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Opsins outside the eye and the skin: a more complex scenario than originally thought for a classical light sensor. Cell Tissue Res 2021; 385:519-538. [PMID: 34236517 DOI: 10.1007/s00441-021-03500-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 06/23/2021] [Indexed: 12/19/2022]
Abstract
Since the discovery of melanopsin as a retinal non-visual photopigment, opsins have been described in several organs and cells. This distribution is strikingly different from the classical localization of photopigments in light-exposed tissues such as the eyes and the skin. More than 10 years ago, a new paradigm in the field was created as opsins were shown, to detect not only light, but also thermal energy in Drosophila. In agreement with these findings, thermal detection by opsins was also reported in mammalian cells. Considering the presence of opsins in tissues not reached by light, an intriguing question has emerged: What is the role of a classical light-sensor, and more recently appreciated thermo-sensor, in these tissues? To tackle this question, we address in this review the most recent studies in the field, with emphasis in mammals. We provide the present view about the role of opsins in peripheral tissues, aiming to integrate the current knowledge of the presence and function of opsins in organs that are not directly affected by light.
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Kouyama T, Ihara K, Maki K, Chan SK. Three-Step Isomerization of the Retinal Chromophore during the Anion Pumping Cycle of Halorhodopsin. Biochemistry 2018; 57:6013-6026. [PMID: 30211543 DOI: 10.1021/acs.biochem.8b00631] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The anion pumping cycle of halorhodopsin from Natronomonas pharaonis ( pHR) is initiated when the all- trans/15- anti isomer of retinal is photoisomerized into the 13- cis/15- anti configuration. A recent crystallographic study suggested that a reaction state with 13- cis/15- syn retinal occurred during the anion release process, i.e., after the N state with the 13- cis/15- anti retinal and before the O state with all- trans/15- anti retinal. In this study, we investigated the retinal isomeric composition in a long-living reaction state at various bromide ion concentrations. It was found that the 13- cis isomer (csHR'), in which the absorption spectrum was blue-shifted by ∼8 nm compared with that of the trans isomer (taHR), accumulated significantly when a cold suspension of pHR-rich claret membranes in 4 M NaBr was illuminated with continuous light. Analysis of flash-induced absorption changes suggested that the branching of the trans photocycle into the 13- cis isomer (csHR') occurs during the decay of an O-like state (O') with 13- cis/15- syn retinal; i.e., O' can decay to either csHR' or O with all- trans/15- anti retinal. The efficiency of the branching reaction was found to be dependent on the bromide ion concentration. At a very high bromide ion concentration, the anion pumping cycle is described by the scheme taHR -( hν) → K → L1a ↔ L1b ↔ N ↔ N' ↔ O' ↔ csHR' ↔ taHR. At a low bromide ion concentration, on the other hand, O' decays into taHR via O.
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Affiliation(s)
- Tsutomu Kouyama
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
| | - Kunio Ihara
- Center for Gene Research , Nagoya University , Nagoya 464-8602 , Japan
| | - Kosuke Maki
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
| | - Siu Kit Chan
- Department of Physics, Graduate School of Science , Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8602 , Japan
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3
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Moraes MN, de Assis LVM, Magalhães-Marques KK, Poletini MO, de Lima LHRG, Castrucci AMDL. Melanopsin, a Canonical Light Receptor, Mediates Thermal Activation of Clock Genes. Sci Rep 2017; 7:13977. [PMID: 29070825 PMCID: PMC5656685 DOI: 10.1038/s41598-017-13939-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/03/2017] [Indexed: 01/09/2023] Open
Abstract
Melanopsin (OPN4) is a photo-pigment found in a small subset of intrinsically photosensitive ganglion cells (ipRGCs) of the mammalian retina. These cells play a role in synchronizing the central circadian pacemaker to the astronomical day by conveying information about ambient light to the hypothalamic suprachiasmatic nucleus, the site of the master clock. We evaluated the effect of a heat stimulus (39.5 °C) on clock gene (Per1 and Bmal1) expression in cultured murine Melan-a melanocytes synchronized by medium changes, and in B16-F10 melanoma cells, in the presence of the selective OPN4 antagonist AA92593, or after OPN4 knockdown by small interfering RNA (siRNA). In addition, we evaluated the effects of heat shock on the localization of melanopsin by immunocytochemistry. In both cell lines melanopsin was found in a region capping the nucleus and heat shock did not affect its location. The heat-induced increase of Per1 expression was inhibited when melanopsin was pharmacologically blocked by AA92593 as well as when its protein expression was suppressed by siRNA in both Melan-a and B16-F10 cells. These data strongly suggest that melanopsin is required for thermo-reception, acting as a thermo-opsin that ultimately feeds the local circadian clock in mouse melanocytes and melanoma cells.
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Affiliation(s)
- Maria Nathália Moraes
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | | | | | - Maristela Oliveira Poletini
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Minas Gerais, Brazil
| | | | - Ana Maria de Lauro Castrucci
- Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil. .,Department of Biology, University of Virginia, Charlottesville, VA, USA.
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Tamogami J, Kikukawa T, Nara T, Demura M, Kimura-Someya T, Shirouzu M, Yokoyama S, Miyauchi S, Shimono K, Kamo N. Existence of two O-like intermediates in the photocycle of Acetabularia rhodopsin II, a light-driven proton pump from a marine alga. Biophys Physicobiol 2017; 14:49-55. [PMID: 28560129 PMCID: PMC5437830 DOI: 10.2142/biophysico.14.0_49] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/02/2017] [Indexed: 12/01/2022] Open
Abstract
A spectrally silent change is often observed in the photocycle of microbial rhodopsins. Here, we suggest the presence of two O intermediates in the photocycle of Acetabularia rhodopsin II (ARII or also called Ace2), a light-driven algal proton pump from Acetabularia acetabulum. ARII exhibits a photocycle including a quasi-equilibrium state of M, N, and O (M⇄N⇄O→) at near neutral and above pH values. However, acidification of the medium below pH ~5.5 causes no accumulation of N, resulting in that the photocycle of ARII can be described as an irreversible scheme (M→O→). This may facilitate the investigation of the latter part of the photocycle, especially the rise and decay of O, during which molecular events have not been sufficiently understood. Thus we analyzed the photocycle under acidic conditions (pH ≤ 5.5). Analysis of the absorbance change at 610 nm, which mainly monitors the fractional concentration changes of K and O, was performed and revealed a photocycle scheme containing two sequential O-states with the different molar extinction coefficients. These photoproducts, termed O1 and O2, may be even produced at physiological pH, although they are not clearly observed under this condition due to the existence of a long M-N-O equilibrium.
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Affiliation(s)
- Jun Tamogami
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan
| | - Takashi Kikukawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.,Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0021, Japan
| | - Toshifumi Nara
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan
| | - Makoto Demura
- Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.,Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo 001-0021, Japan
| | - Tomomi Kimura-Someya
- RIKEN Systems and Structural Biology Center, Yokohama 230-0045, Japan.,RIKEN Center for Life Science Technologies, Yokohama 230-0045, Japan
| | - Mikako Shirouzu
- RIKEN Systems and Structural Biology Center, Yokohama 230-0045, Japan.,RIKEN Center for Life Science Technologies, Yokohama 230-0045, Japan
| | - Shigeyuki Yokoyama
- RIKEN Systems and Structural Biology Center, Yokohama 230-0045, Japan.,RIKEN Structural Biology Laboratory, Yokohama 230-0045, Japan
| | - Seiji Miyauchi
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan.,Graduate School of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Kazumi Shimono
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan.,Graduate School of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Naoki Kamo
- College of Pharmaceutical Sciences, Matsuyama University, Matsuyama, Ehime 790-8578, Japan.,Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan
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Wang T, Oppawsky C, Duan Y, Tittor J, Oesterhelt D, Facciotti MT. Stable closure of the cytoplasmic half-channel is required for efficient proton transport at physiological membrane potentials in the bacteriorhodopsin catalytic cycle. Biochemistry 2014; 53:2380-90. [PMID: 24660845 PMCID: PMC4004217 DOI: 10.1021/bi4013808] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The bacteriorhodopsin (BR) Asp96Gly/Phe171Cys/Phe219Leu
triple
mutant has been shown to translocate protons 66% as efficiently as
the wild-type protein. Light-dependent ATP synthesis in haloarchaeal
cells expressing the triple mutant is 85% that of the wild-type BR
expressing cells. Therefore, the functional activity of BR seems to
be largely preserved in the triple mutant despite the observations
that its ground-state structure resembles that of the wild-type M
state (i.e., the so-called cytoplasmically open state) and that the
mutant shows no significant structural changes during its photocycle,
in sharp contrast to what occurs in the wild-type protein in which
a large structural opening and closing occurs on the cytoplasmic side.
To resolve the contradiction between the apparent functional robustness
of the triple mutant and the presumed importance of the opening and
closing that occurs in the wild-type protein, we conducted additional
experiments to compare the behavior of wild-type and mutant proteins
under different operational loads. Specifically, we characterized
the ability of the two proteins to generate light-driven proton currents
against a range of membrane potentials. The wild-type protein showed
maximal conductance between −150 and −50 mV, whereas
the mutant showed maximal conductance at membrane potentials >+50
mV. Molecular dynamics (MD) simulations of the triple mutant were
also conducted to characterize structural changes in the protein and
in solvent accessibility that might help to functionally contextualize
the current–voltage data. These simulations revealed that the
cytoplasmic half-channel of the triple mutant is constitutively open
and dynamically exchanges water with the bulk. Collectively, the data
and simulations help to explain why this mutant BR does not mediate
photosynthetic growth of haloarchaeal cells, and they suggest that
the structural closing observed in the wild-type protein likely plays
a key role in minimizing substrate back flow in the face of electrochemical
driving forces present at physiological membrane potentials.
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Affiliation(s)
- Ting Wang
- Department of Biomedical Engineering and Genome Center, 451 East Health Science Drive, University of California , Davis, California 95616-8816, United States
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