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Functional consequences of the disease‐causing T613M mutation of NKAalpha3 for hippocampal neurons
Author(s) -
Fritz Nicolas,
Akkuratov Evgeny,
Liebmann Thomas,
Lindskog Maria,
Brismar Hjalmar,
Aperia Anita
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.845.29
Subject(s) - membrane potential , hippocampal formation , neuroscience , mutation , intracellular , mutant , depolarization , hippocampus , chemistry , dystonia , deep brain stimulation , soma , sodium channel , microbiology and biotechnology , medicine , biology , biophysics , sodium , disease , biochemistry , gene , parkinson's disease , organic chemistry
Mutations in ATP1A3, the gene encoding the neuron‐specific sodium‐potassium pump Na + , K + , ATPase alpha 3 subunit (NKAalpha3), lead to Rapid‐onset Dystonia‐Parkinsonism (RDP), a rare brain disorder arising during childhood. Symptoms, including dystonia and cognitive disorders, are triggered by intense stress. The most common mutation observed in RDP patients, T613M, is critically located at the interface between the pump's actuator and nucleotide‐binding domains. Here, functional consequences of this mutation were tested on primary cultures of hippocampal neurons expressing fluorescently tagged WT‐NKAalpha3 or NKAalpha3 carrying the T613M mutation. To evaluate and compare membrane expression of the engineered NKAalpha3, we developed an imaging‐based method using calibrated fluorescent beads. T613M mutants were consistently expressed at the plasma membrane, and total levels of expression were similar to that of the WT. Live imaging experiments using the Na+‐sensitive dye ANG2 were performed to analyze intracellular Na + (Na i ) homeostasis in both soma and dendrites. Expression of T613M led to robust changes in both baseline Na i and rate of Na i recovery after electrical stimulation and NMDA challenges to provoke and mimic intense neuronal activity. Further, analysis of both resting membrane potential and spontaneous spiking activity during current clamp recordings supported the notion that T613M‐expressing neurons have a lower threshold for activation. Thus, our study shows that the pathophysiology of RDP can involve increased intracellular Na i , decreased maximum rate of restoration of Na i and increased excitability which during severe stress that triggers RDP can result in neuronal malfunction.