Lipopolysaccharide activates Akt in human alveolar macrophages resulting in nuclear accumulation and transcriptional activity of beta-catenin.
Exposure of human alveolar macrophages to bacterial LPS results in activation of a number of signal transduction pathways. An early event after the alveolar macrophage comes in contact with LPS is activation of the phosphatidylinositol 3 kinase (PI 3-kinase). This study evaluates the downstream effects of that activation. We observed that LPS exposure results in phosphorylation of Akt (serine 473). We found this using both phosphorylation-specific Abs and also by in vivo phosphorylation with (32)P-loaded cells. AKT activation resulted in the phosphorylation-dependent inactivation of glycogen synthase kinase (GSK-3) (serine 21/9). We found that both of these events were linked to PI 3-kinase because the PI 3-kinase inhibitors, wortmannin and LY294002, inhibited LPS-induced phosphorylation of both AKT and GSK-3. Inactivation of GSK-3 has been shown to reduce the ubiquitination of beta-catenin, resulting in nuclear accumulation and transcriptional activity of beta-catenin. Consistent with this, we found that LPS caused an increase in the amounts of PI 3-kinase-dependent nuclear beta-catenin in human alveolar macrophages and expression of genes that require nuclear beta-catenin for their activation. This is the first demonstration that LPS exposure activates AKT, inactivates GSK-3, and causes accumulation and transcriptional activity of beta-catenin in the nucleus of any cell, including alveolar macrophages.
Monick
M M
MM
Department of Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, IA 52242, USA. martha-monick@uiowa.edu
Carter
A B
AB
Robeff
P K
PK
Flaherty
D M
DM
Peterson
M W
MW
Hunninghake
G W
GW
D064413:3-Phosphoinositide-Dependent Protein Kinases; D021581:Active Transport, Cell Nucleus / Q000276:immunology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D002467:Cell Nucleus / Q000276:immunology / Q000378:metabolism*; D002469:Cell Separation; D018031:Connexin 43 / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000276:immunology; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D008070:Lipopolysaccharides / Q000494:pharmacology*; D016676:Macrophages, Alveolar / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015534:Trans-Activators; D015533:Transcriptional Activation / Q000276:immunology*; D015854:Up-Regulation / Q000276:immunology; D051176:beta Catenin
D064413:3-Phosphoinositide-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018031:Connexin 43; D019938:Cyclin D1; D003598:Cytoskeletal Proteins; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D008070:Lipopolysaccharides; D019869:Phosphatidylinositol 3-Kinases; D010761:Phosphorus Radioisotopes; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D015534:Trans-Activators; D051176:beta Catenin