Journal Article

A novel family of transmembrane proteins interacting with β subunits of the Na,K-ATPase

Svetlana Gorokhova, Stéphanie Bibert, Käthi Geering and Nathaniel Heintz

in Human Molecular Genetics

Volume 16, issue 20, pages 2394-2410
Published in print October 2007 | ISSN: 0964-6906
Published online July 2007 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddm167
A novel family of transmembrane proteins interacting with β subunits of the Na,K-ATPase

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We characterized a family consisting of four mammalian proteins of unknown function (NKAIN1, 2, 3 and 4) and a single Drosophila ortholog dNKAIN. Aside from highly conserved transmembrane domains, NKAIN proteins contain no characterized functional domains. Striking amino acid conservation in the first two transmembrane domains suggests that these proteins are likely to function within the membrane bilayer. NKAIN family members are neuronally expressed in multiple regions of the mouse brain, although their expression is not ubiquitous. We demonstrate that mouse NKAIN1 interacts with the β1 subunit of the Na,K-ATPase, whereas Drosophila ortholog dNKAIN interacts with Nrv2.2, a Drosophila homolog of the Na,K-ATPase β subunits. We also show that NKAIN1 can form a complex with another β subunit-binding protein, MONaKA, when binding to the β1 subunit of the Na,K-ATPase. Our results suggest that a complex between mammalian NKAIN1 and MONaKA is required for NKAIN function, which is carried out by a single protein, dNKAIN, in Drosophila. This hypothesis is supported by the fact that dNKAIN, but not NKAIN1, induces voltage-independent amiloride-insensitive Na+-specific conductance that can be blocked by lanthanum. Drosophila mutants with decreased dNKAIN expression due to a P-element insertion in the dNKAIN gene exhibit temperature-sensitive paralysis, a phenotype also caused by mutations in the Na,K-ATPase α subunit and several ion channels. The neuronal expression of NKAIN proteins, their membrane localization and the temperature-sensitive paralysis of NKAIN Drosophila mutants strongly suggest that this novel protein family may be critical for neuronal function.

Journal Article.  9232 words.  Illustrated.

Subjects: Genetics and Genomics

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