Differential distribution of classical inwardly rectifying potassium channel mRNAs in the brain: comparison of IRK2 with IRK1 and IRK3

Abstract

Distribution of IRK2 inwardly rectifying potassium channel mRNA in the mouse brain was studied using in situ hybridization histochemistry and compared with those of other classical inwardly rectifying potassium channel (IRK1 and IRK3) mRNAs. All these IRK channel mRNAs were detected in neurons, but not in glial cells. Their distribution patterns in the brain were, however, quite divergent: IRK2 mRNA was detected extremely high in granule cells of cerebellum, relatively high in motor trigeminai nucleus and moderate in olfactory bulb, piriform cortex, cerebral cortex, CA1 through CA3 regions of hippocampus, dentate gyrus and pontine nucleus. On the other hand, IRK1 mRNA was expressed throughout whole brain but in particular subsets of neurons, and IRK3 mRNA was in forebrain. Expression of these three IRK mRNAs overlapped in hippocampus, olfactory bulb, and cerebral cortex. This differential distribution of IRK mRNAs suggests that each of these channels has its specific function in regulation of the excitability of brain neurons.

Inward rectifier K+ channel Kir2.3 is localized at the postsynaptic membrane of excitatory synapses

“…2, D-F). The distribution of Kir2.3 immunoreactivity was consistent with that of its mRNA shown by in situ hybridization studies (5,11,16,17). Figure 2, C-F, depicts the immunolocalization of Kir2.3 in mouse OB at higher magnification.…”

“…2F). Whereas Kir2.3 mRNA was expressed predominantly in the granule cells (5,11,16), no clear immunoreactivity was detected in somata of granule cells (Fig. 2F).…”

“…The classical Kir2.0 channels are responsible for formation of the deep resting membrane potential near the K ϩ equilibrium potential in a variety of cells, such as cardiac and skeletal myocytes, glial cells, and some neurons. It was shown at the level of mRNA that Kir2.0 subunits are expressed differentially in various regions of the brain (11,16,36): Kir2.1 is expressed diffusely but weakly in the whole brain, Kir2.2 mainly in the cerebellum, Kir2.3 mainly in the forebrain, and Kir2.4 in motor neurons of the spinal cord. These observations indicate that members of the Kir2.0 subfamily may play different physiological roles in control of neuronal function.…”

“…In situ hybridization studies revealed that most Kir2.3 mRNA is found in neurons, rather than in glial cells (5,11,16). Furthermore, Kir2.3 binds to PSD-95, which scaffolds various functional proteins at the postsynaptic membrane of asymmetric synaptic junctions (5,7,23,30).…”

Dendritic Excitability of Mouse Frontal Cortex Pyramidal Neurons Is Shaped by the Interaction among HCN, Kir2, and KleakChannels

“…Double-label immunofluorescence controls included dual-channel recordings of single-labeled cultures to exclude possible bleeding-through of the detected signals. Specificity of the affinity-purified Kir2.2 and Kir2.3 antibodies also was checked by examining sections of rat brain to determine whether the staining pattern matched that found using mRNA localization techniques (Falk et al, 1995;Horio et al, 1996); these experiments revealed a consistent match between antibody staining and mRNA distributions. The distribution pattern was also similar to that of a recent report using a different set of antibodies (Pruss et al, 2005).…”