The γ subunit of Na +, K +-ATPase: Role on ATPase activity and regulatory phosphorylation by PKA

• Published in: The international journal of biochemistry & cell biology Vol. 38; no. 11; pp. 1901 - 1913
• Main Authors: Cortes, Vanessa Faria, Veiga-Lopes, Fabio Eduardo, Barrabin, Hector, Alves-Ferreira, Marcelo, Fontes, Carlos Frederico Leite
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 2006
• Subjects: Adenosine Triphosphate - metabolism; Animals; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Kidney - enzymology; Kidney - metabolism; Kinetics; Lipids - chemistry; Lipids - isolation & purification; Lipids - pharmacology; Na +, K +-ATPase; Ouabain - pharmacology; Phosphorylation; Phosphorylation - drug effects; Pig kidney; PKA; Protein Structure, Quaternary; Protein Subunits - chemistry; Protein Subunits - metabolism; Sodium-Potassium-Exchanging ATPase - antagonists & inhibitors; Sodium-Potassium-Exchanging ATPase - chemistry; Sodium-Potassium-Exchanging ATPase - metabolism; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Swine; γ subunit; Phosphorylation; Na +, K +-ATPase; Pig kidney; γ subunit; PKA
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2006.05.002

In kidney, Na +, K +-ATPase is an oligomer (αβγ) with equimolar amounts of essential α and β subunits and one small hydrophobic FXYD protein (γ subunit). This report describes γ subunit as an activator of pig kidney outer medulla Na +, K +-ATPase in aqueous medium. The effects of γ subunit on Na +, K +-ATPase were dose-dependent and preincubation-dependent. Changes in αβ/γ stoichiometry did not alter K m1 for ATP, and slightly increased K m2, but V max was increased at both catalytic and regulatory sites. Hydroxylamine treatment of enzyme phosphorylated by ATP (E-P), in the presence of additional γ subunit, revealed that 52% of the E-P accumulation was not via acyl-phosphate formation. The γ subunit was phosphorylated by endogenous kinases and by commercial catalytic subunit of protein kinase A (PKA). Additionally, we demonstrated that PKA phosphorylation of γ subunit increased its capacity to stimulate ATP hydrolysis. These results suggest that γ subunit can act as an intrinsic Na +, K +-ATPase regulator in kidney.