Ghrelin regulates cell cycle-related gene expression in cultured hippocampal neural stem cells.
We have previously demonstrated that ghrelin stimulates the cellular proliferation of cultured adult rat hippocampal neural stem cells (NSCs). However, little is known about the molecular mechanisms by which ghrelin regulates cell cycle progression. The purpose of this study was to investigate the potential effects of ghrelin on cell cycle regulatory molecules in cultured hippocampal NSCs. Ghrelin treatment increased proliferation assessed by CCK-8 proliferation assay. The expression levels of proliferating cell nuclear antigen and cell division control 2, well-known cell-proliferating markers, were also increased by ghrelin. Fluorescence-activated cell sorting analysis revealed that ghrelin promoted progression of cell cycle from G0/G1 to S phase, whereas this progression was attenuated by the pretreatment with specific inhibitors of MEK/extracellular signal-regulated kinase 1/2, phosphoinositide 3-kinase/Akt, mammalian target of rapamycin, and janus kinase 2/signal transducer and activator of transcription 3. Ghrelin-induced proliferative effect was associated with increased expression of E2F1 transcription factor in the nucleus, as determined by Western blotting and immunofluorescence. We also found that ghrelin caused an increase in protein levels of positive regulators of cell cycle, such as cyclin A and cyclin-dependent kinase (CDK) 2. Moreover, p27(KIP1) and p57(KIP2) protein levels were reduced when cell were exposed to ghrelin, suggesting downregulation of CDK inhibitors may contribute to proliferative effect of ghrelin. Our data suggest that ghrelin targets both cell cycle positive and negative regulators to stimulate proliferation of cultured hippocampal NSCs.
Department of Core Research LaboratoryClinical Research Institute, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
Hyunju
H
Chung
Department of Pharmacology and Medical Research Center for Bioreaction to ROS and Biomedical Science InstituteSchool of Medicine, Kyung Hee University, Seoul, Korea sjpark@khu.ac.kr.
Seungjoon
S
Park
D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D019925:Cyclin A / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005786:Gene Expression Regulation; D054439:Ghrelin / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D058953:Neural Stem Cells / Q000378:metabolism*; D055495:Neurogenesis; D011916:Rats, Inbred F344
C493962:Cdkn1b protein, rat; D019925:Cyclin A; D050761:Cyclin-Dependent Kinase Inhibitor p57; D050687:E2F1 Transcription Factor; C493755:E2f1 protein, rat; D054439:Ghrelin; D050760:Cyclin-Dependent Kinase Inhibitor p27; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2
cell cycle; ghrelin; hippocampus; progenitor; proliferation