Author/Editor | Križaj, David; Copenhagen, David R | |
Title | Calcium regulation in photoreceptors | |
Type | članek | |
Source | Front Biosci | |
Vol. and No. | Letnik 7 | |
Publication year | 2002 | |
Volume | str. d2023-44 | |
Language | eng | |
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. | |
Descriptors | ADAPTATION, PHYSIOLOGICAL ANIMALS CALCIUM ION CHANNEL GATING ION TRANSPORT MODELS, BIOLOGICAL RETINAL DISEASES |