The Par6alpha/aPKC complex regulates Akt1 activity by phosphorylating Thr34 in the PH-domain.
A single nucleotide polymorphism in the partitioning defective protein-6alpha (Par6alpha) promoter is coupled with lower Par6alpha expression and better insulin sensitivity, whereas overexpression of Par6alpha in C2C12 myoblasts inhibits insulin-induced protein kinase B/Akt1 activation and glycogen synthesis. Here we show that a direct interaction of Par6alpha with atypical protein kinase C (aPKC) is crucial for this inhibition. A DeltaPB1-Par6alpha deletion mutant that does not interact with aPKC neither increased aPKC activity nor interfered with insulin-induced Akt1 activation in C2C12 cells. Further, T34 phosphorylation of Akt1 through aPKC is important for inhibition of Akt1. When Par6alpha was overexpressed, activation of wild-type Akt1 (-59.3%; p=0.049), but not T34A-Akt1 (+2.9%, p=0.41) was reduced after insulin stimulation. The resistance of T34A-Akt1 to Par6alpha/aPKC-mediated inhibition was also reflected by reconstitution of insulin-induced glycogen synthesis. In summary, Par6alpha-mediated inhibition of insulin-dependent glycogen synthesis in C2C12 cells depends on the direct interaction of Par6alpha with aPKC and on aPKC-mediated T34 phosphorylation of Akt1.
Weyrich
P
P
Department of Internal Medicine IV, University of Tübingen, Otfried-Müller-Str. 10, D-72076 Tübingen, Germany.
Neuscheler
D
D
Melzer
M
M
Hennige
A M
AM
Häring
H-U
HU
Lammers
R
R
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006003:Glycogen / Q000096:biosynthesis; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D050505:Mutant Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010769:Phosphothreonine / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007328:Insulin; D050505:Mutant Proteins; C499657:PARD6A protein, human; C518597:Par6 protein, mouse; D010769:Phosphothreonine; D006003:Glycogen; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt; C115015:PKC-3 protein; D011493:Protein Kinase C