Raf kinase inhibitory protein inhibits beta-cell proliferation.
Surgery
; 136(3): 708-15, 2004 Sep.
Article
em En
| MEDLINE
| ID: mdl-15349122
ABSTRACT
BACKGROUND:
Raf-1 kinase inhibitory protein (RKIP) was recently identified as a physiologic endogenous inhibitor of the extracellular signal-regulated kinase (ERK) pathway. The expression and role of RKIP within the pancreas are unknown.METHODS:
RKIP expression in normal pancreas and human insulinomas was examined by using paraffin-embedded sections. Co-localization of RKIP within islet cell subtypes was performed by using double immunofluorescence staining with antibodies directed toward RKIP and endocrine markers. To examine the role of RKIP in beta-cell proliferation, stable expression of sense (ss) and antisense (as) RKIP was established in HIT-T15 beta cells. The effect of RKIP on the ERK-signaling pathway in beta cells was determined by Western blotting with the use of phospho-specific antibodies directed against mitogen-activated protein kinase kinase (MEK) and ERK. The role of RKIP in beta-cell proliferation was assessed by using MTS assay and FACS analysis.RESULTS:
RKIP was expressed only within pancreatic islet cells. Immunofluorescent double staining revealed that RKIP was expressed in most beta cells and a subset of pancreatic polypeptide-expressing cells. Based on the known function of RKIP, we hypothesized that RKIP expression would be downregulated in insulinomas 8 of 9 human insulinomas demonstrated no RKIP staining, with decreased expression in 1 of 9 insulinomas. Studies using asRKIP and ssRKIP demonstrated that RKIP blocked activation of MEK and ERK by Raf-1 in beta cells. We also showed that RKIP inhibited beta-cell proliferation by altering cell cycle distribution, rather than by promoting apoptosis.CONCLUSIONS:
RKIP is important in beta-cell proliferation, and its downregulation may play a role in islet neoplasia.
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Base de dados:
MEDLINE
Assunto principal:
Divisão Celular
/
Ilhotas Pancreáticas
/
Proteína de Ligação a Androgênios
/
Insulinoma
Limite:
Animals
/
Humans
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article