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Okamoto M, Yamamoto M. TCR Signals Controlling Adaptive Immunity against Toxoplasma and Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1444:177-193. [PMID: 38467980 DOI: 10.1007/978-981-99-9781-7_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
T cells play a crucial role in adaptive immunity by recognizing and eliminating foreign pathogens and abnormal cells such as cancer cells. T cell receptor (TCR), which is expressed on the surface of T cells, recognizes and binds to specific antigens presented by major histocompatibility complex (MHC) molecules on antigen-presenting cells (APCs). This activation process leads to the proliferation and differentiation of T cells, allowing them to carry out their specific immune response functions. This chapter outlines the TCR signaling pathways that are common to different T cell subsets, as well as the recently elucidated TCR signaling pathway specific to CD8+ T cells and its role in controlling anti-Toxoplasma and anti-tumor immunity.
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Affiliation(s)
- Masaaki Okamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
- Laboratory of Immunoparasitology, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
- Laboratory of Immunoparasitology, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan.
- Department of Immunoparasitology, Center for Infectious Disease Education and Research, Osaka University, Osaka, Japan.
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2
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Li G, Chen L, Jiang Z, Yau KW. Coexistence within one cell of microvillous and ciliary phototransductions across M1- through M6-IpRGCs. Proc Natl Acad Sci U S A 2023; 120:e2315282120. [PMID: 38109525 PMCID: PMC10756192 DOI: 10.1073/pnas.2315282120] [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: 09/02/2023] [Accepted: 11/16/2023] [Indexed: 12/20/2023] Open
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) serve as primary photoceptors by expressing the photopigment, melanopsin, and also as retinal relay neurons for rod and cone signals en route to the brain, in both cases for the purpose of non-image vision as well as aspects of image vision. So far, six subtypes of ipRGCs (M1 through M6) have been characterized. Regarding their phototransduction mechanisms, we have previously found that, unconventionally, rhabdomeric (microvillous) and ciliary signaling motifs co-exist within a given M1-, M2-, and M4-ipRGC, with the first mechanism involving PLCβ4 and TRPC6,7 channels and the second involving cAMP and HCN channels. We have now examined M3-, M5-, and M6-cells and found that each cell likewise uses both signaling pathways for phototransduction, despite differences in the percentage representation by each pathway in a given ipRGC subtype for bright-flash responses (and saturated except for M6-cells). Generally, M3- and M5-cells show responses quite similar in kinetics to M2-responses, and M6-cell responses resemble broadly those of M1-cells although much lower in absolute sensitivity and amplitude. Therefore, similar to rod and cone subtypes in image vision, ipRGC subtypes possess the same phototransduction mechanism(s) even though they do not show microvilli or cilia morphologically.
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Affiliation(s)
- Guang Li
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Lujing Chen
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
- Neuroscience Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - Zheng Jiang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
| | - King-Wai Yau
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD21205
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3
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Ubeysinghe S, Wijayaratna D, Kankanamge D, Karunarathne A. Molecular regulation of PLCβ signaling. Methods Enzymol 2023; 682:17-52. [PMID: 36948701 DOI: 10.1016/bs.mie.2023.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Phospholipase C (PLC) enzymes convert the membrane phospholipid phosphatidylinositol-4,5-bisphosphate (PIP2) into inositol-1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3 and DAG regulate numerous downstream pathways, eliciting diverse and profound cellular changes and physiological responses. In the six PLC subfamilies in higher eukaryotes, PLCβ is intensively studied due to its prominent role in regulating crucial cellular events underlying many processes including cardiovascular and neuronal signaling, and associated pathological conditions. In addition to GαqGTP, Gβγ generated upon G protein heterotrimer dissociation also regulates PLCβ activity. Here, we not only review how Gβγ directly activates PLCβ, and also extensively modulates Gαq-mediated PLCβ activity, but also provide a structure-function overview of PLC family members. Given that Gαq and PLCβ are oncogenes, and Gβγ shows unique cell-tissue-organ specific expression profiles, Gγ subtype-dependent signaling efficacies, and distinct subcellular activities, this review proposes that Gβγ is a major regulator of Gαq-dependent and independent PLCβ signaling.
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Affiliation(s)
| | | | - Dinesh Kankanamge
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Ajith Karunarathne
- Department of Chemistry, St. Louis University, St. Louis, MO, United States.
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4
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Pasquaré SJ, Chamorro-Aguirre E, Gaveglio VL. The endocannabinoid system in the visual process. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2022. [DOI: 10.1016/j.jpap.2022.100159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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Phan HTN, Kim NH, Wei W, Tall GG, Smrcka AV. Uveal melanoma-associated mutations in PLCβ4 are constitutively activating and promote melanocyte proliferation and tumorigenesis. Sci Signal 2021; 14:eabj4243. [PMID: 34905385 DOI: 10.1126/scisignal.abj4243] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Hoa T N Phan
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nam Hoon Kim
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Wenhui Wei
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gregory G Tall
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alan V Smrcka
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
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6
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Sasai M, Ma JS, Okamoto M, Nishino K, Nagaoka H, Takashima E, Pradipta A, Lee Y, Kosako H, Suh PG, Yamamoto M. Uncovering a novel role of PLCβ4 in selectively mediating TCR signaling in CD8+ but not CD4+ T cells. J Exp Med 2021; 218:212085. [PMID: 33970189 PMCID: PMC8111461 DOI: 10.1084/jem.20201763] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 02/24/2021] [Accepted: 03/23/2021] [Indexed: 11/08/2022] Open
Abstract
Because of their common signaling molecules, the main T cell receptor (TCR) signaling cascades in CD4+ and CD8+ T cells are considered qualitatively identical. Herein, we show that TCR signaling in CD8+ T cells is qualitatively different from that in CD4+ T cells, since CD8α ignites another cardinal signaling cascade involving phospholipase C β4 (PLCβ4). TCR-mediated responses were severely impaired in PLCβ4-deficient CD8+ T cells, whereas those in CD4+ T cells were intact. PLCβ4-deficient CD8+ T cells showed perturbed activation of peripheral TCR signaling pathways downstream of IP3 generation. Binding of PLCβ4 to the cytoplasmic tail of CD8α was important for CD8+ T cell activation. Furthermore, GNAQ interacted with PLCβ4, mediated double phosphorylation on threonine 886 and serine 890 positions of PLCβ4, and activated CD8+ T cells in a PLCβ4-dependent fashion. PLCβ4-deficient mice exhibited defective antiparasitic host defense and antitumor immune responses. Altogether, PLCβ4 differentiates TCR signaling in CD4+ and CD8+ T cells and selectively promotes CD8+ T cell–dependent adaptive immunity.
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Affiliation(s)
- Miwa Sasai
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.,Laboratory of Immunoparasitology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Ji Su Ma
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.,Laboratory of Immunoparasitology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Masaaki Okamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Kohei Nishino
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Tokushima University, Tokushima, Japan
| | - Hikaru Nagaoka
- Division of Malaria Research, Proteo-Science Center, Ehime University, Ehime, Japan
| | - Eizo Takashima
- Division of Malaria Research, Proteo-Science Center, Ehime University, Ehime, Japan
| | - Ariel Pradipta
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Youngae Lee
- Laboratory of Immunoparasitology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Hidetaka Kosako
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Tokushima University, Tokushima, Japan
| | - Pann-Ghill Suh
- School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, South Korea.,Korea Brain Research Institute, Daegu, South Korea
| | - Masahiro Yamamoto
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.,Laboratory of Immunoparasitology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
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7
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Abstract
The field of phosphoinositide signaling has expanded significantly in recent years. Phosphoinositides (also known as phosphatidylinositol phosphates or PIPs) are universal signaling molecules that directly interact with membrane proteins or with cytosolic proteins containing domains that directly bind phosphoinositides and are recruited to cell membranes. Through the activities of phosphoinositide kinases and phosphoinositide phosphatases, seven distinct phosphoinositide lipid molecules are formed from the parent molecule, phosphatidylinositol. PIP signals regulate a wide range of cellular functions, including cytoskeletal assembly, membrane budding and fusion, ciliogenesis, vesicular transport, and signal transduction. Given the many excellent reviews on phosphoinositide kinases, phosphoinositide phosphatases, and PIPs in general, in this review, we discuss recent studies and advances in PIP lipid signaling in the retina. We specifically focus on PIP lipids from vertebrate (e.g., bovine, rat, mouse, toad, and zebrafish) and invertebrate (e.g., Drosophila, horseshoe crab, and squid) retinas. We also discuss the importance of PIPs revealed from animal models and human diseases, and methods to study PIP levels both in vitro and in vivo. We propose that future studies should investigate the function and mechanism of activation of PIP-modifying enzymes/phosphatases and further unravel PIP regulation and function in the different cell types of the retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology, Physiology, and Cell Biology, and Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104.
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8
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Phosphoinositides in Retinal Function and Disease. Cells 2020; 9:cells9040866. [PMID: 32252387 PMCID: PMC7226789 DOI: 10.3390/cells9040866] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 03/26/2020] [Accepted: 03/30/2020] [Indexed: 02/06/2023] Open
Abstract
Phosphatidylinositol and its phosphorylated derivatives, the phosphoinositides, play many important roles in all eukaryotic cells. These include modulation of physical properties of membranes, activation or inhibition of membrane-associated proteins, recruitment of peripheral membrane proteins that act as effectors, and control of membrane trafficking. They also serve as precursors for important second messengers, inositol (1,4,5) trisphosphate and diacylglycerol. Animal models and human diseases involving defects in phosphoinositide regulatory pathways have revealed their importance for function in the mammalian retina and retinal pigmented epithelium. New technologies for localizing, measuring and genetically manipulating them are revealing new information about their importance for the function and health of the vertebrate retina.
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Hughes S, Rodgers J, Hickey D, Foster RG, Peirson SN, Hankins MW. Characterisation of light responses in the retina of mice lacking principle components of rod, cone and melanopsin phototransduction signalling pathways. Sci Rep 2016; 6:28086. [PMID: 27301998 PMCID: PMC4908426 DOI: 10.1038/srep28086] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/26/2016] [Indexed: 11/09/2022] Open
Abstract
Gnat(-/-), Cnga3(-/-), Opn4(-/-) triple knockout (TKO) mice lack essential components of phototransduction signalling pathways present in rods, cones and photosensitive retinal ganglion cells (pRGCs), and are therefore expected to lack all sensitivity to light. However, a number of studies have shown that light responses persist in these mice. In this study we use multielectrode array (MEA) recordings and light-induced c-fos expression to further characterise the light responses of the TKO retina. Small, but robust electroretinogram type responses are routinely detected during MEA recordings, with properties consistent with rod driven responses. Furthermore, a distinctive pattern of light-induced c-fos expression is evident in the TKO retina, with c-fos expression largely restricted to a small subset of amacrine cells that express disabled-1 (Dab1) but lack expression of glycine transporter-1 (GlyT-1). Collectively these data are consistent with the persistence of a novel light sensing pathway in the TKO retina that originates in rod photoreceptors, potentially a rare subset of rods with distinct functional properties, and which is propagated to an atypical subtype of AII amacrine cells. Furthermore, the minimal responses observed following UV light stimulation suggest only a limited role for the non-visual opsin OPN5 in driving excitatory light responses within the mouse retina.
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Affiliation(s)
- Steven Hughes
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
| | - Jessica Rodgers
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
| | - Doron Hickey
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
| | - Russell G Foster
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
| | - Stuart N Peirson
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
| | - Mark W Hankins
- The Nuffield Laboratory of Ophthalmology, Sleep and Circadian Neuroscience Institute, Nuffield Department of Clinical Neurosciences, University of Oxford, Sir William Dunn School of Pathology, OMPI G, South Parks Road, Oxford, OX1 3RE, UK
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10
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Tian M, Wang W, Delimont D, Cheung L, Zallocchi M, Cosgrove D, Peng YW. Photoreceptors in whirler mice show defective transducin translocation and are susceptible to short-term light/dark changes-induced degeneration. Exp Eye Res 2014; 118:145-53. [PMID: 24211856 PMCID: PMC4408763 DOI: 10.1016/j.exer.2013.10.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 09/26/2013] [Accepted: 10/29/2013] [Indexed: 12/12/2022]
Abstract
Usher syndrome combines congenital hearing loss and retinitis pigmentosa (RP). Mutations in the whirlin gene (DFNB31/WHRN) cause a subtype of Usher syndrome (USH2D). Whirler mice have a defective whirlin gene. They have inner ear defects but usually do not develop retinal degeneration. Here we report that, in whirler mouse photoreceptors, the light-activated rod transducin translocation is delayed and its activation threshold is shifted to a higher level. Rhodopsin mis-localization is observed in rod inner segments. Continuous moderate light exposure can induce significant rod photoreceptor degeneration. Whirler mice reared under a 1500 lux light/dark cycle also develop severe photoreceptor degeneration. Previously, we have reported that shaker1 mice, a USH1B model, show moderate light-induced photoreceptor degeneration with delayed transducin translocation. Here, we further show that, in both whirler and shaker1 mice, short-term moderate light/dark changes can induce rod degeneration as severe as that induced by continuous light exposure. The results from shaker1 and whirler mice suggest that defective transducin translocation may be functionally related to light-induced degeneration, and these two symptoms may be caused by defects in Usher protein function in rods. Furthermore, these results indicate that both Usher syndrome mouse models possess a light-induced retinal phenotype and may share a closely related pathobiological mechanism.
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Affiliation(s)
- Mei Tian
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA; National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China
| | - Weimin Wang
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA
| | - Duane Delimont
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA
| | - Linda Cheung
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA
| | - Marisa Zallocchi
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA
| | - Dominic Cosgrove
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA; University of Nebraska Medical Center, 600 S 42nd, Omaha, NE 68198, USA
| | - You-Wei Peng
- Sensory Neuroscience Department, Boys Town National Research Hospital, 555 North 30th St., Omaha, NE 68131, USA.
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Semple-Rowland S, Madorsky I, Bolch S, Berry J, Smith WC. Activation of phospholipase C mimics the phase shifting effects of light on melatonin rhythms in retinal photoreceptors. PLoS One 2013; 8:e83378. [PMID: 24386190 PMCID: PMC3873303 DOI: 10.1371/journal.pone.0083378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/02/2013] [Indexed: 12/04/2022] Open
Abstract
Many aspects of retinal photoreceptor function and physiology are regulated by the circadian clocks in these cells. It is well established that light is the primary stimulus that entrains these clocks; yet, the biochemical cascade(s) mediating light’s effects on these clocks remains unknown. This deficiency represents a significant gap in our fundamental understanding of photoreceptor signaling cascades and their functions. In this study, we utilized re-aggregated spheroid cultures prepared from embryonic chick retina to determine if activation of phospholipase C in photoreceptors in the absence of light can phase shift the melatonin secretion rhythms of these cells in a manner similar to that induced by light. We show that spheroid cultures rhythmically secrete melatonin and that these melatonin rhythms can be dynamically phase shifted by exposing the cultures to an appropriately timed light pulse. Importantly, we show that activation of phospholipase C using m-3M3FBS in the absence of light induces a phase delay in photoreceptor melatonin rhythms that mirrors that induced by light. The implication of this finding is that the light signaling cascade that entrains photoreceptor melatonin rhythms involves activation of phospholipase C.
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Affiliation(s)
- Susan Semple-Rowland
- Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
| | - Irina Madorsky
- Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America
| | - Susan Bolch
- Department of Ophthalmology, University of Florida, Gainesville, Florida, United States of America
| | - Jonathan Berry
- Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America
| | - W. Clay Smith
- Department of Ophthalmology, University of Florida, Gainesville, Florida, United States of America
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12
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Hozumi Y, Matsui H, Sakane F, Watanabe M, Goto K. Distinct expression and localization of diacylglycerol kinase isozymes in rat retina. J Histochem Cytochem 2013; 61:462-76. [PMID: 23467923 DOI: 10.1369/0022155413483574] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Recent studies have revealed that phosphoinositide (PI) signaling molecules are expressed in mammalian retinas, suggesting their importance in its signal transduction. We previously showed that diacylglycerol kinase (DGK) isozymes are expressed in distinct patterns in rat retina at the mRNA level. However, little is known about the nature and morphological aspects of DGKs in the retina. For this study, we performed immunohistochemical analyses to investigate in the retina the expression and localization of DGK isozymes at the protein level. Here, we show that both DGKβ and DGKι localize in the outer plexiform layer, within which photoreceptor cells make contact with bipolar and horizontal cells. These isozymes exhibit distinct subcellular localization patterns: DGKι localizes to the synaptic area of bipolar cells in a punctate manner, whereas DGKβ distributes diffusely in the subsynaptic and dendritic regions of bipolar and horizontal cells. However, punctate labeling for DGKε is evident in the outer limiting membrane. DGKζ and DGKα localize predominantly to the nucleus of ganglion cells. These findings show distinct expression and localization of DGK isozymes in the retina, suggesting a different role of each isozyme.
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Affiliation(s)
- Yasukazu Hozumi
- Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
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13
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Wang J, Zhang N, Beuve A, Townes-Anderson E. Mislocalized opsin and cAMP signaling: a mechanism for sprouting by rod cells in retinal degeneration. Invest Ophthalmol Vis Sci 2012; 53:6355-69. [PMID: 22899763 DOI: 10.1167/iovs.12-10180] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
PURPOSE In human retinal degeneration, rod photoreceptors reactively sprout neurites. The mechanism is unknown in part because of the paucity of animal models displaying this feature of human pathology. We tested the role of cAMP and opsin in sprouting by tiger salamander rod cells, photoreceptors that can produce reactive growth. METHODS In vitro systems of isolated photoreceptor cells and intact neural retina were used. cAMP signaling was manipulated with nucleotide analogues, enzyme stimulators, agonists for adenosine and dopamine receptors, and the opsin agonist, β-ionone. Levels of cAMP were determined by radioimmunoassay, and protein levels by Western blot and quantitative immunocytochemistry. Neuritic growth was assayed by image analysis and conventional and confocal microscopy. RESULTS cAMP analogues and stimulation of adenylyl cyclase (AC) directly or through G-protein-coupled receptors resulted in significant increases in neuritic growth of isolated rod, but not cone, cells. The signaling pathway included protein kinase A (PKA) and phosphorylation of the transcription factor cAMP response element-binding protein (pCREB). Opsin, a G-linked receptor, is present throughout the plasmalemma of isolated cells; its activation also induced sprouting. In neural retina, rod sprouting was significantly increased by β-ionone with concomitant increases in cAMP, pCREB, and synaptic proteins. Notably, opsin stimulated sprouting only when mislocalized to the plasmalemma of the rod cell body. CONCLUSIONS cAMP causes neuritic sprouting in rod, but not cone, cells through the AC-PKA-CREB pathway known to be associated with synaptic plasticity. We propose that in retinal disease, mislocalized rod opsin gains access to cAMP signaling, which leads to neuritic sprouting.
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Affiliation(s)
- Jianfeng Wang
- Department of Neurology and Neuroscience, New Jersey Medical School–University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA
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14
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Vila A, Satoh H, Rangel C, Mills SL, Hoshi H, O'Brien J, Marshak DR, Macleish PR, Marshak DW. Histamine receptors of cones and horizontal cells in Old World monkey retinas. J Comp Neurol 2012; 520:528-43. [PMID: 21800315 DOI: 10.1002/cne.22731] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In primates the retina receives input from histaminergic neurons in the posterior hypothalamus that are active during the day. In order to understand how this input contributes to information processing in Old World monkey retinas, we have been localizing histamine receptors (HR) and studying the effects of histamine on the neurons that express them. Previously, we localized HR3 to the tips of ON bipolar cell dendrites and showed that histamine hyperpolarizes the cells via this receptor. We raised antisera against synthetic peptides corresponding to an extracellular domain of HR1 between the 4th and 5th transmembrane domains and to an intracellular domain near the carboxyl terminus of HR2. Using these, we localized HR1 to horizontal cells and a small number of amacrine cells and localized HR2 to puncta closely associated with synaptic ribbons inside cone pedicles. Consistent with this, HR1 mRNA was detected in horizontal cell perikarya and primary dendrites and HR2 mRNA was found in cone inner segments. We studied the effect of 5 μM exogenous histamine on primate cones in macaque retinal slices. Histamine reduced I(h) at moderately hyperpolarized potentials, but not the maximal current. This would be expected to increase the operating range of cones and conserve ATP in bright, ambient light. Thus, all three major targets of histamine are in the outer plexiform layer, but the retinopetal axons containing histamine terminate in the inner plexiform layer. Taken together, the findings in these three studies suggest that histamine acts primarily via volume transmission in primate retina.
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Affiliation(s)
- Alejandro Vila
- Department of Neurobiology and Anatomy, Medical School, University of Texas at Health Science Center at Houston, Houston, Texas, USA
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15
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Sato S, Hozumi Y, Saino-Saito S, Yamashita H, Goto K. Enzymatic activity and gene expression of diacylglycerol kinase isozymes in developing retina of rats. ACTA ACUST UNITED AC 2012; 32:329-36. [PMID: 22033302 DOI: 10.2220/biomedres.32.329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Photoreceptors contain highly specialized structures for phototransduction, which is mediated by rhodopsins and heterotrimeric G-proteins. The signal is transmitted through the cGMP cascade, which controls cGMP-gated cation channels in mammals, while in flies it is operated by phosphoinositide (PI) cascade through a second messenger diacylglycerol (DG), which engenders the opening of Ca2+ channels. Recent studies suggest that PI-related signaling cascade is also involved in the phototransduction in mammalian retina. This study examined whether one PI-related enzyme, diacylglycerol kinase (DGK), which is regarded as a regulator of the DG signal through its metabolism, is expressed in mammalian retina. Enzymatic assay, Northern blot and RT-PCR analyses, and in situ hybridization histochemistry were performed to assess the expression profile of DGK isozymes and their cellular localization. In rat retina DGKε, DGKζ, and DGKι are the dominant species with distinct patterns of expression. At the cellular level, DGKε is the only one detected intensely in the photoreceptor layer, although DGKι and DGKζ are observed in bipolar and ganglion cell layers. These results suggest that each DGK isozyme plays a different role in the signal transduction in distinct cell types and that DGKε is a candidate involved in the photoreceptor PI signaling machinery.
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Affiliation(s)
- Sakura Sato
- Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata 990-9585, Japan
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16
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Abstract
This review lays out the emerging evidence for the fundamental role of Ca(2+) stores and store-operated channels in the Ca(2+) homeostasis of rods and cones. Calcium-induced calcium release (CICR) is a major contributor to steady-state and light-evoked photoreceptor Ca(2+) homeostasis in the darkness whereas store-operated Ca(2+) channels play a more significant role under sustained illumination conditions. The homeostatic response includes dynamic interactions between the plasma membrane, endoplasmic reticulum (ER), mitochondria and/or outer segment disk organelles which dynamically sequester, accumulate and release Ca(2+). Coordinated activation of SERCA transporters, ryanodine receptors (RyR), inositol triphosphate receptors (IP3Rs) and TRPC channels amplifies cytosolic voltage-operated signals but also provides a memory trace of previous exposures to light. Store-operated channels, activated by the STIM1 sensor, prevent pathological decrease in [Ca(2+)]i mediated by excessive activation of PMCA transporters in saturating light. CICR and SOCE may also modulate the transmission of afferent and efferent signals in the outer retina. Thus, Ca(2+) stores provide additional complexity, adaptability, tuneability and speed to photoreceptor signaling.
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Affiliation(s)
- David Križaj
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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17
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Unknown Mechanisms Regulating the GPCR Signal Cascade in Vertebrate Photoreceptors. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11055-011-9551-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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18
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Abstract
Lower vertebrates have an intrinsically-photosensitive iris and thus a local pupillary light reflex (PLR). In contrast, it has been a dogma that the PLR in mammals generally requires neuronal circuitry connecting the eye and the brain. We report here that an intrinsic component of the PLR is actually widespread in nocturnal and crepuscular mammals. In mouse, this intrinsic PLR requires the visual pigment, melanopsin. It also requires PLCβ4, the vertebrate homolog of the Drosophila NorpA phospholipase C mediating rhabdomeric phototransduction. The Plcβ4−/− genotype, besides removing the intrinsic PLR, also essentially eliminates the intrinsic light response of the M1-subtype of melanopsin-expressing, intrinsically-photosensitive retinal ganglion cells (M1-ipRGCs), by far the most photosensitive ipRGCs and with the largest responses. Ablating in mouse the expression of both TRPC6 and TRPC7, members of the TRP channel superfamily, likewise essentially eliminated the M1-ipRGC light response, but spared the intrinsic PLR. Thus, melanopsin signaling exists in both iris and retina, involving a PLCβ4-mediated pathway that nonetheless diverges in the two locations.
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19
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Hardie RC. Phototransduction mechanisms in Drosophila microvillar photoreceptors. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/wmts.20] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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20
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Abstract
The importance of phosphoinositides (phosphorylated phosphatidyl inositol derivatives, PIs) for normal cellular function cannot be overstated. Although they represent a small fraction of the total phospholipid within the cell, they are essential regulators of many cellular functions. They direct membrane trafficking by functioning as recruitment factors for vesicular trafficking components, they can modulate ion channel activity through direct binding within cellular membranes, and their hydrolysis generates second messenger signaling molecules. Despite an explosion of information regarding the importance of these lipids in cellular biology, their precise roles in vertebrate retinal photoreceptors has not been established. This review summarizes the literature on potential roles for different phosphoinositides and their regulators in vertebrate rods and cones. A brief description of the importance of PI signaling in other photosensitive cells is also presented. The highly specialized functions of the vertebrate photoreceptor, combined with the established importance of phosphoinositides, promise significant future discoveries in this field.
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Affiliation(s)
- Susan E Brockerhoff
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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21
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Peng YW, Zallocchi M, Wang WM, Delimont D, Cosgrove D. Moderate light-induced degeneration of rod photoreceptors with delayed transducin translocation in shaker1 mice. Invest Ophthalmol Vis Sci 2011; 52:6421-7. [PMID: 21447681 DOI: 10.1167/iovs.10-6557] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE. Usher syndrome is characterized by congenital deafness associated with retinitis pigmentosa (RP). Mutations in the myosin VIIa gene (MYO7A) cause a common and severe subtype of Usher syndrome (USH1B). Shaker1 mice have mutant MYO7A. They are deaf and have vestibular dysfunction but do not develop photoreceptor degeneration. The goal of this study was to investigate abnormalities of photoreceptors in shaker1 mice. METHODS. Immunocytochemistry and hydroethidine-based detection of intracellular superoxide production were used. Photoreceptor cell densities under various conditions of light/dark exposures were evaluated. RESULTS. In shaker1 mice, the rod transducin translocation is delayed because of a shift of its light activation threshold to a higher level. Even moderate light exposure can induce oxidative damage and significant rod degeneration in shaker1 mice. Shaker1 mice reared under a moderate light/dark cycle develop severe retinal degeneration in less than 6 months. CONCLUSIONS. These findings show that, contrary to earlier studies, shaker1 mice possess a robust retinal phenotype that may link to defective rod protein translocation. Importantly, USH1B animal models are likely vulnerable to light-induced photoreceptor damage, even under moderate light.
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Affiliation(s)
- You-Wei Peng
- National Usher Syndrome Center, Boys Town National Research Hospital, Omaha, Nebraska, USA.
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22
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Kim ES, Kim JS, Kim SG, Hwang S, Lee CH, Moon A. Sphingosine 1-phosphate regulates matrix metalloproteinase-9 expression and breast cell invasion through S1P3-Gαq coupling. J Cell Sci 2011; 124:2220-30. [PMID: 21652634 DOI: 10.1242/jcs.076794] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Recent evidence suggests that inflammation is involved in malignant progression of breast cancer. Sphingosine 1-phosphate (S1P), acting on the G-protein-coupled receptors, is known as a potent inflammatory mediator. In this study, the effect of the inflammatory lipid S1P on the regulation of invasive/migratory phenotypes of MCF10A human breast epithelial cells was investigated to elucidate a causal relationship between inflammation and the control of invasiveness of breast cells. We show that S1P causes induction of matrix metalloproteinase-9 (MMP-9) in vitro and in vivo, and thus enhances invasion and migration. We also show that fos plays a crucial role in the transcriptional activation of MMP-9 by S1P. In addition, activation of extracellular-signal-regulated kinases 1 and 2 (ERK1/2), p38 and alpha serine/threonine-protein kinase (Akt) are involved in the process of S1P-mediated induction of MMP-9 expression and invasion. Activation of the S1P receptor S1P₃ and G(αq) are required for S1P-induced invasive/migratory responses, suggesting that the enhancement of S1P-mediated invasiveness is triggered by the specific coupling of S1P₃ to the heterotrimeric G(αq) subunit. Activation of phospholipase C-β₄ and intracellular Ca²⁺ release are required for S1P-induced MMP-9 upregulation. Taken together, this study demonstrated that S1P regulates MMP-9 induction and invasiveness through coupling of S1P₃ and G(αq) in MCF10A cells, thus providing a molecular basis for the crucial role of S1P in promoting breast cell invasion.
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Affiliation(s)
- Eun-Sook Kim
- College of Pharmacy, Duksung Women's University, Seoul 132-714, Korea
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23
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Allen AE, Cameron MA, Brown TM, Vugler AA, Lucas RJ. Visual responses in mice lacking critical components of all known retinal phototransduction cascades. PLoS One 2010; 5:e15063. [PMID: 21124780 PMCID: PMC2993945 DOI: 10.1371/journal.pone.0015063] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 11/01/2010] [Indexed: 01/22/2023] Open
Abstract
The mammalian visual system relies upon light detection by outer-retinal rod/cone photoreceptors and melanopsin-expressing retinal ganglion cells. Gnat1−/−;Cnga3−/−;Opn4−/− mice lack critical elements of each of these photoreceptive mechanisms via targeted disruption of genes encoding rod α transducin (Gnat1); the cone-specific α3 cyclic nucleotide gated channel subunit (Cnga3); and melanopsin (Opn4). Although assumed blind, we show here that these mice retain sufficiently widespread retinal photoreception to drive a reproducible flash electroretinogram (ERG). The threshold sensitivity of this ERG is similar to that of cone-based responses, however it is lost under light adapted conditions. Its spectral efficiency is consistent with that of rod opsin, but not cone opsins or melanopsin, indicating that it originates with light absorption by the rod pigment. The TKO light response survives intravitreal injection of U73122 (a phospholipase C antagonist), but is inhibited by a missense mutation of cone α transducin (Gnat2cpfl3), suggesting Gnat2-dependence. Visual responses in TKO mice extend beyond the retina to encompass the lateral margins of the lateral geniculate nucleus and components of the visual cortex. Our data thus suggest that a Gnat1-independent phototransduction mechanism downstream of rod opsin can support relatively widespread responses in the mammalian visual system. This anomalous rod opsin-based vision should be considered in experiments relying upon Gnat1 knockout to silence rod phototransduction.
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Affiliation(s)
- Annette E. Allen
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Morven A. Cameron
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Timothy M. Brown
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | - Anthony A. Vugler
- Department of Ocular Biology and Therapeutics, University College London Institute of Ophthalmology, London, United Kingdom
| | - Robert J. Lucas
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
- * E-mail:
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24
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Orisme W, Li J, Goldmann T, Bolch S, Wolfrum U, Smith WC. Light-dependent translocation of arrestin in rod photoreceptors is signaled through a phospholipase C cascade and requires ATP. Cell Signal 2010; 22:447-56. [PMID: 19887106 DOI: 10.1016/j.cellsig.2009.10.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Revised: 10/26/2009] [Accepted: 10/27/2009] [Indexed: 10/20/2022]
Abstract
Partitioning of cellular components is a critical mechanism by which cells can regulate their activity. In rod photoreceptors, light induces a large-scale translocation of arrestin from the inner segments to the outer segments. The purpose of this project is to elucidate the signaling pathway necessary to initiate arrestin translocation to the outer segments and the mechanism for arrestin translocation. Mouse retinal organotypic cultures and eyes from transgenic Xenopus tadpoles expressing a fusion of GFP and rod arrestin were treated with both activators and inhibitors of proteins in the phosphoinositide pathway. Confocal microscopy was used to image the effects of the pharmacological agents on arrestin translocation in rod photoreceptors. Retinas were also depleted of ATP using potassium cyanide to assess the requirement for ATP in arrestin translocation. In this study, we demonstrate that components of the G-protein-linked phospholipase C (PLC) pathway play a role in initiating arrestin translocation. Our results show that arrestin translocation can be stimulated by activators of PLC and protein kinase C (PKC), and by cholera toxin in the absence of light. Arrestin translocation to the outer segments is significantly reduced by inhibitors of PLC and PKC. Importantly, we find that treatment with potassium cyanide inhibits arrestin translocation in response to light. Collectively, our results suggest that arrestin translocation is initiated by a G-protein-coupled cascade through PLC and PKC signaling. Furthermore, our results demonstrate that at least the initiation of arrestin translocation requires energy input.
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Affiliation(s)
- Wilda Orisme
- Department of Ophthalmology, University of Florida, Gainesville, Florida 32610-0284, USA
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25
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Abstract
The phosphoinositide (PI) cycle, discovered over 50 years ago by Mabel and Lowell Hokin, describes a series of biochemical reactions that occur on the inner leaflet of the plasma membrane of cells in response to receptor activation by extracellular stimuli. Studies from our laboratory have shown that the retina and rod outer segments (ROSs) have active PI metabolism. Biochemical studies revealed that the ROSs contain the enzymes necessary for phosphorylation of phosphoinositides. We showed that light stimulates various components of the PI cycle in the vertebrate ROS, including diacylglycerol kinase, PI synthetase, phosphatidylinositol phosphate kinase, phospholipase C, and phosphoinositide 3-kinase (PI3K). This article describes recent studies on the PI3K-generated PI lipid second messengers in the control and regulation of PI-binding proteins in the vertebrate retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology and Cell Biology, and Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. r
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26
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Abstract
Seeing begins in the photoreceptors, where light is absorbed and signaled to the nervous system. Throughout the animal kingdom, photoreceptors are diverse in design and purpose. Nonetheless, phototransduction-the mechanism by which absorbed photons are converted into an electrical response-is highly conserved and based almost exclusively on a single class of photoproteins, the opsins. In this Review, we survey the G protein-coupled signaling cascades downstream from opsins in photoreceptors across vertebrate and invertebrate species, noting their similarities as well as differences.
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Affiliation(s)
- King-Wai Yau
- Solomon H. Snyder Department of Neuroscience and Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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27
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Giusto NM, Pasquaré SJ, Salvador GA, Ilincheta de Boschero MG. Lipid second messengers and related enzymes in vertebrate rod outer segments. J Lipid Res 2009; 51:685-700. [PMID: 19828910 DOI: 10.1194/jlr.r001891] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Rod outer segments (ROSs) are specialized light-sensitive organelles in vertebrate photoreceptor cells. Lipids in ROS are of considerable importance, not only in providing an adequate environment for efficient phototransduction, but also in originating the second messengers involved in signal transduction. ROSs have the ability to adapt the sensitivity and speed of their responses to ever-changing conditions of ambient illumination. A major contributor to this adaptation is the light-driven translocation of key signaling proteins into and out of ROS. The present review shows how generation of the second lipid messengers from phosphatidylcholine, phosphatidic acid, and diacylglycerol is modulated by the different illumination states in the vertebrate retina. Findings suggest that the light-induced translocation of phototransduction proteins influences the enzymatic activities of phospholipase D, lipid phosphate phosphatase, diacylglyceride lipase, and diacylglyceride kinase, all of which are responsible for the generation of the second messenger molecules.
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Affiliation(s)
- Norma M Giusto
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca, Argentina.
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28
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Cho KI, Yi H, Yeh A, Tserentsoodol N, Cuadrado L, Searle K, Hao Y, Ferreira PA. Haploinsufficiency of RanBP2 is neuroprotective against light-elicited and age-dependent degeneration of photoreceptor neurons. Cell Death Differ 2008; 16:287-97. [PMID: 18949001 DOI: 10.1038/cdd.2008.153] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Prolonged light exposure is a determinant factor in inducing neurodegeneration of photoreceptors by apoptosis. Yet, the molecular bases of the pathways and components triggering this cell death event are elusive. Here, we reveal a prominent age-dependent increase in the susceptibility of photoreceptor neurons to undergo apoptosis under light in a mouse model. This is accompanied by light-induced subcellular changes of photoreceptors, such as dilation of the disks at the tip of the outer segments, prominent vesiculation of nascent disks, and autophagy of mitochondria into large multilamellar bodies. Notably, haploinsufficiency of Ran-binding protein-2 (RanBP2) suppresses apoptosis and most facets of membrane dysgenesis observed with age upon light-elicited stress. RanBP2 haploinsufficiency promotes decreased levels of free fatty acids in the retina independent of light exposure and turns the mice refractory to weight gain on a high-fat diet, whereas light promotes an increase in hydrogen peroxide regardless of the genotype. These studies demonstrate the presence of age-dependent and RanBP2-mediated pathways modulating membrane biogenesis of the outer segments and light-elicited neurodegeneration of photoreceptors. Furthermore, the findings support a mechanism whereby the RanBP2-dependent production of free fatty acids, metabolites thereof or the modulation of a cofactor dependent on any of these, promote apoptosis of photoreceptors in concert with the light-stimulated production of reactive oxygen species.
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Affiliation(s)
- K-in Cho
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
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29
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Somatostatin peptides produce multiple effects on gating properties of native cone photoreceptor cGMP-gated channels that depend on circadian phase and previous illumination. J Neurosci 2007; 27:12168-75. [PMID: 17989283 DOI: 10.1523/jneurosci.3541-07.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
A subpopulation of avian amacrine cells expresses somatostatin-14 (SS14) and somatostatin-28 (SS28), which provide a potential efferent limb for light-dependent regulation of photoreceptors. Here, we demonstrate that SS14 and SS28 modulate cone photoreceptor cGMP-gated channels (CNGCs) through multiple mechanisms. In chicken cones cultured in constant darkness for 2 d after previous entrainment to light-dark (LD) cycles or in cells maintained in LD, application of 100 nm SS14 or 100 nm SS28 for either 15 min or 2 h caused a decrease in the sensitivity of CNGCs to cGMP during the night, at circadian time 16 (CT16)-CT20 or zeitgeber time 16 (ZT16)-ZT20. SS14 had no effect during the day (CT4-CT8 or ZT4-ZT8). These effects persist in cells pretreated with pertussis toxin (PTX) and, like dopamine, may work to reinforce long-term circadian fluctuations in CNGCs driven by oscillators within the photoreceptors themselves. In contrast, a 15 min exposure to SS28 caused a seemingly paradoxical increase in the sensitivity of CNGCs to cGMP during the early day (ZT4-ZT6), but only in cones maintained in LD. This effect of SS28 desensitizes rapidly, is blocked by pretreatment with PTX, and is selectively mimicked by the cyclohexapeptide agonist MK-678. This transient response also requires activation of phospholipase C and protein kinase C. The transient response to SS28 may play a role in photoreceptor adaptation to rapid changes in ambient illumination. These data also show that photoreceptor responses to at least some peptide neurotransmitters depend on the previous history of light exposure.
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30
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Rajala A, Anderson RE, Ma JX, Lem J, Al-Ubaidi MR, Rajala RVS. G-protein-coupled receptor rhodopsin regulates the phosphorylation of retinal insulin receptor. J Biol Chem 2007; 282:9865-9873. [PMID: 17272282 DOI: 10.1074/jbc.m608845200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have shown previously that phosphoinositide 3-kinase in the retina is activated in vivo through light-induced tyrosine phosphorylation of the insulin receptor (IR). The light effect is localized to photoreceptor neurons and is independent of insulin secretion (Rajala, R. V., McClellan, M. E., Ash, J. D., and Anderson, R. E. (2002) J. Biol. Chem. 277, 43319-43326). These results suggest that there exists a cross-talk between phototransduction and other signal transduction pathways. In this study, we examined the stage of phototransduction that is coupled to the activation of the IR. We studied IR phosphorylation in mice lacking the rod-specific alpha-subunit of transducin to determine if phototransduction events are required for IR activation. To confirm that light-induced tyrosine phosphorylation of the IR is signaled through bleachable rhodopsin, we examined IR activation in retinas from RPE65(-/-) mice that are deficient in opsin chromophore. We observed that IR phosphorylation requires the photobleaching of rhodopsin but not transducin signaling. To determine whether the light-dependent activation of IR is mediated through the rod or cone transduction pathway, we studied the IR activation in mice lacking opsin, a mouse model of pure cone function. No light-dependent activation of the IR was found in the retinas of these mice. We provide evidence for the existence of a light-mediated IR pathway in the retina that is different from the known insulin-mediated pathway in nonneuronal tissues. These results suggest that IR phosphorylation in rod photoreceptors is signaled through the G-protein-coupled receptor rhodopsin. This is the first study demonstrating that rhodopsin can initiate signaling pathway(s) in addition to its classical phototransduction.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Robert E Anderson
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Jian-Xing Ma
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Janis Lem
- Department of Ophthalmology, New England Medical Center and Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Muayyad R Al-Ubaidi
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Raju V S Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104.
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31
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Inglis-Broadgate SL, Ocaka L, Banerjee R, Gaasenbeek M, Chapple JP, Cheetham ME, Clark BJ, Hunt DM, Halford S. Isolation and characterization of murine Cds (CDP-diacylglycerol synthase) 1 and 2. Gene 2005; 356:19-31. [PMID: 16023307 DOI: 10.1016/j.gene.2005.04.037] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Revised: 03/14/2005] [Accepted: 04/13/2005] [Indexed: 11/19/2022]
Abstract
Phototransduction in Drosophila is a phosphoinositide-mediated signalling pathway. Phosphatidylinositol 4,5-bisphosphate (PIP2) plays a central role in this process, and its levels are tightly regulated. A photoreceptor-specific form of the enzyme CDP-diacylglycerol synthase (CDS), which catalyzes the formation of CDP-diacylglycerol from phosphatidic acid, is a key regulator of the amount of PIP2 available for signalling. cds mutants develop light-induced retinal degeneration. We report here the isolation and characterization of two murine genes encoding this enzyme, Cds1 and Cds2. The genes encode proteins that are 73% identical and 92% similar but exhibit very different expression patterns. Cds1 shows a very restricted expression pattern but is expressed in the inner segments of the photoreceptors whilst Cds2 shows a ubiquitous pattern of expression. Using fluorescent in situ hybridization we have mapped Cds1 and Cds2 to chromosomes 5E3 and 2G1 respectively. These are regions of synteny with the corresponding human gene localization (4q21 and 20p13). Transient transfection experiments with epitope tagged proteins have also demonstrated that both are associated with the endoplasmic reticulum.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- CHO Cells
- Chromosome Mapping
- Chromosomes, Mammalian/genetics
- Cricetinae
- Cricetulus
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- Diacylglycerol Cholinephosphotransferase/genetics
- Diacylglycerol Cholinephosphotransferase/metabolism
- Endoplasmic Reticulum/metabolism
- Exons
- Female
- Gene Expression Profiling
- Gene Expression Regulation, Enzymologic
- Genes/genetics
- In Situ Hybridization, Fluorescence
- Introns
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Male
- Mice
- Microscopy, Confocal
- Microscopy, Fluorescence
- Molecular Sequence Data
- Plasmids/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Transfection
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32
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Iuvone PM, Tosini G, Pozdeyev N, Haque R, Klein DC, Chaurasia SS. Circadian clocks, clock networks, arylalkylamine N-acetyltransferase, and melatonin in the retina. Prog Retin Eye Res 2005; 24:433-56. [PMID: 15845344 DOI: 10.1016/j.preteyeres.2005.01.003] [Citation(s) in RCA: 247] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Circadian clocks are self-sustaining genetically based molecular machines that impose approximately 24h rhythmicity on physiology and behavior that synchronize these functions with the solar day-night cycle. Circadian clocks in the vertebrate retina optimize retinal function by driving rhythms in gene expression, photoreceptor outer segment membrane turnover, and visual sensitivity. This review focuses on recent progress in understanding how clocks and light control arylalkylamine N-acetyltransferase (AANAT), which is thought to drive the daily rhythm in melatonin production in those retinas that synthesize the neurohormone; AANAT is also thought to detoxify arylalkylamines through N-acetylation. The review will cover evidence that cAMP is a major output of the circadian clock in photoreceptor cells; and recent advances indicating that clocks and clock networks occur in multiple cell types of the retina.
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Affiliation(s)
- P Michael Iuvone
- Department of Pharmacology, Emory University School of Medicine, 1510 Clifton Road, rm. 5107, Atlanta, GA 30322, USA.
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33
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Semo M, Lupi D, Peirson SN, Butler JN, Foster RG. Light-induced c-fos in melanopsin retinal ganglion cells of young and aged rodless/coneless (rd/rd cl) mice. Eur J Neurosci 2004; 18:3007-17. [PMID: 14656296 DOI: 10.1111/j.1460-9568.2003.03061.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Non-rod, non-cone ocular photoreceptors have been shown to mediate a range of irradiance detection tasks. The strongest candidates for these receptors are melanopsin-positive retinal ganglion cells (RGCs). To provide a more complete understanding of these receptors in vivo, we have utilized a mouse that lacks rod and cone photoreceptors (rd/rd cl) and compared these animals to congenic wild-types. Using real-time polymerase chain reaction and immunohistochemistry, we address the following. (1) Is Fos expression within these RGCs driven by an input from the rods/cones or is it the product of the intrinsic photosensitivity of these neurons? We demonstrate that most Fos expression across the entire retina is due to the rods/cones, but in the absence of these photoreceptors, light will induce Fos within melanopsin RGCs. (2) Could the reported age-related decline in circadian photosensitivity of rodents be linked to changes in the population of melanopsin RGCs? We show that old mice experience an approximately 40% reduction in melanopsin RGCs. (3) Does the loss of inner retinal neurons affect the responses of melanopsin RGCs? Aged (approximately 700 days) rd/rd cl mice lose most of their inner retina but retain the retinal ganglion cell layer. In these mice, the proportion of melanopsin RGCs that express Fos in response to light is significantly reduced. Collectively, our data suggest that melanopsin RGCs form a heterogeneous population of neurons, and that most of the light-induced c-fos expression within these cells is associated with the endogenous photosensitivity of these neurons.
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Affiliation(s)
- Ma'ayan Semo
- Department of Integrative and Molecular Neuroscience, Imperial College London, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK
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He F, Mao M, Wensel TG. Enhancement of phototransduction g protein-effector interactions by phosphoinositides. J Biol Chem 2003; 279:8986-90. [PMID: 14699118 DOI: 10.1074/jbc.m311488200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Light responses in photoreceptor cells are mediated by the action of the G protein transducin (G(t)) on the effector enzyme cGMP phosphodiesterase (PDE6) at the surface of disk membranes. The enzymatic components needed for phosphoinositide-based signaling are known to be present in rod cells, but it has remained uncertain what role phosphoinositides play in vertebrate phototransduction. Reconstitution of PDE6 and activated G(alphat), on the surface of large unilamellar vesicles containing d-myo-phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)), stimulated PDE activity nearly 4-fold above the level observed with membranes containing no phosphoinositides, whereas G protein-independent activation by trypsin was unaffected by the presence of phosphoinositides. PDE activity was similarly stimulated by d-myo-phosphatidylinositol-3,4-bisphosphate and d-myo-phosphatidylinositol-4-phosphate (PI(4)P), but much less by d-myo-phosphatidylinositol-5-phosphate (PI(5)P) or d-myo-phosphatidylinositol-3,5-bisphosphate. Incubation of rod outer segment membranes with phosphoinositide-specific phospholipase C decreased G protein-stimulated activation of endogenous PDE6, but not trypsin-stimulated PDE activity. Binding experiments using phosphoinositide-containing vesicles revealed patterns of PDE6 binding and PDE6-enhanced G(alphat)-GTPgammaS binding, consistent with the activation profile PI(4,5)P(2) > PI(4)P > PI(5)P approximately control vesicles. These results suggest that enhancement of effector-G protein interactions represents a possible mechanism for modulation of phototransduction gain by changes in phosphoinositide levels, perhaps occurring in response to longterm changes in illumination or other environmental cues.
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Affiliation(s)
- Feng He
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Light-dependent translocation of arrestin in the absence of rhodopsin phosphorylation and transducin signaling. J Neurosci 2003. [PMID: 12716919 DOI: 10.1523/jneurosci.23-08-03124.2003] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Visual arrestin plays a crucial role in the termination of the light response in vertebrate photoreceptors by binding selectively to light-activated, phosphorylated rhodopsin. Arrestin localizes predominantly to the inner segments and perinuclear region of dark-adapted rod photoreceptors, whereas light induces redistribution of arrestin to the rod outer segments. The mechanism by which arrestin redistributes in response to light is not known, but it is thought to be associated with the ability of arrestin to bind photolyzed, phosphorylated rhodopsin in the outer segment. In this study, we show that light-driven translocation of arrestin is unaffected in two different mouse models in which rhodopsin phosphorylation is lacking. We further show that arrestin movement is initiated by rhodopsin but does not require transducin signaling. These results exclude passive diffusion and point toward active transport as the mechanism for light-dependent arrestin movement in rod photoreceptor cells.
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Mendez A, Lem J, Simon M, Chen J. Light-dependent translocation of arrestin in the absence of rhodopsin phosphorylation and transducin signaling. J Neurosci 2003; 23:3124-9. [PMID: 12716919 PMCID: PMC6742335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023] Open
Abstract
Visual arrestin plays a crucial role in the termination of the light response in vertebrate photoreceptors by binding selectively to light-activated, phosphorylated rhodopsin. Arrestin localizes predominantly to the inner segments and perinuclear region of dark-adapted rod photoreceptors, whereas light induces redistribution of arrestin to the rod outer segments. The mechanism by which arrestin redistributes in response to light is not known, but it is thought to be associated with the ability of arrestin to bind photolyzed, phosphorylated rhodopsin in the outer segment. In this study, we show that light-driven translocation of arrestin is unaffected in two different mouse models in which rhodopsin phosphorylation is lacking. We further show that arrestin movement is initiated by rhodopsin but does not require transducin signaling. These results exclude passive diffusion and point toward active transport as the mechanism for light-dependent arrestin movement in rod photoreceptor cells.
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Affiliation(s)
- Ana Mendez
- Zilkha Neurogenetic Institute, The Mary D. Allen Laboratory for Vision Research, Beckman Macular Research Center, Doheny Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, California 90089-2821, USA
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37
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Abstract
Light is a major environmental signal for entrainment of the circadian clock, but little is known about the intracellular phototransduction pathway triggered by light activation of the photoreceptive molecule(s) responsible for the phase shift of the clock in vertebrates. The chicken pineal gland and retina contain the autonomous circadian oscillators together with the photic entrainment pathway, and hence they represent useful experimental models for the clock system. Here we show the expression of G11alpha, an alpha subunit of heterotrimeric G-protein, in both tissues by cDNA cloning, Northern blot, and Western blot analyses. G11alpha immunoreactivity was colocalized with pinopsin in the chicken pineal cells and also with rhodopsin in the outer segments of retinal photoreceptor cells, suggesting functional coupling of G11alpha with opsins in the clock-containing photosensitive tissues. The physical interaction was examined by coimmunoprecipitation experiments, the results of which provided evidence for light- and GTP-dependent coupling between rhodopsin and G11alpha. To examine whether activation of endogenous G11 leads to a phase shift of the oscillator, Gq/11-coupled m1-type muscarinic acetylcholine receptor (mAChR) was ectopically expressed in the cultured pineal cells. Subsequent treatment of the cells with carbamylcholine (CCh), an agonist of mAChR, induced phase-dependent phase shifts of the melatonin rhythm in a manner very similar to the effect of light. In contrast, CCh treatment induced no measurable effect on the rhythm of nontransfected (control) cells or cells expressing G(i/o)-coupled m2-type mAChR, indicating selectivity of the G-protein activation. Together, our results demonstrate the existence of a G11-mediated opsin-signaling pathway contributing to the photic entrainment of the circadian clock.
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Cheung R, Kassirian S, Mitchell J. Diurnal Regulation of the G Protein G11α and Guanine Nucleotide-regulated Phospholipase C Activity in Rat Retina. Exp Eye Res 2002. [DOI: 10.1006/exer.2002.2006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Kasahara T, Okano T, Haga T, Fukada Y. Opsin-G11-mediated signaling pathway for photic entrainment of the chicken pineal circadian clock. J Neurosci 2002; 22:7321-5. [PMID: 12196552 PMCID: PMC6757971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023] Open
Abstract
Light is a major environmental signal for entrainment of the circadian clock, but little is known about the intracellular phototransduction pathway triggered by light activation of the photoreceptive molecule(s) responsible for the phase shift of the clock in vertebrates. The chicken pineal gland and retina contain the autonomous circadian oscillators together with the photic entrainment pathway, and hence they represent useful experimental models for the clock system. Here we show the expression of G11alpha, an alpha subunit of heterotrimeric G-protein, in both tissues by cDNA cloning, Northern blot, and Western blot analyses. G11alpha immunoreactivity was colocalized with pinopsin in the chicken pineal cells and also with rhodopsin in the outer segments of retinal photoreceptor cells, suggesting functional coupling of G11alpha with opsins in the clock-containing photosensitive tissues. The physical interaction was examined by coimmunoprecipitation experiments, the results of which provided evidence for light- and GTP-dependent coupling between rhodopsin and G11alpha. To examine whether activation of endogenous G11 leads to a phase shift of the oscillator, Gq/11-coupled m1-type muscarinic acetylcholine receptor (mAChR) was ectopically expressed in the cultured pineal cells. Subsequent treatment of the cells with carbamylcholine (CCh), an agonist of mAChR, induced phase-dependent phase shifts of the melatonin rhythm in a manner very similar to the effect of light. In contrast, CCh treatment induced no measurable effect on the rhythm of nontransfected (control) cells or cells expressing G(i/o)-coupled m2-type mAChR, indicating selectivity of the G-protein activation. Together, our results demonstrate the existence of a G11-mediated opsin-signaling pathway contributing to the photic entrainment of the circadian clock.
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Affiliation(s)
- Takaoki Kasahara
- Department of Biophysics and Biochemistry, Graduate School of Science, Faculty of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
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Matthews HR, Fain GL. Time course and magnitude of the calcium release induced by bright light in salamander rods. J Physiol 2002; 542:829-41. [PMID: 12154182 PMCID: PMC2290437 DOI: 10.1113/jphysiol.2001.013218] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Changes in fluorescence were measured with an argon ion laser from the outer segments of isolated salamander rods containing the Ca(2+)-sensitive fluorescent dye fluo-5F. When the outer segments were exposed to a 0Ca(2+)/0Na(+) solution designed to minimise surface membrane Ca(2+) fluxes, exposure to intense light from the laser evoked a slow increase in fluorescence, reflecting a light-induced rise in outer segment [Ca(2+)](i). The time course of this slow fluorescence rise could be fitted with the sum of two asymptotic exponential functions of approximately equal amplitude, having time constants of approximately 200 ms and 5.7 s. When rods were exposed to saturating background light to reduce outer segment [Ca(2+)](i) before laser illumination, the relative amplitude of the two exponentials was altered so as to reduce the contribution from the one with the shorter time constant. Examination of the initial time course of fluorescence when recording at high temporal resolution revealed a further rapid rise with a time constant of 1-2 ms, which could be observed even from rods in Ringer solution. This initial rapid rise could be abolished by pre-exposing the rod to bleaching illumination, whether the bleach was given in Ringer solution or in 0Ca(2+)/0Na(+) solution. It would therefore appear that the rapid rise in fluorescence is generated in some way by the bleaching of the photopigment. Unlike the slower components of fluorescence increase, the rapid initial rise was virtually unaffected in waveform or amplitude when rods were pre-exposed in Ringer solution to light which was bright enough to suppress completely the circulating current but which bleached a negligible fraction of the photopigment. Furthermore, pre-incubation with the AM ester of the Ca(2+) chelator BAPTA, although completely abolishing the slower components of fluorescence increase, had virtually no effect on the rapid rise. These results indicate that the rapid component, though triggered by rhodopsin bleaching, does not reflect an increase in outer segment [Ca(2+)](i). Neither the rapid nor the slower components of fluorescence increase were affected by exposure of the outer segment to 10 microM of the membrane-permeant compound N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine (TPEN), which chelates heavy metals such as Zn(2+), or 100 microM 2-aminoethoxydiphenylborate (2-APB), a membrane-permeant blocker of IP(3) receptors. These results appear to exclude a role for changes in heavy metal concentration or Ca(2+) release via IP(3) receptors in the light-induced increases in dye fluorescence. Estimates of absolute Ca(2+) concentration and of rod buffering capacity suggest that the slower components of fluorescence increase represent the release of around 10-50 micromoles Ca(2+) per litre cytoplasmic volume from bound or sequestered stores after bleaching.
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Affiliation(s)
- Hugh R Matthews
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
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Kramer RH, Molokanova E. Modulation of cyclic-nucleotide-gated channels and regulation of vertebrate phototransduction. J Exp Biol 2001; 204:2921-31. [PMID: 11551982 DOI: 10.1242/jeb.204.17.2921] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Cyclic-nucleotide-gated (CNG) channels are crucial for sensory transduction in the photoreceptors (rods and cones) of the vertebrate retina. Light triggers a decrease in the cytoplasmic concentration of cyclic GMP in the outer segments of these cells, leading to closure of CNG channels and hyperpolarization of the membrane potential. Hence, CNG channels translate a chemical change in cyclic nucleotide concentration into an electrical signal that can spread through the photoreceptor cell and be transmitted to the rest of the visual system. The sensitivity of phototransduction can be altered by exposing the cells to light, through adaptation processes intrinsic to photoreceptors. Intracellular Ca2+ is a major signal in light adaptation and, in conjunction with Ca2+-binding proteins, one of its targets for modulation is the CNG channel itself. However, other intracellular signals may be involved in the fine-tuning of light sensitivity in response to cues internal to organisms. Several intracellular signals are candidates for mediating changes in cyclic GMP sensitivity including transition metals, such as Ni2+ and Zn2+, and lipid metabolites, such as diacylglycerol. Moreover, CNG channels are associated with protein kinases and phosphatases that catalyze changes in phosphorylation state and allosterically modulate channel activity. Recent studies suggest that the effects of circadian rhythms and retinal transmitters on CNG channels may be mediated by such changes in phosphorylation. The goal of this paper is to review the molecular mechanisms underlying modulation of CNG channels and to relate these forms of modulation to the regulation of light sensitivity.
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Affiliation(s)
- R H Kramer
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA.
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42
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Matthews HR, Fain GL. A light-dependent increase in free Ca2+ concentration in the salamander rod outer segment. J Physiol 2001; 532:305-21. [PMID: 11306652 PMCID: PMC2278555 DOI: 10.1111/j.1469-7793.2001.0305f.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. The Ca(2+) indicator dye fluo-5F was excited by an argon ion laser to measure changes in free Ca(2+) concentration ([Ca2+]i) in the outer segments of isolated salamander rods rapidly exposed to a 0 Ca(2+), 0 Na(+) solution designed to minimise surface membrane Ca(2+) fluxes. Over 30-60 s of laser illumination, the fluorescence first increased rapidly and then declined at a rate that was much slower than in Ringer solution and consistent with previous physiological evidence that 0 Ca(2+), 0 Na(+) solution greatly retards light-induced changes in [Ca(2+)]i. 2. The initial increase in fluorescence was investigated with a sequence of 100 ms laser flashes presented at 5 s intervals. The fluorescence evoked by the second laser flash was on average 30 % larger than the first, and subsequent responses exhibited a slow decline like that measured with continuous laser exposures. The initial increase in fluorescence did not depend upon the timing of exposure to 0 Ca(2+), 0 Na(+) solution but appeared to be evoked by exposure to the laser light. 3. Both the increase and subsequent decline in fluorescence measured with brief laser flashes could be reduced by incorporation of the Ca(2+) chelator BAPTA. This and other results indicate that the fluorescence increase was unlikely to have been caused by a change in the affinity of fluo-5F for Ca(2+) or an increase in the quantity of incorporated dye available to bind Ca(2+) but reflects an actual release of intracellular Ca(2+) within the outer segment. 4. The pool of Ca(2+) available to be released could be decreased if, before the first laser flash, the rod was exposed to light bright enough to bleach a substantial fraction of the photopigment. The releasable pool could also be depleted by exposure to saturating light of much lower intensity if delivered in Ringer solution but not if delivered in 0 Ca(2+), 0 Na(+) solution. We conclude that Ca(2+) can be released within the outer segment both by the bleaching of rhodopsin and by the reduction in [Ca(2+)]i which normally accompanies illumination in Ringer solution. 5. The activation of rhodopsin appears somehow to induce the release of Ca(2+) from a binding site or store within the outer segment. Substantial release, however, required stimulating light of an intensity sufficient to bleach a considerable fraction of the visual pigment. It therefore seems unlikely that such release contributes to the normal Ca(2+)-mediated modulation of transduction during light adaptation. The mechanism and physiological function of light-induced Ca(2+) release are unknown.
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Affiliation(s)
- H R Matthews
- Physiological Laboratory, University of Cambridge, UK.
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43
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Abstract
When light is absorbed within the outer segment of a vertebrate photoreceptor, the conformation of the photopigment rhodopsin is altered to produce an activated photoproduct called metarhodopsin II or Rh(*). Rh(*) initiates a transduction cascade similar to that for metabotropic synaptic receptors and many hormones; the Rh(*) activates a heterotrimeric G protein, which in turn stimulates an effector enzyme, a cyclic nucleotide phosphodiesterase. The phosphodiesterase then hydrolyzes cGMP, and the decrease in the concentration of free cGMP reduces the probability of opening of channels in the outer segment plasma membrane, producing the electrical response of the cell. Photoreceptor transduction can be modulated by changes in the mean light level. This process, called light adaptation (or background adaptation), maintains the working range of the transduction cascade within a physiologically useful region of light intensities. There is increasing evidence that the second messenger responsible for the modulation of the transduction cascade during background adaptation is primarily, if not exclusively, Ca(2+), whose intracellular free concentration is decreased by illumination. The change in free Ca(2+) is believed to have a variety of effects on the transduction mechanism, including modulation of the rate of the guanylyl cyclase and rhodopsin kinase, alteration of the gain of the transduction cascade, and regulation of the affinity of the outer segment channels for cGMP. The sensitivity of the photoreceptor is also reduced by previous exposure to light bright enough to bleach a substantial fraction of the photopigment in the outer segment. This form of desensitization, called bleaching adaptation (the recovery from which is known as dark adaptation), seems largely to be due to an activation of the transduction cascade by some form of bleached pigment. The bleached pigment appears to activate the G protein transducin directly, although with a gain less than Rh(*). The resulting decrease in intracellular Ca(2+) then modulates the transduction cascade, by a mechanism very similar to the one responsible for altering sensitivity during background adaptation.
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Affiliation(s)
- G L Fain
- Department of Physiological Science, University of California, Los Angeles, California 90095-1527, USA.
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Yamashita T, Terakita A, Shichida Y. Distinct roles of the second and third cytoplasmic loops of bovine rhodopsin in G protein activation. J Biol Chem 2000; 275:34272-9. [PMID: 10930404 DOI: 10.1074/jbc.m002954200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In contrast to the extensive studies of light-induced conformational changes in rhodopsin, the cytoplasmic architecture of rhodopsin related to the G protein activation and the selective recognition of G protein subtype is still unclear. Here, we prepared a set of bovine rhodopsin mutants whose cytoplasmic loops were replaced by those of other ligand-binding receptors, and we compared their ability for G protein activation in order to obtain a clue to the roles of the second and third cytoplasmic loops of rhodopsin. The mutants bearing the third loop of four other G(o)-coupled receptors belonging to the rhodopsin superfamily showed significant G(o) activation, indicating that the third loop of rhodopsin possibly has a putative site(s) related to the interaction of G protein and that it is simply exchangeable with those of other G(o)-coupled receptors. The mutants bearing the second loop of other receptors, however, had little ability for G protein activation, suggesting that the second loop of rhodopsin contains a specific region essential for rhodopsin to be a G protein-activating form. Systematic chimeric and point mutational studies indicate that three amino acids (Glu(134), Val(138), and Cys(140)) in the N-terminal region of the second loop of rhodopsin are crucial for efficient G protein activation. These results suggest that the second and third cytoplasmic loops of bovine rhodopsin have distinct roles in G protein activation and subtype specificity.
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Affiliation(s)
- T Yamashita
- Department of Biophysics, Graduate School of Science, Kyoto University, Japan
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Pasquaré SJ, Salvador GA, Roque ME, Giusto NM. Effect of light on phosphatidate phosphohydrolase activity of retina rod outer segments: the role of transducin. Arch Biochem Biophys 2000; 379:299-306. [PMID: 10898948 DOI: 10.1006/abbi.2000.1861] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of the present paper is to evaluate the modulation of phosphatidate phosphohydrolase (PAPase) and diacylglyceride lipase (DGL) activities in bovine rod outer segment (ROS) under dark and light conditions and to evaluate the role of transducin (T) in this phenomenon. In dark-adapted ROS membranes exposed to light, PAPase activity is inhibited by 20% with respect to the activity found under dark conditions. To determine whether the retinal G protein, T, participates in the regulation of PAPase activity in these membranes, the effects of GTPgammaS and GDPbetaS on enzyme activity were examined. Under dark conditions in the presence of GTPgammaS, which stabilizes T in its active form (Talpha + Tbetagamma), enzyme activity was inhibited and approached control values under light conditions. GDPbetaS, on the other hand, which stabilizes the inactive state of T (Talphabetagamma), stimulated PAPase activity by 36% with respect to control light conditions. ADP-ribosylation by cholera and pertussis toxin was also studied. In ADP-rybosilated ROS membranes with pertussis toxin under dark conditions, PAPase activity was 36% higher than the activity found under control light conditions. ADP-ribosylation by CTx, on the other hand, inhibited PAPase activity by 22%, with respect to dark control conditions, mimicking light effect. The effects of GTPgammaS and GDPbetaS and conditions of ADP-ribosylation by PTx and CTx on DGL activity were similar to those of PAPase activities. Based on NEM sensitivity we have also demonstrated that the PAPase present in ROS is the PAP 2 isoform. Our findings therefore suggest that light inhibition of PAP 2 in ROS is a transducin-mediated mechanism.
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Affiliation(s)
- S J Pasquaré
- Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas, Bahía Blanca, CC 857, B8000FWB, Argentina
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Giusto NM, Pasquaré SJ, Salvador GA, Castagnet PI, Roque ME, Ilincheta de Boschero MG. Lipid metabolism in vertebrate retinal rod outer segments. Prog Lipid Res 2000; 39:315-91. [PMID: 10856601 DOI: 10.1016/s0163-7827(00)00009-6] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- N M Giusto
- Instituto de Investigaciones Bioquímicas, Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas, CC 857, B 8000 FWB, Bahia Blanca, Argentina.
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Abstract
Mammalian rod cyclic nucleotide gated (CNG) channels (i.e., alpha plus beta subunits) are strongly inhibited by phosphatidylinositol 4, 5-bisphosphate (PIP(2)) when they are expressed in Xenopus oocytes and studied in giant membrane patches. Cytoplasmic Mg-ATP inhibits CNG currents similarly, and monoclonal antibodies to PIP(2) reverse the effect and hyperactivate currents. When alpha subunits are expressed alone, PIP(2) inhibition is less strong; olfactory CNG channels are not inhibited. In giant patches from rod outer segments, inhibition by PIP(2) is intermediate. Other anionic lipids (e.g., phosphatidyl serine and phosphatidic acid), a phosphatidylinositol-specific phospholipase C, and full-length diacylglycerol have stimulatory effects. Although ATP also potently inhibits cGMP-activated currents in rod patches, the following findings indicate that ATP is used to transphosphorylate GMP, generated from cGMP, to GTP. First, a phosphodiesterase (PDE) inhibitor, Zaprinast, blocks inhibition by ATP. Second, inhibition can be rapidly reversed by exogenous regulator of G-protein signaling 9, suggesting G-protein activation by ATP. Third, the reversal of ATP effects is greatly slowed when cyclic inosine 5'-monophosphate is used to activate currents, as expected for slow inosine 5' triphosphate hydrolysis by G-proteins. Still, other results remain suggestive of regulatory roles for PIP(2). First, the cGMP concentration producing half-maximal CNG channel activity (K(1/2)) is decreased by PIP(2) antibody in the presence of PDE inhibitors. Second, the activation of PDE activity by several nucleotides, monitored electrophysiologically and biochemically, is reversed by PIP(2) antibody. Third, exogenous PIP(2) can enhance PDE activation by nucleotides.
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48
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Zólyomi A, Zhao X, Downing GJ, Balla T. Localization of two distinct type III phosphatidylinositol 4-kinase enzyme mRNAs in the rat. Am J Physiol Cell Physiol 2000; 278:C914-20. [PMID: 10794665 DOI: 10.1152/ajpcell.2000.278.5.c914] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Inositol lipid kinases generate polyphosphoinositides, important regulators of several cellular functions. We have recently cloned two distinct phosphatidylinositol (PI) 4-kinase enzymes, the 210-kDa PI4KIIIalpha and the 110-kDa PI4KIIIbeta, from bovine tissues. In the present study, the distribution of mRNAs encoding these two enzymes was analyzed by in situ hybridization histochemistry in the rat. PI4KIIIalpha was found predominantly expressed in the brain, with low expression in peripheral tissues. PI4KIIIbeta was more uniformly expressed being also present in various peripheral tissues. Within the brain, PI4KIIIbeta showed highest expression in the gray matter, especially in neurons of the olfactory bulb and the hippocampus, but also gave a signal in the white matter indicating its presence in glia. PI4KIIIalpha was highly expressed in neurons, but lacked a signal in the white matter and the choroid plexus. Both enzymes showed expression in the pigment layer and nuclear layers as well as in the ganglion cells of the retina. In a 17-day-old rat fetus, PI4KIIIbeta was found to be more widely distributed and PI4KIIIalpha was primarily expressed in neurons. These results indicate that PI4KIIIbeta is more widely expressed than PI4KIIIalpha, and that the two enzymes are probably coexpressed in many neurons. Such expression pattern and the conservation of these two proteins during evolution suggest their nonredundant functions in mammalian cells.
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Affiliation(s)
- A Zólyomi
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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49
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Womack KB, Gordon SE, He F, Wensel TG, Lu CC, Hilgemann DW. Do phosphatidylinositides modulate vertebrate phototransduction? J Neurosci 2000; 20:2792-9. [PMID: 10751430 PMCID: PMC6772201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
Mammalian rod cyclic nucleotide gated (CNG) channels (i.e., alpha plus beta subunits) are strongly inhibited by phosphatidylinositol 4, 5-bisphosphate (PIP(2)) when they are expressed in Xenopus oocytes and studied in giant membrane patches. Cytoplasmic Mg-ATP inhibits CNG currents similarly, and monoclonal antibodies to PIP(2) reverse the effect and hyperactivate currents. When alpha subunits are expressed alone, PIP(2) inhibition is less strong; olfactory CNG channels are not inhibited. In giant patches from rod outer segments, inhibition by PIP(2) is intermediate. Other anionic lipids (e.g., phosphatidyl serine and phosphatidic acid), a phosphatidylinositol-specific phospholipase C, and full-length diacylglycerol have stimulatory effects. Although ATP also potently inhibits cGMP-activated currents in rod patches, the following findings indicate that ATP is used to transphosphorylate GMP, generated from cGMP, to GTP. First, a phosphodiesterase (PDE) inhibitor, Zaprinast, blocks inhibition by ATP. Second, inhibition can be rapidly reversed by exogenous regulator of G-protein signaling 9, suggesting G-protein activation by ATP. Third, the reversal of ATP effects is greatly slowed when cyclic inosine 5'-monophosphate is used to activate currents, as expected for slow inosine 5' triphosphate hydrolysis by G-proteins. Still, other results remain suggestive of regulatory roles for PIP(2). First, the cGMP concentration producing half-maximal CNG channel activity (K(1/2)) is decreased by PIP(2) antibody in the presence of PDE inhibitors. Second, the activation of PDE activity by several nucleotides, monitored electrophysiologically and biochemically, is reversed by PIP(2) antibody. Third, exogenous PIP(2) can enhance PDE activation by nucleotides.
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Affiliation(s)
- K B Womack
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-9040, USA
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Xu S, Ladak R, Swanson DA, Soltyk A, Sun H, Ploder L, Vidgen D, Duncan AM, Garami E, Valle D, McInnes RR. PHR1 encodes an abundant, pleckstrin homology domain-containing integral membrane protein in the photoreceptor outer segments. J Biol Chem 1999; 274:35676-85. [PMID: 10585447 DOI: 10.1074/jbc.274.50.35676] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We cloned human and murine cDNAs of a gene (designated PHR1), expressed preferentially in retina and brain. In both species, PHR1 utilizes two promoters and alternative splicing to produce four PHR1 transcripts, encoding isoforms of 243, 224, 208, and 189 amino acids, each with a pleckstrin homology domain at their N terminus and a transmembrane domain at their C terminus. Transcript 1 originates from a 5'-photoreceptor-specific promoter with at least three Crx elements ((C/T)TAATCC). Transcript 2 originates from the same promoter but lacks exon 7, which encodes 35 amino acids immediately C-terminal to the pleckstrin homology domain. Transcripts 3 and 4 originate from an internal promoter in intron 2 and either include or lack exon 7, respectively. In situ hybridization shows that PHR1 is highly expressed in photoreceptors, with lower expression in retinal ganglion cells. Immunohistochemistry localizes the PHR1 protein to photoreceptor outer segments where chemical extraction studies confirm it is an integral membrane protein. Using a series of PHR1 glutathione S-transferase fusion proteins to perform in vitro binding assays, we found PHR1 binds transducin betagamma subunits but not inositol phosphates. This activity and subcellular location suggests that PHR1 may function as a previously unrecognized modulator of the phototransduction pathway.
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Affiliation(s)
- S Xu
- Predoctoral Training Program in Human Genetics, Department of Pediatrics, Baltimore, Maryland 21205, USA
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