The retinal photoreceptors and the pigment epithelium. Structure and function. Transduction

Nilsson, Sven Erik G.

doi:10.1111/j.1755-3768.1985.tb06826.x

Cited by 3 publications

(1 citation statement)

References 16 publications

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“…According to a simple compartmental model, photoreceptors consist of two anatomically and functionally distinct segments-an outer segment (OS) that hosts the phototransduction cascades and an "inner segment" (IS) comprised of the ellipsoid, cell body and the synaptic terminal. The non-OS regions are traversed by contiguous cisternae of smooth ER extending between the synaptic terminal and the cell body, whereas the ellipsoid itself is packed with mitochondria (Nilsson, 1985;Mercurio & Holtzman, 1982;Hoang et al, 2002). These studies focused on Ca 2+ regulation in the cell body and ellipsoid regions that contain the two classes of Ca 2+ store (Nilsson, 1985;Mercurio & Holtzman, 1982;Townes-Anderson et al, 1985).…”

Section: Resultsmentioning

confidence: 99%

Intracellular organelles and calcium homeostasis in rods and cones

Szikra

Križaj

2007

Vis Neurosci

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The role of intracellular organelles in Ca2+ homeostasis was studied in salamander rod and cone photoreceptors under conditions that simulate photoreceptor activation by darkness and light. Sustained depolarization evoked a Ca2+ gradient between the cell body and ellipsoid regions of the inner segment (IS). The standing pattern of calcium fluxes was created by interactions between the plasma membrane, endoplasmic reticulum (ER), and mitochondria. Pharmacological experiments suggested that mitochondria modulate both baseline [Ca2+]i in hyperpolarized cells as well as kinetics of Ca2+ entry via L type Ca2+ channels in cell bodies and ellipsoids of depolarized rods and cones. Inhibition of mitochondrial Ca2+ sequestration by antimycin/oligomycin caused a three-fold reduction in the amount of Ca2+ accumulated into intracellular organelles in both cell bodies and ellipsoids. A further 50% decrease in intracellular Ca2+ content within cell bodies, but not ellipsoids, was observed after suppression of SERCA-mediated Ca2+ uptake into the ER. Inhibition of Ca2+ sequestration into the endoplasmic reticulum by thapsigargin or cyclopiazonic acid decreased the magnitude and kinetics of depolarization-evoked Ca2+ signals in cell bodies of rods and cones and decreased the amount of Ca2+ accumulated into internal stores. These results suggest that steady-state [Ca2+]i in photoreceptors is regulated in a region-specific manner, with the ER contribution predominant in the cell body and mitochondrial buffering [Ca2+] the ellipsoid. Local [Ca2+]i levels are set by interactions between the plasma membrane Ca2+ channels and transporters, ER and mitochondria. Mitochondria are likely to play an essential role in temporal and spatial buffering of photoreceptor Ca2+.

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Section: Resultsmentioning

confidence: 99%

Intracellular organelles and calcium homeostasis in rods and cones

Szikra

Križaj

2007

Vis Neurosci

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The dynamic range and domain-specific signals of intracellular calcium in photoreceptors

Szikra

Križaj²

2006

Neuroscience

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Vertebrate photoreceptors consist of strictly delimited subcellular domains: the outer segment, ellipsoid, cell body and synaptic terminal, each hosting crucial cellular functions, including phototransduction, oxidative metabolism, gene expression and transmitter release. We used optical imaging to explore the spatiotemporal dynamics of Ca(2+) signaling in non-outer segment regions of rods and cones. Sustained depolarization, designed to emulate photoreceptor activation in the darkness, evoked a standing Ca(2+) gradient in tiger salamander photoreceptors with spatially-averaged intracellular Ca(2+) concentration within synaptic terminals of approximately 2 microM and lower (approximately 750 nM) intracellular calcium concentration in the ellipsoid. Measurements from axotomized cell bodies and isolated ellipsoids showed that Ca(2+) enters the two compartments via both local L-type Ca(2+) channels and diffusion. The results from optical imaging studies were supported by immunostaining analysis. L-type voltage-operated Ca(2+) channels and plasma membrane Ca(2+) ATPases were highly expressed in synaptic terminals with progressively lower expression levels in the cell body and ellipsoid. These results show photoreceptor Ca(2+) homeostasis is controlled in a region-specific manner by direct Ca(2+) entry and diffusion as well as Ca(2+) extrusion. Moreover, quantitative measurement of intracellular calcium concentration levels in different photoreceptor compartments indicates that the dynamic range of Ca(2+) signaling in photoreceptors is approximately 40-fold, from approximately 50 nM in the light to approximately 2 microM in darkness.

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Structure, function, and pathologic responses of pigment epithelium: a review

Duvall

1987

Seminars in Ophthalmology

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The retinal photoreceptors and the pigment epithelium. Structure and function. Transduction

Cited by 3 publications

References 16 publications

Intracellular organelles and calcium homeostasis in rods and cones

Intracellular organelles and calcium homeostasis in rods and cones

The dynamic range and domain-specific signals of intracellular calcium in photoreceptors

Structure, function, and pathologic responses of pigment epithelium: a review

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