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Articles by L Xia
Total Records ( 6 ) for L Xia
  L Xia , M Zhou , T. F Kalhorn , H. T. B Ho and J. Wang

Plasma membrane monoamine transporter (PMAT) is a novel polyspecific organic cation transporter that transports organic cations and the purine nucleoside, adenosine. PMAT is expressed in the kidney, but the specific localization and function of this transporter in renal cells are unclear. In this study, we developed a polyclonal antibody toward a 14-amino acid sequence in the last intracellular loop of PMAT and determined the precise cellular localization of PMAT in human and rat kidneys. Surprisingly, we found that the PMAT protein was predominantly expressed in the glomerulus with minimal expression in tubular cells. Within the glomerulus, dual-color immunofluorescence labeling showed that the PMAT protein was specifically localized to the visceral glomerular epithelial cells, i.e., podocytes. There was no significant PMAT immunoreactivity in mesangial or glomerular endothelial cells. We further showed that puromycin aminonucleoside (PAN), a classic podocyte toxin that induces massive proteinuria and severe glomerulopathy, is transported by PMAT. Expression of PMAT in Madin-Darby canine kidney cells significantly increased cell sensitivity to PAN. Decynium 22, a potent PMAT inhibitor, abolished PAN toxicity in PMAT-expressing cells. Together, our data suggest that PMAT is specifically expressed in podocytes and may play an important role in PAN-induced kidney injury.

  X. Y Zhao , T. T Chen , L Xia , M Guo , Y Xu , F Yue , Y Jiang , G. Q Chen and K. W. Zhao

The expression of galectin-1, one of the most important lectins participating in the malignant tumor development, has been shown to be regulated by hypoxia, but its exact mechanism remains elusive. Here, we find that ectopically expressed hypoxia-inducible factor (HIF) 1 protein, an oxygen-sensitive subunit of HIF-1 that is a master factor for cellular response to hypoxia, significantly increases galectin-1 expression in both messenger RNA and protein levels in all four colorectal cancer (CRC) cell lines tested. However, hypoxia-induced galectin-1 expression cannot be seen in sentrin/SUMO-specific protease 1 homozygous-null mouse embryonic fibroblasts that fail to accumulate HIF-1 protein. Furthermore, silence of HIF-1 or HIF-1β expression by specific short hairpin RNAs (shRNAs) antagonizes hypoxia-induced galectin-1 expression. All these results propose that galectin-1 is a direct target of transcriptional factor HIF-1. Applying luciferase reporter assay and chromatin immunoprecipitation, we identify that two hypoxia-responsive elements located at –441 to –423 bp upstream to transcriptional start site of galectin-1 gene are essential for HIF-1-mediated galectin-1 expression. Finally, the knockdown of galectin-1 by its specific shRNA can significantly reduce hypoxia-induced invasion and migration of CRC cell line, and the ectopic expression of galectin-1 can remarkably restore invasion and migration abilities of HIF-1-knocked SW620 cells, proposing that galectin-1 mediates the HIF-1-induced migration and invasion of CRC cells during hypoxia. Taken together, our results shed new light for understanding mechanism for hypoxia/HIF-1-mediated migration/invasion of CRC cells.

  L Xia , Y Zhu , J Yang , J Ye and Z. Gu

As power dissipation causes thermal issues in cooling costs, lifetime and reliability, thermal management has become an important issue in today's OS and processor design. Early OS-level thermal management schemes were proposed and evaluated mainly with simulators or analytical models. In this paper, we implement a thermal-aware round-robin scheduling algorithm in the Linux kernel, and compare its performance with the ‘Heat-and-Run’ algorithm and the default Linux baseline scheduler on an Intel Core 2 Duo processor using representative benchmarks from SPEC2000, MiBench and NetBench. Our results indicate that the current Linux scheduler can easily be enhanced with thermal-awareness to show improved performance in terms of both the on-chip temperature condition and application throughput.

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