Chromophore regeneration: Melanopsin does its own thing

Lucas, Robert J.

doi:10.1073/pnas.0603955103

Cited by 23 publications

(15 citation statements)

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“…Recent studies have suggested that melanopsin does not require the enzymatic machinery of the outer retina for its chromophore regeneration. [32][33][34] Studies examining photosensitivity in neuronal cell lines and Xenopus oocytes heterologously expressing melanopsin are potentially consistent with a such a bistable pigment/photoreisomerization model. 12,13 Partially purified, heterologously expressed, cephalochordate Amphioxus melanopsin has also been shown to be bistable in vitro; exposure to blue light results in a red shift in the absorption spectrum of the pigment.…”

Section: Discussionmentioning

confidence: 83%

Melanopsin-Dependent Persistence and Photopotentiation of Murine Pupillary Light Responses

Zhu

Denner

et al. 2007

Invest. Ophthalmol. Vis. Sci.

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Section: Discussionmentioning

confidence: 83%

Melanopsin-Dependent Persistence and Photopotentiation of Murine Pupillary Light Responses

Zhu

Denner

et al. 2007

Invest. Ophthalmol. Vis. Sci.

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“…These retain alltrans retinal and use a second photon to regenerate the cisisoform. Phylogenetic analyses show that melanopsins are more closely related to invertebrate opsins than other vertebrate opsins, and there have subsequently been suggestions that melanopsin also employs such an intrinsic bleach recovery mechanism (see [143] for review). The most comprehensive analysis of this issue has been undertaken for Amphioxus melanopsin which, when reconstituted with 11-cis retinal, was shown to form a stable photoproduct whose spectral sensitivity was shifted to longer (redder) wavelengths.…”

Section: Melanopsin Spectral Sensitivity and Photobiologymentioning

confidence: 99%

Melanopsin and inner retinal photoreception

Bailes

Lucas

2009

Cell. Mol. Life Sci.

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103

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Over the last ten years there has been growing acceptance that retinal photoreception among mammals extends beyond rods and cones to include a small number of intrinsically photosensitive retinal ganglion cells (ipRGCs). These ipRGCs are capable of responding to light in the absence of rod/cone input thanks to expression of an opsin photopigment called melanopsin. They are specialised for measuring ambient levels of light (irradiance) for a wide variety of so-called non-image-forming light responses. These include synchronisation of circadian clocks to light:dark cycles and the regulation of pupil size, sleep propensity and pineal melatonin production. Here, we provide a review of some of the landmark discoveries in this fast developing field, paying particular emphasis to recent findings and key areas for future investigation.

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“…This result appeared to suggest that melanopsin depended at least in part on an extrinsic enzymatic retinoid cascade for its normal function. However, more recent evidence indicates that this effect is secondary to the devastating effects of the knockout on rod and cone function ( [59]; see also [13,34]). In mice with degenerative loss of rods and cones, neither RPE65 deletion nor acute pharmacological disruption of the retinoid cycle has any significant impact on ipRGC sensitivity [59].…”

Section: Identity and Properties Of The Iprgc Photopigmentmentioning

confidence: 99%

Phototransduction in ganglion-cell photoreceptors

Berson

2007

Pflugers Arch - Eur J Physiol

145

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A third class of photoreceptors has recently been identified in the mammalian retina. They are a rare cell type within the class of ganglion cells, which are the output cells of the retina. These intrinsically photosensitive retinal ganglion cells support a variety of physiological responses to daylight, including synchronization of circadian rhythms, modulation of melatonin release, and regulation of pupil size. The goal of this review is to summarize what is currently known concerning the cellular and biochemical basis of phototransduction in these cells. I summarize the overwhelming evidence that melanopsin serves as the photopigment in these cells and review the emerging evidence that the downstream signaling cascade, including the light-gated channel, might resemble those found in rhabdomeric invertebrate photoreceptors.Keywords Melanopsin . ipRGC . Photoreceptor . Rhabdomeric . Retina . Ganglion cell . Suprachiasmatic nucleus . TRPC Within the past decade, the existence of a previously unknown class of photoreceptor in the mammalian retina has come to light. These directly photosensitive neurons differ radically in form and function from the well-known rod and cone photoreceptors. They are a rare variety of retinal ganglion cells (RGCs), the class of retinal neurons sending axons through the optic nerve to synapse in the brain. For at least the prior century, it had gone without question that ganglion cells were entirely dependent on polysynaptic influences from rods and cones for their responsiveness to light (indeed, even today there is no reason to doubt this for most ganglion cells). However, as the new millennium dawned, this dogma was being challenged by behavioral studies showing the persistence of certain reflex responses to light in photoreceptor degenerate animals, e.g., [14,15,35,36], and the presence of a possible photopigment, melanopsin, in a rare population of ganglion cells [18,19,21,49,50]. In short order, it became clear that these cells possessed a capacity for autonomous phototransduction [5]. These intrinsically photosensitive RGCs (ipRGCs) are now recognized as playing key roles in synchronizing circadian rhythms to the day-night cycle, mediating the pupillary response to light, and modulation of melatonin release by the pineal gland. Many aspects of this rapidly developing story have been thoroughly summarized elsewhere [4,6,14,16,31,44,54,61]. The reader is referred to these reviews for background on the intellectual origins of the discovery of melanopsin and the ipRGCs, on their structure and physiology, and on their contribution to circadian photoentrainment and other nonimage-forming visual functions. The goal of the present review is to summarize the current state of knowledge concerning the nature of the transduction process in ipRGCs. Structural and functional properties of ipRGCs relevant to the phototransduction processThe ipRGCs represent a tiny minority of the RGCs of mammalian retinas (<1-2%) [9,21,51]. Like other ganglion cells, ipRGCs extend dendritic processes...

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Chromophore regeneration: Melanopsin does its own thing

Cited by 23 publications

References 24 publications

Melanopsin-Dependent Persistence and Photopotentiation of Murine Pupillary Light Responses

Melanopsin-Dependent Persistence and Photopotentiation of Murine Pupillary Light Responses

Melanopsin and inner retinal photoreception

Phototransduction in ganglion-cell photoreceptors

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