Relationship between intracellular Na+ concentration and reduced Na+ affinity in Na+,K+-ATPase mutants causing neurological disease.

Abstract

The neurological disorders familial hemiplegic migraine type 2 (FHM2), alternating hemiplegia of childhood (AHC), and rapid-onset dystonia parkinsonism (RDP) are caused by mutations of Na(+),K(+)-ATPase α2 and α3 isoforms, expressed in glial and neuronal cells, respectively. Although these disorders are distinct, they overlap in phenotypical presentation. Two Na(+),K(+)-ATPase mutations, extending the C terminus by either 28 residues ("+28" mutation) or an extra tyrosine ("+Y"), are associated with FHM2 and RDP, respectively. We describe here functional consequences of these and other neurological disease mutations as well as an extension of the C terminus only by a single alanine. The dependence of the mutational effects on the specific α isoform in which the mutation is introduced was furthermore studied. At the cellular level we have characterized the C-terminal extension mutants and other mutants, addressing the question to what extent they cause a change of the intracellular Na(+) and K(+) concentrations ([Na(+)]i and [K(+)]i) in COS cells. C-terminal extension mutants generally showed dramatically reduced Na(+) affinity without disturbance of K(+) binding, as did other RDP mutants. No phosphorylation from ATP was observed for the +28 mutation of α2 despite a high expression level. A significant rise of [Na(+)]i and reduction of [K(+)]i was detected in cells expressing mutants with reduced Na(+) affinity and did not require a concomitant reduction of the maximal catalytic turnover rate or expression level. Moreover, two mutations that increase Na(+) affinity were found to reduce [Na(+)]i. It is concluded that the Na(+) affinity of the Na(+),K(+)-ATPase is an important determinant of [Na(+)]i.

• Authors: Mads S Toustrup-Jensen, Anja P Einholm, Vivien R Schack, Hang N Nielsen, Rikke Holm, María-Jesús Sobrido, Jens P Andersen, Torben Clausen, Bente Vilsen
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 6 Pg. 3186-97 (Feb 07 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 24356962 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ATP1A3 protein, human
• Sodium
• ATP1A2 protein, human
• Atp1a2 protein, rat
• Atp1a3 protein, rat
• Sodium-Potassium-Exchanging ATPase
• Potassium

Topics

• Animals
• COS Cells
• Chlorocebus aethiops
• Dystonic Disorders (genetics, metabolism)
• Humans
• Ion Transport (genetics)
• Migraine with Aura (genetics, metabolism)
• Mutation, Missense
• Potassium (metabolism)
• Protein Structure, Tertiary
• Rats
• Sodium (metabolism)
• Sodium-Potassium-Exchanging ATPase (genetics, metabolism)