Selective ligands for Na(+)/K(+)-ATPase α isoforms differentially and cooperatively regulate excitability of pyramidal neurons in distinct brain regions (original) (raw)
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Sodium-potassium ATPase (NaKA) is a plasma membrane enzyme responsible for influencing membrane physiology by direct electrogenic activity. It determines cellular excitability and synaptic neurotransmission, thus affecting learning and memory processes. A principle catalytic a subunit of NaKA has development-specific expression pattern. There are two a isoforms, a1 and a3, in adult brain neurons. Although NaKA is a housekeeping enzyme, the physiological differences between these two a isoforms in different brain regions have not been well explored. Endogenous cardiotonic steroids, including Marinobufagenin and Ouabain, control the cell homeostasis and cell functions via inhibiting NaKA. Here we employed selective inhibition of a1 and a3 NaKA isoforms by Marinobufagenin and Ouabain respectively, to measure the contribution of a subunits in cellular physiology of three distinct mouse brain regions. The results of the whole cell recording demonstrated that a1 isoform predominated in layer-5 pyramidal cells at rostral motor cortex, while a3 isoform governed the pyramidal neurons at hippocampal CA1 region and to a lesser extent the layer-5 pyramidal neurons of parietal cortex. Furthermore, selective a isoform inhibition induced differential effects on distinct physiological properties even within the same brain region. In addition, our results supported the existence of synergism between two NaKA a isoforms. To conclude, this systematic study of NaKA a isoforms demonstrated their broader roles in neuronal functioning in a region-specific manner.
The Journal of Physiology, 2007
The sodium pump (Na + /K +-ATPase), maintains intracellular and extracellular concentrations of sodium and potassium by catalysing ATP. Three sodium pump α subunits, ATP1A1, ATP1A2 and ATP1A3, are expressed in brain. We compared their role in pyramidal cells and a subset of interneurones in the subiculum. Interneurones were identified by their expression of GFP under the GAD-65 promoter. We used the sensitivity to the cardiac glycoside, ouabain, to discriminate between different α subunit isoforms. GFP-positive interneurones were depolarized by nanomolar doses of ouabain, but higher concentrations were needed to depolarize pyramidal cells. Comparison of pump currents in these cells revealed a current sensitive to low doses of ouabain in interneurones, while micromolar doses of ouabain were needed to suppress the pump current in subicular pyramidal cells. As predicted, nanomolar doses of ouabain increased the frequency but not the amplitudes of IPSPs in pyramidal cells. Immunostaining confirmed a differential distribution of α-subunits of the Na + /K +-ATPase in subicular interneurones and pyramidal cells. In conclusion, these data suggest that while ATP1A3-isoforms regulate sodium and potassium homeostasis in subicular interneurones, ATP1A1-isoforms assume this function in pyramidal cells. This differential expression of sodium pump isoforms may contribute to differences in resting membrane potential of subicular interneurones and pyramidal cells.
Neurochemistry International, 2019
α1, α2, α3 as well as β1, β2 and β3 isoforms are expressed in dependence of cell type and age in mouse cortex, hippocampus, cerebellum and midbrain. • The expression levels of all Na + /K + ATPase isoforms are consistently higher in adult mouse brain compared with neonatal mouse brain albeit with varying levels of significance. • The β3 isoform is the only subunit that shows a significant postnatal increase in all brain regions investigated. • The α2 Na + /K + ATPase isoform shows a glial cell specific expression and α3 a neuron specific expression. • α1/β1 and α3/β2 Na + /K + ATPase complexes are upregulated in adult mouse brain.
Neurons and astroglia express distinct subsets of Na,K-ATPase α and β subunits
Molecular Brain Research, 1994
We have analyzed the expression pattern of Na,K-ATPase a and fl subunit isoforms within the rodent and primate central nervous system. Membrane fractions prepared from rat cerebral cortical type-1 astroeytes and rat cerebellar granule and hippoeampal neurons were characterized by immunoblot analyses using a panel of a and /3 subunit isoform-specific antisera. Each cell type was found to express the al isoform but showed differences in the expression of other subunits. Cortical astroeytes displayed a2 and/32 subunits, whereas cerebellar granule neurons showed expression of a3 and /31 subunits. All three a subunit isotypes were detected in hippocampal neurons. A survey of the immunofluorescent staining pattern of the a3 subunit in rat and monkey brain confirmed that expression of this Na,K-ATPase a subunit isoform was restricted exclusively to neurons. These results suggest that both neurons and astrocytes express multiple, yet distinct, Na,K-ATPase isoenzymes. The identification of cell types expressing limited combinations of a and/3 subunits should provide a framework for understanding the physiological significance of Na,K-ATPase isoenzyme diversity and may provide useful tools for the analysis of cell lineage in the mammalian central nervous system.
General physiology and biophysics, 1997
The activities and basic enzymatic properties of Na,K-ATPase were examined in synaptosomal plasma membranes (SPM) prepared from rat hippocampus and striatum. A kinetic analysis showed profound differences in apparent affinities for ATP (Km) between hippocampal (1.21 mmol/l) and striatal (0.76 mmol/l) enzyme preparations, as well as in the corresponding Vmax values. However, physiological efficiencies were almost the same. The complex pattern of dose-response curves to ouabain indicated the presence of two high-affinity forms of Na,K-ATPase in the striatum ("very high-": Ki = 3.73 x 10(-8) mol/l and "high-": Ki = 4.21 x 10(-5) mol/l), and one high affinity form in the hippocampus (Ki = 6.6 x 10(-7) mol/l). In addition, both SPM preparations contained one low affinity form with similar Ki. The "very high-affinity" form had positive cooperativity for ouabain inhibition of Na,K-ATPase activity, in contrast to "high" and "low-affinity" fo...
Brain Research Bulletin, 1996
We have used isoform-specific antisera against the Na,K-ATPase/]1 (SpETbl) and/~2(AMOG) (SpETb2) subunit isoforms in order to establish their specific cellular and subcellular localization in several developmental stages of the rat central nervous system. Immunocytochemical preparations revealed/~1 isoform protein in most neural cells, being predominantly located in the soma of neurons and astrocytes, with no appreciable developmental variations. In the newborn rat,/~2(AMOG) immunoreactivity was present in cellular processes of astroglia and in the somas of neurons and decreasing in intensity with maturation until adulthood, where no/~2 isoform was detected in neurons. The differential location of these isoforms, both developmentally and at the cellular level suggest a complex regulation of their genes expression and mechanisms of subcellular distribution, as well as functional differences.
Regulation of Neuronal Na+/K+-ATPase by Specific Protein Kinases and Protein Phosphatases
The Journal of Neuroscience, 2019
The Na ϩ /K ϩ-ATPase (NKA) is a ubiquitous membrane-bound enzyme responsible for generating and maintaining the Na ϩ and K ϩ electrochemical gradients across the plasmalemma of living cells. Numerous studies in non-neuronal tissues have shown that this transport mechanism is reversibly regulated by phosphorylation/dephosphorylation of the catalytic ␣ subunit and/or associated proteins. In neurons, Na ϩ /K ϩ transport by NKA is essential for almost all neuronal operations, consuming up to two-thirds of the neuron's energy expenditure. However, little is known about its cellular regulatory mechanisms. Here we have used an electrophysiological approach to monitor NKA transport activity in male rat hippocampal neurons in situ. We report that this activity is regulated by a balance between serine/threonine phosphorylation and dephosphorylation. Phosphorylation by the protein kinases PKG and PKC inhibits NKA activity, whereas dephosphorylation by the protein phosphatases PP-1 and PP-2B (calcineurin) reverses this effect. Given that these kinases and phosphatases serve as downstream effectors in key neuronal signaling pathways, they may mediate the coupling of primary messengers, such as neurotransmitters, hormones, and growth factors, to the NKAs, through which multiple brain functions can be regulated or dysregulated.
Brain Na(+), K(+)-ATPase Activity In Aging and Disease
International journal of biomedical science : IJBS, 2014
Na(+)/K(+) pump or sodium- and potassium-activated adenosine 5'-triphosphatase (Na(+), K(+)-ATPase), its enzymatic version, is a crucial protein responsible for the electrochemical gradient across the cell membranes. It is an ion transporter, which in addition to exchange cations, is the ligand for cardenolides. This enzyme regulates the entry of K(+) with the exit of Na(+) from cells, being the responsible for Na(+)/K(+) equilibrium maintenance through neuronal membranes. This transport system couples the hydrolysis of one molecule of ATP to exchange three sodium ions for two potassium ions, thus maintaining the normal gradient of these cations in animal cells. Oxidative metabolism is very active in brain, where large amounts of chemical energy as ATP molecules are consumed, mostly required for the maintenance of the ionic gradients that underlie resting and action potentials which are involved in nerve impulse propagation, neurotransmitter release and cation homeostasis. Prote...