3-Phosphoinositide-dependent Protein Kinase 1, an Akt1 Kinase, is Involved in Dephosphorylation of Thr-308 of Akt1 in Chinese Hamster Ovary Cells

Tetsuya Yamada, Hideki Katagiri, Tomoichiro Asano, Kouichi Inukai, Masatoshi Tsuru, Tatsuhiko Kodama, Masatoshi Kikuchi, Yoshitomo Oka

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

To investigate the role of 3-phosphoinositide-dependent protein kinase 1 (PDK1) in the Akt1 phosphorylation state, wild-type (wt) PDK1 and its kinase dead (kd) mutant were expressed using an adenovirus gene transduction system in Chinese hamster ovary cells stably expressing insulin receptor. Immunoblotting using antiphosphorylated Akt1 antibody revealed Thr-308 already to be maximally phosphorylated at 1 min but completely dephosphorylated at 5 min, with insulin stimulation, whereas insulin-induced Akt1 activation was maintained even after dephosphorylation of Thr-308. Overexpression of wt-PDK1 further increased insulin-stimulated phosphorylation of Thr-308, also followed by rapid dephosphorylation. The insulin-stimulated Aktl activity was also enhanced by wt-PDK1 expression but was maintained even at 15 min. Thus, phosphorylation of Thr-308 is not essential for maintaining the Aktl activity once it has been achieved. Interestingly, the insulin-stimulated phosphorylation state of Thr-308 was maintained even at 15 min in cells expressing kd-PDK1, suggesting that kd-PDK1 has a dominant negative effect on dephosphorylation of Thr-308 of Akt1. Calyculin A, an inhibitor of PP1 and PP2A, also prolonged the insulin-stimulated phosphorylation state of Thr-308. In addition, in vitro experiments revealed PP2A, but not PP1, to dephosphorylate completely Thr-308 of Akt1. These findings suggest that a novel pathway involving dephosphorylation of Akt1 at Thr-308 by a phosphatase, possibly PP2A, originally, identified as is regulated downstream from PDK1, an Akt1 kinase.

Original languageEnglish
Pages (from-to)5339-5345
Number of pages7
JournalJournal of Biological Chemistry
Volume276
Issue number7
DOIs
Publication statusPublished - 2001 Feb 16

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of '3-Phosphoinositide-dependent Protein Kinase 1, an Akt1 Kinase, is Involved in Dephosphorylation of Thr-308 of Akt1 in Chinese Hamster Ovary Cells'. Together they form a unique fingerprint.

Cite this