Role of PDK1 in insulin-signaling pathway for glucose metabolism in 3T3-L1 adipocytes.
To investigate the role of 3-phosphoinositide-dependent protein kinase 1 (PDK1) in the insulin-signaling pathway for glucose metabolism, wild-type (wt), the kinase-dead (kd), or the plecstrin homology (PH) domain deletion (DeltaPH) mutant of PDK1 was expressed using an adenovirus gene transduction system in 3T3-L1 adipocytes. wt-PDK1 and kd-PDK1 were found in both membrane and cytosol fractions, whereas DeltaPH-PDK1, which exhibited PDK1 activity similar to that of wt-PDK1, was detected exclusively in the cytosol fraction. Insulin dose dependently activated protein kinase B (PKB) but did not change atypical protein kinase C (aPKC) activity in control cells. aPKC activity was not affected by expression of wt-, kd-, or DeltaPH-PDK1 in either the presence or the absence of insulin. Overexpression of wt-PDK1 enhanced insulin-induced activation of PKB as well as insulin-induced phosphorylation of glycogen synthase kinase (GSK)3alpha/beta, a direct downstream target of PKB, although insulin-induced glycogen synthesis was not significantly enhanced by wt-PDK1 expression. Neither DeltaPH-PDK1 nor kd-PDK1 expression affected PKB activity, GSK3 phosphorylation, or glycogen synthesis. Thus membrane localization of PDK1 via its PH domain is essential for insulin signaling through the PDK1-PKB-GSK3alpha/beta pathway. Glucose transport activity was unaffected by expression of wt-PDK1, kd-PDK1, or DeltaPH-PDK1 in either the presence or the absence of insulin. These findings suggest the presence of a signaling pathway for insulin-stimulated glucose transport in which PDK1 to PKB or aPKC is not involved.
Yamada
Tetsuya
T
Division of Molecular Metabolism and Diabetes, Department of Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, 980-8574, Japan.
Katagiri
Hideki
H
Asano
Tomoichiro
T
Tsuru
Masatoshi
M
Inukai
Kouichi
K
Ono
Hiraku
H
Kodama
Tatsuhiko
T
Kikuchi
Masatoshi
M
Oka
Yoshitomo
Y
D064413:3-Phosphoinositide-Dependent Protein Kinases; D016475:3T3 Cells / Q000378:metabolism*; D000256:Adenoviridae / Q000235:genetics; D017667:Adipocytes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry; D003847:Deoxyglucose / Q000378:metabolism; D015870:Gene Expression; D005822:Genetic Vectors; D005947:Glucose / Q000378:metabolism; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000096:biosynthesis; D015151:Immunoblotting; D007163:Immunosorbent Techniques; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000032:analysis / Q000378:metabolism; D009124:Muscle Proteins; D016296:Mutagenesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D014162:Transfection
D064413:3-Phosphoinositide-Dependent Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D003847:Deoxyglucose; D005947:Glucose; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006003:Glycogen; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C495693:Slc2a4 protein, mouse; C578564:Pdpk1 protein, mouse