OBJECTIVE Degeneration of chronically demyelinated axons is a major cause of irreversible neurological decline in the human central nervous system disease, multiple sclerosis (MS). Although the molecular mechanisms responsible for this axonal degeneration remain to be elucidated, dysfunction of axonal Na+/K+ ATPase is thought to be central. To date, however, the distribution of Na+/K+ ATPase ha...

Phosphorylation of purified Na+,K(+)-ATPase by cAMP-dependent protein kinase (protein kinase A) decreases the activity of this enzyme. We have now shown, using several experimental approaches, that a highly conserved seryl residue on the catalytic (alpha) subunit of Na+,K(+)-ATPase, corresponding to Ser943 of the rat alpha 1 isoform, is the phosphorylation site for protein kinase A. cDNAs corre...

A pharmacological screen identified the H+ and K+ ATPase transporter as obligatory for normal orientation of the left-right body axis in Xenopus. Maternal H+/K+-ATPase mRNA is symmetrically expressed in the 1-cell Xenopus embryo but becomes localized during the first two cell divisions, demonstrating that asymmetry is generated within two hours postfertilization. Although H+/K+-ATPase subunit m...

The transport activity of the Na,K-ATPase (a 3 Na+ for 2 K+ ion exchange) is electrogenic, whereas the closely related gastric and non-gastric H,K-ATPases perform electroneutral cation exchange. We have studied the role of a highly conserved serine residue in the fifth transmembrane segment of the Na,K-ATPase, which is replaced with a lysine in all known H,K-ATPases. Ouabain-sensitive 86Rb upta...

Most vital cellular functions are dependent on a fine-tuned regulation of intracellular ion homeostasis. Here we have demonstrated, using COS cells that were untransfected or transfected with wild-type rat ouabain-resistant Na(+)-K(+)-ATPase, that partial inhibition of Na(+)-K(+)-ATPase has a dramatic influence on cell attachment to fibronectin. Ouabain dose-dependently decreased attachment in ...

The content and distribution of the membrane-bound enzyme (Na+ + K+)-ATPase in a rat cerebral C6 glioma was determined by immunocytochemistry, immunoblots and enzyme assay. In the C6 glioma cell culture (Na+ + K+)-ATPase activity was about 20% of (Mg2+ + Na+ + K+)-ATPase activity. However, (Mg2+ + Na+ + K+)-ATPase activity in the cerebral C6 gliomas was very close to Mg2+ baseline and not signi...

Na,K-ATPase is essential for the regulation of cytoplasmic Na+ and K+ levels in lens cells. Studies on the intact lens suggest activation of tyrosine kinases may inhibit Na,K-ATPase function. Here, we tested the influence of Lyn kinase, a Src-family member, on tyrosine phosphorylation and Na,K-ATPase activity in membrane material isolated from porcine lens epithelium. Western blot studies indic...

Short term effects of insulin on total brain and branchial Na+K+ ATPase, Ca2+ ATPase and Na+, K+ and Ca2+ ions were investigated in A. testudineus. The increase in brain Ca2+ ATPase after alloxan treatment may account for an increased amount of intracellular calcium required for biochemical events taking place inside the cells. Branchial Na+K+ATPase was significantly stimulated while Ca2+ ATPas...

We have examined two distinct protein kinases, cAMP-dependent protein kinase and protein kinase C, for their ability to phosphorylate and regulate the activity of three different types of Na+,K(+)-ATPase preparation. cAMP-dependent protein kinase phosphorylated purified shark rectal gland Na+,K(+)-ATPase to a stoichiometry of approximately 1 mol of phosphate per mol of alpha subunit. Protein ki...