IMR Press / FBL / Volume 7 / Issue 4 / DOI: 10.2741/krizaj

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
Calcium regulation in photoreceptors
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1 Depts. of Physiology and Ophthalmology, University of California San Francisco School of Medicine, San Francisco, CA 94143- 0730, USA
Academic Editor:Emanuel Strehler
Front. Biosci. (Landmark Ed) 2002, 7(4), 2023–2044; https://doi.org/10.2741/krizaj
Published: 1 September 2002
(This article belongs to the Special Issue Calcium homeostasis and calcium signaling in health and disease)
Abstract

In this review we describe some of the remarkable and intricate mechanisms through which the calcium ion (Ca2+) contributes to detection, transduction and synaptic transfer of light stimuli in rod and cone photoreceptors. The function of Ca2+ is highly compartmentalized. In the outer segment, Ca2+ controls photoreceptor light adaptation by independently adjusting the gain of phototransduction at several stages in the transduction chain. In the inner segment and synaptic terminal, Ca2+ regulates cells' metabolism, glutamate release, cytoskeletal dynamics, gene expression and cell death. We discuss the mechanisms of Ca2+ entry, buffering, sequestration, release from internal stores and Ca2+ extrusion from both outer and inner segments, showing that these two compartments have little in common with respect to Ca2+ homeostasis. We also investigate the various roles played by Ca2+ as an integrator of intracellular signaling pathways, and emphasize the central role played by Ca2+ as a second messenger in neuromodulation of photoreceptor signaling by extracellular ligands such as dopamine, adenosine and somatostatin. Finally, we review the intimate link between dysfunction in photoreceptor Ca2+ homeostasis and pathologies leading to retinal dysfunction and blindness.

Keywords
Retina
Photoreceptor
Rod
Cone
Calcium
Plasma Membrane Calcium Atpase
Na-Ca Exchange
Calcium Store
Calcium Buffering
Calcium Channel
Calcium Extrusion
Ryanodine
Inner Segment
Dystrophy
Synaptic Transmission
Review
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