl groups between the “phosphines arms” (alkyl=ethyl, methyl). Complexes 2 and 5 have been fully characterized by X-ray analysis. Nickel-based activation of an unstrained C-O single bond was observed as well. Reaction of the aryl-methoxy bisphosphine {1-OMe-2,6-(CH2PiPr2)2-C6H3} (8) with NiI2 results in the formation of the phenoxy complex [Ni{1-O-2,6-(CH2PiPr2)2-C6H3}I] (9) by selective sp3-sp3 C-O bond activation. 相似文献
148.
Intestinal fatty acid binding protein (IFABP) and liver FABP (LFABP), homologous proteins expressed at high levels in intestinal absorptive cells, employ markedly different mechanisms for the transfer of fatty acids (FAs) to acceptor membranes. Transfer from IFABP occurs during protein-membrane collisional interactions, while for LFABP, transfer occurs by diffusion through the aqueous phase. Earlier, we had shown that the helical domain of IFABP is critical in determining its collisional FA transfer mechanism. In the study presented here, we have engineered a pair of chimeric proteins, one with the "body" (ligand binding domain) of IFABP and the alpha-helical region of LFABP (alphaLbetaIFABP) and the other with the ligand binding pocket of LFABP and the helical domain of IFABP (alphaIbetaLFABP). The objective of this work was to determine whether the change in the alpha-helical domain of each FABP would alter the rate and mechanism of transfer of FA from the chimeric proteins in comparison with those of the wild-type proteins. The fatty acid transfer properties of the FABP chimeras were examined using a fluorescence resonance transfer assay. The results showed a significant modification of the absolute rate of FA transfer from the chimeric proteins compared to that of the wild type, indicating that the slower rate of FA transfer observed for wild-type LFABP relative to that of wild-type IFABP is, in part, determined by the helical domain of the proteins. In addition to these quantitative changes, it was of great interest to observe that the apparent mechanism of FA transfer also changed when the alpha-helical domain was exchanged, with transfer from alphaLbetaIFABP occurring by aqueous diffusion and transfer from alphaIbetaLFABP occurring via protein-membrane collisional interactions. These results demonstrate that the alpha-helical region of LFABP is responsible for its diffusional mechanism of fatty acid transfer to membranes. 相似文献
149.
Lu KP Liou YC Vincent I 《BioEssays : news and reviews in molecular, cellular and developmental biology》2003,25(2):174-181
The reversible phosphorylation of proteins on serine/threonine residues preceding proline (Ser/Thr-Pro) is a major regulatory mechanism for the control of a series of cell cycle events. Although phosphorylation is thought to regulate protein function by inducing conformational changes, little is known about most of these conformational changes and their significance. Recent studies indicate that the conformation and function of a subset of these phosphorylated proteins are controlled by the prolyl isomerase Pin1 through isomerization of specific phosphorylated Ser/Thr-Pro bonds. Furthermore, compelling evidence supports the idea that proline-directed phosphorylation and subsequent isomerization play a critical role not only in cell cycle control, but also in the development of Alzheimer's disease, where postmitotic neurons display various cell cycle markers, especially mitotic events, prior to degeneration. 相似文献
150.
Shompole S Henon KT Liou LE Dziewanowska K Bohach GA Bayles KW 《Molecular microbiology》2003,49(4):919-927
Staphylococcus aureus invades a variety of mammalian cells and escapes from the endosome to multiply in the cytoplasm. We had previously hypothesized that the molecular events leading to escape of S. aureus from the endosome involved the Agr virulence factor regulatory system. In this report we demonstrate that temporal changes in intracellular activation of the Agr regulon correlates with expression of membrane active toxins. Also, the initial expression of Agr by even small numbers of staphylococci resulted in the permeabilization of the endosomal membrane and the eventual escape of bacteria into the cytoplasm by 3 h post invasion. After Agr downregulation, a second peak of expression coincided with increased permeability of the host cell membrane. In contrast to the parental strain, an Agr-mutant was unable to escape into the cytoplasm and was observed in intact endosomes as late as 5 h post invasion. These data provide evidence that staphylococcal virulence factor production during invasion of host cells is mediated by an Agr-dependent process that is most accurately described in the context of diffusion sensing. 相似文献