Type

Journal Article

Authors

J H M Prehn
M M Byrne
J J Nolan
C Bonner
H Wobser

Subjects

Biochemistry

Topics
time factors metabolism phosphatidylinositol 3 kinases pharmacology proto oncogene proteins c akt animals protein kinase inhibitors wortmannin down regulation apoptosis rats hepatocyte nuclear factor 1 alpha androstadienes drug effects genetics phosphoserine antagonists inhibitors insulinoma cell line tumor cell proliferation pathology

Downregulation of protein kinase B/Akt-1 mediates INS-1 insulinoma cell apoptosis induced by dominant-negative suppression of hepatocyte nuclear factor-1alpha function. (2005)

Abstract Inactivating mutations in Tcf1, which encodes the transcription factor hepatocyte nuclear factor (HNF)-1alpha, cause maturity-onset diabetes of the young-3. We have previously shown that a dominant-negative mutant (DN-HNF-1alpha) renders INS-1 insulinoma cells sensitive to the mitochondrial apoptosis pathway, but the underlying alterations in signal transduction remain unknown. Using a reverse tetracycline-dependent transactivator system, DN-HNF-1alpha-induced apoptosis was assessed by immunoblotting and caspase assays. Alterations in AKT1 kinase/protein kinase B (AKT1) survival signalling during DN-HNF-1alpha-induced apoptosis were investigated by phospho-specific immunodetection and transient transfection experiments. Induction of DN-HNF-1alpha caused significant changes in the activation-specific phosphorylation status of AKT1 that were preceded by a downregulation of Ins1 gene transcription. Phosphorylation of AKT1 at Ser473 was dramatically reduced after 36 to 48 h of DN-HNF-1alpha induction and coincided with maximal apoptosis activation. Overexpression of a constitutively active mutant of Akt1 rescued INS-1 cells from DN-HNF-1alpha-induced apoptosis, while ectopic expression of a dominant-negative mutant mimicked the effect of DN-HNF-1alpha on apoptosis activation. Pharmacological suppression of growth factor survival signalling through administration of the phosphatidylinositol-3 kinase (PI-3K) inhibitor wortmannin accelerated the induction of apoptosis by DN-HNF-1alpha. These data suggest that a decrease in PI-3K/AKT1 survival signalling mediates DN-HNF-1alpha-induced apoptosis in insulin-secreting cells.
Collections Ireland -> Royal College of Surgeons in Ireland -> PubMed

Full list of authors on original publication

J H M Prehn, M M Byrne, J J Nolan, C Bonner, H Wobser

Experts in our system

1
Jochen H M Prehn
Royal College of Surgeons in Ireland
Total Publications: 206