title: Signaling pathways implicated in the stimulation of beta-cell proliferation by extracellular matrix.
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.
authors.affiliation: Department of Genetic Medicine and Development, University of Geneva University Medical Center, Geneva, Switzerland. geraldine.parnaud@.unige.ch
authors.forename: Géraldine
authors.initials: G
authors.lastname: Parnaud
authors.forename: Eva
authors.initials: E
authors.lastname: Hammar
authors.forename: Pascale
authors.initials: P
authors.lastname: Ribaux
authors.forename: Marc Y
authors.initials: MY
authors.lastname: Donath
authors.forename: Thierry
authors.initials: T
authors.lastname: Berney
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000737:chemistry; D049109:Cell Proliferation; D005109:Extracellular Matrix / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D050417:Insulin-Secreting Cells / Q000166:cytology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000097794:Kalinin
chemical_list: D002118:Calcium; D015815:Cell Adhesion Molecules; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D048031:JNK Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D019869:Phosphatidylinositol 3-Kinases; D014157:Transcription Factors; D048051:p38 Mitogen-Activated Protein Kinases; D000097794:Kalinin; C000605508:Gsk3b protein, rat