title: Overexpression of Reg3alpha increases cell growth and the levels of cyclin D1 and CDK4 in insulinoma cells.
abstract: Regenerating gene (Reg) family protein Reg3alpha is normally expressed in pancreatic acinar and endocrine cells. In order to explore its effect on islet beta-cell replication, insulinoma MIN6 cells were stably transfected with murine Reg3alpha cDNA. Determined using real-time PCR and Western blots, the levels of Reg3alpha mRNA and protein in Reg3alpha-transfected clones were increased 10- and 6-fold, respectively. Western blots also revealed that the protein was released into the culture medium, consistent with an endocrine effect. In MTT cell proliferation assay, Reg3alpha-overexpressing cells exhibited a 2-fold increase in the rate of cell growth. In order to investigate the intracellular mechanism, we studied cell cycle regulatory proteins. In Reg3alpha-expressing cells, we detected 2.2- and 2.5-fold increased levels of cyclin D1 and CDK4, respectively, which paralleled a 1.8-fold increase in the rate of Akt phosphorylation. It is established that beta-cell replication is associated with increased cyclin D1 and CDK4 levels; deficiency in CDK4 or cyclin D2 results in reduced beta-cell mass and diabetes. Our results suggest that Reg3alpha stimulates beta-cell replication, by activating Akt kinase and increasing the levels of cyclin D1/CDK4.
authors.affiliation: School of Medicine, The First Affiliated Hospital, Xi'an Jiao Tong University, Xi'an, Shaanxi, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
authors.forename: Kristine
authors.initials: K
authors.lastname: De Jesus
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Shin
authors.initials: S
authors.lastname: Takasawa
authors.forename: Bingyin
authors.initials: B
authors.lastname: Shi
authors.forename: Coimbatore B
authors.initials: CB
authors.lastname: Srikant
authors.forename: Jun-Li
authors.initials: JL
authors.lastname: Liu