Signaling pathways implicated in the stimulation of beta-cell proliferation by extracellular matrix

Mol Endocrinol. 2009 Aug;23(8):1264-71. doi: 10.1210/me.2009-0008. Epub 2009 May 14.

Abstract

Laminin-5-rich extracellular matrix derived from 804G cells (804G-ECM) induces spreading, improves glucose-stimulated insulin secretion, and increases survival and proliferation of rat pancreatic beta-cells. The aim of the study was to determine growth signaling pathways activated by ECM with a particular focus on Ca(2+)-dependent transcription factors. 804G-ECM increased rat beta-cell proliferation, and this stimulation was glucose and Ca(2+) dependent. NF-kappaB nuclear translocation as well as IkappaBalpha gene expression were also Ca(2+) dependent. Inhibition of NF-kappaB almost completely blocked 804G-ECM-stimulated beta-cell proliferation as did the soluble IL-1 receptor antagonist IL-1Ra. 804G-ECM-induced proliferation was also blocked by cyclosporin A and the VIVIT peptide, suggesting involvement of nuclear factor of activated T cells (NFAT)/calcineurin. Use of selective inhibitors further implicated other pathways in this process. Inhibition of phosphatidylinositol 3-kinase and protein kinase A both prevented beta-cell replication stimulated by 804G-ECM. Conversely, inhibition of MAPK, c-Jun N-terminal kinase, p38, and glycogen synthase kinase-3beta increased beta-cell proliferation on 804G-ECM. Our results suggest that Ca(2+) entry, which is necessary for increased beta-cell proliferation on 804G-ECM, is also involved in 804G-ECM-induced NF-kappaB activity. It is proposed that increased cytosolic Ca(2+) leads to activation of the transcription factors NFAT and NF-kappaB that in turn increase beta-cell proliferation. Activation of phosphatidylinositol 3-kinase by 804G-ECM also increases proliferation possibly by synergistic coactivation of NFAT via inhibition of glycogen synthase kinase-3beta, whereas IL-1beta may amplify the process by feed-forward activation of NF-kappaB. Conversely, inhibition of the MAPK pathway increased beta-cell proliferation, indicating a counterregulatory restraining role for this signaling pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Cell Adhesion Molecules / chemistry
  • Cell Proliferation
  • Extracellular Matrix / metabolism*
  • Glycogen Synthase Kinase 3 / metabolism
  • Glycogen Synthase Kinase 3 beta
  • Insulin-Secreting Cells / cytology*
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • MAP Kinase Signaling System
  • Male
  • NF-kappa B / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Rats
  • Rats, Wistar
  • Signal Transduction*
  • Transcription Factors / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Cell Adhesion Molecules
  • NF-kappa B
  • Transcription Factors
  • kalinin
  • Phosphatidylinositol 3-Kinases
  • Glycogen Synthase Kinase 3 beta
  • Gsk3b protein, rat
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • Glycogen Synthase Kinase 3
  • Calcium