Subcellular Localization of Na/Ca+K-exchanger, NCKX2, in Hippocampus and Its Potential Role in Neuronal Plasticity
Date
2014-09-30
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Abstract
The Na+/Ca2++K+-exchanger (NCKX) family is encoded by five related genes, of which NCKX2 (solute carrier family 24, member 2) is the most abundant member present in the brain. In 2006, an NCKX2 knockout mouse was created, which displayed profound loss of hippocampal long term potentiation, and selective deficits in motor learning and spatial working memory. The molecular mechanisms underlying these changes have not been established. Thus, the overall goals of my thesis research project were to identify the exact subcellular localization of NCKX2 in hippocampus, which is an important prerequisite for understanding the physiological role NCKX2 has in neuronal function, and to examine if there were any secondary changes in the expression of synaptically-related molecules in nckx2 knockout animals. To achieve these goals, I used dual immunofluorescent confocal microscopy immuno-electron microscopy, and confocal immunofluorescence analysis and western blotting. My data demonstrate that the majority of NCKX2 is co-localized with the dendritic marker, microtubule associated protein 2. A smaller fraction is co-localized with the presynaptic marker, synapsin, and the smallest amount is co-localized with the glutamatergic spine marker, N-methyl-D-aspartate receptor 1 (NMDA receptor 1). There is a small but significant amount of NCKX2 co-localized with the dendritic potassium channels, BK and IK and with the chloride channel, TM16B, especially in the molecular layer. Immuno-electron microscopy demonstrates that the majority of NCKX2 is located on the fine branches of the proximal dendritic tufts. I did not observe in NCKX2 knockout animals any change of the spatial distribution or expression level of the following molecules: Ca2+/calmodulin-dependent kinase II, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, NMDAR1, post synaptic density protein 95, synapsin 1, vesicular glutamate transporter 1, BK channel, IK channel or the TMEM16B chloride channel. These studies describe for the first time the exact location of NCKX2 in the hippocampus of adult mice and suggest that the function of NCKX2 in neuronal plasticity may be mediated directly by its kinetic effect on the local calcium concentration that influences dendritic integration. These data provide a working hypothesis for the role of NCKX2 in neuronal plasticity at CA1 synapses, which may be the foundation for future mechanistic studies.
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Biology--Molecular, Neuroscience
Citation
Zhang, Y. (2014). Subcellular Localization of Na/Ca+K-exchanger, NCKX2, in Hippocampus and Its Potential Role in Neuronal Plasticity (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27924