Regulation of apoptosis by the Ft1 protein, a new modulator of protein kinase B/Akt.
The serine/threonine kinase protein kinase B (PKB)/Akt plays a central role in many cellular processes, including cell growth, glucose metabolism, and apoptosis. However, the identification and validation of novel regulators or effectors is key to future advances in understanding the multiple functions of PKB. Here we report the identification of a novel PKB binding protein, called Ft1, from a cDNA library screen using a green fluorescent protein-based protein-fragment complementation assay. We show that the Ft1 protein interacts directly with PKB, enhancing the phosphorylation of both of its regulatory sites by promoting its interaction with the upstream kinase PDK1. Further, the modulation of PKB activity by Ft1 has a strong effect on the apoptosis susceptibility of T lymphocytes treated with glucocorticoids. We demonstrate that this phenomenon occurs via a PDK1/PKB/GSK3/NF-ATc signaling cascade that controls the production of the proapoptotic hormone Fas ligand. The wide distribution of Ft1 in adult tissues suggests that it could be a general regulator of PKB activity in the control of differentiation, proliferation, and apoptosis in many cell types.
Pubmed ID: 14749367 RIS Download
3-Phosphoinositide-Dependent Protein Kinases | Adaptor Proteins, Signal Transducing | Amino Acid Sequence | Animals | Apoptosis | Apoptosis Regulatory Proteins | Cell Line | DNA-Binding Proteins | Dexamethasone | Enzyme Activation | Fas Ligand Protein | Humans | Jurkat Cells | Membrane Glycoproteins | Molecular Sequence Data | NFATC Transcription Factors | Nuclear Proteins | Phosphorylation | Protein Binding | Protein Structure, Tertiary | Protein-Serine-Threonine Kinases | Proteins | Proto-Oncogene Proteins | Proto-Oncogene Proteins c-akt | T-Lymphocytes | Transcription Factors