Expression Of NDRG2in Pancreatic β Cells And Its Influence On Insulin Synthesis

ObjectiveNDRG2is one of the important members of N-Myc down-stream regulated gene family,the gene family was constituted by the NDRG1,2,3and the NDRG4. The presentstudies have found that NDRG family is related to cell proliferation, differentiation, stressreaction and hormone relatd metabolic regulation, etc. Human NDRG2was discoveredand cloned firstly by our research group, which had been included in GenBank namedAF159092. It shared95%identity with mouse NDRG2. Our previous findings hadsuggested that NDRG2is mainly expressed in the cytoplasm of pancreatic cells, whichshowed similarity with that of insulin. In order to further verify the relationship betweenNDRG2and insulin, we studied the expression and localization of NDRG2in insulinomacell lines and pancreatic tissues, so as to further elucidate its biological function and mechanism of action.Methodsâ‘ Indirect immunofluorescence and immunohistochemistry were used to define thedistribution and localization of NDRG2in four kinds of islet cell lines (MIN6, TC3, TC6, INS-1) and mouse pancreatic tissue;â‘¡Western blotting and RT-PCR were used todetect the protein and mRNA expression level of NDRG2in four kinds of islet cell lines(MIN6, TC3, TC6, INS-1);â‘¢NDRG2RNAi method was used to observe the changesof insulin mRNA expression between the control group and the siRNA down-regulatedNDRG2group in INS-1and MIN6cells;â‘£Indirect immunofluorescence assay was usedto observe the expression and distribution variation trend of NDRG2, PDX-1between thecontrol group and the siRNA down-regulated NDRG2group in MIN6cell.Resultsâ‘ NDRG2and insulin positive reacitivity co-localized in the cytoplasm of pancreatic cells.â‘¡NDRG2is expressed in four kinds of pancreatic cell lines, which have therelatively high expression in INS-1and MIN6cells.â‘¢In MIN6and INS-1cells,afterdown-regulate NDRG2, real-time quantitative PCR to detect insulin mRNA levels, andfound that NDRG2negatively correlate with insulin mRNA expression.â‘£In MIN6cells,down-regulating NDRG2failed to affect the expression and activity of PDX-1, thefluorescent intensity and subcellular localization of PDX-1did not change significantly.Conclusionsâ‘ NDRG2mainly localized in the cytoplasm of pancreatic cells. The distribution ofNDRG2shows similarity of insulin in the four cell lines and pancreatic tissues. It suggeststhat NDRG2plays an important role in the biological function of pancreatic cells.â‘¡Infour kinds pancreatic cell lines, at the level of protein and mRNA were detected NDRG2expression, which expressed in INS-1and MIN6cells are relatively high. Speculated thatthe expression may be associated with the cell itself.â‘¢In the pancreatic cell line INS-1and MIN6,down-regulating NDRG2found that there exists negative correlation betweenNDRG2and INSULIN mRNA expression, which suggests that NDRG2may act as thesubstrates of protein kinase Akt to participate in insulin signaling pathway. â‘£Down-regulating NDRG2in MIN6cell has no effect on the expression and distributionof PDX-1.Prompt that the correlation between NDRG2and INSULIN may not depend onPDX-1.