Retinal Attachment Instability Is Diversified among Mammalian Melanopsins

Tsukamoto, Hisao; Kubo, Yoshihiro; Farrens, David; Koyanagi, Mitsumasa; Terakita, Akihisa; Furutani, Yuji

doi:10.1074/jbc.m115.666305

Cited by 25 publications

(16 citation statements)

References 71 publications

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“…This claim is consistent with the heterologous expression of melanopsin-producing responses that are similar across cell types, and differing as one would expect for different melanopsins (26,27). The melanopsin-containing photoreceptors of amphioxus produce fast light responses (28).…”

supporting

confidence: 81%

Ectopic Expression of Mouse Melanopsin in Drosophila Photoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation

Yasin¹,

Kohn²,

Peters³

et al. 2017

Journal of Biological Chemistry

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The intrinsically photosensitive M1 retinal ganglion cells (ipRGC) initiate non-image-forming light-dependent activities and express the melanopsin (OPN4) photopigment. Several features of ipRGC photosensitivity are characteristic of fly photoreceptors. However, the light response kinetics of ipRGC is much slower due to unknown reasons. Here we used transgenic Drosophila, in which the mouse OPN4 replaced the native Rh1 photopigment of Drosophila R1-6 photoreceptors, resulting in deformed rhabdomeric structure. Immunocytochemistry revealed OPN4 expression at the base of the rhabdomeres, mainly at the rhabdomeral stalk. Measurements of the early receptor current, a linear manifestation of photopigment activation, indicated large expression of OPN4 in the plasma membrane. Comparing the early receptor current amplitude and action spectra between WT and the Opn4-expressing Drosophila further indicated that large quantities of a blue absorbing photopigment were expressed, having a dark stable blue intermediate state. Strikingly, the light-induced current of the Opn4-expressing fly photoreceptors was ϳ40-fold faster than that of ipRGC. Furthermore, an intense white flash induced a small amplitude prolonged dark current composed of discrete unitary currents similar to the Drosophila single photon responses. The induction of prolonged dark currents by intense blue light could be suppressed by a following intense green light, suggesting induction and suppression of prolonged depolarizing afterpotential. This is the first demonstration of heterologous functional expression of mammalian OPN4 in the genetically emendable Drosophila photoreceptors. Moreover, the fast OPN4-activated ionic current of Drosophila photoreceptors relative to that of mouse ipRGC, indicates that the slow light response of ipRGC does not arise from an intrinsic property of melanopsin.The intrinsically photosensitive retinal ganglion cells (ipRGC) 2 are a subclass of retinal ganglion cells expressing the visual pigment, melanopsin (OPN4), which calibrates by direct photic input the circadian pacemaker of the master circadian clock and supports some non-image forming light-dependent functions (reviewed in Ref. 1). There are difficulties in advancing understanding of ipRGC phototransduction. The main obstacle is the scarcity of ipRGC and the low expression levels of phototransduction proteins in these cells. This difficulty makes it nearly impossible to investigate phototransduction of the ipRGC by employing the same set of biochemical and electrophysiological approaches that proved successful in characterizing rhodopsin signaling processes in image-forming rod photoreceptor cells. Therefore, at present, the knowledge of phototransduction of ipRGC is still fragmented (1). A promising way to characterize the OPN4 photopigment arises from the apparent similarity between phototransduction of ipRGC and invertebrates. It has been well established that several features of ipRGC photosensitivity are also characteristic of invertebrate photoreceptor cells. (i)...

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supporting

confidence: 81%

Ectopic Expression of Mouse Melanopsin in Drosophila Photoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation

Yasin¹,

Kohn²,

Peters³

et al. 2017

Journal of Biological Chemistry

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“…Platynereis c-opsin WT and mutants were transiently expressed in COS-1 cells (typically 10 -20 plates), and the cells were harvested 48 h after transfection as described previously (7,70). The collected cells were incubated with 11-cis-retinal overnight, and membrane proteins were solubilized with 1.25% DDM (Dojindo, Kumamoto, Japan), 20 mM HEPES, 140 mM NaCl, 0.25% cholesterol hemisuccinate (Sigma-Aldrich, St. Louis, MO) 25 mM Tris, and 10% glycerol (pH 7.0).…”

Section: Protein Expression and Purificationmentioning

confidence: 99%

“…Retinal configurations of Platynereis c-opsin samples (Figs. 1C and 2B) were analyzed as described previously (7,10). Briefly, this analysis involved mixing 0.2 ml of each purified c-opsin sample after incubation at 37°C with 50 l of 1 M hydroxylamine and 400 l of cold 90% methanol to convert retinal chromophore into retinal oxime, followed by extraction of the retinal oxime with 0.7 ml of n-hexane.…”

Section: Hplc Analysis To Determine Retinal Isomer Contentmentioning

confidence: 99%

A ciliary opsin in the brain of a marine annelid zooplankton is ultraviolet-sensitive, and the sensitivity is tuned by a single amino acid residue

Tsukamoto

Chen

Kubo

et al. 2017

Journal of Biological Chemistry

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Ciliary opsins were classically thought to function only in vertebrates for vision, but they have also been identified recently in invertebrates for non-visual photoreception. Larvae of the annelid are used as a zooplankton model, and this zooplankton species possesses a "vertebrate-type" ciliary opsin (named c-opsin) in the brain. c-opsin is suggested to relay light signals for melatonin production and circadian behaviors. Thus, the spectral and biochemical characteristics of this c-opsin would be directly related to non-visual photoreception in this zooplankton model. Here we demonstrate that the c-opsin can sense UV to activate intracellular signaling cascades and that it can directly bind exogenous all--retinal. These results suggest that this c-opsin regulates circadian signaling in a UV-dependent manner and that it does not require a supply of 11--retinal for photoreception. Avoidance of damaging UV irradiation is a major cause of large-scale daily zooplankton movement, and the observed capability of the c-opsin to transmit UV signals and bind all-retinal is ideally suited for sensing UV radiation in the brain, which presumably lacks enzymes producing 11--retinal. Mutagenesis analyses indicated that a unique amino acid residue (Lys-94) is responsible for c-opsin-mediated UV sensing in the brain. We therefore propose that acquisition of the lysine residue in the c-opsin would be a critical event in the evolution of to enable detection of ambient UV light. In summary, our findings indicate that the c-opsin possesses spectral and biochemical properties suitable for UV sensing by the zooplankton model.

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“…The basis of these unique ipRGC light-response kinetics might be attributed to molecular features of the visual pigment that prolong its desensitization, such as its proposed bi-or possible tri-stability [7], which would prevent photobleaching of the visual pigment and thus support sustained light responses. Additionally, melanopsin's proposed lower affinity for the chromophore compared to rhodopsin, particularly in diurnal mammals [8], could contribute to the ipRGC's lower light sensitivity and sluggish kinetics, compared to rod and cone photoreceptor cells.…”

Section: Introductionmentioning

confidence: 99%

Melanopsin Carboxy-terminus phosphorylation plasticity and bulk negative charge, not strict site specificity, achieves phototransduction deactivation

et al. 2020

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Melanopsin is a visual pigment expressed in a small subset of ganglion cells in the mammalian retina known as intrinsically photosensitive retinal ganglion cells (ipRGCs) and is implicated in regulating non-image forming functions such as circadian photoentrainment and pupil constriction and contrast sensitivity in image formation. Mouse melanopsin's Carboxyterminus (C-terminus) possesses 38 serine and threonine residues, which can potentially serve as phosphorylation sites for a G-protein Receptor Kinase (GRK) and be involved in the deactivation of signal transduction. Previous studies suggest that S388, T389, S391, S392, S394, S395 on the proximal region of the C-terminus of mouse melanopsin are necessary for melanopsin deactivation. We expressed a series of mouse melanopsin C-terminal mutants in HEK293 cells and using calcium imaging, and we found that the necessary cluster of six serine and threonine residues, while being critical, are insufficient for proper melanopsin deactivation. Interestingly, the additional six serine and threonine residues adjacent to the required six sites, in either proximal or distal direction, are capable of restoring wild-type deactivation of melanopsin. These findings suggest an element of plasticity in the molecular basis of melanopsin phosphorylation and deactivation. In addition, C-terminal chimeric mutants and molecular modeling studies support the idea that the initial steps of deactivation and β-arrestin binding are centered around these critical phosphorylation sites (S388-S395). The degree of functional versatility described in this study, along with ipRGC biophysical heterogeneity and the possible use of multiple signal transduction cascades, might contribute to the diverse ipRGC light responses for use in non-image and image forming behaviors, even though all six sub types of ipRGCs express the same melanopsin gene OPN4.

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Retinal Attachment Instability Is Diversified among Mammalian Melanopsins

Cited by 25 publications

References 71 publications

Ectopic Expression of Mouse Melanopsin in Drosophila Photoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation

Ectopic Expression of Mouse Melanopsin in Drosophila Photoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation

A ciliary opsin in the brain of a marine annelid zooplankton is ultraviolet-sensitive, and the sensitivity is tuned by a single amino acid residue

Melanopsin Carboxy-terminus phosphorylation plasticity and bulk negative charge, not strict site specificity, achieves phototransduction deactivation

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