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- Title
Expression of Orai genes and I activation in the human retinal pigment epithelium.
- Authors
Cordeiro, Sönke; Strauss, Olaf
- Abstract
Background: The retinal pigment epithelium (RPE) fulfills a large variety of tasks that are important for visual function. Many of these tasks, such as phagocytosis, growth factor secretion, or transepithelial ion transport, are regulated by increases in intracellular Ca as second-messenger. Despite the multitude of Ca-dependently regulated functions, only few Ca channels have been described so far in the RPE to couple Ca conductance and Ca signaling. Methods: RT-PCR experiments with mRNA of freshly isolated RPE cells as well as from the RPE cell line ARPE-19 and measurements of the intracellular free Ca concentration were performed. Results: The RT-PCR experiments revealed the expression of the I channel proteins Orai 1, 2, and 3 and their stimulators Stim-1 and Stim-2. The classic maneuver to stimulate capacitive Ca entry (depletion of Ca stores by 1 μM thapsigargin under extracellular Ca-free conditions and then re-adding extracellular Ca) led to an increase in intracellular free Ca, which could be blocked by application of a high concentration of 2-APB (75 μM) either before or during induction of capacitive Ca entry. On the other hand, application of a low concentration of 2-APB (2 μM) led to enhancement of the Ca increase induced by capacitive Ca entry. Depletion of cytosolic Ca stores by administration of an extracellular divalent cation-free solution led to an increase in the whole-cell conductance. Conclusions: With these data we show a new Ca entry pathway linked to the Ca/inositolphosphate second-messenger system in RPE cells which help to further understand regulatory pathways of agonists. The expression of Orai channels enables the RPE cells to generate sustained or repetitive Ca signals as they are known to be induced by different stimuli like ATP, bFGF, and the stimulation with photoreceptor outer segments.
- Subjects
RHODOPSIN; INTRACELLULAR calcium; ION channels; CALCIUM channels; CELLULAR signal transduction; GENE expression; POLYMERASE chain reaction
- Publication
Graefe's Archive of Clinical & Experimental Ophthalmology, 2011, Vol 249, Issue 1, p47
- ISSN
0721-832X
- Publication type
Article
- DOI
10.1007/s00417-010-1445-3