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Articles by Thomas L. Clemens
Total Records ( 2 ) for Thomas L. Clemens
  Chang Hyun Byon , Amjad Javed , Qun Dai , John C. Kappes , Thomas L. Clemens , Victor M. Darley-Usmar , Jay M. McDonald and Yabing Chen
  Oxidative stress plays a critical role in the pathogenesis of atherosclerosis including the formation of lipid laden macrophages and the development of inflammation. However, oxidative stress-induced molecular signaling that regulates the development of vascular calcification has not been investigated in depth. Osteogenic differentiation of vascular smooth muscle cells (VSMC) is critical in the development of calcification in atherosclerotic lesions. An important contributor to oxidative stress in atherosclerotic lesions is the formation of hydrogen peroxide from diverse sources in vascular cells. In this study we defined molecular signaling that is operative in the H2O2-induced VSMC calcification. We found that H2O2 promotes a phenotypic switch of VSMC from contractile to osteogenic phenotype. This response was associated with an increased expression and transactivity of Runx2, a key transcription factor for osteogenic differentiation. The essential role of Runx2 in oxidative stress-induced VSMC calcification was further confirmed by Runx2 depletion and overexpression. Inhibition of Runx2 using short hairpin RNA blocked VSMC calcification, and adenovirus-mediated overexpression of Runx2 alone induced VSMC calcification. Inhibition of H2O2-activated AKT signaling blocked VSMC calcification and Runx2 induction concurrently. This blockage did not cause VSMC apoptosis. Taken together, our data demonstrate a critical role for AKT-mediated induction of Runx2 in oxidative stress-induced VSMC calcification.
  Yi Tang , Zhongyu Liu , Ling Zhao , Thomas L. Clemens and Xu Cao
  β-Catenin functions both as an adherens junction adhesion protein and as an essential mediator of the canonical Wnt signaling pathway. Wnts stabilize β-catenin and promote its accumulation in the nucleus, where it regulates transcription of the target genes. Here we show that Smad7 promotes cell-cell adhesion by stabilizing β-catenin and consequently increases the β-catenin-E-cadherin complex level at the plasma membrane. A Smad7-Axin interaction disassociates GSK-3β and β-catenin from Axin, as well as inhibits the recruitment of Smurf2, an E3 ligase, to β-catenin, thus protecting β-catenin from phosphorylation and degradation. Smad7 increases the stabilized β-catenin to form a complex with E-cadherin and stabilizes the E-cadherin-β-catenin complex. Thereby, rather than being translocated to the nucleus for regulating the target gene transcription, Smad7-stabilized-β-catenin is shunted to the E-cadherin complex to modulate cell-cell adhesion.
 
 
 
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