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Articles by E Zhang
Total Records ( 2 ) for E Zhang
  L Sun , X Shen , Y Liu , G Zhang , J Wei , H Zhang , E Zhang and F. Ma
 

The mechanism underlining human papillomaviruses (HPVs) causing cancer has been studied extensively, and it was concluded that the high-risk HPVs' E6 targeted and degraded tumor suppressor protein p53, leading to infected cells malignant transformation. In contrast, the low-risk HPVs only cause proliferative but non-invasive lesions of infected epithelia. Therefore, we hypothesized that low-risk HPVs' E6 might interact with p53 in a different pattern. We used a mammalian green fluorescent protein (GFP) expression system to express HPV-18E6 and HPV-6E6 fusion proteins in wild-type (wt) p53 cell lines, 293T and HEK293 cells, to investigate the traffic and location of E6s and p53. The results indicated GFP-18E6 was mainly expressed in nucleus, whereas GFP-6E6 was expressed exclusively in cytoplasm. Endogenous wt p53 was shown to be localized in the nuclei of cells transfected with GFP-18E6. Interestingly, for the first time, we observed that p53 was trapped in the cytoplasm and never translocated into the cell nuclei transfected with GFP-6E6. In conclusion, HPV-6E6 was responsible for the cytoplasmic localization of p53. Therefore, our experiments provide a new insight into the pathogenesis of HPV.

  T. M Reinbothe , R Ivarsson , D. Q Li , O Niazi , X Jing , E Zhang , L Stenson , U Bryborn and E. Renstrom
 

Nicotinamide adenine dinucleotide phosphate (NADPH) enhances Ca2+-induced exocytosis in pancreatic β-cells, an effect suggested to involve the cytosolic redox protein glutaredoxin-1 (GRX-1). We here detail the role of GRX-1 in NADPH-stimulated β-cell exocytosis and glucose-stimulated insulin secretion. Silencing of GRX-1 by RNA interference reduced glucose-stimulated insulin secretion in both clonal INS-1 832/13 cells and primary rat islets. GRX-1 silencing did not affect cell viability or the intracellular redox environment, suggesting that GRX-1 regulates the exocytotic machinery by a local action. By contrast, knockdown of the related protein thioredoxin-1 (TRX-1) was ineffective. Confocal immunocytochemistry revealed that GRX-1 locates to the cell periphery, whereas TRX-1 expression is uniform. These data suggest that the distinct subcellular localizations of TRX-1 and GRX-1 result in differences in substrate specificities and actions on insulin secretion. Single-cell exocytosis was likewise suppressed by GRX-1 knockdown in both rat β-cells and clonal 832/13 cells, whereas after overexpression exocytosis increased by approximately 40%. Intracellular addition of NADPH (0.1 mm) stimulated Ca2+-evoked exocytosis in both cell types. Interestingly, the stimulatory action of NADPH on the exocytotic machinery coincided with an approximately 30% inhibition in whole-cell Ca2+ currents. After GRX-1 silencing, NADPH failed to amplify insulin release but still inhibited Ca2+ currents in 832/13 cells. In conclusion, NADPH stimulates the exocytotic machinery in pancreatic β-cells. This effect is mediated by the NADPH acceptor protein GRX-1 by a local redox reaction that accelerates β-cell exocytosis and, in turn, insulin secretion.

 
 
 
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