Phosphatidylinositol 3-kinase-mediated endocytosis of renal Na+, K+-ATPase alpha subunit in response to dopamine.
Dopamine (DA) inhibition of Na+,K+-ATPase in proximal tubule cells is associated with increased endocytosis of its alpha and beta subunits into early and late endosomes via a clathrin vesicle-dependent pathway. In this report we evaluated intracellular signals that could trigger this mechanism, specifically the role of phosphatidylinositol 3-kinase (PI 3-K), the activation of which initiates vesicular trafficking and targeting of proteins to specific cell compartments. DA stimulated PI 3-K activity in a time- and dose-dependent manner, and this effect was markedly blunted by wortmannin and LY 294002. Endocytosis of the Na+,K+-ATPase alpha subunit in response to DA was also inhibited in dose-dependent manner by wortmannin and LY 294002. Activation of PI 3-K generally occurs by association with tyrosine kinase receptors. However, in this study immunoprecipitation with a phosphotyrosine antibody did not reveal PI 3-K activity. DA-stimulated endocytosis of Na+, K+-ATPase alpha subunits required protein kinase C, and the ability of DA to stimulate PI 3-K was blocked by specific protein kinase C inhibitors. Activation of PI 3-K is mediated via the D1 receptor subtype and the sequential activation of phospholipase A2, arachidonic acid, and protein kinase C. The results indicate a key role for activation of PI 3-K in the endocytic sequence that leads to internalization of Na+,K+-ATPase alpha subunits in response to DA, and suggest a mechanism for the participation of protein kinase C in this process.
Chibalin
A V
AV
Department of Molecular Medicine, Karolinska Institute, Karolinska Hospital, 171 76 Stockholm, Sweden.
Zierath
J R
JR
Katz
A I
AI
Berggren
P O
PO
Bertorello
A M
AM
D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology*; D004705:Endocytosis / Q000502:physiology*; D004789:Enzyme Activation; D007672:Kidney Cortex / Q000201:enzymology*; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D004298:Dopamine; D019869:Phosphatidylinositol 3-Kinases; D000254:Sodium-Potassium-Exchanging ATPase