The excitation cascade of Limulus ventral photoreceptors: guanylate cyclase as the link between InsP3-mediated Ca2+release and the opening of cGMP-gated channels

Garger, Alexander V; Richard, Edwin A.; Lisman, John

doi:10.1186/1471-2202-5-7

Cited by 17 publications

(2 citation statements)

References 55 publications

(90 reference statements)

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“…Our data, together with the recent literature (28,29), are making clear that the distinction has to be made between rhabdomeric and ciliary photoreceptors rather than between vertebrate and invertebrate photoreceptors. The terminal effector of rhabdomeric photoreception is typically a transient receptor potential (trp) channel (16). These channels mediate lightinduced calcium influx and could be activated by melanopsin coupling to a phosphoinositide second messenger system in mammalian ganglion cells, cells that have an action spectrum similar to the spectral sensitivity we observed in the amphibian melanophore cell line studied here.…”

Section: Discussionmentioning

confidence: 72%

Rhabdomeric phototransduction initiated by the vertebrate photopigment melanopsin

Isoldi

Rollag

Castrucci

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

144

143

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Melanopsin is the photopigment that confers light sensitivity on intrinsically photosensitive retinal ganglion cells. Mammalian intrinsically photosensitive retinal ganglion cells are involved in the photic synchronization of circadian rhythms to the day-night cycle. Here, we report molecular components of melanopsin signaling using the cultured Xenopus dermal melanophore system. Photoactivated melanopsin is shown to initiate a phosphoinositide signaling pathway similar to that found in invertebrate phototransduction. In melanophores, light increases the intracellular level of inositol trisphosphate and causes the dispersion of melanosomes. Inhibition of phospholipase C and protein kinase C and chelation of intracellular calcium block the effect of light on melanophores. At least four proteins, 43, 74, 90, and 134 kDa, are phosphorylated by protein kinase C upon light stimulation. This provides evidence of an invertebrate-like light-activated signaling cascade within vertebrate cells.melanophore ͉ phosphoinositide ͉ phospholipase C ͉ photoreception T he canonical visual photoreceptors (rods and cones) are not the only photosensitive cells in the mammalian retina. A subpopulation of retinal ganglion cells are intrinsically photosensitive, depolarizing in response to light (1). These cells project to the master circadian clock, the hypothalamic suprachiasmatic nucleus, and other brain sites known to participate in nonvisual responses to light (2-4). It has been demonstrated that these intrinsically photosensitive retinal ganglion cells (ipRGC) are important for photic regulation of the circadian oscillator, acute suppression of pineal melatonin, and acute suppression of activity (masking) in rodents (5, 6). Melanopsin (gene symbol Opn4), a recently identified opsin-based photopigment (7,8), is expressed in ipRGC and is required for their photosensitivity (9). Melanopsin was initially cloned from cultured photosensitive dermal melanophores derived from Xenopus laevis embryos (7). Its peptide sequence is consistent with melanopsin being a member of the superfamily of heptahelical G protein-coupled receptors; specifically, the family of photopigment proteins known as opsins. Despite its vertebrate source, melanopsin's predicted peptide sequence bears greater homology to invertebrate than to vertebrate opsins (7). Although phototransduction is well understood in vertebrate visual photoreceptors and the photoreceptors of some invertebrates, virtually nothing is known currently about intracellular melanopsin-initiated signaling pathways (1).Photosensitive amphibian melanophores are an ideal model in which to investigate melanopsin signal transduction. These cells grow at room temperature by using atmospheric air and show a robust melanosome dispersion in response to illumination. Scoring of this photoresponse can be automated through absorbance monitoring in a microtiter plate reader (10-12). Although ipRGC and Xenopus melanophores naturally express melanopsin, the ultimate cellular responses to melanopsin activation ar...

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Section: Discussionmentioning

confidence: 72%

Rhabdomeric phototransduction initiated by the vertebrate photopigment melanopsin

Isoldi

Rollag

Castrucci

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

144

143

View full text Add to dashboard Cite

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“…For instance, horseshoe crab ( Limulus ) and Drosophila light sensation both begin with an R-opsin/PLC cascade, but Drosophila phototransduction culminates in Trp channel opening (Katz and Minke, 2009). By contrast, most evidence from Limulus indicates that opening of cyclic nucleotide-gated (CNG) ion channels (preceded by IP3-dependent intracellular calcium release and changes in cGMP levels) is responsible for photoreceptor depolarization (Garger et al, 2004). We observed robust expression for orthologs of nearly all central Drosophila phototransduction components in planarian photoreceptors, including two Trp channels.…”

Section: Discussionmentioning

confidence: 99%

Transcriptome Analysis of the Planarian Eye Identifies ovo as a Specific Regulator of Eye Regeneration

2012

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Summary Among the millions of invertebrate species with visual systems, the genetic basis of eye development and function is well understood only in Drosophila melanogaster. We describe an eye transcriptome for the planarian Schmidtea mediterranea. Planarian photoreceptors expressed orthologs of genes required for phototransduction and microvillus structure in Drosophila and vertebrates, and optic pigment cells expressed solute transporters and melanin synthesis enzymes similar to those active in the vertebrate retinal pigment epithelium. Orthologs of several planarian eye genes, such as bestrophin-1 and Usher syndrome genes, cause eye defects in mammals when perturbed and were not previously described to have roles in invertebrate eyes. Five previously undescribed planarian eye transcription factors were required for normal eye formation during head regeneration. In particular, a conserved, transcription factor-encoding ovo gene was expressed from the earliest stages of eye regeneration and was required for regeneration of all cell types of the eye.

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2014

Intracellular Calcium

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The excitation cascade of Limulus ventral photoreceptors: guanylate cyclase as the link between InsP3-mediated Ca2+release and the opening of cGMP-gated channels

Cited by 17 publications

References 55 publications

Rhabdomeric phototransduction initiated by the vertebrate photopigment melanopsin

Rhabdomeric phototransduction initiated by the vertebrate photopigment melanopsin

Transcriptome Analysis of the Planarian Eye Identifies ovo as a Specific Regulator of Eye Regeneration

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