Functional Investigation Of NDRG2 In Pancreatic Islet

Human NDRG2 was firstly cloned and reported by our lab (GenBank Number: AF 159092). Human NDRG2 is located at chromosome 14q11.2 and encodes a protein about 41 KD which is composed of 357 amino acids.When we studied the expression profile of Ndrg2 by immunohistochemistry,we found that Ndrg2 specially expressed in pancreatic islets. The result supported that Ndrg2 might be related to the function of B cells,because 60%-80% of islet cells are B cells which can synthesize and secret insulin,so we aimed to address the relations between Ndrg2 expression and insulin secretion of B cells.To explore the function of NDRG2,we analyzed the function of NDRG2 by comparative genomics.We found that INSM1 and PAX6 which specifically expressed in islets might regulate the expression of NDRG2.This might account for specifical expression of NDRG2 in islets. Additionally ,MESK2,which is a homologous protein of NDRG2 in Drosophila melanogaster,act as a suppressor of HNT whose homologous protein is RREB1. RREB1 could enhance the transcription of insulin through combining to Beta2/NeuroD1. According to this,we speculated that NDRG2 had the ability to negatively regulate the expression of insulin.To define whether Ndrg2 can regulate the expression of insulin,we stimulated ?TC3 cells with glucose and palmitate,then we examined the relations between insulin secretion and Ndrg2 expression.The results shown that insulin mRNA decreased while Ndrg2 mRNA increased.Furthermore,overexpression of Ndrg2 leaded to decrease of insulin secretion in pancreatic B cells.However,whether the mechanism accounting for this observation is what described before need to be further determined.We also conducted an experiment in vivo to explore the relations between Ndrg2 and insulin secretion. we collected serum sample and determined the insulin level by radioimmunity after the mouce intaking glucose orally, then we examined expression patterns of Ndrg2 in islets by immunohistochemistry. The significant correlations between Ndrg2 and insulin secretion was not observed.In addition,to investigate the function of Miz1,we designed and constructed a Miz1 siRNA expression vector. The pSilencer? 3.1-H1 neo-Miz1 plasmids were transiently transfected into HeLa cells.RT-PCR and Western blot were used to detect expression of Miz1.The cell growth was accessed by MTT assay.we found the plasmids targeting Miz1 inhibited the expression of Miz1 and the growth of HeLa cells transfected with pSilencer? 3.1-H1 neo-Miz1 was inhibited more significantly in response to Adriamycin compared with that of the control goups.Therefore, the siRNA targeting Miz1 inhibited the expression of Miz1 in HeLa cells and enhanced sensitivity of HeLa cells to Adriamycin.