Dissociation and redistribution of Na+,K(+)-ATPase from its surface membrane actin cytoskeletal complex during cellular ATP depletion.

Establishment and maintenance of a polar distribution of Na+,K+-ATPase is essential for efficient Na+ reabsorption by proximal tubule cells and is dependent upon the formation of a metabolically stable, detergent-insoluble complex of Na+,K+-ATPase with the actin membrane cytoskeleton. The present studies show that cellular ATP depletion results in a rapid duration-dependent dissociation of Na+,K+-ATPase from the actin cytoskeleton and redistribution of Na+,K+-ATP- ase to the apical membrane. During ATP depletion, total cellu- lar Na+,K+-ATPase activity was unaltered, but the Triton- X-100-insoluble fraction (cytoskeleton associated) of Na+,K+-ATPase activity decreased (P < 0.01), with a cor- responding increase in the detergent-soluble fraction of Na+,K+-ATPase (P < 0.01). Indirect immunofluorescent stud- ies of cells with depleted ATP revealed a redistribution of Na+,K+-ATPase from the basolateral membrane into the apical membrane and throughout the cytoplasm. ATP depletion also resulted in the redistribution of F-actin from a primarily corti- cal concentration to a perinuclear location. There was also a rapid, duration-dependent conversion of monomeric G-actin to F-actin starting during the first 5 min of ATP depletion. Taken together, these data suggest that ATP depletion causes pro- found alterations in cell polarity by inducing major changes in the actin cytoskeletal architecture. (J. Clin. Invest. 1991 . 88:462-469.) Key words: epithelial polarity -cytoskeleton. an- kyrin ischemia * acute renal failure detergent-insoluble complex with elements of the actin mem- brane-cytoskeleton (2-4). Na+,K+-ATPase binds directly to an- kyrin (4-6) via its a subunit (5). Madin-Darby canine kidney (MDCK) cells plated as monolayers display a gradual shift in