May 2006
Volume 47, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2006
Molecular Basis Of Ca2+ Flux in Retinal Pigment Epithelial Cells
Author Affiliations & Notes
  • S. Wimmers
    Experimentelle Ophthalmologie, Univ Hospital Hamburg–Eppendorf, Hamburg, Germany
  • S. Ehmer
    Experimentelle Ophthalmologie, Univ Hospital Hamburg–Eppendorf, Hamburg, Germany
  • O. Strauss
    Experimentelle Ophthalmologie, Univ Hospital Hamburg–Eppendorf, Hamburg, Germany
  • Footnotes
    Commercial Relationships  S. Wimmers, None; S. Ehmer, None; O. Strauss, None.
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science May 2006, Vol.47, 2864. doi:
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      S. Wimmers, S. Ehmer, O. Strauss; Molecular Basis Of Ca2+ Flux in Retinal Pigment Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2864.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : The retinal pigment epithelium (RPE) fulfills a multitude of tasks in maintaining normal retinal function. These include light absorption, phagocytosis of shed photoreceptor outer segments, secretion of diverse growth factors and cytokines, and the transport of ions, nutrients and metabolites. It is known that all these processes are regulated by changes in the concentration of intracellular free Ca2+. However, the diversity of Ca2+ transporting membrane proteins in the RPE is hardly investigated. Therefore, we investigated the expression profile of possible Ca2+ transporters and channels in the RPE.

Methods: : We extracted the RNA from freshly isolated RPE cells from human donor eyes for subsequent RT PCR investigations. The results were compared with the expression pattern of the RPE cell line ARPE–19.

Results: : We found a variety of Ca2+ transporting membrane proteins to be expressed in the RPE. Besides the yet described α1D subunit of the voltage–gated Ca2+ channels all three other L type Ca2+ channel subunits and two T type subunits could be detected. Additionally, two subunits of the cyclic nucleotide–gated channels are expressed in the RPE. The transient receptor potential channels (TRP) are subdivided into 6 subgroups. Altogether transcripts for 15 members of 5 subfamilies were found in the RPE. The family of ATP–gated ion channels (P2XR) is represented by 5 members. Finally, all four plasma membrane Ca2+ ATPases and one Na+/Ca2+ exchanger were found to be expressed in the RPE. Apart from some differences freshly isolated and ARPE–19 cells have very similar expression patterns.

Conclusions: : The complex pattern of Ca2+ signalling in the RPE is reflected by the expression of great diversity of Ca2+ transporting membrane proteins. With their different activation mechanisms, such as voltage, cyclic nucleotides, ATP, temperature, etc., the RPE is able to react to different environmental changes by opening of Ca2+ channels. To fulfill their specific tasks, the different Ca2+ influxes could be coupled to their specific intracellular signalling cascade by different subcellular distribution of the channels or by direct coupling to their intracellular effectors.

Keywords: calcium • retinal pigment epithelium • ion channels 
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