Diversity of Kir channel subunit mRNA expressed by retinal glial cells of the guinea-pig

Raap, Maik; Biedermann, Bernd; Braun, Peter E.; Milenković, Ivan; Skatchkov, Serguei N.; Bringmann, Andreas; Reichenbach, Andreas

doi:10.1097/00001756-200206120-00012

Cited by 44 publications

(32 citation statements)

References 22 publications

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“…However, two recent reports surprisingly showed no expression of Kir5.1 in retina (13,27). The immunohistochemical analyses (13) (27). Although we cannot explain the discrepancy between these results and ours, we can speculate that it may be attributable to differences of quality of the antibodies and the primer sequences for RT-PCR.…”

Section: Discussioncontrasting

confidence: 93%

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Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Ishii

Fujita²,

Iwai³

et al. 2003

American Journal of Physiology-Cell Physiology

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Kir5.1 is an inwardly rectifying K+ channel subunit whose functional role has not been fully elucidated. Expression and distribution of Kir5.1 in retina were examined with a specific polyclonal antibody. Kir5.1 immunoreactivity was detected in glial Müller cells and in some retinal neurons. In the Kir5.1-positive neurons the expression of glutamic acid decarboxylase (GAD65) was detected, suggesting that they may be GABAergic-amacrine cells. In Müller cells, spots of Kir5.1 immunoreactivity distributed diffusely at the cell body and in the distal portions, where Kir4.1 immunoreactivity largely overlapped. In addition, Kir4.1 immunoreactivity without Kir5.1 was strongly concentrated at the endfoot of Müller cells facing the vitreous surface or in the processes surrounding vessels. The immunoprecipitant obtained from retina with anti-Kir4.1 antibody contained Kir5.1. These results suggest that heterotetrameric Kir4.1/Kir5.1 channels may exist in the cell body and distal portion of Müller cells, whereas homomeric Kir4.1 channels are clustered in the endfeet and surrounding vessels. It is possible that homomeric Kir4.1 and heteromeric Kir4.1/Kir5.1 channels play different functional roles in the K+-buffering action of Müller cells.

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Section: Discussioncontrasting

confidence: 93%

“…However, two recent reports surprisingly showed no expression of Kir5.1 in retina (13,27). The immunohistochemical analyses (13) (27).…”

Section: Discussionmentioning

confidence: 96%

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Ishii

Fujita²,

Iwai³

et al. 2003

American Journal of Physiology-Cell Physiology

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“…We also included cortical astrocytes in our Western blots to ensure that we were not limiting our comparison to astrocytes from a single brain region. Surprisingly, our Western blots show expression of several K ir channel proteins that have previously been described in astrocytes and Müller cells (Kofuji et al, 2000;Raap et al, 2002;Schroder et al, 2002;Li et al, 2001) in both glioma cell lines (Fig. 4).…”

Section: Glioma Cells Express Several K Ir Channel Proteinssupporting

confidence: 53%

Mislocalization of K_ir channels in malignant glia

Olsen

Sontheimer

2004

Glia

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Inwardly rectifying potassium (K ir ) channels are a prominent feature of mature, postmitotic astrocytes. These channels are believed to set the resting membrane potential near the potassium equilibrium potential (E K ) and are implicated in potassium buffering. A number of previous studies suggest that K ir channel expression is indicative of cell differentiation. We therefore set out to examine K ir channel expression in malignant glia, which are incapable of differentiation. We used two established and widely used glioma cell lines, D54MG (a WHO grade 4 glioma) and STTG-1 (a WHO grade 3 glioma), and compared them to immature and differentiated astrocytes. Both glioma cell lines were characterized by large outward K + currents, depolarized resting membrane potentials (V m )(-38.5 ± 4.2 mV, D54 and -28.1 ± 3.5 mV, STTG1), and relatively high input resistances (R m ) (260.6 ± 64.7 MΩ, D54 and 687.2 ± 160.3 MΩ, STTG1). These features were reminiscent of immature astrocytes, which also displayed large outward K + currents, had a mean V m of -51.1 ± 3.7 and a mean R m value of 627.5 ± 164 MΩ. In contrast, mature astrocytes had a significantly more negative resting membrane potential (-75.2 ± 0.56 mV), and a mean R m of 25.4 ± 7.4 MΩ. Barium (Ba 2+ ) sensitive K ir currents were >20-fold larger in mature astrocytes (4.06 ± 1.1 nS/pF) than in glioma cells (0.169 ± 0.033 nS/pF D54, 0.244 ± 0.04 nS/pF STTG1), which had current densities closer to those of dividing, immature astrocytes (0.474 ± 0.12 nS/pF). Surprisingly, Western blot analysis shows expression of several K ir channel subunits in glioma cells (K ir 2.3, 3.1, and 4.1). However, while in astrocytes these channels localize diffusely throughout the cell, in glioma cells they are found almost exclusively in either the cell nucleus (K ir 2.3 and 4.1) or ER/Golgi (3.1). These data suggest that mislocalization of K ir channel proteins to intracellular compartments is responsible for a lack of appreciable K ir currents in glioma cells.

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“…Among the various inward rectifier K ϩ channel genes expressed by Mü ller cells (24), the Kir4.1 channel has been proposed to be most important for the mediation of spatial-buffering K ϩ currents (25). The Kir4.1 protein shows a polarized arrangement in Mü ller cells; though the protein exists in the whole retinal tissue, it shows a strong enrichment in such membrane domains across which Mü ller cells in situ are proposed to release excess K ϩ into extraretinal fluid-filled spaces, i.e., at perivascular membrane domains and at the inner and outer limiting membranes (Fig.…”

Section: Diabetes Causes a Redistribution Of The Glial Kmentioning

confidence: 99%

Diabetes Alters Osmotic Swelling Characteristics and Membrane Conductance of Glial Cells in Rat Retina

Pannicke

Iandiev²,

Wurm³

et al. 2006

Diabetes

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165

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Diversity of Kir channel subunit mRNA expressed by retinal glial cells of the guinea-pig

Cited by 44 publications

References 22 publications

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Mislocalization of K_ir channels in malignant glia

Diabetes Alters Osmotic Swelling Characteristics and Membrane Conductance of Glial Cells in Rat Retina

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Diversity of Kir channel subunit mRNA expressed by retinal glial cells of the guinea-pig

Cited by 44 publications

References 22 publications

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K+ channels in retina

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K+ channels in retina

Mislocalization of Kir channels in malignant glia

Diabetes Alters Osmotic Swelling Characteristics and Membrane Conductance of Glial Cells in Rat Retina

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Product

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Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Differential expression and distribution of Kir5.1 and Kir4.1 inwardly rectifying K⁺ channels in retina

Mislocalization of K_ir channels in malignant glia