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ABSTRACT: We assessed the role of PGC-1α (PPARγ coactivator-1 alpha) in glucose-induced proliferation, migration, and inflammatory gene expression of vascular smooth muscle cells (VSMCs). We carried out phagocytosis studies to assess the role of PGC-1α in transdifferentiation of VSMCs by flow cytometry. We found that high glucose stimulated proliferation, migration and inflammatory gene expression of VSMCs, but overexpression of PGC-1α attenuated the effects of glucose. In addition, overexpression of PGC-1α decreased mRNA and protein level of VSMCs-related genes, and induced macrophage-related gene expression, as well as phagocytosis of VSMCs. Therefore, PGC-1α inhibited glucose-induced proliferation, migration and inflammatory gene expression of VSMCs, which are key features in the pathology of atherosclerosis. More importantly, PGC-1α transdifferentiated VSMCs to a macrophage-like state. Such transdifferentiation possibly increased the portion of VSMCs-derived foam cells in the plaque and favored plaque stability.
Journal of Biomedicine and Biotechnology 01/2012; 2012:756426. · 2.44 Impact Factor
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Xiaoqiang Qi,
François Loiseau,
Wee Lee Chan,
Yahui Yan,
Zhenquan Wei,
Lech-Gustav Milroy,
Rebecca M. Myers,
Steven V. Ley,
Randy J. Read,
Robin W. Carrell,
Aiwu Zhou
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ABSTRACT: The release of hormones from thyroxine-binding globulin (TBG) and corticosteroid-binding globulin (CBG) is regulated by movement
of the reactive center loop in and out of the β-sheet A of the molecule. To investigate how these changes are transmitted
to the hormone-binding site, we developed a sensitive assay using a synthesized thyroxine fluorophore and solved the crystal
structures of reactive loop cleaved TBG together with its complexes with thyroxine, the thyroxine fluorophores, furosemide,
and mefenamic acid. Cleavage of the reactive loop results in its complete insertion into the β-sheet A and a substantial but
incomplete decrease in binding affinity in both TBG and CBG. We show here that the direct interaction between residue Thr342 of the reactive loop and Tyr241 of the hormone binding site contributes to thyroxine binding and release following reactive loop insertion. However, a much
larger effect occurs allosterically due to stretching of the connecting loop to the top of the D helix (hD), as confirmed
in TBG with shortening of the loop by three residues, making it insensitive to the S-to-R transition. The transmission of
the changes in the hD loop to the binding pocket is seen to involve coherent movements in the s2/3B loop linked to the hD
loop by Lys243, which is, in turn, linked to the s4/5B loop, flanking the thyroxine-binding site, by Arg378. Overall, the coordinated movements of the reactive loop, hD, and the hormone binding site allow the allosteric regulation
of hormone release, as with the modulation demonstrated here in response to changes in temperature.
Journal of Biological Chemistry 05/2011; 286(18):16163-16173. · 4.77 Impact Factor
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Xiaoqiang Qi,
François Loiseau,
Wee Lee Chan,
Yahui Yan,
Zhenquan Wei,
Lech-Gustav Milroy,
Rebecca M Myers,
Steven V Ley,
Randy J Read,
Robin W Carrell,
Aiwu Zhou
[show abstract]
[hide abstract]
ABSTRACT: The release of hormones from thyroxine-binding globulin (TBG) and corticosteroid-binding globulin (CBG) is regulated by movement of the reactive center loop in and out of the β-sheet A of the molecule. To investigate how these changes are transmitted to the hormone-binding site, we developed a sensitive assay using a synthesized thyroxine fluorophore and solved the crystal structures of reactive loop cleaved TBG together with its complexes with thyroxine, the thyroxine fluorophores, furosemide, and mefenamic acid. Cleavage of the reactive loop results in its complete insertion into the β-sheet A and a substantial but incomplete decrease in binding affinity in both TBG and CBG. We show here that the direct interaction between residue Thr(342) of the reactive loop and Tyr(241) of the hormone binding site contributes to thyroxine binding and release following reactive loop insertion. However, a much larger effect occurs allosterically due to stretching of the connecting loop to the top of the D helix (hD), as confirmed in TBG with shortening of the loop by three residues, making it insensitive to the S-to-R transition. The transmission of the changes in the hD loop to the binding pocket is seen to involve coherent movements in the s2/3B loop linked to the hD loop by Lys(243), which is, in turn, linked to the s4/5B loop, flanking the thyroxine-binding site, by Arg(378). Overall, the coordinated movements of the reactive loop, hD, and the hormone binding site allow the allosteric regulation of hormone release, as with the modulation demonstrated here in response to changes in temperature.
Journal of Biological Chemistry 02/2011; 286(18):16163-73. · 4.77 Impact Factor
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ABSTRACT: The hormone-carrying serpins, thyroxine- and corticosteroid-binding globulins, TBG and CBG, provide a clear example of the way the serpin conformational mechanism can be adapted not only to give an irreversible switching-off of function but also more significantly to allow a constant dynamic modulation of activity. This is illustrated here with the demonstration that hormone release from both TBG and CBG is responsive to changes in ambient temperature and specifically to changes in body temperature. An exception to this adaptation of the serpin mechanism is seen with another family member, angiotensinogen, in which hormone release is modulated by a redox switch and is apparently independent of changes in the serpin framework.
Methods in enzymology 01/2011; 501:89-103. · 1.90 Impact Factor
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Xiaohong Jiang,
Yan Zhang,
Dongxia Hou,
Lingyun Zhu,
Wei Xu,
Li Ding, Xiaoqiang Qi,
Guoxun Sun,
Chang Liu,
Junfeng Zhang,
Ke Zen,
Yang Xiang,
Chen-Yu Zhang
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ABSTRACT: Estrogen shows a vasoprotective role through inhibiting the proliferation and migration of vascular smooth muscle cells (VSMCs). The mechanism underlying the effect of estrogen, however, is not completely understood. Here, we explored the role of peroxisome proliferator-activated receptor-gamma (PPARgamma) coactivator-1alpha (PGC-1alpha) in estrogen-mediated vasoprotection. Firstly, we showed that oleic acid (OA) decreased PGC-1alpha expression while stimulating VSMC proliferation and migration. In contrast, administration of VSMCs with 17beta-estradiol (E(2), 1 or 10nM) significantly restored OA-decreased PGC-1alpha expression, treatment with 10nM E(2) almost completely abolished OA-induced VSMC proliferation and migration. Secondly, by using PGC-1alpha siRNA, the inhibitory effect of E(2) on VSMC growth is strongly reduced via suppressing PGC-1alpha expression, indicating that E(2) may exert its role through restoring PGC-1alpha. Finally, E(2) (10nM) treatment inhibits OA-induced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, however, suppression of PGC-1alpha expression abolishes this inhibitory effect of E(2). Our findings demonstrate for the first time that in OA-stimulated rat VSMCs, treatment with E(2) (1 or 10nM) diminishes VSMC proliferation and migration via restoring OA-decreased PGC-1alpha expression. This observation offers a novel molecular basis of the vasoprotective effect of estrogen.
Molecular and Cellular Endocrinology 09/2009; 315(1-2):74-80. · 4.19 Impact Factor
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ABSTRACT: Glucagon, a peptide hormone produced by alpha-cells of Langerhans islets, is a physiological antagonist of insulin and stimulator of its secretion. In order to improve its bioactivity, we modified its structure at the C-terminus by amidation catalyzed by a recombinant amidase in bacterial cells. The human gene coding for glucagon-gly was PCR amplified using three overlapping primers and cloned together with a rat alpha-amidase gene in plasmid pMGA. Both genes were expressed under control of the strong constitutive promoter of aph and secretion signal melC1 in Streptomyces lividans. With Phenyl-Sepharose 6 FF, Q-Sepharose FF, SP-Sepharose FF chromatographies and HPLC, the peptide was purified to about 93.4% purity. The molecular mass of the peptide is 3.494 kDa as analyzed by MALDI TOF, which agrees with the theoretical mass value of the C-terminal amidated glucagon. The N-terminal sequence of the peptide was also determined, confirming its identity with human glucagon at the N-terminal part. ELISA showed that the purified peptide amide is bioactive in reacting with glucagon antibodies.
Journal of Microbiology and Biotechnology 07/2008; 18(6):1076-80. · 1.38 Impact Factor
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Yan Zhang,
Chang Liu,
Lingyun Zhu,
Xiaohong Jiang,
Xi Chen, Xiaoqiang Qi,
Xiangying Liang,
Sonia Jin,
Peixiang Zhang,
Qingguo Li,
Dongjin Wang,
Xiaofeng Liu,
Ke Zeng,
Junfeng Zhang,
Yang Xiang,
Chen-Yu Zhang
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ABSTRACT: Oleic acid (OA) stimulates vascular smooth muscle cell (VSMC) proliferation and migration. The precise mechanism is still unclear. We sought to investigate the effects of peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator-1 alpha (PGC-1alpha) on OA-induced VSMC proliferation and migration.
Oleate and palmitate, the most abundant monounsaturated fatty acid and saturated fatty acid in plasma, respectively, differently affect the mRNA and protein levels of PGC-1alpha in VSMCs. OA treatment resulted in a reduction of PGC-1alpha expression, which may be responsible for the increase in VSMC proliferation and migration caused by this fatty acid. In fact, overexpression of PGC-1alpha prevented OA-induced VSMC proliferation and migration while suppression of PGC-1alpha by siRNA enhanced the effects of OA. In contrast, palmitic acid (PA) treatment led to opposite effects. This saturated fatty acid induced PGC-1alpha expression and prevented OA-induced VSMC proliferation and migration. Mechanistic study demonstrated that the effects of PGC-1alpha on VSMC proliferation and migration result from its capacity to prevent ERK phosphorylation.
OA and PA regulate PGC-1alpha expression in VSMCs differentially. OA stimulates VSMC proliferation and migration via suppression of PGC-1alpha expression while PA reverses the effects of OA by inducing PGC-1alpha expression. Upregulation of PGC-1alpha in VSMCs provides a potential novel strategy in preventing atherosclerosis.
PLoS ONE 02/2007; 2(11):e1137. · 4.09 Impact Factor
