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Expression profile of voltage-dependent Ca2+ channel subunits in the human retinal pigment epithelium

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Abstract

Background

The secretion of a variety of factors by the retinal pigment epithelium (RPE) is essential for the structural integrity of the neuronal retina and choroid, but also plays a pivotal role in the etiology of diseases such as choroidal neovascularisation. A recent study showed that the secretory activity of the RPE is regulated by the activity of a certain type of voltage-dependent Ca2+ channels, the L-type channel. In order to provide a better base for the understanding of the underlying Ca2+ signalling in these cells, we investigated the expression profile of voltage-dependent Ca2+ channel subunits in RPE cells.

Methods

Using RT-PCR techniques with cDNA isolated from RPE cells, we investigated the expression pattern of Ca2+ channel subunits. Furthermore, we analysed Ba2+ currents through voltage-dependent Ca2+ channels in RPE cells by the patch-clamp technique.

Results

We detected the expression of two L-type channel subtypes and the expression of two different T-type channel subtypes. As accessory subunits, they expressed β2 and β4 and all known α2δ subunits. In general, we were able to confirm these data with cDNA from the ARPE-19 cell line. They only showed some differences in their expression pattern of accessory subunits. Since the expression of T-type channels was so far unknown in RPE cells, we confirmed their expression in the RPE using cDNA isolated from freshly isolated human RPE cells. Furthermore, the patch-clamp analysis of Ba2+ currents showed a heterogeneous pattern of voltage-dependent inward currents in RPE cells. In some cells, typical slowly inactivating L-type currents were detected, whereas in other cells fast inactivating T-type currents could be detected.

Conclusions

These data indicate the expression of a so far not detected subtype of voltage-dependent Ca2+ channels, the T-type channels. Together with the expression of L-type channels, RPE cells show a comparable expression pattern to that of other secretory cells, such as β-islets of the pancreas.

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Acknowledgements

The authors gratefully acknowledge the technical assistance of Stefanie Ehmer, Sabine Helbing and Birgit Grafelmann. The work was supported by the Deutsche Forschungsgemeinschaft grants DFG STR480/8-2 and STR480/9-1.

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Authors and Affiliations

  1. Experimentelle Ophthalmologie, Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany

    Sönke Wimmers & Linn Coeppicus

  2. Institut für Klinische Physiologie, Charite Universitätsmedizin, Campus Benjamin Franklin, Berlin, Germany

    Rita Rosenthal

  3. Experimentelle Ophthalmologie, Klinik und Poliklinik für Augenheilkunde, Klinikum der Universität Regensburg, Regensburg, Germany

    Olaf Strauß

Authors
  1. Sönke Wimmers
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  2. Linn Coeppicus
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  3. Rita Rosenthal
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  4. Olaf Strauß
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Correspondence to Sönke Wimmers.

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Wimmers, S., Coeppicus, L., Rosenthal, R. et al. Expression profile of voltage-dependent Ca2+ channel subunits in the human retinal pigment epithelium. Graefes Arch Clin Exp Ophthalmol 246, 685–692 (2008). https://doi.org/10.1007/s00417-008-0778-7

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  • DOI: https://doi.org/10.1007/s00417-008-0778-7

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