title: Overexpression of protein tyrosine phosphatase 1B impairs glucose-stimulated insulin secretion in INS-1 cells.
abstract: BACKGROUND
  Protein tyrosine phosphatase 1B (PTP1B) has been implicated as a negative regulator of insulin signaling. We reported previously that impaired glucose-stimulated insulin secretion (GSIS) in rats fed high-fat diet was associated with higher PTP1B protein levels in islets. The aim of the present study was to investigate the effect of increasing PTP1B on insulin secretion in β-cells.
  
  
  METHODS
  INS-1 cells were transduced with recombinant adenoviruses containing human PTP1B cDNA (Ad-PTP1B), or no exogenous gene (Ad-ctrl). The expression levels of PTP1B, insulin receptor (IR), insulin receptor substrate-1(IRS-1), glucokinase and glucose transporter-2 were evaluated by Western blot. Then insulin-stimulated IR and IRS tyrosine phosphorylation, and Akt pathway activation were measured. GSIS was also performed to evaluate INS-1 cells function.
  
  
  RESULTS
  PTP1B expression level was increased 5.9-fold at 48h post-transduction. The overexpression of PTP1B had no effect on proliferation and apoptosis of INS-1 cells. Compared with control cells, INS-1 cells overexpressing PTP1B showed decrease in insulin-stimulated tyrosine phosphorylation of the insulin receptor (IR) and insulin receptor substrate-1(IRS-1) by 56.4% and 53.1%, respectively. In addition, Akt phosphorylation was reduced 59.6%. Moreover, in Ad-PTP1B-transduced cells, 16.7mM glucose caused a 1.6±0.2 fold increase (vs. 3.9±0.7 fold in nontransduced cells) in insulin secretion relative to secretion at 2.8mM glucose. Further analysis determined that overexpression of PTP1B induced down-regulated expression of glucokinase (42%) and glucose transporter-2 (48%).
  
  
  CONCLUSIONS
  Our findings suggested that overexpression of PTP1B can inhibit GSIS in INS-1 cells through negatively regulating insulin signaling.
authors.affiliation: Department of Endocrinology, School of Medicine, Nanjing University/Southern Medical University, Jinling Hospital, Nanjing, China - shaojiaq@hotmail.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Lu
authors.forename: Ping
authors.initials: P
authors.lastname: Gu
authors.forename: Yixin
authors.initials: Y
authors.lastname: Xu
authors.forename: Xiaozhen
authors.initials: X
authors.lastname: Ye
authors.forename: Yingzhijie
authors.initials: Y
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: DU
authors.forename: Jiaqing
authors.initials: J
authors.lastname: Shao
mesh_terms: D000818:Animals; D002460:Cell Line; D005941:Glucokinase / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D051273:Glucose Transporter Type 2 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D008297:Male; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics* / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis; D051381:Rats
chemical_list: D051273:Glucose Transporter Type 2; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D005941:Glucokinase; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; C516610:Ptpn1 protein, rat; D005947:Glucose