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Sato K, Ohuchi H. Molecular Property, Manipulation, and Potential Use of Opn5 and Its Homologs. J Mol Biol 2024; 436:168319. [PMID: 37865286 DOI: 10.1016/j.jmb.2023.168319] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 10/08/2023] [Accepted: 10/16/2023] [Indexed: 10/23/2023]
Abstract
Animal opsin is a G-protein coupled receptor (GPCR) and binds retinal as a chromophore to form a photopigment. The Opsin 5 (Opn5) group within the animal opsin family comprises a diverse array of related proteins, such as Opn5m, a protein conserved across all vertebrate lineages including mammals, and other members like Opn5L1 and Opn5L2 found in non-mammalian vertebrate genomes, and Opn6 found in non-therian vertebrate genomes, along with Opn5 homologs present in invertebrates. Although these proteins collectively constitute a single clade within the molecular phylogenetic tree of animal opsins, they exhibit markedly distinct molecular characteristics in areas such as retinal binding properties, photoreaction, and G-protein coupling specificity. Based on their molecular features, they are believed to play a significant role in physiological functions. However, our understanding of their precise physiological functions and molecular characteristics is still developing and only partially realized. Furthermore, their unique molecular characteristics of Opn5-related proteins suggest a high potential for their use as optogenetic tools through more specialized manipulations. This review intends to encapsulate our current understanding of Opn5, discuss potential manipulations of its molecular attributes, and delve into its prospective utility in the burgeoning field of animal opsin optogenetics.
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Affiliation(s)
- Keita Sato
- Department of Cytology and Histology, Faculty of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama City, Okayama 700-8558, Japan.
| | - Hideyo Ohuchi
- Department of Cytology and Histology, Faculty of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama City, Okayama 700-8558, Japan
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2
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Kong F, Ran Z, Zhang M, Liao K, Chen D, Yan X, Xu J. Eyeless razor clam Sinonovacula constricta discriminates light spectra through opsins to guide Ca 2+ and cAMP signaling pathways. J Biol Chem 2024; 300:105527. [PMID: 38043801 PMCID: PMC10788561 DOI: 10.1016/j.jbc.2023.105527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Revised: 11/17/2023] [Accepted: 11/26/2023] [Indexed: 12/05/2023] Open
Abstract
Phototransduction is based on opsins that drive distinct types of Gα cascades. Although nonvisual photosensitivity has long been known in marine bivalves, the underlying molecular basis and phototransduction mechanism are poorly understood. Here, we introduced the eyeless razor clam Sinonovacula constricta as a model to clarify this issue. First, we showed that S. constricta was highly diverse in opsin family members, with a significant expansion in xenopsins. Second, the expression of putative S. constricta opsins was highly temporal-spatio specific, indicating their potential roles in S. constricta development and its peripheral photosensitivity. Third, by cloning four S. constricta opsins with relatively higher expression (Sc_opsin1, 5, 7, and 12), we found that they exhibited different expression levels in response to different light environments. Moreover, we demonstrated that these opsins (excluding Sc_opsin7) couple with Gαq and Gαi cascades to mediate the light-dependent Ca2+ (Sc_opsin1 and 5) and cAMP (Sc_opsin12) signaling pathways. The results indicated that Sc_opsin1 and 5 belonged to Gq-opsins, Sc_opsin12 belonged to Gi-opsins, while Sc_opsin7 might act as a photo-isomerase. Furthermore, we found that the phototransduction function of S. constricta Gq-opsins was dependent on the lysine at the seventh transmembrane domain, and greatly influenced by the external light spectra in a complementary way. Thus, a synergistic photosensitive system mediated by opsins might exist in S. constricta to rapidly respond to the transient or subtle changes of the external light environment. Collectively, our findings provide valuable insights into the evolution of opsins in marine bivalves and their potential functions in nonvisual photosensitivity.
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Affiliation(s)
- Fei Kong
- Key Laboratory of Aquacultural Biotechnology Ministry of Education, Ningbo University, Ningbo, Zhejiang, China
| | - Zhaoshou Ran
- Key Laboratory of Aquacultural Biotechnology Ministry of Education, Ningbo University, Ningbo, Zhejiang, China; Key Laboratory of Marine Biotechnology of Zhejiang Province, Ningbo University, Ningbo, Zhejiang, China.
| | - Mengqi Zhang
- Key Laboratory of Aquacultural Biotechnology Ministry of Education, Ningbo University, Ningbo, Zhejiang, China
| | - Kai Liao
- Key Laboratory of Aquacultural Biotechnology Ministry of Education, Ningbo University, Ningbo, Zhejiang, China
| | - Deshui Chen
- Fujian Dalai Seedling Technology Co, LTD, Luoyuan, Fujian, China
| | - Xiaojun Yan
- Key Laboratory of Marine Biotechnology of Zhejiang Province, Ningbo University, Ningbo, Zhejiang, China
| | - Jilin Xu
- Key Laboratory of Aquacultural Biotechnology Ministry of Education, Ningbo University, Ningbo, Zhejiang, China; Key Laboratory of Marine Biotechnology of Zhejiang Province, Ningbo University, Ningbo, Zhejiang, China; Fujian Dalai Seedling Technology Co, LTD, Luoyuan, Fujian, China.
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3
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McElroy KE, Audino JA, Serb JM. Molluscan Genomes Reveal Extensive Differences in Photopigment Evolution Across the Phylum. Mol Biol Evol 2023; 40:msad263. [PMID: 38039155 PMCID: PMC10733189 DOI: 10.1093/molbev/msad263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/14/2023] [Accepted: 11/14/2023] [Indexed: 12/03/2023] Open
Abstract
In animals, opsins and cryptochromes are major protein families that transduce light signals when bound to light-absorbing chromophores. Opsins are involved in various light-dependent processes, like vision, and have been co-opted for light-independent sensory modalities. Cryptochromes are important photoreceptors in animals, generally regulating circadian rhythm, they belong to a larger protein family with photolyases, which repair UV-induced DNA damage. Mollusks are great animals to explore questions about light sensing as eyes have evolved multiple times across, and within, taxonomic classes. We used molluscan genome assemblies from 80 species to predict protein sequences and examine gene family evolution using phylogenetic approaches. We found extensive opsin family expansion and contraction, particularly in bivalve xenopsins and gastropod Go-opsins, while other opsins, like retinochrome, rarely duplicate. Bivalve and gastropod lineages exhibit fluctuations in opsin repertoire, with cephalopods having the fewest number of opsins and loss of at least 2 major opsin types. Interestingly, opsin expansions are not limited to eyed species, and the highest opsin content was seen in eyeless bivalves. The dynamic nature of opsin evolution is quite contrary to the general lack of diversification in mollusk cryptochromes, though some taxa, including cephalopods and terrestrial gastropods, have reduced repertoires of both protein families. We also found complete loss of opsins and cryptochromes in multiple, but not all, deep-sea species. These results help set the stage for connecting genomic changes, including opsin family expansion and contraction, with differences in environmental, and biological features across Mollusca.
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Affiliation(s)
- Kyle E McElroy
- Ecology, Evolutionary, and Organismal Biology, Iowa State University, Ames, IA, USA
| | - Jorge A Audino
- Ecology, Evolutionary, and Organismal Biology, Iowa State University, Ames, IA, USA
- Department of Zoology, University of São Paulo, São Paulo, Brazil
| | - Jeanne M Serb
- Ecology, Evolutionary, and Organismal Biology, Iowa State University, Ames, IA, USA
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4
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Hofmann KP, Lamb TD. Rhodopsin, light-sensor of vision. Prog Retin Eye Res 2023; 93:101116. [PMID: 36273969 DOI: 10.1016/j.preteyeres.2022.101116] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 11/06/2022]
Abstract
The light sensor of vertebrate scotopic (low-light) vision, rhodopsin, is a G-protein-coupled receptor comprising a polypeptide chain with bound chromophore, 11-cis-retinal, that exhibits remarkable physicochemical properties. This photopigment is extremely stable in the dark, yet its chromophore isomerises upon photon absorption with 70% efficiency, enabling the activation of its G-protein, transducin, with high efficiency. Rhodopsin's photochemical and biochemical activities occur over very different time-scales: the energy of retinaldehyde's excited state is stored in <1 ps in retinal-protein interactions, but it takes milliseconds for the catalytically active state to form, and many tens of minutes for the resting state to be restored. In this review, we describe the properties of rhodopsin and its role in rod phototransduction. We first introduce rhodopsin's gross structural features, its evolution, and the basic mechanisms of its activation. We then discuss light absorption and spectral sensitivity, photoreceptor electrical responses that result from the activity of individual rhodopsin molecules, and recovery of rhodopsin and the visual system from intense bleaching exposures. We then provide a detailed examination of rhodopsin's molecular structure and function, first in its dark state, and then in the active Meta states that govern its interactions with transducin, rhodopsin kinase and arrestin. While it is clear that rhodopsin's molecular properties are exquisitely honed for phototransduction, from starlight to dawn/dusk intensity levels, our understanding of how its molecular interactions determine the properties of scotopic vision remains incomplete. We describe potential future directions of research, and outline several major problems that remain to be solved.
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Affiliation(s)
- Klaus Peter Hofmann
- Institut für Medizinische Physik und Biophysik (CC2), Charité, and, Zentrum für Biophysik und Bioinformatik, Humboldt-Unversität zu Berlin, Berlin, 10117, Germany.
| | - Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2600, Australia.
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5
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Matsuo R, Kotoh S, Takishita K, Sakamoto K, Uebi T, Ozaki M, Matsuo Y, Nishi T. Opsins in the Cephalic and Extracephalic Photoreceptors in the Marine Gastropod Onchidium verruculatum. THE BIOLOGICAL BULLETIN 2022; 243:339-352. [PMID: 36716483 DOI: 10.1086/723013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
AbstractThe marine gastropod Onchidium verruculatum has a pair of ocular photoreceptors, the stalk eyes, on the tip of its stalk near the head, as well as several extracephalic photosensory organs. The retinas of the stalk eye consist of two morphologically distinct visual cells, namely, the type I cells equipped with well-developed microvilli and the type II cells with less developed microvilli. The extracephalic photosensors comprise the dorsal eye, dermal photoreceptor, and brain photosensitive neurons. The characteristics of these cephalic and extracephalic photosensory organs have been studied from morphological and electrophysiological perspectives. However, little is known about the visual pigment molecules responsible for light detection in these organs. In the present study, we searched for opsin molecules that are expressed in the neural tissues of Onchidium and identified six putative signaling-competent opsin species, including Xenopsin1, Xenopsin2, Gq-coupled rhodopsin1, Gq-coupled rhodopsin2, Opsin-5B, and Gq-coupled rhodopsin-like. Immunohistochemical staining of four of the six opsins revealed that Xenopsin1, Gq-coupled rhodopsin1, and Gq-coupled rhodopsin2 are expressed in the rhabdomere of the stalk eye and in the dermal photoreceptor. Xenopsin2 was expressed in the type II photoreceptors of the stalk eye and in the ciliary photoreceptors of the dorsal eye. These immunohistochemical data were consistent with the results of the expression analysis, revealed by quantitative reverse transcription polymerase chain reaction. This study clarified the identities of opsins expressed in the extracephalic photosensory organs of Onchidium and the distinct molecular compositions among the photoreceptors.
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6
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Döring CC, Kumar S, Tumu SC, Kourtesis I, Hausen H. The visual pigment xenopsin is widespread in protostome eyes and impacts the view on eye evolution. eLife 2020; 9:55193. [PMID: 32880369 PMCID: PMC7529461 DOI: 10.7554/elife.55193] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 09/01/2020] [Indexed: 12/31/2022] Open
Abstract
Photoreceptor cells in the eyes of Bilateria are often classified into microvillar cells with rhabdomeric opsin and ciliary cells with ciliary opsin, each type having specialized molecular components and physiology. First data on the recently discovered xenopsin point towards a more complex situation in protostomes. In this study, we provide clear evidence that xenopsin enters cilia in the eye of the larval bryozoan Tricellaria inopinata and triggers phototaxis. As reported from a mollusc, we find xenopsin coexpressed with rhabdomeric-opsin in eye photoreceptor cells bearing both microvilli and cilia in larva of the annelid Malacoceros fuliginosus. This is the first organism known to have both xenopsin and ciliary opsin, showing that these opsins are not necessarily mutually exclusive. Compiling existing data, we propose that xenopsin may play an important role in many protostome eyes and provides new insights into the function, evolution, and possible plasticity of animal eye photoreceptor cells.
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Affiliation(s)
| | - Suman Kumar
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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7
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Rawlinson KA, Lapraz F, Ballister ER, Terasaki M, Rodgers J, McDowell RJ, Girstmair J, Criswell KE, Boldogkoi M, Simpson F, Goulding D, Cormie C, Hall B, Lucas RJ, Telford MJ. Extraocular, rod-like photoreceptors in a flatworm express xenopsin photopigment. eLife 2019; 8:45465. [PMID: 31635694 PMCID: PMC6805122 DOI: 10.7554/elife.45465] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 08/15/2019] [Indexed: 11/17/2022] Open
Abstract
Animals detect light using opsin photopigments. Xenopsin, a recently classified subtype of opsin, challenges our views on opsin and photoreceptor evolution. Originally thought to belong to the Gαi-coupled ciliary opsins, xenopsins are now understood to have diverged from ciliary opsins in pre-bilaterian times, but little is known about the cells that deploy these proteins, or if they form a photopigment and drive phototransduction. We characterized xenopsin in a flatworm, Maritigrella crozieri, and found it expressed in ciliary cells of eyes in the larva, and in extraocular cells around the brain in the adult. These extraocular cells house hundreds of cilia in an intra-cellular vacuole (phaosome). Functional assays in human cells show Maritigrella xenopsin drives phototransduction primarily by coupling to Gαi. These findings highlight similarities between xenopsin and c-opsin and reveal a novel type of opsin-expressing cell that, like jawed vertebrate rods, encloses the ciliary membrane within their own plasma membrane. Eyes are elaborate organs that many animals use to detect light and see, but light can also be sensed in other, simpler ways and for purposes other than seeing. All animals that perceive light rely on cells called photoreceptors, which come in two main types: ciliary or rhabdomeric. Sometimes, an organism has both types of photoreceptors, but one is typically more important than the other. For example, most vertebrates see using ciliary photoreceptors, while rhabdomeric photoreceptors underpin vision in invertebrates. Flatworms are invertebrates that have long been studied due to their ability to regenerate following injuries. These worms have rhabdomeric photoreceptors in their eyes, but they also have unusual cells outside their eyes that have cilia – slender protuberances from the cell body - and could potentially be light sensitive. One obvious way to test if a cell is a photoreceptor is to see if it produces any light-sensing proteins, such as opsins. Until recently it was thought that each type of photoreceptor produced a different opsin, which were therefore classified into rhabdomeric of ciliary opsins. However, recent work has identified a new type of opsin, called xenopsin, in the ciliary photoreceptors of the larvae of some marine invertebrates. To determine whether the cells outside the flatworm’s eye were ciliary photoreceptors, Rawlinson et al. examined the genetic code of 30 flatworm species looking for ciliary opsin and xenopsin genes. This search revealed that all the flatworm species studied contained the genetic sequence for xenopsin, but not for the ciliary opsin. Rawlinson et al. chose the tiger flatworm to perform further experiments. First, they showed that, in this species, xenopsin genes are active both in the eyes of larvae and in the unusual ciliary cells found outside the eyes of the adult. Next, they put the xenopsin from the tiger flatworm into human embryonic kidney cells, and found that when the protein is present these cells can respond to light. This demonstrates that the newly discovered xenopsin is light-sensitive, suggesting that the unusual ciliary cells found expressing this protein outside the eyes in flatworms are likely photoreceptive cells. It is unclear why flatworms have developed these unusual ciliary photoreceptor cells or what their purpose is outside the eye. Often, photoreceptor cells outside the eyes are used to align the ‘body clock’ with the day-night cycle. This can be a factor in healing, hinting perhaps that these newly found cells may have a role in flatworms’ ability to regenerate.
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Affiliation(s)
- Kate A Rawlinson
- Wellcome Sanger Institute, Hinxton, United Kingdom.,Department of Zoology, University of Cambridge, Cambridge, United Kingdom.,Marine Biological Laboratory, Woods Hole, United States
| | - Francois Lapraz
- Université Côte D'Azur, CNRS, Institut de Biologie Valrose, Nice, France
| | - Edward R Ballister
- New York University School of Medicine, New York, United States.,Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Mark Terasaki
- Marine Biological Laboratory, Woods Hole, United States.,University of Connecticut Health Center, Farmington, United States
| | - Jessica Rodgers
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Richard J McDowell
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Johannes Girstmair
- Centre for Life's Origins and Evolution, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.,Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Katharine E Criswell
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom.,Marine Biological Laboratory, Woods Hole, United States
| | - Miklos Boldogkoi
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Fraser Simpson
- Centre for Life's Origins and Evolution, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | | | | | - Brian Hall
- Department of Biology, Dalhousie University, Halifax, Canada
| | - Robert J Lucas
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Maximilian J Telford
- Centre for Life's Origins and Evolution, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
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8
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Pandey A, LeBlanc DM, Parmar HB, Phạm TTT, Sarker M, Xu L, Duncan R, Liu XQ, Rainey JK. Structure, amphipathy, and topology of the membrane-proximal helix 8 influence apelin receptor plasma membrane localization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183036. [PMID: 31394100 DOI: 10.1016/j.bbamem.2019.183036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 07/08/2019] [Accepted: 08/02/2019] [Indexed: 12/11/2022]
Abstract
G-protein coupled receptors (GPCRs) typically have an amphipathic helix ("helix 8") immediately C-terminal to the transmembrane helical bundle. To date, a number of functional roles have been associated with GPCR helix 8 segments, but structure-function analysis for this region remains limited. Here, we examine helix 8 of the apelin receptor (AR or APJ), a class A GPCR with wide physiological and pathophysiological relevance. The 71 residue C-terminal tail of the AR is primarily intrinsically disordered, with a detergent micelle-induced increase in helical character. This helicity was localized to the helix 8 region, in good agreement with the recent AR crystal structure. A series of helix 8 mutants were made to reduce helicity, remove amphipathy, or flip the hydrophobic and hydrophilic faces. Each mutant AR was tested both biophysically, in the isolated C-terminal tail, and functionally in HEK 293 T cells, for full-length AR. In all instances, micelle interactions were maintained, and steady-state AR expression was efficient. However, removal of amphipathy or helical character led to a significant decrease in cell surface localization. Flipping of helix 8 amphipathic topology restored cell surface localization to some degree, but still was significantly reduced relative to wild-type. Structural integrity, amphipathy to drive membrane association, and correct topology of helix 8 membrane association all thus appear important for cell surface localization of the AR. This behavior correlates well to GPCR C-terminal tail sequence motifs, implying that these serve to specify key topological features of helix 8 and its proximity to the transmembrane domain.
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Affiliation(s)
- Aditya Pandey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Danielle M LeBlanc
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Hirendrasinh B Parmar
- Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Trần Thanh Tâm Phạm
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Muzaddid Sarker
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Lingling Xu
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Roy Duncan
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Xiang-Qin Liu
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Jan K Rainey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
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9
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Matsuo R, Koyanagi M, Nagata A, Matsuo Y. Co‐expression of opsins in the eye photoreceptor cells of the terrestrial slug
Limax valentianus. J Comp Neurol 2019; 527:3073-3086. [DOI: 10.1002/cne.24732] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/29/2019] [Accepted: 06/17/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Ryota Matsuo
- Department of Environmental Sciences, International College of Arts and SciencesFukuoka Women's University Fukuoka Japan
| | - Mitsumasa Koyanagi
- Department of Biology and Geosciences, Graduate School of ScienceOsaka City University Osaka Japan
| | - Akane Nagata
- Department of Environmental Sciences, International College of Arts and SciencesFukuoka Women's University Fukuoka Japan
| | - Yuko Matsuo
- Department of Environmental Sciences, International College of Arts and SciencesFukuoka Women's University Fukuoka Japan
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10
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Arginine 313 of the putative 8th helix mediates Gα q/14 coupling of human CC chemokine receptors CCR2a and CCR2b. Cell Signal 2018; 53:170-183. [PMID: 30321592 DOI: 10.1016/j.cellsig.2018.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 01/29/2023]
Abstract
In man, two CC chemokine receptor isoforms, CCR2a and CCR2b, are present that belong to the rhodopsin-like G protein-coupled receptor family, and couple to Gi and Gq family members. The CCR2 receptors are known to regulate canonical functions of chemokines such as directed migration of leukocytes, and to potentially control non-canonical functions such as differentiation, proliferation, and gene transcription of immune and non-immune cells. We recently reported on the activation of phospholipase C isoenzymes and RhoA GTPases by coupling of the two CCR2 receptors to members of the Gq family, in particular Gαq and Gα14. So far little is known about the structural requirements for the CCR2/Gq/14 interaction. Interestingly, the CCR2 receptor isoforms are identical up to arginine 313 (R313) that is part of the putative 8th helix in CCR2 receptors, and the 8th helix has been implicated in the interaction of rhodopsin-like G protein-coupled receptors with Gαq. In the present work we describe that the 8th helix of both CCR2a and CCR2b is critically involved in selectively activating Gαq/14-regulated signaling. Refined analysis using various CCR2a and CCR2b mutants and analyzing their cellular signaling, e.g. ligand-dependent (i) activation of phospholipase C isoenzymes, (ii) stimulation of serum response factor-mediated gene transcription, (iii) activation of mitogen-activated protein kinases, (iv) internalization, and (v) changes in intracellular calcium concentrations, identified arginine 313 within the amino terminal portion of helix 8 to play a role for the agonist-mediated conformational changes and the formation of a Gαq/14 binding surface. We show that R313 determines Gαq/14 protein-dependent but not Gi protein-dependent cellular signaling, and plays no role in Gq/Gi-independent receptor internalization, indicating a role of R313 in biased signaling of CCR2 receptors.
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11
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Vöcking O, Kourtesis I, Tumu SC, Hausen H. Co-expression of xenopsin and rhabdomeric opsin in photoreceptors bearing microvilli and cilia. eLife 2017; 6:23435. [PMID: 28876222 PMCID: PMC5648526 DOI: 10.7554/elife.23435] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 09/01/2017] [Indexed: 12/22/2022] Open
Abstract
Ciliary and rhabdomeric opsins are employed by different kinds of photoreceptor cells, such as ciliary vertebrate rods and cones or protostome microvillar eye photoreceptors, that have specialized structures and molecular physiologies. We report unprecedented cellular co-expression of rhabdomeric opsin and a visual pigment of the recently described xenopsins in larval eyes of a mollusk. The photoreceptors bear both microvilli and cilia and express proteins that are orthologous to transporters in microvillar and ciliary opsin trafficking. Highly conserved but distinct gene structures suggest that xenopsins and ciliary opsins are of independent origin, irrespective of their mutually exclusive distribution in animals. Furthermore, we propose that frequent opsin gene loss had a large influence on the evolution, organization and function of brain and eye photoreceptor cells in bilaterian animals. The presence of xenopsin in eyes of even different design might be due to a common origin and initial employment of this protein in a highly plastic photoreceptor cell type of mixed microvillar/ciliary organization. Animal eyes have photoreceptor cells that contain light-sensitive molecules called opsins. Although all animal photoreceptor cells of this kind share a common origin, the cells found in different organisms can differ considerably. The photoreceptor cells in flies, squids and other invertebrates store a type of opsin called r-opsin in thin projections on the surface known as microvilli. On the other hand, the visual photoreceptor cells in human and other vertebrate eyes transport another type of opsin (known as c-opsin) into more prominent extensions called cilia. It has been suggested that the fly and vertebrate photoreceptor cells represent clearly distinct evolutionary lineages of cells, which diverged early in animal evolution. However, several organisms that are more closely related to flies than to vertebrates have eye photoreceptor cells with cilia. Do all eye photoreceptors with cilia have a common origin in evolution or did they emerge independently in vertebrates and certain invertebrates? The photoreceptor cells of a marine mollusc called Leptochiton asellus, are unusual because they bear both microvilli and cilia, suggesting they have intermediate characteristics between the two well-known types of photoreceptor cells. Previous studies have shown that these photoreceptor cells use r-opsin, but Vöcking et al. have now detected the presence of an additional opsin in the cells. This opsin is a member of the recently discovered xenopsin family of molecules. Further analyses support the findings of previous studies that suggested this type of opsin emerged early on in animal evolution, independently from c-opsin. Other invertebrates that have cilia on their eye photoreceptors also use xenopsin and not c-opsin. The findings of Vöcking et al. suggest that, in addition to c-opsin and r-opsin, xenopsin has also driven the evolution of photoreceptor cells in animals. Eye photoreceptor cells in invertebrates with cilia probably share a common origin with the microvilli photoreceptor cells that is distinct from that of vertebrate visual cells. The observation that two very different types of opsin can be produced within a single cell suggests that the molecular processes that respond to light in photoreceptor cells may be much more complex than previously anticipated. Further work on these processes may help us to understand how animal eyes work and how they are affected by disease.
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Affiliation(s)
- Oliver Vöcking
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway.,Department of Ophthalmology, University of Pittsburgh, Pittsburgh, United States
| | - Ioannis Kourtesis
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Sharat Chandra Tumu
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Harald Hausen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
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12
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Sato T, Kawasaki T, Mine S, Matsumura H. Functional Role of the C-Terminal Amphipathic Helix 8 of Olfactory Receptors and Other G Protein-Coupled Receptors. Int J Mol Sci 2016; 17:ijms17111930. [PMID: 27869740 PMCID: PMC5133925 DOI: 10.3390/ijms17111930] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/09/2016] [Accepted: 11/14/2016] [Indexed: 11/23/2022] Open
Abstract
G protein-coupled receptors (GPCRs) transduce various extracellular signals, such as neurotransmitters, hormones, light, and odorous chemicals, into intracellular signals via G protein activation during neurological, cardiovascular, sensory and reproductive signaling. Common and unique features of interactions between GPCRs and specific G proteins are important for structure-based design of drugs in order to treat GPCR-related diseases. Atomic resolution structures of GPCR complexes with G proteins have revealed shared and extensive interactions between the conserved DRY motif and other residues in transmembrane domains 3 (TM3), 5 and 6, and the target G protein C-terminal region. However, the initial interactions formed between GPCRs and their specific G proteins remain unclear. Alanine scanning mutagenesis of the murine olfactory receptor S6 (mOR-S6) indicated that the N-terminal acidic residue of helix 8 of mOR-S6 is responsible for initial transient and specific interactions with chimeric Gα15_olf, resulting in a response that is 2.2-fold more rapid and 1.7-fold more robust than the interaction with Gα15. Our mutagenesis analysis indicates that the hydrophobic core buried between helix 8 and TM1–2 of mOR-S6 is important for the activation of both Gα15_olf and Gα15. This review focuses on the functional role of the C-terminal amphipathic helix 8 based on several recent GPCR studies.
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Affiliation(s)
- Takaaki Sato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorioka, Ikeda, Osaka 563-8577, Japan.
| | - Takashi Kawasaki
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorioka, Ikeda, Osaka 563-8577, Japan.
| | - Shouhei Mine
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorioka, Ikeda, Osaka 563-8577, Japan.
| | - Hiroyoshi Matsumura
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
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13
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Porath-Krause AJ, Pairett AN, Faggionato D, Birla BS, Sankar K, Serb JM. Structural differences and differential expression among rhabdomeric opsins reveal functional change after gene duplication in the bay scallop, Argopecten irradians (Pectinidae). BMC Evol Biol 2016; 16:250. [PMID: 27855630 PMCID: PMC5114761 DOI: 10.1186/s12862-016-0823-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 11/01/2016] [Indexed: 11/10/2022] Open
Abstract
Background Opsins are the only class of proteins used for light perception in image-forming eyes. Gene duplication and subsequent functional divergence of opsins have played an important role in expanding photoreceptive capabilities of organisms by altering what wavelengths of light are absorbed by photoreceptors (spectral tuning). However, new opsin copies may also acquire novel function or subdivide ancestral functions through changes to temporal, spatial or the level of gene expression. Here, we test how opsin gene copies diversify in function and evolutionary fate by characterizing four rhabdomeric (Gq-protein coupled) opsins in the scallop, Argopecten irradians, identified from tissue-specific transcriptomes. Results Under a phylogenetic analysis, we recovered a pattern consistent with two rounds of duplication that generated the genetic diversity of scallop Gq-opsins. We found strong support for differential expression of paralogous Gq-opsins across ocular and extra-ocular photosensitive tissues, suggesting that scallop Gq-opsins are used in different biological contexts due to molecular alternations outside and within the protein-coding regions. Finally, we used available protein models to predict which amino acid residues interact with the light-absorbing chromophore. Variation in these residues suggests that the four Gq-opsin paralogs absorb different wavelengths of light. Conclusions Our results uncover novel genetic and functional diversity in the light-sensing structures of the scallop, demonstrating the complicated nature of Gq-opsin diversification after gene duplication. Our results highlight a change in the nearly ubiquitous shadow response in molluscs to a narrowed functional specificity for visual processes in the eyed scallop. Our findings provide a starting point to study how gene duplication may coincide with eye evolution, and more specifically, different ways neofunctionalization of Gq-opsins may occur. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0823-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Anita J Porath-Krause
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 50011, IA, USA
| | - Autum N Pairett
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 50011, IA, USA
| | - Davide Faggionato
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 50011, IA, USA
| | - Bhagyashree S Birla
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, 50011, IA, USA.,Interdepartmental Graduate Program in Bioinformatics and Computational Biology, Iowa State University, Ames, 50011, IA, USA
| | - Kannan Sankar
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, 50011, IA, USA.,Interdepartmental Graduate Program in Bioinformatics and Computational Biology, Iowa State University, Ames, 50011, IA, USA
| | - Jeanne M Serb
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 50011, IA, USA.
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14
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Abstract
The melanocortin-3 receptor (MC3R) is a member of the family A G protein-coupled receptors (GPCRs). The MC3R remains the most enigmatic of the melanocortin receptors with regard to its physiological functions, especially its role in energy homeostasis. The N/DPxxY motif and the eighth helix (helix 8) in the carboxyl terminus of GPCRs have been identified to be important for receptor expression, ligand binding, signal transduction and internalization. To gain a better understanding of the structure-function relationship of MC3R, we performed a systematic study of all 20 residues in this domain using alanine-scanning mutagenesis. We showed that although all mutants were expressed normally on the cell surface, eleven residues were important for ligand binding and one was indispensable for downstream cAMP generation. F347A showed constitutive activity in cAMP signaling while all the other mutants had normal basal activities. We studied the signaling capacity of nine mutants in the ERK1/2 signaling pathway. All of these mutants showed normal basal ERK1/2 phosphorylation levels. The pERK1/2 levels of six binding- or signaling-defective mutants were enhanced upon agonist stimulation. The unbalanced cAMP and pERK1/2 signaling pathways suggested the existence of biased signaling in MC3R mutants. In summary, we showed that the DPLIY motif and helix 8 was important for MC3R activation and signal transduction. Our data led to a better understanding of the structure-function relationship of MC3R.
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Affiliation(s)
- Zhao Yang
- Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USASchool of Applied Chemistry and Biological TechnologyShenzhen Polytechnic, Shenzhen 518055, China
| | - Zhi-Li Huang
- Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USASchool of Applied Chemistry and Biological TechnologyShenzhen Polytechnic, Shenzhen 518055, China Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USASchool of Applied Chemistry and Biological TechnologyShenzhen Polytechnic, Shenzhen 518055, China
| | - Ya-Xiong Tao
- Department of AnatomyPhysiology and Pharmacology, College of Veterinary Medicine, Auburn University, 212 Greene Hall, Auburn, Alabama 36849, USASchool of Applied Chemistry and Biological TechnologyShenzhen Polytechnic, Shenzhen 518055, China
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15
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Manfra O, Van Craenenbroeck K, Skieterska K, Frimurer T, Schwartz TW, Levy FO, Andressen KW. Downregulation of 5-HT7 Serotonin Receptors by the Atypical Antipsychotics Clozapine and Olanzapine. Role of Motifs in the C-Terminal Domain and Interaction with GASP-1. ACS Chem Neurosci 2015; 6:1206-18. [PMID: 25706089 DOI: 10.1021/cn500339p] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The human 5-HT7 serotonin receptor, a G-protein-coupled receptor (GPCR), activates adenylyl cyclase constitutively and upon agonist activation. Biased ligands differentially activate 5-HT7 serotonin receptor desensitization, internalization and degradation in addition to G protein activation. We have previously found that the atypical antipsychotics clozapine and olanzapine inhibited G protein activation and, surprisingly, induced both internalization and lysosomal degradation of 5-HT7 receptors. Here, we aimed to determine the mechanism of clozapine- and olanzapine-mediated degradation of 5-HT7 receptors. In the C-terminus of the 5-HT7 receptor, we identified two YXXΦ motifs, LR residues, and a palmitoylated cysteine anchor as potential sites involved in receptor trafficking to lysosomes followed by receptor degradation. Mutating either of these sites inhibited clozapine- and olanzapine-mediated degradation of 5-HT7 receptors and also interfered with G protein activation. In addition, we tested whether receptor degradation was mediated by the GPCR-associated sorting protein-1 (GASP-1). We show that GASP-1 binds the 5-HT7 receptor and regulates the clozapine-mediated degradation. Mutations of the identified motifs and residues, located in or close to Helix-VIII of the 5-HT7 receptor, modified antipsychotic-stimulated binding of proteins (such as GASP-1), possibly by altering the flexibility of Helix-VIII, and also interfered with G protein activation. Taken together, our data demonstrate that binding of clozapine or olanzapine to the 5-HT7 receptor leads to antagonist-mediated lysosomal degradation by exposing key residues in the C-terminal tail that interact with GASP-1.
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Affiliation(s)
- Ornella Manfra
- Department of Pharmacology,
Institute of Clinical Medicine, University of Oslo and Oslo University Hospital,
P.O. Box 1057 Blindern, 0316 Oslo, Norway
- K.G.
Jebsen Cardiac Research Centre and Center for Heart Failure Research,
Institute of Clinical Medicine, University of Oslo, 0316 Oslo, Norway
| | - Kathleen Van Craenenbroeck
- Laboratory of GPCR
Expression and Signal Transduction (LEGEST), Ghent University-Ghent, 9000 Ghent, Belgium
| | - Kamila Skieterska
- Laboratory of GPCR
Expression and Signal Transduction (LEGEST), Ghent University-Ghent, 9000 Ghent, Belgium
| | - Thomas Frimurer
- The Novo Nordisk Foundation Center for Basic Metabolic Research,
Faculty of Health and Medical Sciences, University of Copenhagen, DK-1165 Copenhagen, Denmark
| | - Thue W. Schwartz
- The Novo Nordisk Foundation Center for Basic Metabolic Research,
Faculty of Health and Medical Sciences, University of Copenhagen, DK-1165 Copenhagen, Denmark
- Laboratory for Molecular Pharmacology, Department of Pharmacology,
Panum Institute, University of Copenhagen, DK-22 00 Copenhagen, Denmark
| | - Finn Olav Levy
- Department of Pharmacology,
Institute of Clinical Medicine, University of Oslo and Oslo University Hospital,
P.O. Box 1057 Blindern, 0316 Oslo, Norway
- K.G.
Jebsen Cardiac Research Centre and Center for Heart Failure Research,
Institute of Clinical Medicine, University of Oslo, 0316 Oslo, Norway
| | - Kjetil Wessel Andressen
- Department of Pharmacology,
Institute of Clinical Medicine, University of Oslo and Oslo University Hospital,
P.O. Box 1057 Blindern, 0316 Oslo, Norway
- K.G.
Jebsen Cardiac Research Centre and Center for Heart Failure Research,
Institute of Clinical Medicine, University of Oslo, 0316 Oslo, Norway
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16
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Liegertová M, Pergner J, Kozmiková I, Fabian P, Pombinho AR, Strnad H, Pačes J, Vlček Č, Bartůněk P, Kozmik Z. Cubozoan genome illuminates functional diversification of opsins and photoreceptor evolution. Sci Rep 2015; 5:11885. [PMID: 26154478 PMCID: PMC5155618 DOI: 10.1038/srep11885] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 06/05/2015] [Indexed: 11/09/2022] Open
Abstract
Animals sense light primarily by an opsin-based photopigment present in a photoreceptor cell. Cnidaria are arguably the most basal phylum containing a well-developed visual system. The evolutionary history of opsins in the animal kingdom has not yet been resolved. Here, we study the evolution of animal opsins by genome-wide analysis of the cubozoan jellyfish Tripedalia cystophora, a cnidarian possessing complex lens-containing eyes and minor photoreceptors. A large number of opsin genes with distinct tissue- and stage-specific expression were identified. Our phylogenetic analysis unequivocally classifies cubozoan opsins as a sister group to c-opsins and documents lineage-specific expansion of the opsin gene repertoire in the cubozoan genome. Functional analyses provided evidence for the use of the Gs-cAMP signaling pathway in a small set of cubozoan opsins, indicating the possibility that the majority of other cubozoan opsins signal via distinct pathways. Additionally, these tests uncovered subtle differences among individual opsins, suggesting possible fine-tuning for specific photoreceptor tasks. Based on phylogenetic, expression and biochemical analysis we propose that rapid lineage- and species-specific duplications of the intron-less opsin genes and their subsequent functional diversification promoted evolution of a large repertoire of both visual and extraocular photoreceptors in cubozoans.
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Affiliation(s)
- Michaela Liegertová
- Department of Transcriptional Regulation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Jiří Pergner
- Department of Transcriptional Regulation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Iryna Kozmiková
- Department of Transcriptional Regulation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Peter Fabian
- Department of Transcriptional Regulation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Antonio R Pombinho
- Department of Cell Differentiation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Hynek Strnad
- Department of Genomics and Bioinformatics, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Jan Pačes
- Department of Genomics and Bioinformatics, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Čestmír Vlček
- Department of Genomics and Bioinformatics, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Petr Bartůněk
- Department of Cell Differentiation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
| | - Zbyněk Kozmik
- Department of Transcriptional Regulation, Institute of Molecular Genetics, Videnska 1083, Prague, CZ-14220, Czech Republic
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17
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Eriksson BJ, Fredman D, Steiner G, Schmid A. Characterisation and localisation of the opsin protein repertoire in the brain and retinas of a spider and an onychophoran. BMC Evol Biol 2013; 13:186. [PMID: 24010579 PMCID: PMC3851285 DOI: 10.1186/1471-2148-13-186] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 09/03/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Opsins have been found in the majority of animals and their most apparent functions are related to vision and light-guided behaviour. As an increasing number of sequences have become available it has become clear that many opsin-like transcripts are expressed in tissues other than the eyes. Opsins can be divided into three main groups: rhabdomeric opsins (r-opsins), ciliary opsins (c-opsins) and group 4 opsins. In arthropods, the main focus has been on the r-opsins involved in vision. However, with increased sequencing it is becoming clear that arthropods also possess opsins of the c-type, group 4 opsins and the newly discovered arthropsins but the functions of these opsins are unknown in arthropods and data on their localisation is limited or absent. RESULTS We identified opsins from the spider Cupiennius salei and the onychophoran Euperipatoides kanangrensis and characterised the phylogeny and localisation of these transcripts. We recovered all known visual opsins in C. salei, and in addition found a peropsin, a c-opsin and an opsin resembling Daphnia pulex arthropsin. The peropsin was expressed in all eye types except the anterior median eyes. The arthropsin and the c-opsin were expressed in the central nervous system but not the eyes. In E. kanangrensis we found: a c-opsin; an opsin resembling D. pulex arthropsins; and an r-opsin with high sequence similarity to previously published onychophoran onychopsins. The E. kanangrensis c-opsin and onychopsin were expressed in both the eyes and the brain but the arthropsin only in the brain. CONCLUSION Our novel finding that opsins of both the ciliary and rhabdomeric type are present in the onychophoran and a spider suggests that these two types of opsins were present in the last common ancestor of the Onychophora and Euarthropoda. The expression of the c-opsin in the eye of an onychophoran indicates that c-opsins may originally have been involved in vision in the arthropod clade. The lack of c-opsin expression in the spider retina suggests that the role for c-opsin in vision was lost in the euarthropods. Our discovery of arthropsin in onychophorans and spiders dates the emergence of arthropsin to the common ancestor of Onychophora and Euarthropoda and their expression in the brain suggests a non-visual function.
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Affiliation(s)
- Bo Joakim Eriksson
- Department of Neurobiology, Faculty of Life Sciences, University of Vienna, Vienna, Austria.
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18
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Moreira IS. Structural features of the G-protein/GPCR interactions. Biochim Biophys Acta Gen Subj 2013; 1840:16-33. [PMID: 24016604 DOI: 10.1016/j.bbagen.2013.08.027] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023]
Abstract
BACKGROUND The details of the functional interaction between G proteins and the G protein coupled receptors (GPCRs) have long been subjected to extensive investigations with structural and functional assays and a large number of computational studies. SCOPE OF REVIEW The nature and sites of interaction in the G-protein/GPCR complexes, and the specificities of these interactions selecting coupling partners among the large number of families of GPCRs and G protein forms, are still poorly defined. MAJOR CONCLUSIONS Many of the contact sites between the two proteins in specific complexes have been identified, but the three dimensional molecular architecture of a receptor-Gα interface is only known for one pair. Consequently, many fundamental questions regarding this macromolecular assembly and its mechanism remain unanswered. GENERAL SIGNIFICANCE In the context of current structural data we review the structural details of the interfaces and recognition sites in complexes of sub-family A GPCRs with cognate G-proteins, with special emphasis on the consequences of activation on GPCR structure, the prevalence of preassembled GPCR/G-protein complexes, the key structural determinants for selective coupling and the possible involvement of GPCR oligomerization in this process.
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Affiliation(s)
- Irina S Moreira
- REQUIMTE/Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
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19
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Bailes HJ, Zhuang LY, Lucas RJ. Reproducible and sustained regulation of Gαs signalling using a metazoan opsin as an optogenetic tool. PLoS One 2012; 7:e30774. [PMID: 22292038 PMCID: PMC3265508 DOI: 10.1371/journal.pone.0030774] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 12/26/2011] [Indexed: 01/18/2023] Open
Abstract
Originally developed to regulate neuronal excitability, optogenetics is increasingly also used to control other cellular processes with unprecedented spatiotemporal resolution. Optogenetic modulation of all major G-protein signalling pathways (Gq, Gi and Gs) has been achieved using variants of mammalian rod opsin. We show here that the light response driven by such rod opsin-based tools dissipates under repeated exposure, consistent with the known bleaching characteristics of this photopigment. We continue to show that replacing rod opsin with a bleach resistant opsin from Carybdea rastonii, the box jellyfish, (JellyOp) overcomes this limitation. Visible light induced high amplitude, reversible, and reproducible increases in cAMP in mammalian cells expressing JellyOp. While single flashes produced a brief cAMP spike, repeated stimulation could sustain elevated levels for 10s of minutes. JellyOp was more photosensitive than currently available optogenetic tools, responding to white light at irradiances ≥1 µW/cm(2). We conclude that JellyOp is a promising new tool for mimicking the activity of Gs-coupled G protein coupled receptors with fine spatiotemporal resolution.
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Affiliation(s)
- Helena J Bailes
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
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20
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Eisenhauer K, Kuhne J, Ritter E, Berndt A, Wolf S, Freier E, Bartl F, Hegemann P, Gerwert K. In channelrhodopsin-2 Glu-90 is crucial for ion selectivity and is deprotonated during the photocycle. J Biol Chem 2012; 287:6904-11. [PMID: 22219197 PMCID: PMC3307317 DOI: 10.1074/jbc.m111.327700] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The light-activated microbial ion channel channelrhodopsin-2 (ChR2) is a powerful tool to study cellular processes with high spatiotemporal resolution in the emerging field of optogenetics. To customize the channel properties for optogenetic experiments, a detailed understanding of its molecular reaction mechanism is essential. Here, Glu-90, a key residue involved in the gating and selectivity mechanism of the ion channel is characterized in detail. The deprotonation of Glu-90 during the photocycle is elucidated by time-resolved FTIR spectroscopy, which seems to be part of the opening mechanism of the conductive pore. Furthermore, Glu-90 is crucial to ion selectivity as also revealed by mutation of this residue combined with voltage clamp experiments. By dynamic homology modeling, we further hypothesized that the conductive pore is flanked by Glu-90 and located between helices A, B, C, and G.
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Affiliation(s)
- Kirstin Eisenhauer
- Department of Biophysics, Ruhr-University Bochum, Universitätsstrasse 150, Bochum 44801, Germany
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21
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Fanelli F, De Benedetti PG. Update 1 of: computational modeling approaches to structure-function analysis of G protein-coupled receptors. Chem Rev 2011; 111:PR438-535. [PMID: 22165845 DOI: 10.1021/cr100437t] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Francesca Fanelli
- Dulbecco Telethon Institute, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy.
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22
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The role of palmitoylation in signalling, cellular trafficking and plasma membrane localization of protease-activated receptor-2. PLoS One 2011; 6:e28018. [PMID: 22140500 PMCID: PMC3226677 DOI: 10.1371/journal.pone.0028018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 10/29/2011] [Indexed: 01/05/2023] Open
Abstract
Protease-activated receptor-2 (PAR2) is a G protein coupled receptor (GPCR) activated by proteolytic cleavage of its amino terminal domain by trypsin-like serine proteases. This irreversible activation mechanism leads to rapid receptor desensitization by internalisation and degradation. We have explored the role of palmitoylation, the post-translational addition of palmitate, in PAR2 signalling, trafficking, cell surface expression and desensitization. Experiments using the palmitoylation inhibitor 2-bromopalmitate indicated that palmitate addition is important in trafficking of PAR2 endogenously expressed by prostate cancer cell lines. This was supported by palmitate labelling using two approaches, which showed that PAR2 stably expressed by CHO-K1 cells is palmitoylated and that palmitoylation occurs on cysteine 361. Palmitoylation is required for optimal PAR2 signalling as Ca2+ flux assays indicated that in response to trypsin agonism, palmitoylation deficient PAR2 is ∼9 fold less potent than wildtype receptor with a reduction of about 33% in the maximum signal induced via the mutant receptor. Confocal microscopy, flow cytometry and cell surface biotinylation analyses demonstrated that palmitoylation is required for efficient cell surface expression of PAR2. We also show that receptor palmitoylation occurs within the Golgi apparatus and is required for efficient agonist-induced rab11a-mediated trafficking of PAR2 to the cell surface. Palmitoylation is also required for receptor desensitization, as agonist-induced β-arrestin recruitment and receptor endocytosis and degradation were markedly reduced in CHO-PAR2-C361A cells compared with CHO-PAR2 cells. These data provide new insights on the life cycle of PAR2 and demonstrate that palmitoylation is critical for efficient signalling, trafficking, cell surface localization and degradation of this receptor.
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Qin K, Dong C, Wu G, Lambert NA. Inactive-state preassembly of G(q)-coupled receptors and G(q) heterotrimers. Nat Chem Biol 2011; 7:740-7. [PMID: 21873996 PMCID: PMC3177959 DOI: 10.1038/nchembio.642] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 06/29/2011] [Indexed: 12/29/2022]
Abstract
G protein-coupled receptors (GPCRs) transmit signals by forming active-state complexes with heterotrimeric G proteins. It has been suggested that some GPCRs also assemble with G proteins before ligand-induced activation and that inactive-state preassembly facilitates rapid and specific G protein activation. However, no mechanism of preassembly has been described, and no functional consequences of preassembly have been demonstrated. Here we show that M(3) muscarinic acetylcholine receptors (M3R) form inactive-state complexes with G(q) heterotrimers in intact cells. The M3R C terminus is sufficient, and a six-amino-acid polybasic sequence distal to helix 8 ((565)KKKRRK(570)) is necessary for preassembly with G(q). Replacing this sequence with six alanine residues prevents preassembly, slows the rate of G(q) activation and decreases steady-state agonist sensitivity. That other G(q)-coupled receptors possess similar polybasic regions and also preassemble with G(q) suggests that these GPCRs may use a common preassembly mechanism to facilitate activation of G(q) heterotrimers.
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Affiliation(s)
- Kou Qin
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, USA
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Abstract
A fundamental question of cell signaling biology is how faint external signals produce robust physiological responses. One universal mechanism relies on signal amplification via intracellular cascades mediated by heterotrimeric G-proteins. This high amplification system allows retinal rod photoreceptors to detect single photons of light. Although much is now known about the role of the α-subunit of the rod-specific G-protein transducin in phototransduction, the physiological function of the auxiliary βγ-complex in this process remains a mystery. Here, we show that elimination of the transducin γ-subunit drastically reduces signal amplification in intact mouse rods. The consequence is a striking decline in rod visual sensitivity and severe impairment of nocturnal vision. Our findings demonstrate that transducin βγ-complex controls signal amplification of the rod phototransduction cascade and is critical for the ability of rod photoreceptors to function in low light conditions.
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Abstract
The visual pigment rhodopsin (rh1) constitutes the first step in the sensory transduction cascade in the rod photoreceptors of the vertebrate eye, forming the basis of vision at low light levels. In most vertebrates, rhodopsin is a single-copy gene whose function in rod photoreceptors is highly conserved. We found evidence for a second rhodopsin-like gene (rh1-2) in the zebrafish genome. This novel gene was not the product of a zebrafish-specific gene duplication event and contains a number of unique amino acid substitutions. Despite these differences, expression of rh1-2 in vitro yielded a protein that not only bound chromophore, producing an absorption spectrum in the visible range (λmax ≈ 500 nm), but also activated in response to light. Unlike rh1, rh1-2 is not expressed during the first 4 days of embryonic development; it is expressed in the retina of adult fish but not the brain or muscle. Similar rh1-2 sequences were found in two other Danio species, as well as a more distantly related cyprinid, Epalzeorhynchos bicolor. While sequences were only identified in cyprinid fish, phylogenetic analyses suggest an older origin for this gene family. Our study suggests that rh1-2 is a functional opsin gene that is expressed in the retina later in development. The discovery of a new previously uncharacterized opsin gene in zebrafish retina is surprising given its status as a model system for studies of vertebrate vision and visual development.
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Two intracellular helices of G-protein coupling receptors could generally support oligomerization and coupling with transducers. Amino Acids 2010; 40:261-8. [PMID: 20571842 DOI: 10.1007/s00726-010-0616-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 04/27/2010] [Indexed: 10/19/2022]
Abstract
For many G-protein coupling receptors (GPCRs), the upkeep of receptor dimers could depend on association with functional Gi α subunits. This is known for Y1, Y2 and Y4 neuropeptide Y receptors [presented in the companion paper (Estes et al., Amino Acids, doi: 10.1007/s00726-010-0642-z , 2010)]. Interactions with transducers use mainly intracellular domains of the receptors. Intracellular loops 1 and 2 in GPCRs are short and lack extensive helicity that could support transducer anchoring. Interaction with G-proteins is known to use the juxtamembrane Helix 8 in the fourth intracellular domain, for which we document a helix-stabilizing n/(n + 4) pattern of large hydrophobic sidechains. Another intracellular helix located in the C-terminal portion of the third intracellular loop does not display a strong stabilizing pattern, and is found in many studies to serve dynamically in association and activation of transducers and effectors. We show that these tracts share features across metazoan phyla not only in opsins and opsin-like receptors (including the Y receptors), but also in Taste-2 and Frizzled receptors. Similarities of these helices across GPCR groups could have both phylogenetic and functional roots.
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Abstract
S-palmitoylation is a conserved feature in many G protein-coupled receptors (GPCRs) involved in a broad array of signaling processes. The prototypical GPCR, rhodopsin, is S-palmitoylated on two adjacent C-terminal Cys residues at its cytoplasmic surface. Surprisingly, absence of palmitoylation has only a modest effect on in vitro or in vivo signaling. Here, we report that palmitoylation-deficient (Palm(-/-)) mice carrying two Cys to Thr and Ser mutations in the opsin gene displayed profound light-induced retinal degeneration that first involved rod and then cone cells. After brief bright light exposure, their retinas exhibited two types of deposits containing nucleic acid and invasive phagocytic macrophages. When Palm(-/-) mice were crossed with Lrat(-/-) mice lacking lecithin:retinol acyl transferase to eliminate retinoid binding to opsin and thereby rendering the eye insensitive to light, rapid retinal degeneration occurred even in 3- to 4-week-old animals. This rapid degeneration suggests that nonpalmitoylated rod opsin is unstable. Treatment of 2-week-old Palm(-/-)Lrat(-/-) mice with an artificial chromophore precursor prevented this retinopathy. In contrast, elimination of signaling to G protein in Palm(-/-)Gnat1(-/-) mice had no effect, indicating that instability of unpalmitoylated opsin lacking chromophore rather than aberrant signal transduction resulted in retinal pathology. Together, these observations provide evidence for a structural role of rhodopsin S-palmitoylation that may apply to other GPCRs as well.
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Ahn KH, Nishiyama A, Mierke DF, Kendall DA. Hydrophobic residues in helix 8 of cannabinoid receptor 1 are critical for structural and functional properties. Biochemistry 2010; 49:502-11. [PMID: 20025243 DOI: 10.1021/bi901619r] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In addition to the heptahelical transmembrane domain shared by all G protein-coupled receptors (GPCRs), many class A GPCRs adopt a helical domain, termed helix 8, in the membrane-proximal region of the C terminus. We investigated the role of residues in the hydrophobic and hydrophilic faces of amphiphilic helix 8 of human cannabinoid receptor 1 (CB1). To differentiate between a role for specific residues and global features, we made two key mutants: one involving replacement of the highly hydrophobic groups, Leu404, Phe408, and Phe412, all with alanine and the second involving substitution of the basic residues, Lys402, Arg405, and Arg409, all with the neutral glutamine. The former showed a very low B(max) based on binding isotherms, a minimal E(max) based on GTPgammaS binding analysis, and defective localization relative to the wild-type CB1 receptor as revealed by confocal microscopy. However, the latter mutant and the wild-type receptors were indistinguishable. Circular dichroism spectroscopy of purified peptides with corresponding sequences indicated that the highly hydrophobic residues are critical for maintaining a strong helical structure in detergent, whereas the positively charged residues are not. Further investigation of mutant receptors revealed that CB1 localization requires a threshold level of hydrophobicity but not specific amino acids. Moreover, mutant receptors carrying two- to six-residue insertions amino-terminal to helix 8 revealed a graded decrease in B(max) values. Our results identify the key helix 8 components (including hydrophobicity of specific residues, structure, and location relative to TM7) determinant for receptor localization leading to robust ligand binding and G protein activation.
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Affiliation(s)
- Kwang H Ahn
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
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Plachetzki DC, Fong CR, Oakley TH. The evolution of phototransduction from an ancestral cyclic nucleotide gated pathway. Proc Biol Sci 2010; 277:1963-9. [PMID: 20219739 DOI: 10.1098/rspb.2009.1797] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The evolutionary histories of complex traits are complicated because such traits are comprised of multiple integrated and interacting components, which may have different individual histories. Phylogenetic studies of complex trait evolution often do not take this into account, instead focusing only on the history of whole, integrated traits; for example, mapping eyes as simply present or absent through history. Using the biochemistry of animal vision as a model, we demonstrate how investigating the individual components of complex systems can aid in elucidating both the origins and diversification of such systems. Opsin-based phototransduction underlies all visual phenotypes in animals, using complex protein cascades that translate light information into changes in cyclic nucleotide gated (CNG) or canonical transient receptor potential (TRPC) ion-channel activity. Here we show that CNG ion channels play a role in cnidarian phototransduction. Transcripts of a CNG ion channel co-localize with opsin in specific cell types of the eyeless cnidarian Hydra magnipapillata. Further, the CNG inhibitor cis-diltiazem ablates a stereotypical photoresponse in the hydra. Our findings in the Cnidaria, the only non-bilaterian lineage to possess functional opsins, allow us to trace the history of CNG-based photosensitivity to the very origin of animal phototransduction. Our general analytical approach, based on explicit phylogenetic analysis of individual components, contrasts the deep evolutionary history of CNG-based phototransduction, today used in vertebrate vision, with the more recent assembly of TRPC-based systems that are common to protostome (e.g. fly and mollusc) vision.
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Affiliation(s)
- David C Plachetzki
- Department of Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.
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30
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Kato A, Touhara K. Mammalian olfactory receptors: pharmacology, G protein coupling and desensitization. Cell Mol Life Sci 2009; 66:3743-53. [PMID: 19652915 PMCID: PMC11115879 DOI: 10.1007/s00018-009-0111-6] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 07/10/2009] [Accepted: 07/15/2009] [Indexed: 12/14/2022]
Abstract
The vertebrate olfactory system recognizes and discriminates between thousands of structurally diverse odorants. Detection of odorants in mammals is mediated by olfactory receptors (ORs), which comprise the largest superfamily of G protein-coupled receptors (GPCRs). Upon odorant binding, ORs couple to G proteins, resulting in an increase in intracellular cAMP levels and subsequent receptor signaling. In this review, we will discuss recently published studies outlining the molecular basis of odor discrimination, focusing on pharmacology, G protein activation, and desensitization of ORs. A greater understanding of the molecular mechanisms underlying OR activity may help in the discovery of agonists and antagonists of ORs, and of GPCRs with potential therapeutic applications.
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Affiliation(s)
- Aya Kato
- Department of Integrated Biosciences, The University of Tokyo, Room 201, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8562 Japan
| | - Kazushige Touhara
- Department of Integrated Biosciences, The University of Tokyo, Room 201, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8562 Japan
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31
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Gehret AU, Jones BW, Tran PN, Cook LB, Greuber EK, Hinkle PM. Role of helix 8 of the thyrotropin-releasing hormone receptor in phosphorylation by G protein-coupled receptor kinase. Mol Pharmacol 2009; 77:288-97. [PMID: 19906838 DOI: 10.1124/mol.109.059733] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The thyrotropin-releasing hormone (TRH) receptor undergoes rapid and extensive agonist-dependent phosphorylation attributable to G protein-coupled receptor (GPCR) kinases (GRKs), particularly GRK2. Like many GPCRs, the TRH receptor is predicted to form an amphipathic helix, helix 8, between the NPXXY motif at the cytoplasmic end of the seventh transmembrane domain and palmitoylation sites at Cys335 and Cys337. Mutation of all six lysine and arginine residues between the NPXXY and residue 340 to glutamine (6Q receptor) did not prevent the receptor from stimulating inositol phosphate turnover but almost completely prevented receptor phosphorylation in response to TRH. Phosphorylation at all sites in the cytoplasmic tail was inhibited. The phosphorylation defect was not reversed by long incubation times or high TRH concentrations. As expected for a phosphorylation-defective receptor, the 6Q-TRH receptor did not recruit arrestin, undergo the typical arrestin-dependent increase in agonist affinity, or internalize well. Lys326, directly before phenylalanine in the common GPCR motif NPXXY(X)(5-6)F(R/K), was critical for phosphorylation. The 6Q-TRH receptor was not phosphorylated effectively in cells overexpressing GRK2 or in in vitro kinase assays containing purified GRK2. Phosphorylation of the 6Q receptor was partially restored by coexpression of a receptor with an intact helix 8 but without phosphorylation sites. Phosphorylation was inhibited but not completely prevented by alanine substitution for cysteine palmitoylation sites. Positively charged amino acids in the proximal tail of the beta2-adrenergic receptor were also important for GRK-dependent phosphorylation. The results indicate that positive residues in helix 8 of GPCRs are important for GRK-dependent phosphorylation.
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Affiliation(s)
- Austin U Gehret
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA
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32
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Parker MS, Parker SL. The fourth intracellular domain of G-protein coupling receptors: helicity, basicity and similarity to opsins. Amino Acids 2009; 38:1-13. [DOI: 10.1007/s00726-009-0316-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Accepted: 06/15/2009] [Indexed: 11/27/2022]
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33
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Park PSH, Sapra KT, Jastrzebska B, Maeda T, Maeda A, Pulawski W, Kono M, Lem J, Crouch RK, Filipek S, Müller DJ, Palczewski K. Modulation of molecular interactions and function by rhodopsin palmitylation. Biochemistry 2009; 48:4294-304. [PMID: 19348429 DOI: 10.1021/bi900417b] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodopsin is palmitylated at two cysteine residues in its carboxyl terminal region. We have looked at the effects of palmitylation on the molecular interactions formed by rhodopsin using single-molecule force spectroscopy and the function of rhodopsin using both in vitro and in vivo approaches. A knockin mouse model expressing palmitate-deficient rhodopsin was used for live animal in vivo studies and to obtain native tissue samples for in vitro assays. We specifically looked at the effects of palmitylation on the chromophore-binding pocket, interactions of rhodopsin with transducin, and molecular interactions stabilizing the receptor structure. The structure of rhodopsin is largely unperturbed by the absence of palmitate linkage. The binding pocket for the chromophore 11-cis-retinal is minimally altered as palmitate-deficient rhodopsin exhibited the same absorbance spectrum as wild-type rhodopsin. Similarly, the rate of release of all-trans-retinal after light activation was the same both in the presence and absence of palmitylation. Significant differences were observed in the rate of transducin activation by rhodopsin and in the force required to unfold the last stable structural segment in rhodopsin at its carboxyl terminal end. A 1.3-fold reduction in the rate of transducin activation by rhodopsin was observed in the absence of palmitylation. Single-molecule force spectroscopy revealed a 2.1-fold reduction in the normalized force required to unfold the carboxyl terminal end of rhodopsin. The absence of palmitylation in rhodopsin therefore destabilizes the molecular interactions formed in the carboxyl terminal end of the receptor, which appears to hinder the activation of transducin by light-activated rhodopsin.
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Affiliation(s)
- Paul S-H Park
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Structural and kinetic modeling of an activating helix switch in the rhodopsin-transducin interface. Proc Natl Acad Sci U S A 2009; 106:10660-5. [PMID: 19541654 DOI: 10.1073/pnas.0900072106] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extracellular signals prompt G protein-coupled receptors (GPCRs) to adopt an active conformation (R*) and catalyze GDP/GTP exchange in the alpha-subunit of intracellular G proteins (Galphabetagamma). Kinetic analysis of transducin (G(t)alphabetagamma) activation shows that an intermediary R*xG(t)alphabetagamma.GDP complex is formed that precedes GDP release and formation of the nucleotide-free R*xG protein complex. Based on this reaction sequence, we explore the dynamic interface between the proteins during formation of these complexes. We start from the R* conformation stabilized by a G(t)alpha C-terminal peptide (GalphaCT) obtained from crystal structures of the GPCR opsin. Molecular modeling allows reconstruction of the fully elongated C-terminal alpha-helix of G(t)alpha (alpha5) and shows how alpha5 can be docked to the open binding site of R*. Two modes of interaction are found. One of them--termed stable or S-interaction--matches the position of the GalphaCT peptide in the crystal structure and reproduces the hydrogen-bonding networks between the C-terminal reverse turn of GalphaCT and conserved E(D)RY and NPxxY(x)(5,6)F regions of the GPCR. The alternative fit--termed intermediary or I-interaction--is distinguished by a tilt (42 degrees ) and rotation (90 degrees ) of alpha5 relative to the S-interaction and shows different alpha5 contacts with the NPxxY(x)(5,6)F region and the second cytoplasmic loop of R*. From the 2 alpha5 interactions, we derive a "helix switch" mechanism for the transition of R*xG(t)alphabetagamma.GDP to the nucleotide-free R*xG protein complex that illustrates how alpha5 might act as a transmission rod to propagate the conformational change from the receptor-G protein interface to the nucleotide binding site.
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35
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Leontiadis LJ, Papakonstantinou MP, Georgoussi Z. Regulator of G protein signaling 4 confers selectivity to specific G proteins to modulate mu- and delta-opioid receptor signaling. Cell Signal 2009; 21:1218-28. [PMID: 19324084 DOI: 10.1016/j.cellsig.2009.03.013] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 03/12/2009] [Accepted: 03/15/2009] [Indexed: 10/21/2022]
Abstract
In vitro studies have shown that the Regulator of G protein Signaling 4 (RGS4) interacts with the C-termini of mu- and delta-opioid receptors (mu-OR, delta-OR) (Georgoussi et al., 2006, Cell. Signal.18, 771-782). Herein we demonstrate that RGS4 associates with these receptors in living cells and forms selective complexes with Gi/Go proteins in a receptor dependent manner. This interaction occurs within the predicted fourth intracellular loop of mu, delta-ORs as part of a signaling complex consisting of the opioid receptor, activated Galpha and RGS4. RGS4 is recruited to the plasma membrane upon opioid receptor stimulation. Expression of RGS4 in HEK293 cells attenuated agonist-mediated extracellular signal regulated kinase (ERK1,2) phosphorylation for both receptors and accelerated agonist-induced internalization of the delta-OR. RGS4 lacking its N-terminal domain failed to interact with both opioid receptors and to modulate opioid receptor signaling. Our findings demonstrate that RGS4 plays a key role in G protein coupling selectivity and signaling of the mu- and delta-OmicronRs.
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Affiliation(s)
- Leonidas J Leontiadis
- Laboratory of Cellular Signaling and Molecular Pharmacology, Institute of Biology, National Center for Scientific Research Demokritos, Ag. Paraskevi-Attikis, Athens, Greece
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36
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Hoersch D, Otto H, Wallat I, Heyn MP. Monitoring the Conformational Changes of Photoactivated Rhodopsin from Μicroseconds to Seconds by Transient Fluorescence Spectroscopy. Biochemistry 2008; 47:11518-27. [DOI: 10.1021/bi801397e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daniel Hoersch
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Harald Otto
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Ingrid Wallat
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Maarten P. Heyn
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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37
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Kato A, Katada S, Touhara K. Amino acids involved in conformational dynamics and G protein coupling of an odorant receptor: targeting gain-of-function mutation. J Neurochem 2008; 107:1261-70. [PMID: 18803693 DOI: 10.1111/j.1471-4159.2008.05693.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thousands of different odorants are recognized and discriminated by odorant receptors (ORs) in the guanine nucleotide-binding protein (G protein)-coupled seven-transmembrane receptor family. Odorant-bound ORs stimulate Gs-type G proteins, Galphaolf, which in turn activates cAMP-mediated signaling pathway in olfactory sensory neurons. To better understand the molecular basis for OR activation and G protein coupling, we analyzed the effects of a series of site-directed mutations of mouse ORs, on function. Mutations of conserved amino acid residues in an intracellular loop or the C-terminus resulted in loss of activity without impairing ligand-binding activity, indicating that these residues are involved in Galphas/olf coupling. Moreover, mutation of the serine in KAFSTC, the OR-specific sequence motif, resulted in a dramatic increase in odorant responsiveness, suggesting that the motif is involved in a conformational change of the receptor that regulates G protein coupling efficiency. Our results provide insights into how ORs switch from an inactive to an active state, as well as where and how activated ORs interact with G proteins.
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Affiliation(s)
- Aya Kato
- Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan
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38
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Preininger AM, Parello J, Meier SM, Liao G, Hamm HE. Receptor-mediated changes at the myristoylated amino terminus of Galpha(il) proteins. Biochemistry 2008; 47:10281-93. [PMID: 18771287 DOI: 10.1021/bi800741r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
G protein-coupled receptors (GPCRs) catalyze nucleotide release in heterotrimeric G proteins, the slow step in G protein activation. G i/o family proteins are permanently, cotranslationally myristoylated at the extreme amino terminus. While myristoylation of the amino terminus has long been known to aid in anchoring G i proteins to the membrane, the role of myristoylation with regard to interaction with activated receptors is not known. Previous studies have characterized activation-dependent changes in the amino terminus of Galpha proteins in solution [Medkova, M. (2002) Biochemistry 41, 9963-9972; Preininger, A. M. (2003) Biochemistry 42, 7931-7941], but changes in the environment of specific residues within the Galpha i1 amino terminus during receptor-mediated G i activation have not been reported. Using site-specific fluorescence labeling of individual residues along a stretch of the Galpha il amino terminus, we found specific changes in the environment of these residues upon interaction with the activated receptor and following GTPgammaS binding. These changes map to a distinct surface of the amino-terminal helix opposite the Gbetagamma binding interface. The receptor-dependent fluorescence changes are consistent with a myristoylated amino terminus in the proximity of the membrane and/or receptor. Myristoylation affects both the rate and intensity of receptor activation-dependent changes detected at several residues along the amino terminus (with no significant effect on the rate of receptor-mediated GTPgammaS binding). This work demonstrates that the myristoylated amino terminus of Galpha il proteins undergoes receptor-mediated changes during the dynamic process of G protein signaling.
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Affiliation(s)
- Anita M Preininger
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, USA
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39
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Taylor CM, Barda Y, Kisselev OG, Marshall GR. Modulating G-protein coupled receptor/G-protein signal transduction by small molecules suggested by virtual screening. J Med Chem 2008; 51:5297-303. [PMID: 18707087 DOI: 10.1021/jm800326q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modulation of interactions between activated GPCRs (G-protein coupled receptors) and the intracellular (IC) signal transducers, heterotrimeric G-proteins, is an attractive, yet essentially unexplored, paradigm for treatment of certain diseases. Regulating downstream signaling for treatment of congenital diseases due to constitutively active GPCRs, as well as tumors where GPCRs are often overexpressed, requires the development of new methodologies. Modeling, experimental data, docking, scoring, and experimental testing (MEDSET) was developed to discover inhibitors that target the IC loops of activated GPCRs. As proof-of-concept, MEDSET developed and utilized a model of the interface between photoactivated rhodopsin (R*) and transducin (Gt), its G-protein. A National Cancer Institute (NCI) compound library was screened to identify compounds that bound at the interface between R* and its G-protein. High-scoring compounds from this virtual screen were obtained and tested experimentally for their ability to stabilize R* and prevent Gt from binding to R*. Several compounds that modulate signal transduction have been identified.
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Affiliation(s)
- Christina M Taylor
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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40
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Conner M, Hicks MR, Dafforn T, Knowles TJ, Ludwig C, Staddon S, Overduin M, Günther UL, Thome J, Wheatley M, Poyner DR, Conner AC. Functional and biophysical analysis of the C-terminus of the CGRP-receptor; a family B GPCR. Biochemistry 2008; 47:8434-44. [PMID: 18636754 DOI: 10.1021/bi8004126] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G-protein coupled receptors (GPCRs) typically have a functionally important C-terminus which, in the largest subfamily (family A), includes a membrane-parallel eighth helix. Mutations of this region are associated with several diseases. There are few C-terminal studies on the family B GPCRs and no data supporting the existence of a similar eighth helix in this second major subfamily, which has little or no sequence homology to family A GPCRs. Here we show that the C-terminus of a family B GPCR (CLR) has a disparate region from N400 to C436 required for CGRP-mediated internalization, and a proximal region of twelve residues (from G388 to W399), in a similar position to the family A eighth helix, required for receptor localization at the cell surface. A combination of circular and linear dichroism, fluorescence and modified waterLOGSY NMR spectroscopy (SALMON) demonstrated that a peptide mimetic of this domain readily forms a membrane-parallel helix anchored to the liposome by an interfacial tryptophan residue. The study reveals two key functions held within the C-terminus of a family B GPCR and presents support for an eighth helical region with striking topological similarity to the nonhomologous family A receptor. This helix structure appears to be found in most other family B GPCRs.
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41
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Abstract
Heterotrimeric G proteins couple the activation of heptahelical receptors at the cell surface to the intracellular signaling cascades that mediate the physiological responses to extracellular stimuli. G proteins are molecular switches that are activated by receptor-catalyzed GTP for GDP exchange on the G protein alpha subunit, which is the rate-limiting step in the activation of all downstream signaling. Despite the important biological role of the receptor-G protein interaction, relatively little is known about the structure of the complex and how it leads to nucleotide exchange. This chapter will describe what is known about receptor and G protein structure and outline a strategy for assembling the current data into improved models for the receptor-G protein complex that will hopefully answer the question as to how receptors flip the G protein switch.
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Affiliation(s)
- William M Oldham
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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42
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Assembly of the cnidarian camera-type eye from vertebrate-like components. Proc Natl Acad Sci U S A 2008; 105:8989-93. [PMID: 18577593 DOI: 10.1073/pnas.0800388105] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Animal eyes are morphologically diverse. Their assembly, however, always relies on the same basic principle, i.e., photoreceptors located in the vicinity of dark shielding pigment. Cnidaria as the likely sister group to the Bilateria are the earliest branching phylum with a well developed visual system. Here, we show that camera-type eyes of the cubozoan jellyfish, Tripedalia cystophora, use genetic building blocks typical of vertebrate eyes, namely, a ciliary phototransduction cascade and melanogenic pathway. Our findings indicative of parallelism provide an insight into eye evolution. Combined, the available data favor the possibility that vertebrate and cubozoan eyes arose by independent recruitment of orthologous genes during evolution.
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43
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Role of the carboxyl terminal di-leucine in phosphorylation and internalization of C5a receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1261-70. [PMID: 18346468 DOI: 10.1016/j.bbamcr.2008.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 01/13/2008] [Accepted: 02/04/2008] [Indexed: 01/15/2023]
Abstract
The carboxyl tail of G protein-coupled receptors contains motifs that regulate receptor interactions with intracellular partners. Activation of the human neutrophil complement fragment C5a receptor (C5aR) is terminated by phosphorylation of the carboxyl tail followed by receptor internalization. In this study, we demonstrated that bulky hydrophobic residues in the membrane-proximal region of the C5aR carboxyl tail play an important role in proper structure and function of the receptor: Substitution of leucine 319 with alanine (L319A) resulted in receptor retention in the endoplasmic reticulum, whereas a L318A substitution allowed receptor transport to the cell surface, but showed slow internalization upon activation, presumably due to a defect in phosphorylation by both PKC and GRK. Normal agonist-induced activation of ERK1/2 and intracellular calcium release suggested that the L318A mutation did not affect receptor signaling. Binding of GRK2 and PKCbetaII to intracellular loop 3 of C5aR in vitro indicated that mutagenesis of L318 did not affect kinase binding. Limited proteolysis with trypsin revealed a conformational difference between wild type and mutant receptor. Our studies support a model in which the L318/L319 stabilizes an amphipathic helix (Q305-R320) in the membrane-proximal region of C5aR.
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44
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Plachetzki DC, Degnan BM, Oakley TH. The origins of novel protein interactions during animal opsin evolution. PLoS One 2007; 2:e1054. [PMID: 17940617 PMCID: PMC2013938 DOI: 10.1371/journal.pone.0001054] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 09/17/2007] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Biologists are gaining an increased understanding of the genetic bases of phenotypic change during evolution. Nevertheless, the origins of phenotypes mediated by novel protein-protein interactions remain largely undocumented. METHODOLOGY/PRINCIPLE FINDINGS Here we analyze the evolution of opsin visual pigment proteins from the genomes of early branching animals, including a new class of opsins from Cnidaria. We combine these data with existing knowledge of the molecular basis of opsin function in a rigorous phylogenetic framework. We identify adaptive amino acid substitutions in duplicated opsin genes that correlate with a diversification of physiological pathways mediated by different protein-protein interactions. CONCLUSIONS/SIGNIFICANCE This study documents how gene duplication events early in the history of animals followed by adaptive structural mutations increased organismal complexity by adding novel protein-protein interactions that underlie different physiological pathways. These pathways are central to vision and other photo-reactive phenotypes in most extant animals. Similar evolutionary processes may have been at work in generating other metazoan sensory systems and other physiological processes mediated by signal transduction.
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Affiliation(s)
- David C. Plachetzki
- Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, California, United States of America
| | - Bernard M. Degnan
- School of Integrative Biology, University of Queensland, Brisbane, Queensland, Australia
| | - Todd H. Oakley
- Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, California, United States of America
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45
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Abstract
Rhodopsin is a member of the family of G-protein-coupled receptors (GPCRs), and is an excellent molecular switch for converting light signals into electrical response of the rod photoreceptor cells. Light initiates cis-trans isomerization of the retinal chromophore of rhodopsin and leads to the formation of several thermolabile intermediates during the bleaching process. Recent investigations have identified spectrally distinguishable two intermediate states that can interact with the retinal G-protein, transducin, and have elucidated the functional sharing of these intermediates. The initial contact with GDP-bound G-protein occurs in the meta-Ib intermediate state, which has a protonated Schiff base as its chromophore. The meta-Ib intermediate in the complex with the G-protein converts to the meta-II intermediate with releasing GDP from the alpha-subunit of the G protein. Meta-II has a de-protonated Schiff base chromophore and induces binding of GTP to the alpha-subunit of the G-protein. Thus, the GDP-GTP exchange reaction, namely G-protein activation, by rhodopsin proceeds through at least two steps, with conformational changes in both rhodopsin and the G-protein.
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Affiliation(s)
- Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, CREST, Japan Science and Technology Agency, Japan.
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46
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Anavi-Goffer S, Fleischer D, Hurst DP, Lynch DL, Barnett-Norris J, Shi S, Lewis DL, Mukhopadhyay S, Howlett AC, Reggio PH, Abood ME. Helix 8 Leu in the CB1 cannabinoid receptor contributes to selective signal transduction mechanisms. J Biol Chem 2007; 282:25100-13. [PMID: 17595161 DOI: 10.1074/jbc.m703388200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The intracellular C-terminal helix 8 (H8) of the CB(1) cannabinoid receptor deviates from the highly conserved NPXXY(X)(5,6)F G-protein-coupled receptor motif, possessing a Leu instead of a Phe. We compared the signal transduction capabilities of CB(1) with those of an L7.60F mutation and an L7.60I mutation that mimics the CB(2) sequence. The two mutant receptors differed from wild type (WT) in their ability to regulate G-proteins in the [(35)S]guanosine 5'-3-O-(thio)triphosphate binding assay. The L7.60F receptor exhibited attenuated stimulation by agonists WIN-55,212-2 and CP-55,940 but not HU-210, whereas the L7.60I receptor exhibited impaired stimulation by all agonists tested as well as by the inverse agonist rimonabant. The mutants internalized more rapidly than WT receptors but could equally sequester G-proteins from the somatostatin receptor. Both the time course and maximal N-type Ca(2+) current inhibition by WIN-55,212-2 were reduced in the mutants. Reconstitution experiments with pertussis toxin-insensitive G-proteins revealed loss of coupling to Galpha(i3) but not Galpha(0A) in the L7.60I mutant, whereas the reduction in the time course for the L7.60F mutant was governed by Galpha(i3). Furthermore, Galpha(i3) but not Galpha(0A) enhanced basal facilitation ratio, suggesting that Galpha(i3) is responsible for CB(1) tonic activity. Co-immunoprecipitation studies revealed that both mutant receptors were associated with Galpha(i1) or Galpha(i2) but not with Galpha(i3). Molecular dynamics simulations of WT CB(1) receptor and each mutant in a 1-palmitoyl-2-oleoylphosphatidylcholine bilayer suggested that the packing of H8 is different in each. The hydrogen bonding patterns along the helix backbones of each H8 also are different, as are the geometries of the elbow region of H8 (R7.56(400)-K7.58(402)). This study demonstrates that the evolutionary modification to NPXXY(X)(5,6)L contributes to maximal activity of the CB(1) receptor and provides a molecular basis for the differential coupling observed with chemically different agonists.
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Affiliation(s)
- Sharon Anavi-Goffer
- California Pacific Medical Center Research Institute, San Francisco, California 94107, USA
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47
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Taylor CM, Nikiforovich GV, Marshall GR. Defining the interface between the C-terminal fragment of alpha-transducin and photoactivated rhodopsin. Biophys J 2007; 92:4325-34. [PMID: 17351008 PMCID: PMC1877773 DOI: 10.1529/biophysj.106.099242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Accepted: 01/30/2007] [Indexed: 12/26/2022] Open
Abstract
A novel combination of experimental data and extensive computational modeling was used to explore probable protein-protein interactions between photoactivated rhodopsin (R*) and experimentally determined R*-bound structures of the C-terminal fragment of alpha-transducin (Gt(alpha)(340-350)) and its analogs. Rather than using one set of loop structures derived from the dark-adapted rhodopsin state, R* was modeled in this study using various energetically feasible sets of intracellular loop (IC loop) conformations proposed previously in another study. The R*-bound conformation of Gt(alpha)(340-350) and several analogs were modeled using experimental transferred nuclear Overhauser effect data derived upon binding R*. Gt(alpha)(340-350) and its analogs were docked to various conformations of the intracellular loops, followed by optimization of side-chain spatial positions in both R* and Gt(alpha)(340-350) to obtain low-energy complexes. Finally, the structures of each complex were subjected to energy minimization using the OPLS/GBSA force field. The resulting residue-residue contacts at the interface between R* and Gt(alpha)(340-350) were validated by comparison with available experimental data, primarily from mutational studies. Computational modeling performed for Gt(alpha)(340-350) and its analogs when bound to R* revealed a consensus of general residue-residue interactions, necessary for efficient complex formation between R* and its Gt(alpha) recognition motif.
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Affiliation(s)
- Christina M Taylor
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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48
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Sachdev P, Menon S, Kastner DB, Chuang JZ, Yeh TY, Conde C, Caceres A, Sung CH, Sakmar TP. G protein beta gamma subunit interaction with the dynein light-chain component Tctex-1 regulates neurite outgrowth. EMBO J 2007; 26:2621-32. [PMID: 17491591 PMCID: PMC1888676 DOI: 10.1038/sj.emboj.7601716] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 04/12/2007] [Indexed: 11/08/2022] Open
Abstract
Tctex-1, a light-chain component of the cytoplasmic dynein motor complex, can function independently of dynein to regulate multiple steps in neuronal development. However, how dynein-associated and dynein-free pools of Tctex-1 are maintained in the cell is not known. Tctex-1 was recently identified as a Gbetagamma-binding protein and shown to be identical to the receptor-independent activator of G protein signaling AGS2. We propose a novel role for the interaction of Gbetagamma with Tctex-1 in neurite outgrowth. Ectopic expression of either Tctex-1 or Gbetagamma promotes neurite outgrowth whereas interfering with their function inhibits neuritogenesis. Using embryonic mouse brain extracts, we demonstrate an endogenous Gbetagamma-Tctex-1 complex and show that Gbetagamma co-segregates with dynein-free fractions of Tctex-1. Furthermore, Gbeta competes with the dynein intermediate chain for binding to Tctex-1, regulating assembly of Tctex-1 into the dynein motor complex. We propose that Tctex-1 is a novel effector of Gbetagamma, and that Gbetagamma-Tctex-1 complex plays a key role in the dynein-independent function of Tctex-1 in regulating neurite outgrowth in primary hippocampal neurons, most likely by modulating actin and microtubule dynamics.
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Affiliation(s)
- Pallavi Sachdev
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Santosh Menon
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, New York, NY, USA
| | - David B Kastner
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, New York, NY, USA
| | - Jen-Zen Chuang
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY, USA
| | - Ting-Yu Yeh
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY, USA
| | | | | | - Ching-Hwa Sung
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY, USA
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, New York, NY, USA
| | - Thomas P Sakmar
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, New York, NY, USA
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, 1230 York Avenue, Box 187, New York City, NY 10021, USA. Tel.: +1 212 327 8288; Fax: +1 212 327 7904; E-mail:
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49
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Oliveira L, Costa-Neto CM, Nakaie CR, Schreier S, Shimuta SI, Paiva ACM. The Angiotensin II AT1 Receptor Structure-Activity Correlations in the Light of Rhodopsin Structure. Physiol Rev 2007; 87:565-92. [PMID: 17429042 DOI: 10.1152/physrev.00040.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The most prevalent physiological effects of ANG II, the main product of the renin-angiotensin system, are mediated by the AT1 receptor, a rhodopsin-like AGPCR. Numerous studies of the cardiovascular effects of synthetic peptide analogs allowed a detailed mapping of ANG II's structural requirements for receptor binding and activation, which were complemented by site-directed mutagenesis studies on the AT1 receptor to investigate the role of its structure in ligand binding, signal transduction, phosphorylation, binding to arrestins, internalization, desensitization, tachyphylaxis, and other properties. The knowledge of the high-resolution structure of rhodopsin allowed homology modeling of the AT1 receptor. The models thus built and mutagenesis data indicate that physiological (agonist binding) or constitutive (mutated receptor) activation may involve different degrees of expansion of the receptor's central cavity. Residues in ANG II structure seem to control these conformational changes and to dictate the type of cytosolic event elicited during the activation. 1) Agonist aromatic residues (Phe8 and Tyr4) favor the coupling to G protein, and 2) absence of these residues can favor a mechanism leading directly to receptor internalization via phosphorylation by specific kinases of the receptor's COOH-terminal Ser and Thr residues, arrestin binding, and clathrin-dependent coated-pit vesicles. On the other hand, the NH2-terminal residues of the agonists ANG II and [Sar1]-ANG II were found to bind by two distinct modes to the AT1 receptor extracellular site flanked by the COOH-terminal segments of the EC-3 loop and the NH2-terminal domain. Since the [Sar1]-ligand is the most potent molecule to trigger tachyphylaxis in AT1 receptors, it was suggested that its corresponding binding mode might be associated with this special condition of receptors.
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Affiliation(s)
- Laerte Oliveira
- Department of Biophysics, Escola Paulista de Medicina, Federal University of São Paulo, Brazil.
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50
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Lehmann N, Alexiev U, Fahmy K. Linkage Between the Intramembrane H-bond Network Around Aspartic Acid 83 and the Cytosolic Environment of Helix 8 in Photoactivated Rhodopsin. J Mol Biol 2007; 366:1129-41. [PMID: 17196983 DOI: 10.1016/j.jmb.2006.11.098] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2006] [Revised: 11/21/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
Understanding the coupling between conformational changes in the intramembrane domain and at the membrane-exposed surface of the bovine photoreceptor rhodopsin, a prototypical G protein-coupled receptor (GPCR), is crucial for the elucidation of molecular mechanisms in GPCR activation. Here, we have combined Fourier transform infrared (FTIR) and fluorescence spectroscopy to address the coupling between conformational changes in the intramembrane region around the retinal and the environment of helix 8, a putative cytosolic surface switch region in class-I GPCRs. Using FTIR/fluorescence cross-correlation we show specifically that surface alterations monitored by emission changes of fluorescein bound to Cys316 in helix 8 of rhodopsin are highly correlated with (i) H-bonding to Asp83 proximal of the retinal Schiff base but not to Glu122 close to the beta-ionone and (ii) with a metarhodopsin II (MII)-specific 1643 cm(-1) IR absorption change, indicative of a partial loss of secondary structure in helix 8 upon MII formation. These correlations are disrupted by limited C-terminal proteolysis but are maintained upon binding of a transducin alpha-subunit (G(talpha))-derived peptide, which stabilizes the MII state. Our results suggest that additional C-terminal cytosolic loop contacts monitored by an amide II absorption at 1557 cm(-1) play a functionally crucial role in keeping helix 8 in the position in which its environment is strongly coupled to the retinal-binding site near the Schiff base. In the intramembrane region, this coupling is mediated by the H-bonding network that connects Asp83 to the NPxxY(x)F motif preceding helix 8.
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Affiliation(s)
- Nicole Lehmann
- Institute of Radiation Physics, Biophysics Division, Forschungszentrum Dresden-Rossendorf, PF 510119, D-01314 Dresden, Germany
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