AS160 Associates with the Na,K-ATPase and Mediates the AMPK-dependent Regulation of Sodium Pump Surface Expression

The Na, K-ATPase is the major active transport protein found in the plasma membranes of most epithelial cell types. The regulation of Na, K-ATPase activity involves a variety of mechanisms, including regulated endocytosis and recycling. Our efforts to identify novel Na, K-ATPase binding partners revealed a direct association between the Na, K-ATPase and AS160, a Rab-GTPase-activating protein. In COS cells, coexpression of AS160 and Na, K-ATPase led to the intracellular retention of the sodium pump. We find that AS160 interacts with the large cytoplasmic NP domain of the α-subunit of the Na, K-ATPase. Inhibition of the activity of the adenosine monophosphate-stimulated protein kinase (AMPK) in MDCK cells through treatment with Compound C induces Na, K-ATPase endocytosis. This effect of Compound C is prevented through the shRNA-mediated knockdown of AS160, demonstrating that AMPK and AS160 participate in a common pathway to modulate the cell surface expression of the Na, KATPase.