Akihisa Terakita

Osaka City University, Ōsaka, Ōsaka, Japan

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Publications (79)337.52 Total impact

  • Akihisa Terakita, Takashi Nagata
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    ABSTRACT: Many animals have developed systems for sensing environmental conditions during evolution. In sensory cells, receptor molecules are responsible for their sensing abilities. In light sensing, most animals capture light information via rhodopsin-like photoreceptive proteins known as opsin-based pigments. A body of evidence from comparisons of amino acid sequences and in vitro experiments demonstrates that opsins have phylogenetically and functionally diversified during evolution and suggests that the phylogenetic diversity in opsins correlates with the variety of molecular properties of opsin-based pigments. In this review, we discuss the various molecular properties of opsin-based pigments and their contribution to light-sensing ability by providing two examples: i) contribution of photoregeneration ability and Chromophore retinal binding property of an Opn3 homolog to non-visual photoreception, and ii) contribution of an absorption characteristic of a visual pigment to depth perception in jumping spiders.
    ZOOLOGICAL SCIENCE 10/2014; 31(10):653-9. · 1.08 Impact Factor
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    ABSTRACT: Rhodopsin undergoes rearrangements of its transmembrane helices after photon absorption to transfer a light signal to the G protein transducin. To investigate the mechanism by which rhodopsin adopts the transducin-activating conformation, the local environmental changes in the transmembrane region were probed using the cysteine S-H group, whose stretching frequency is well isolated from the other protein vibrational modes. The S-H stretching modes of cysteine residues introduced into Helix III, which contains several key residues for the helical movements, and of native cysteine residues were measured by Fourier transform infrared spectroscopy. This method was applied to metarhodopsin IIa, a precursor of the transducin-activating state in which the intramolecular interactions are likely to produce a state ready for helical movements. No environmental change was observed near the ionic lock between Arg135 in Helix III and Glu247 in Helix VI that maintains the inactive conformation. Rather, the cysteine residues that showed environmental changes were located around the chromophore, Ala164, His211, and Phe261. These findings imply that the hydrogen bond between Helix III and Helix V involving Glu122 and His211 and the hydrophobic packing between Helix III and Helix VI involving Gly121, Leu125, Phe261, and Trp265 are altered before the helical rearrangement leading towards the active conformation.
    Journal of Biological Chemistry 04/2014; · 4.65 Impact Factor
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    ABSTRACT: Mammals contain 1 melanopsin (Opn4) gene that is expressed in a subset of retinal ganglion cells to serve as a photopigment involved in non-image-forming vision such as photoentrainment of circadian rhythms. In contrast, most nonmammalian vertebrates possess multiple melanopsins that are distributed in various types of retinal cells; however, their functions remain unclear. We previously found that the lamprey has only 1 type of mammalian-like melanopsin gene, which is similar to that observed in mammals. Here we investigated the molecular properties and localization of melanopsin in the lamprey and other cyclostome hagfish retinas, which contribute to visual functions including image-forming vision and mainly to non-image-forming vision, respectively. We isolated 1 type of mammalian-like melanopsin cDNA from the eyes of each species. We showed that the recombinant lamprey melanopsin was a blue light-sensitive pigment and that both the lamprey and hagfish melanopsins caused light-dependent increases in calcium ion concentration in cultured cells in a manner that was similar to that observed for mammalian melanopsins. We observed that melanopsin was distributed in several types of retinal cells, including horizontal cells and ganglion cells, in the lamprey retina, despite the existence of only 1 melanopsin gene in the lamprey. In contrast, melanopsin was almost specifically distributed to retinal ganglion cells in the hagfish retina. Furthermore, we found that the melanopsin-expressing horizontal cells connected to the rhodopsin-containing short photoreceptor cells in the lamprey. Taken together, our findings suggest that in cyclostomes, the global distribution of melanopsin in retinal cells might not be related to the melanopsin gene number but to the extent of retinal contribution to visual function.
    PLoS ONE 01/2014; 9(9):e108209. · 3.53 Impact Factor
  • Mitsumasa Koyanagi, Akihisa Terakita
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    ABSTRACT: Most animal opsin-based pigments are typical G protein-coupled receptors (GPCR) and consist of a protein moiety, opsin, and 11-cis retinal as a chromophore. More than several thousand opsins have been identified from a wide variety of animals, which have multiple opsin genes. Accumulated evidence reveals the molecular property of opsin-based pigments, particularly non-conventional visual pigments including non-visual pigments. Opsin-based pigments are generally a bistable pigment having two stable and photointerconvertible states and therefore are bleach-resistant and reusable, unlike vertebrate visual pigments which become bleached. The opsin family contains Gt-coupled, Gq-coupled, Go-coupled, Gs-coupled, Gi-coupled, and Gi/Go-coupled opsins, indicating the existence of a large diversity of light-driven GPCR-signaling cascades. It is suggested that these molecular properties might contribute to different physiologies. In addition, various opsin based-pigments, especially nonconventional visual pigments having different molecular characteristics would facilitate the design and development of promising optogenetic tools for modulating GPCR-signaling, which is involved in a wide variety of physiological responses. We here introduce molecular and functional properties of various kinds of opsins and discuss their physiological function and also their potentials for optogenetic applications. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
    Biochimica et Biophysica Acta 09/2013; · 4.66 Impact Factor
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    ABSTRACT: Most opsins selectively bind 11-cis retinal as a chromophore to form a photosensitive pigment, which underlies various physiological functions, such as vision and circadian photoentrainment. Recently, opsin 3 (Opn3), originally called encephalopsin or panopsin, and its homologs were identified in various tissues including brain, eye, and liver in both vertebrates and invertebrates, including human. Because Opn3s are mainly expressed in tissues that are not considered to contain sufficient amounts of 11-cis retinal to form pigments, the photopigment formation ability of Opn3 has been of interest. Here, we report the successful expression of Opn3 homologs, pufferfish teleost multiple tissue opsin (PufTMT) and mosquito Opn3 (MosOpn3) and show that these proteins formed functional photopigments with 11-cis and 9-cis retinals. The PufTMT- and MosOpn3-based pigments have absorption maxima in the blue-to-green region and exhibit a bistable nature. These Opn3 homolog-based pigments activate Gi-type and Go-type G proteins light dependently, indicating that they potentially serve as light-sensitive Gi/Go-coupled receptors. We also demonstrated that mammalian cultured cells transfected with the MosOpn3 or PufTMT became light sensitive without the addition of 11-cis retinal and the photosensitivity retained after the continuous light exposure, showing a reusable pigment formation with retinal endogenously contained in culture medium. Interestingly, we found that the MosOpn3 also acts as a light sensor when constituted with 13-cis retinal, a ubiquitously present retinal isomer. Our findings suggest that homologs of vertebrate Opn3 might function as photoreceptors in various tissues; furthermore, these Opn3s, particularly the mosquito homolog, could provide a promising optogenetic tool for regulating cAMP-related G protein-coupled receptor signalings.
    Proceedings of the National Academy of Sciences 03/2013; · 9.81 Impact Factor
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    ABSTRACT: Parietopsin is a nonvisual green light-sensitive opsin closely related to vertebrate visual opsins and was originally identified in lizard parietal eye photoreceptor cells. To obtain insight into the functional diversity of opsins, we investigated by UV-visible absorption spectroscopy the molecular properties of parietopsin and its mutants exogenously expressed in cultured cells and compared the properties to those of vertebrate and invertebrate visual opsins. Our mutational analysis revealed that the counterion in parietopsin is the glutamic acid (Glu) in the second extracellular loop, corresponding to Glu181 in bovine rhodopsin. This arrangement is characteristic of invertebrate rather than vertebrate visual opsins. The photosensitivity and the molar extinction coefficient of parietopsin were also lower than those of vertebrate visual opsins, features likewise characteristic of invertebrate visual opsins. On the other hand, irradiation of parietopsin yielded meta-I, meta-II, and meta-III intermediates after batho and lumi intermediates, similar to vertebrate visual opsins. The pH-dependent equilibrium profile between meta-I and meta-II intermediates was, however, similar to that between acid and alkaline metarhodopsins in invertebrate visual opsins. Thus, parietopsin behaves as an "evolutionary intermediate" between invertebrate and vertebrate visual opsins.
    Biochemistry 03/2012; 51(9):1933-41. · 3.38 Impact Factor
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    ABSTRACT: The principal eyes of jumping spiders have a unique retina with four tiered photoreceptor layers, on each of which light of different wavelengths is focused by a lens with appreciable chromatic aberration. We found that all photoreceptors in both the deepest and second-deepest layers contain a green-sensitive visual pigment, although green light is only focused on the deepest layer. This mismatch indicates that the second-deepest layer always receives defocused images, which contain depth information of the scene in optical theory. Behavioral experiments revealed that depth perception in the spider was affected by the wavelength of the illuminating light, which affects the amount of defocus in the images resulting from chromatic aberration. Therefore, we propose a depth perception mechanism based on how much the retinal image is defocused.
    Science 01/2012; 335(6067):469-71. · 31.20 Impact Factor
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    ABSTRACT: Many animals capture light information via opsin-based pigments. Several thousands of opsins have been identified thus far and the opsin family is divided into eight groups. Members belonging to four out of the eight groups have been elucidated to couple to transducin, Go, Gs, and Gq, respectively, in photoreceptor cells. Accumulated evidence suggests a novel classification of the animal phototransductions, cyclic nucleotide signaling mediated by transducin, Go or Gs in ciliary photoreceptor cells and phosphoinositol signaling mediated by Gq in rhabdomeric photoreceptor cells. Varied opsin-based pigments are spectroscopically classified into two types, bleaching and bistable pigments; that is, the photoproduct of vertebrate visual pigments dissociates its chromophore retinal over time and bleaches, whereas most other opsin-based pigments convert to a stable photoproduct, which can revert to original dark state by subsequent light absorption. Mutational analyses of the both types of pigments implied that during molecular evolution of the vertebrae visual pigments, displacement of the counterion, important amino acid residue for visible light absorption of opsin-based pigment, resulted in not only unique bleaching property but also acquisition of red-sensitive visual pigment and higher G-protein activation ability generated by larger light-induced conformational change of the pigment. Interestingly, a bleaching pigment rhodopsin and parapinopsin, which closely relates to the vertebrate visual pigment but has a bistable nature, couple to visual arrestin and β arrestin, respectively, in the lamprey pineal organ, suggesting the bleaching property also might facilitate the evolution of visual arrestin which is specialized for vertebrate visual function. WIREs Membr Transp Signal 2012, 1:104–111. doi: 10.1002/wmts.6For further resources related to this article, please visit the WIREs website.
    Wiley Interdisciplinary Reviews: Membrane Transport and Signaling. 01/2012; 1(1).
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    ABSTRACT: The pineal-related organs of lower vertebrates have the ability to discriminate different wavelengths of light. This wavelength discrimination is achieved through antagonistic light responses to UV or blue and visible light. Previously, we demonstrated that parapinopsin underlies the UV reception in the lamprey pineal organ and identified parapinopsin genes in teleosts and frogs of which the pineal-related organs were reported to discriminate light. In this study, we report the first identification of parapinopsin in the reptile lineage and show its expression in the parietal eye of the green iguana. Spectroscopic analysis revealed that iguana parapinopsin is a UV-sensitive pigment, similar to lamprey parapinopsin. Interestingly, immunohistochemical analyses using antibodies specific to parapinopsin and parietopsin, a parietal eye green-sensitive pigment, revealed that parapinopsin and parietopsin are colocalized in the outer segments of the parietal eye photoreceptor cells in iguanas. These results strongly suggest that parapinopsin underlies the wavelength discrimination involving UV reception in the iguana parietal eye. The current findings support the idea that parapinopsin is a common photopigment underlying the UV-sensitivity in wavelength discrimination of the pineal-related organs found from lampreys to reptiles.
    PLoS ONE 01/2012; 7(6):e39003. · 3.53 Impact Factor
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    ABSTRACT: The light response of vertebrate visual cells is achieved by light-sensing proteins such as opsin-based pigments as well as signal transduction proteins, including visual arrestin. Previous studies have indicated that the pineal pigment parapinopsin has evolutionally and physiologically important characteristics. Parapinopsin is phylogenetically related to vertebrate visual pigments. However, unlike the photoproduct of the visual pigment rhodopsin, which is unstable, dissociating from its chromophore and bleaching, the parapinopsin photoproduct is stable and does not release its chromophore. Here, we investigated arrestin, which regulates parapinopsin signaling, in the lamprey pineal organ, where parapinopsin and rhodopsin are localized to distinct photoreceptor cells. We found that beta-arrestin, which binds to stimulated G protein-coupled receptors (GPCRs) other than opsin-based pigments, was localized to parapinopsin-containing cells. This result stands in contrast to the localization of visual arrestin in rhodopsin-containing cells. Beta-arrestin bound to cultured cell membranes containing parapinopsin light-dependently and translocated to the outer segments of pineal parapinopsin-containing cells, suggesting that beta-arrestin binds to parapinopsin to arrest parapinopsin signaling. Interestingly, beta-arrestin colocalized with parapinopsin in the granules of the parapinopsin-expressing cell bodies under light illumination. Because beta-arrestin, which is a mediator of clathrin-mediated GPCR internalization, also served as a mediator of parapinopsin internalization in cultured cells, these results suggest that the granules were generated light-dependently by beta-arrestin-mediated internalization of parapinopsins from the outer segments. Therefore, our findings imply that beta-arrestin-mediated internalization is responsible for eliminating the stable photoproduct and restoring cell conditions to the original dark state. Taken together with a previous finding that the bleaching pigment evolved from a non-bleaching pigment, vertebrate visual arrestin may have evolved from a "beta-like" arrestin by losing its clathrin-binding domain and its function as an internalization mediator. Such changes would have followed the evolution of vertebrate visual pigments, which generate unstable photoproducts that independently decay by chromophore dissociation.
    PLoS ONE 01/2011; 6(1):e16402. · 3.53 Impact Factor
  • Hisao Tsukamoto, Akihisa Terakita
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    ABSTRACT: Rhodopsin and related opsin-based pigments, which are photosensitive membrane proteins, have been extensively studied using a wide variety of techniques, with rhodopsin being the most understood G protein-coupled receptor (GPCR). Animals use various opsin-based pigments for vision and a wide variety of non-visual functions. Many functionally varied pigments are roughly divided into two kinds, based on their photoreaction: bistable and monostable pigments. Bistable pigments are thermally stable before and after photo-activation, but monostable pigments are stable only before activation. Here, we review the diversity of bistable pigments and their molecular characteristics. We also discuss the mechanisms underlying different molecular characteristics of bistable and monostable pigments. In addition, the potential of bistable pigments as a GPCR model is proposed.
    Photochemical and Photobiological Sciences 11/2010; 9(11):1435-43. · 2.92 Impact Factor
  • Hisao Tsukamoto, Akihisa Terakita, Yoshinori Shichida
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    ABSTRACT: Rhodopsins are photoreceptor proteins that have diverged from ligand-binding G protein-coupled receptors (GPCRs). Unlike other GPCRs, rhodopsins contain an intrinsic antagonist, 11-cis-retinal, which is converted to the agonist all-trans-retinal upon absorption of a photon. Through evolution, vertebrate rhodopsins have lost the ability of direct binding to the agonist, but some invertebrate and vertebrate non-visual rhodopsins have retained this ability. Here, we investigated the difference in the agonist-binding state between these rhodopsins to further our understanding of the structural and functional diversity of rhodopsins. Mutational analyses of agonist-binding rhodopsin showed that replacement of Ala-269, one of the residues constituting the antagonist-binding site, with bulky amino acids resulted in a large spectral shift in its active state and a great reduction in G protein activity, whereas these were rescued by subsequent replacement of Phe-208 with smaller amino acids. Although similar replacements in vertebrate rhodopsin did not cause a spectral shift in the active state, a similar reduction in and recovery of G protein activity was observed. Therefore, the agonist is located close to Ala-269 in the agonist-binding rhodopsin, but not in vertebrate rhodopsins, and Ala-269 with Phe-208 acts as a pivot for the formation of the G protein-activating state in both rhodopsins. The positions corresponding to Ala-269 and Phe-208 in other GPCRs have been reported to form part of an agonist-binding site. Therefore, an agonist-binding rhodopsin has the molecular architecture of the agonist-binding site similar to that of a general GPCR, whereas vertebrate rhodopsins changed the architecture, resulting in loss of agonist binding during molecular evolution.
    Journal of Biological Chemistry 03/2010; 285(10):7351-7. · 4.65 Impact Factor
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    ABSTRACT: The eyes of flower-visiting butterflies are often spectrally highly complex with multiple opsin genes generated by gene duplication, providing an interesting system for a comparative study of color vision. The Small White butterfly, Pieris rapae, has duplicated blue opsins, PrB and PrV, which are expressed in the blue (λ(max) = 453 nm) and violet receptors (λ(max) = 425 nm), respectively. To reveal accurate absorption profiles and the molecular basis of the spectral tuning of these visual pigments, we successfully modified our honeybee opsin expression system based on HEK293s cells, and expressed PrB and PrV, the first lepidopteran opsins ever expressed in cultured cells. We reconstituted the expressed visual pigments in vitro, and analysed them spectroscopically. Both reconstituted visual pigments had two photointerconvertible states, rhodopsin and metarhodopsin, with absorption peak wavelengths 450 nm and 485 nm for PrB and 420 nm and 482 nm for PrV. We furthermore introduced site-directed mutations to the opsins and found that two amino acid substitutions, at positions 116 and 177, were crucial for the spectral tuning. This tuning mechanism appears to be specific for invertebrates and is partially shared by other pierid and lycaenid butterfly species.
    PLoS ONE 01/2010; 5(11):e15015. · 3.53 Impact Factor
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    ABSTRACT: Peropsin, a member of the opsin family, has characteristics of two functionally distinct opsin-groups, that is, amino acid residues conserved among opsins for light-sensing and a retinal-photoisomerase-like molecular property. Although such a bilateral feature of peropsin seems to be important for understanding the diversity of the opsin family, previous studies have been limited to higher deuterostome, vertebrate and amphioxus peropsins. Here, we report a protostome peropsin homologue from a jumping spider. We found a spider opsin that shares amino acid homology and conserved amino acid residues with known peropsins. The spider opsin-based pigment heterologously expressed in cultured cells exhibited photoisomerase-like isomerization characteristics and a bistable nature. Based on the characteristics of both the amino acid homology and its photochemical properties, we concluded that the spider opsin is the first protostome peropsin homologue. These results show that peropsin existed before the deuterostome-protostome split like other members of the opsin family. In addition, the spider peropsin was localized to non-visual cells in the retina, and fluorescence from reduced retinal chromophore was also observed in the region where peropsin was localized. These findings provide the first demonstration that the peropsin can form a photosensitive pigment in vivo and underlie non-visual function.
    Journal of Comparative Physiology 12/2009; 196(1):51-9. · 1.86 Impact Factor
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    ABSTRACT: Light converts rhodopsin, the prototypical G protein-coupled receptor, into a form capable of activating G proteins. Recent work has shown that the light-activated state of different rhodopsins can possess different molecular properties, especially different abilities to activate G protein. For example, bovine rhodopsin is approximately 20-fold more effective at activating G protein than parapinopsin, a non-visual rhodopsin, although these rhodopsins share relatively high sequence similarity. Here we have investigated possible structural aspects that might underlie this difference. Using a site-directed fluorescence labeling approach, we attached the fluorescent probe bimane to cysteine residues introduced in the cytoplasmic ends of transmembrane helices V and VI in both rhodopsins. The fluorescence spectra of these probes as well as their accessibility to aqueous quenching agents changed dramatically upon photoactivation in bovine rhodopsin but only moderately so in parapinopsin. We also compared the relative movement of helices V and VI upon photoactivation of both rhodopsins by introducing a bimane label and the bimane-quenching residue tryptophan into helices VI and V, respectively. Both receptors showed movement in this region upon activation, although the movement appears much greater in bovine rhodopsin than in parapinopsin. Together, these data suggest that a larger conformational change in helices V and VI of bovine rhodopsin explains why it has greater G protein activation ability than other rhodopsins. The different amplitude of the helix movement may also be responsible for functional diversity of G protein-coupled receptors.
    Journal of Biological Chemistry 07/2009; 284(31):20676-83. · 4.65 Impact Factor
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    ABSTRACT: Light sensing starts with phototransduction in photoreceptor cells. The phototransduction cascade has diverged in different species, such as those mediated by transducin in vertebrate rods and cones, by G(q)-type G protein in insect and molluscan rhabdomeric-type visual cells and vertebrate photosensitive retinal ganglion cells, and by G(o)-type G protein in scallop ciliary-type visual cells. Here, we investigated the phototransduction cascade of a prebilaterian box jellyfish, the most basal animal having eyes containing lens and ciliary-type visual cells similar to vertebrate eyes, to examine the similarity at the molecular level and to obtain an implication of the origin of the vertebrate phototransduction cascade. We showed that the opsin-based pigment functions as a green-sensitive visual pigment and triggers the G(s)-type G protein-mediated phototransduction cascade in the ciliary-type visual cells of the box jellyfish lens eyes. We also demonstrated the light-dependent cAMP increase in the jellyfish visual cells and HEK293S cells expressing the jellyfish opsin. The first identified prebilaterian cascade was distinct from known phototransduction cascades but exhibited significant partial similarity with those in vertebrate and molluscan ciliary-type visual cells, because all involved cyclic nucleotide signaling. These similarities imply a monophyletic origin of ciliary phototransduction cascades distributed from prebilaterian to vertebrate.
    Proceedings of the National Academy of Sciences 11/2008; 105(40):15576-80. · 9.81 Impact Factor
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    ABSTRACT: The vertebrate-type opsin, Ci-opsin1, is localized in the outer segments of the photoreceptor cells of larvae of the ascidian Ciona intestinalis. The absorption spectrum of the photopigment reconstituted from Ci-opsin1 and 11-cis-retinal suggested that the photopigment is responsible for photic behavior of the larvae. The structure and function of Ci-opsin1-positive photoreceptor cells were examined by immunohistochemistry, confocal microscopy, electron microscopy, laser ablation, and behavioral analysis. Ciona larvae have three morphologically distinct groups of photoreceptor cells in the brain vesicle. Group I and group II photoreceptor cells are associated with the ocellus pigment cell on the right side of the brain vesicle. The outer segments of the group I photoreceptor cells are regularly arranged inside the small cavity encircled by the cup-shaped pigment cell. The outer segments of the group II photoreceptor cells are located outside the pigment cavity and exposed to the lumen of the brain vesicle. The outer segments of the group III photoreceptor cells are located near the otolith on the left ventral side of the brain vesicle. Thus, the brain vesicle of the ascidian larva has two ocelli: a 'conventional' pigmented ocellus containing the group I and group II photoreceptor cells and a novel nonpigmented ocellus solely consisting of the group III photoreceptor cells. Laser ablation experiments suggest that the pigmented ocellus is responsible for the photic swimming behavior. The nonpigmented ocellus might relate to later developmental or physiological events, such as metamorphosis, because Ci-opsin1 immunoreactivity appears in the late larval stage and becomes intense just before the onset of metamorphosis.
    The Journal of Comparative Neurology 08/2008; 509(1):88-102. · 3.66 Impact Factor
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    ABSTRACT: Rhodopsin is one of the members of the G protein-coupled receptor family that can catalyze a GDP-GTP exchange reaction on the retinal G protein transducin (Gt) upon photon absorption. There are at least two intermediate states, meta-Ib and meta-II, which exhibit direct interaction with Gt. Meta-Ib binds to GDP-bound Gt, while meta-II forms a complex with Gt having no nucleotide, suggesting that meta-Ib is a state that initially interacts with Gt. Here we investigated whether or not meta-Ib exhibits specific interaction with G protein similar to meta-II, by examining the binding efficiencies of meta-Ib and meta-II to Gialpha and its mutants whose C-terminal 11 amino acids were replaced with those of Goalpha, Gqalpha and Gsalpha. The affinity of meta-Ib to the C-terminal 11 amino acids of Gtalpha was similar to those of Gialpha and its mutant with Goalpha's C-terminal 11 amino acids, whereas meta-II exhibited affinity to the C-terminal 11 amino acids of Gialpha mutant with Goalpha's C-terminal 11 amino acids about half of what was seen for Gtalpha and Gialpha. Both intermediates exhibited no affinity to the Gialpha mutants containing the C-terminal 11 amino acids of Gqalpha and Gsalpha. These results suggested that meta-Ib is the state that exhibits specific interaction with G protein as meta-II does, although meta-Ib exhibits a slightly lenient binding selectivity compared to that of meta-II.
    Photochemistry and Photobiology 07/2008; 85(1):57-62. · 2.29 Impact Factor
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    ABSTRACT: G protein-coupled receptors are classified into several families on the basis of their amino acid sequences and the members of the same family exhibit sequence similarity but those of different families do not. In family 1 GPCRs such as rhodopsin and adrenergic receptor, extensive studies have revealed the stimulus-dependent conformational change of the receptor: the rearrangement of transmembrane helices III and VI is essential for G protein activation. In contrast, in family 3 GPCRs such as metabotropic glutamate receptor (mGluR), the inter-protomer relocation upon ligand binding has been observed but there is much less information about the structural changes of the transmsmbrane helices and the cytoplasmic domains. Here we identified constitutively active mutation sites at the cytoplasmic borders of helices II and IV of mGluR8 and successfully inhibited the G protein activation ability by engineering disulfide cross-linking between these cytoplasmic regions. The analysis of all possible single substitution mutants of these residues revealed that some steric interactions around these sites would be important to keep the receptor protein inactive. These results provided the model that the conformational changes at the cytoplasmic ends of helices II and IV of mGluR are involved in the efficient G protein coupling.
    Journal of Neurochemistry 06/2008; 106(2):850-9. · 3.97 Impact Factor
  • Mitsumasa Koyanagi, Akihisa Terakita
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    ABSTRACT: Rhodopsins (rhodopsins and their related photopigments) are phylogenetically classified into at least seven subfamilies, which are also roughly discriminated by molecular function. The Gq-coupled rhodopsin subfamily, members of which activate the Gq type G protein upon light absorption, contains pigments which underlie both visual and nonvisual physiologic functions. Gq-coupled visual pigments have been found in the rhabdomeric photoreceptor cells of varied protostomes, and those of molluskans and arthropods have been extensively investigated. Recently, a novel photopigment, melanopsin, and its homologs have been identified in varied vertebrates. In mammals, melanopsin is localized in retinal ganglion cells and is involved in nonvisual systems, including circadian entrainment and pupillary light responses. More recently, we discovered a melanopsin homolog in amphioxus, the closest living invertebrate to vertebrates. Amphioxus melanopsin is localized in putative nonvisual photoreceptor cells with rhabdomeric morphology and exhibits molecular properties almost identical to those of invertebrate Gq-coupled visual pigments. The localization and properties of amphioxus melanopsin bridged the functional and evolutionary gap between invertebrate Gq-coupled visual pigments and vertebrate circadian photopigment melanopsins. Research into the Gq-coupled rhodopsin subfamily, especially invertebrate melanopsins, will provide an opportunity to investigate the evolution of various physiologic functions, based on orthologous genes, during animal evolution.
    Photochemistry and Photobiology 06/2008; 84(4):1024-30. · 2.29 Impact Factor

Publication Stats

1k Citations
337.52 Total Impact Points

Institutions

  • 2007–2014
    • Osaka City University
      • Graduate School of Science
      Ōsaka, Ōsaka, Japan
  • 1997–2012
    • Kyoto University
      • Department of Biophysics
      Kyoto, Kyoto-fu, Japan
  • 1999–2001
    • The University of Tokyo
      • Faculty of Science and Graduate School of Science
      Tokyo, Tokyo-to, Japan
    • Hyogo College of Medicine
      • Department of Pharmacology
      Nishinomiya, Hyogo-ken, Japan
  • 1998
    • Osaka University
      • Division of Cell Biology
      Suika, Ōsaka, Japan
  • 1996–1998
    • Oita University
      Ōita, Ōita, Japan
  • 1994
    • Osaka Kyoiku University
      Ōsaka, Ōsaka, Japan