Two splice variants of protein kinase B gamma have different regulatory capacity depending on the presence or absence of the regulatory phosphorylation site serine 472 in the carboxyl-terminal hydrophobic domain.
We have reported previously the cloning and characterization of human and mouse protein kinase B gamma (PKB gamma), the third member of the PKB family of second messenger-regulated serine/threonine kinases (Brodbeck, D., Cron, P., and Hemmings, B. A. (1999) J. Biol. Chem. 274, 9133--9136). Here we report the isolation of human and mouse PKB gamma 1, a splice variant lacking the second regulatory phosphorylation site Ser-472 in the hydrophobic C-terminal domain. Expression of PKB gamma 1 is low compared with PKB gamma, and it is regulated in different human tissues. We show that PKB gamma and PKB gamma 1 differ in their response to stimulation by insulin, pervanadate, peroxide, or okadaic acid. Activation of PKB gamma 1 requires phosphorylation at a single regulatory site Thr-305. Interestingly, this site is phosphorylated to a higher extent in PKB gamma compared with PKB gamma 1 upon maximal stimulation by pervanadate, and this is reflected in the respective specific kinase activities. Furthermore, upon insulin stimulation of transfected cells, PKB gamma 1 translocates to the plasma membrane to a lesser extent than PKB gamma. Taken together, these results suggest that phosphorylation of the hydrophobic motif at the extreme C terminus of PKB gamma may facilitate translocation of the kinase to the membrane and/or its phosphorylation on the activation loop site by phosphoinositide-dependent protein kinase-1.
Brodbeck
D
D
Friedrich Miescher-Institut, P. O. Box 2543, Basel 4002, Switzerland.
Hill
M M
MM
Hemmings
B A
BA
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004622:Embryo, Mammalian; D004789:Enzyme Activation; D005091:Exons; D014644:Genetic Variation; D006801:Humans; D007700:Kinetics; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D015513:Oncogene Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009928:Organ Specificity; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012694:Serine; D013379:Substrate Specificity; D014158:Transcription, Genetic
D009842:Oligopeptides; D015513:Oncogene Proteins; D011994:Recombinant Proteins; D012694:Serine; C491754:AKT3 protein, human; C491753:Akt3 protein, mouse; C111490:Akt3 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt