title: Src kinase integrates PI3K/Akt and MAPK/ERK1/2 pathways in T3-induced Na-K-ATPase activity in adult rat alveolar cells.
abstract: We previously reported that the 3,5,3'-triiodo-L-thyronine (T3)-induced increase of Na-K-ATPase activity in rat alveolar epithelial cells (AECs) required activation of Src kinase, PI3K, and MAPK/ERK1/2. In the present study, we assessed the role of Akt in Na-K-ATPase activity and the interaction between the PI3K and MAPK in response to T3 by using MP48 cells, inhibitors, and constitutively active mutants in the MP48 (alveolar type II-like) cell line. The Akt inhibitor VIII blocked T3-induced increases in Na-K-ATPase activity and amount of plasma membrane Na-K-ATPase protein. The Akt inhibitor VIII also abolished the increase in Na-K-ATPase activity induced by constitutively active mutants of either Src kinase or PI3K. Moreover, constitutively active mutants of Akt increased Na-K-ATPase activity in the absence of T3. Thus activation of Akt was required for T3-induced Na-K-ATPase activity in AECs and is sufficient in the absence of T3. Inhibitors of Src kinase (PP1), PI3K (wortmannin), and ERK1/2 (U0126) all blocked the T3-induced Na-K-ATPase activity. PP1 blocked the activation of PI3K and also ERK1/2 by T3, whereas U0126 did not prevent T3 activation of Src kinase or PI3K activity. Wortmannin did not significantly alter T3-increased MAPK/ERK1/2 activity, suggesting that T3-activated PI3K/Akt and MAPK/ERK1/2 pathways acted downstream of the Src kinase. Furthermore, in the absence of T3, a constitutively active mutant of Src kinase increased activities of Na-K-ATPase, PI3K, and MAPK/ERK1/2. A constitutively active mutant of PI3K enhanced Na-K-ATPase activity but did not alter the MAPK/ERK1/2 activity significantly. In summary, in adult rat AECs T3-stimulated Src kinase activity can activate both PI3K/Akt and MAPK/ERK1/2, and activation of Akt is necessary for T3-induced Na-K-ATPase activity.
authors.affiliation: Pulmonary, Allergy, Critical Care and Sleep Medicine Division, Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Jianxun
authors.initials: J
authors.lastname: Lei
authors.forename: David H
authors.initials: DH
authors.lastname: Ingbar
mesh_terms: D056809:Alveolar Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010957:Plasmids; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014162:Transfection; D014284:Triiodothyronine / Q000378:metabolism / Q000494:pharmacology*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000254:Sodium-Potassium-Exchanging ATPase; D014284:Triiodothyronine; D019061:src-Family Kinases