Current Biology
Volume 9, Issue 8, 22 April 1999, Pages 393-404
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Research Paper
PDK1 acquires PDK2 activity in the presence of a synthetic peptide derived from the carboxyl terminus of PRK2

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Abstract

Background: Protein kinase B (PKB) is activated by phosphorylation of Thr308 and of Ser473. Thr308 is phosphorylated by the 3-phosphoinositide-dependent protein kinase-1 (PDK1) but the identity of the kinase that phosphorylates Ser473 (provisionally termed PDK2) is unknown.

Results: The kinase domain of PDK1 interacts with a region of protein kinase C-related kinase-2 (PRK2), termed the PDK1-interacting fragment (PIF). PIF is situated carboxy-terminal to the kinase domain of PRK2, and contains a consensus motif for phosphorylation by PDK2 similar to that found in PKBα, except that the residue equivalent to Ser473 is aspartic acid. Mutation of any of the conserved residues in the PDK2 motif of PIF prevented interaction of PIF with PDK1. Remarkably, interaction of PDK1 with PIF, or with a synthetic peptide encompassing the PDK2 consensus sequence of PIF, converted PDK1 from an enzyme that could phosphorylate only Thr308 of PKBα to one that phosphorylates both Thr308 and Ser473 of PKBα in a manner dependent on phosphatidylinositol (3,4,5) trisphosphate (PtdIns(3,4,5)P3). Furthermore, the interaction of PIF with PDK1 converted the PDK1 from a form that is not directly activated by PtdIns(3,4,5)P3 to a form that is activated threefold by PtdIns(3,4,5)P3. We have partially purified a kinase from brain extract that phosphorylates Ser473 of PKBα in a PtdIns(3,4,5)P3-dependent manner and that is immunoprecipitated with PDK1 antibodies.

Conclusions: PDK1 and PDK2 might be the same enzyme, the substrate specificity and activity of PDK1 being regulated through its interaction with another protein(s). PRK2 is a probable substrate for PDK1.

Cited by (0)

A Balendran, A Casamayor, M Deak, A Paterson and DR Alessi, MRC Protein Phosphorylation Unit, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, UK.

P Gaffney, Ludwig Institute of Cancer Research, London W1P 8BY, UK.

R Currie and C Peter Downes, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, UK.

E-mail address for DR Alessi (corresponding author): [email protected]

A.B. and A.C. contributed equally to this work.