title: Glucose modulates Pax6 expression through the JNK/p38 MAP kinase pathway in pancreatic beta-cells.
abstract: OBJECTIVE
  The paired and homeodomain-containing transcription factor, paired box 6 (Pax6), has shown to play pivotal roles in beta-cell function, including cell survival, insulin biosynthesis and secretion. The present study investigates the signaling events that regulate the modulation of Pax6 expression by glucose and the role of this modulation in cell survival in rat insulinoma-1E (INS-1E) cells.
  
  
  METHODS
  INS-1E cells were incubated on 1mM (low) or 25 mM (high) glucose overnight. To elucidate the signaling pathways that regulate Pax6 expression, we utilized specific inhibitors. The siRNA transfection of Pax6 into INS-1E cells was performed by electroporation. The mRNA and protein levels were determined by real-time PCR and Western blotting, respectively.
  
  
  RESULTS
  We found that the mRNA and protein levels of Pax6 were reduced by approximately 4-fold in high, compared to low, glucose-treated cells. Staurosporine, the c-Jun N-terminal kinase (JNK) inhibitor SP600125 and the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 significantly increased Pax6 levels in high glucose-treated INS-1E cells compared to their respective controls. However, neither calcium ionophore nor the extracellular signal-regulated kinase (ERK) inhibitor U0126 resulted in any alteration in Pax6 protein expression. Further, a siRNA-mediated knockdown of Pax6 significantly decreased the expression of tumor-suppressor phosphatase with tensin homology (PTEN) while increasing cell viability in low glucose-treated INS-1E cells.
  
  
  CONCLUSIONS
  This study addresses the signaling events that regulate the glucose-dependent expression of Pax6 and the role of these events in cell survival in pancreatic beta cells.
authors: Department of Biochemistry, Bharathidasan University, Tiruchirappalli 620 024, India.
authors: Sivasangari
authors: S
authors: Balakrishnan
authors: Department of Biochemistry, Bharathidasan University, Tiruchirappalli 620 024, India.
authors: Mohanraj
authors: M
authors: Sadasivam
authors: Department of Biochemistry, Bharathidasan University, Tiruchirappalli 620 024, India.
authors: Arun
authors: A
authors: Kannan
authors: Department of Biochemistry, Bharathidasan University, Tiruchirappalli 620 024, India.
authors: Antojenifer
authors: A
authors: Panneerselvam
authors: Department of Biochemistry, Bharathidasan University, Tiruchirappalli 620 024, India. Electronic address: prahalath@gmail.com.
authors: Chidambaram
authors: C
authors: Prahalathan
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D015536:Down-Regulation; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007340:Insulinoma / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System; D000071841:PAX6 Transcription Factor; D051059:PTEN Phosphohydrolase / Q000235:genetics; D051761:Paired Box Transcription Factors / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605733:Pax6 protein, rat; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D051059:PTEN Phosphohydrolase; C487216:Pten protein, rat; D005947:Glucose
keywords: Beta-cells; Glucose; JNK; PTEN; Pax6; p38 MAP kinase