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Neurobiol Dis. 2015 May;77:88-93. doi: 10.1016/j.nbd.2015.02.002. Epub 2015 Feb 12.

A functional correlate of severity in alternating hemiplegia of childhood.

Author information

1
Ion Channels & Disease Group, Epilepsy Division, The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia.
2
Research School of Biology, Australian National University, Canberra, Australia.
3
Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA.
4
Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA.
5
Institute for Genomic Medicine, Columbia University, New York, NY 10032, USA; Department of Genetics and Development, Columbia University, New York, NY 10032, USA.
6
Ion Channels & Disease Group, Epilepsy Division, The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia; Centre for Neural Engineering, Department of Electrical Engineering, The University of Melbourne, Victoria, Australia. Electronic address: spetrou@unimelb.edu.au.

Abstract

OBJECTIVE:

Mutations in ATP1A3, the gene that encodes the α3 subunit of the Na(+)/K(+) ATPase, are the primary cause of alternating hemiplegia of childhood (AHC). Correlations between different mutations and AHC severity were recently reported, with E815K identified in severe and D801N and G947R in milder cases. This study aims to explore the molecular pathological mechanisms in AHC and to identify functional correlates for mutations associated with different levels of disease severity.

METHODS:

Human wild type ATP1A3, and E815K, D801N and G947R mutants were expressed in Xenopus laevis oocytes and Na(+)/K(+) ATPase function measured. Structural homology models of the human α3 subunit containing AHC mutations were created.

RESULTS:

The AHC mutations examined all showed similar levels of reduction in forward cycling. Wild type forward cycling was reduced by coexpression with any mutant, indicating dominant negative interactions. Proton transport was measured and found to be selectively impaired only in E815K. Homology modeling showed that D801 and G947 lie within or near known cation binding sites while E815 is more distal. Despite its effect on proton transport, E815K was also distant from the proposed proton transport route.

INTERPRETATION:

Loss of forward cycling and dominant negativity are common and likely necessary pathomechanisms for AHC. In addition, loss of proton transport correlated with severity of AHC. D801N and G947R are likely to directly disrupt normal Na(+)/K(+) binding while E815K may disrupt forward cycling and proton transport via allosteric mechanisms yet to be elucidated.

KEYWORDS:

ATP1A3; Alternating hemiplegia of childhood; Na(+)/K(+) ATPase

PMID:
25681536
DOI:
10.1016/j.nbd.2015.02.002
[Indexed for MEDLINE]

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