PTH-mediated regulation of Na+-K+-ATPase requires Src kinase-dependent ERK phosphorylation.
Parathyroid hormone (PTH) inhibits Na+-K+-ATPase activity by serine phosphorylation of the alpha1-subunit through ERK-dependent phosphorylation and translocation of protein kinase Calpha (PKCalpha). On the basis of previous studies, we postulated that PTH regulates sodium pump activity through Src kinase, PLC, and calcium-dependent ERK phosphorylation. In the present work utilizing opossum kidney cells, a model of renal proximal tubule, PTH-stimulated ERK phosphorylation and membrane translocation of PKCalpha were prevented by inhibition of Src kinase, PLC, and calcium entry. Pharmacological inhibition of PLA2 did not prevent PTH-stimulated ERK phosphorylation but completely prevented PKCalpha translocation. Silencing the expression of cytosolic or calcium-independent PLA2 also prevented PTH-mediated phosphorylation of Na+-K+-ATPase alpha1-subunit and PKCalpha without blocking ERK phosphorylation. Inhibition of Na+-K+-ATPase activity by the PLA2 metabolites arachidonic acid and 20-hydroxyeicosatetraenoic acid was prevented by specific inhibition of PKCalpha but not by U0126, a MEK-1 inhibitor. Transient transfection of constitutively active MEK-1 cDNA induced phosphorylation of Na+-K+-ATPase alpha1-subunit and PKCalpha, which was prevented by PLA2 inhibition. We conclude that PTH stimulates Na+-K+-ATPase phosphorylation and decreases the activity of Na+-K+-ATPase by a sequential activation of a signaling pathway involving Src kinase, PLC, ERK, PLA2, and PKCalpha.
Khundmiri
Syed J
SJ
Department of Medicine, University of Louisville, Louisville, Kentucky, USA. syed.khundmiri@louisville.edu
Ameen
Mohammed
M
Delamere
Nicholas A
NA
Lederer
Eleanor D
ED
D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009893:Opossums; D010281:Parathyroid Hormone / Q000378:metabolism*; D054467:Phospholipases A2 / Q000378:metabolism; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases
D010281:Parathyroid Hormone; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D051571:Protein Kinase C-alpha; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054467:Phospholipases A2; D010738:Type C Phospholipases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium