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Rajala A, Rajala R, Teel K, Rajala RVS. Ribosomal targeting strategy and nuclear labeling to analyze photoreceptor phosphoinositide signatures. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159161. [PMID: 35427794 PMCID: PMC10812878 DOI: 10.1016/j.bbalip.2022.159161] [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: 02/02/2022] [Revised: 04/03/2022] [Accepted: 04/08/2022] [Indexed: 10/18/2022]
Abstract
Reversible phosphorylation of phosphatidylinositol by phosphoinositide (PI) kinases and phosphatases generates seven distinct phosphoinositide phosphates, called phosphoinositides or PIPs. All seven PIPs are formed in the retina and photoreceptor cells. Around 50 genes in the mammalian genome encode PI kinases and PI phosphatases. There are no studies available on the distribution of these enzymes in the retina and photoreceptors. AIM To employ Ribosomal Targeting Strategy and Nuclear Labeling to Analyze Phosphoinositide Signatures in rod-photoreceptor cells. METHODS HA-tagging of ribosomal protein Rpl22 was induced with Cre-recombinase under the control of the rhodopsin promoter. Actively translating mRNAs associated with polyribosomes were isolated by immunoprecipitation with HA antibody, followed by RNA isolation and gene identification. We also isolated biotinylated-rod nuclei from NuTRAP mice under the control of the rhodopsin-Cre promoter and analyzed nuclear phosphoinositides. RESULTS Our results indicate that the expression of class I and class III PI 3-kinase, PI4K IIIβ, PI 5-kinase, PIKfyve, PI3-phosphatases, MTMR2, 4, 6, 7, 14, PI4-phosphatase, TMEM55A, PI 5-phosphatases, SYNJI, INPP5B, INPP5E, INPP5F, SKIP and other phosphatases with dual substrate specificity, PTPMT1, SCAM1, and FIG4 are highly enriched in rod photoreceptor cells compared with the retina and cone-like retina. Our analysis identified the presence of PI(4)P, PI(3,4)P2, PI(3,5)P2, and PI(4,5)P2 in the rod nuclei. CONCLUSIONS Our studies for the first time demonstrate the expression of PI kinases, PI phosphatases, and nuclear PIPs in rod photoreceptor cells. The NuTRAP mice may be useful not only for epigenetic and transcriptomic studies but also for in vivo cell-specific lipidomics research.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean McGee Eye Institute, Oklahoma City, OK 73014, USA
| | - Rahul Rajala
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Cardiovascular Biology Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73014, USA
| | - Kenneth Teel
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean McGee Eye Institute, Oklahoma City, OK 73014, USA
| | - Raju V S Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean McGee Eye Institute, Oklahoma City, OK 73014, USA.
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2
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Martin GJ, Lower SE, Suvorov A, Bybee SM. Molecular Evolution of Phototransduction Pathway Genes in Nocturnal and Diurnal Fireflies (Coleoptera: Lampyridae). INSECTS 2021; 12:insects12060561. [PMID: 34207188 PMCID: PMC8235688 DOI: 10.3390/insects12060561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 06/04/2021] [Accepted: 06/06/2021] [Indexed: 11/16/2022]
Abstract
Most organisms are dependent on sensory cues from their environment for survival and reproduction. Fireflies (Coleoptera: Lampyridae) represent an ideal system for studying sensory niche adaptation due to many species relying on bioluminescent communication; as well as a diversity of ecologies. Here; using transcriptomics; we examine the phototransduction pathway in this non-model organism; and provide some of the first evidence for positive selection in the phototransduction pathway beyond opsins in beetles. Evidence for gene duplications within Lampyridae are found in inactivation no afterpotential C and inactivation no afterpotential D. We also find strong support for positive selection in arrestin-2; inactivation no afterpotential D; and transient receptor potential-like; with weak support for positive selection in guanine nucleotide-binding protein G(q) subunit alpha and neither inactivation nor afterpotential C. Taken with other recent work in flies; butterflies; and moths; this represents an exciting new avenue of study as we seek to further understand diversification and constraint on the phototransduction pathway in light of organism ecology.
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Affiliation(s)
- Gavin J. Martin
- Department of Biology, Brigham Young University, Provo, UT 84602, USA; (A.S.); (S.M.B.)
- Monte L. Bean Museum, Brigham Young University, Provo, UT 84602, USA
- Correspondence:
| | - Sarah E. Lower
- Department of Biology, Bucknell University, Lewisburg, PA 17837, USA;
| | - Anton Suvorov
- Department of Biology, Brigham Young University, Provo, UT 84602, USA; (A.S.); (S.M.B.)
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Seth M. Bybee
- Department of Biology, Brigham Young University, Provo, UT 84602, USA; (A.S.); (S.M.B.)
- Monte L. Bean Museum, Brigham Young University, Provo, UT 84602, USA
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3
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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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4
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Raghuraman BK, Hebbar S, Kumar M, Moon H, Henry I, Knust E, Shevchenko A. Absolute Quantification of Proteins in the Eye of Drosophila melanogaster. Proteomics 2020; 20:e1900049. [PMID: 32663363 DOI: 10.1002/pmic.201900049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 05/29/2020] [Indexed: 01/26/2023]
Abstract
Absolute (molar) quantification of proteins determines their molar ratios in complexes, networks, and metabolic pathways. MS Western workflow is employed to determine molar abundances of proteins potentially critical for morphogenesis and phototransduction (PT) in eyes of Drosophila melanogaster using a single chimeric 264 kDa protein standard that covers, in total, 197 peptides from 43 proteins. The majority of proteins are independently quantified with two to four proteotypic peptides with the coefficient of variation of less than 15%, better than 1000-fold dynamic range and sub-femtomole sensitivity. Here, the molar abundance of proteins of the PT machinery and of the rhabdomere, the photosensitive organelle, is determined in eyes of wild-type flies as well as in crumbs (crb) mutant eyes, which exhibit perturbed rhabdomere morphogenesis.
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Affiliation(s)
- Bharath Kumar Raghuraman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - Sarita Hebbar
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - Mukesh Kumar
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - HongKee Moon
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany.,Centre for Systems Biology Dresden, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - Ian Henry
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany.,Centre for Systems Biology Dresden, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - Elisabeth Knust
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden, 01307, Germany
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Rajala A, McCauley A, Brush RS, Nguyen K, Rajala RV. Phosphoinositide Lipids in Ocular Tissues. BIOLOGY 2020; 9:biology9060125. [PMID: 32545642 PMCID: PMC7345453 DOI: 10.3390/biology9060125] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 06/05/2020] [Accepted: 06/09/2020] [Indexed: 01/04/2023]
Abstract
Inositol phospholipids play an important role in cell physiology. The inositol head groups are reversibly phosphorylated to produce seven distinct phosphorylated inositides, commonly referred to as phosphoinositides (PIs). These seven PIs are dynamically interconverted from one PI to another by the action of PI kinases and PI phosphatases. The PI signals regulate a wide variety of cellular functions, including organelle distinction, vesicular transport, cytoskeletal organization, nuclear events, regulation of ion channels, cell signaling, and host–pathogen interactions. Most of the studies of PIs in ocular tissues are based on the PI enzymes and PI phosphatases. In this study, we examined the PI levels in the cornea, retinal pigment epithelium (RPE), and retina using PI-binding protein as probes. We have examined the lipids PI(3)P, PI(4)P, PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3, and each is present in the cornea, RPE, and retina. Alterations in the levels of these PIs in mouse models of retinal disease and corneal infections have been reported, and the results of our study will help in the management of anomalous phosphoinositide metabolism in ocular tissues.
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Affiliation(s)
- Ammaji Rajala
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.R.); (A.M.); (R.S.B.); (K.N.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Austin McCauley
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.R.); (A.M.); (R.S.B.); (K.N.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Richard S. Brush
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.R.); (A.M.); (R.S.B.); (K.N.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Khuong Nguyen
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.R.); (A.M.); (R.S.B.); (K.N.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Raju V.S. Rajala
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.R.); (A.M.); (R.S.B.); (K.N.)
- Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Departments of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, OK 73104, USA
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Correspondence: ; Tel.: +1-(405)-271-8255; Fax: +1-(405)-271-8128
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Liu X, Lin C, Sun L, Liu S, Sun J, Zhang L, Yang H. Transcriptome analysis of phototransduction-related genes in tentacles of the sea cucumber Apostichopus japonicus. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2020; 34:100675. [PMID: 32109670 DOI: 10.1016/j.cbd.2020.100675] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 02/14/2020] [Accepted: 02/15/2020] [Indexed: 11/18/2022]
Abstract
The sea cucumber Apostichopus japonicus (Selenka)is a typical nocturnal echinoderm, which is believed to be almost completely dependent on light intensity for the regulation of endogenous rhythms. Under conditions of high light intensity, this species shows clear evidence of light avoidance behavior, seeking out shaded areas of reef in which to reside. In this study, we performed RNA-Seq analysis to examine the tentacle transcriptome of A. japonicus specimens that had been subjected to dark and light (5 min and 1 h) conditions. We specifically focused on detecting genes involved in opsin-based light perception, including opsins and members of phototransduction-related pathways. On the basis of comparisons with both vertebrate and invertebrate phototransduction pathways, we determined that components of two of the main metazoan phototransduction pathways were altered in response to illumination. Among the key phototransduction-related genes in tentacles, we identified retinol dehydrogenase, members of the dehydrogenase/reductase family, and myosin III, and also detected a pair of visual pigment-like receptors, peropsin and peropsin-like, the homologous genes of which are believed to have the same function but show opposite expression patterns in response to different light environments. In general, the up-regulation of key genes in sea cucumber exposed to illumination indicated that the tentacles can respond to differences in the light environment at the molecular level.
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Affiliation(s)
- Xiaolu Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Chenggang Lin
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; The Innovation of Seed Design, Chinese Academy of Sciences, Wuhan, 430071, PR China.
| | - Lina Sun
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Shilin Liu
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Jingchun Sun
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Libin Zhang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China
| | - Hongsheng Yang
- CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, PR China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, PR China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, PR China; The Innovation of Seed Design, Chinese Academy of Sciences, Wuhan, 430071, PR China
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7
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Friedman TB, Belyantseva IA, Frolenkov GI. Myosins and Hearing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1239:317-330. [DOI: 10.1007/978-3-030-38062-5_13] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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8
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Ca2+ Signaling in Drosophila Photoreceptor Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:857-879. [DOI: 10.1007/978-3-030-12457-1_34] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Mu Y, Tian Y, Zhang ZC, Han J. Metallophosphoesterase regulates light-induced rhodopsin endocytosis by promoting an association between arrestin and the adaptor protein AP2. J Biol Chem 2019; 294:12892-12900. [PMID: 31324721 DOI: 10.1074/jbc.ra119.009602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/11/2019] [Indexed: 11/06/2022] Open
Abstract
Light-induced endocytosis of rhodopsin in the retina is critical for preventing photoreceptor hyperactivity and for the survival of photoreceptor cells. In Drosophila, this process is mediated by arrestin1 (Arr1). Because Arr1 lacks a clathrin-binding domain required for receptor internalization and the C-terminal sequence that interacts with the β-subunit of the clathrin adaptor protein AP2, the mechanism of how Arr1 mediates endocytosis of the major rhodopsin Rh1 is unclear. Here, using several approaches, including Arr binding and pulldown assays, immunofluorescence techniques, and EM imaging, we found that Drosophila metallophosphoesterase (dMPPE) is involved in light-induced rhodopsin endocytosis. We observed that the photoreceptor cells of a dmppe mutant exhibit impaired light-induced rhodopsin endocytosis and that this impairment is independent of dMPPE phosphoesterase activity. Furthermore, dMPPE directly interacted with Arr1 and promoted the association of Arr1 with AP2. Of note, genetic dmppe deletion largely prevented retinal degeneration in norpA (encoding phospholipase C) mutants, which were reported previously to contribute to retinal degeneration, by suppressing Rh1 endocytosis. Our findings demonstrate that Arr1 interacts with AP2 and that dMPPE functions as a critical regulator in Rh1 endocytosis and retinal degeneration.
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Affiliation(s)
- Yawen Mu
- Institute of Life Sciences, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, 210096, China
| | - Yao Tian
- Institute of Life Sciences, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, 210096, China
| | - Zi Chao Zhang
- Institute of Life Sciences, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, 210096, China.
| | - Junhai Han
- Institute of Life Sciences, the Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, 210096, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, JS 226001, China.
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10
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Schlichting M, Rieger D, Cusumano P, Grebler R, Costa R, Mazzotta GM, Helfrich-Förster C. Cryptochrome Interacts With Actin and Enhances Eye-Mediated Light Sensitivity of the Circadian Clock in Drosophila melanogaster. Front Mol Neurosci 2018; 11:238. [PMID: 30072870 PMCID: PMC6058042 DOI: 10.3389/fnmol.2018.00238] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/19/2018] [Indexed: 11/13/2022] Open
Abstract
Cryptochromes (CRYs) are a class of flavoproteins that sense blue light. In animals, CRYs are expressed in the eyes and in the clock neurons that control sleep/wake cycles and are implied in the generation and/or entrainment of circadian rhythmicity. Moreover, CRYs are sensing magnetic fields in insects as well as in humans. Here, we show that in the fruit fly Drosophila melanogaster CRY plays a light-independent role as "assembling" protein in the rhabdomeres of the compound eyes. CRY interacts with actin and appears to increase light sensitivity of the eyes by keeping the "signalplex" of the phototransduction cascade close to the membrane. By this way, CRY also enhances light-responses of the circadian clock.
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Affiliation(s)
- Matthias Schlichting
- Neurobiology and Genetics, Biocenter, Theodor-Boveri-Institute, University of Würzburg, Würzburg, Germany
- Howard Hughes Medical Institute and National Center for Behavioral Genomics, Department of Biology, Brandeis University, Waltham, MA, United States
| | - Dirk Rieger
- Neurobiology and Genetics, Biocenter, Theodor-Boveri-Institute, University of Würzburg, Würzburg, Germany
| | - Paola Cusumano
- Department of Biology, University of Padova, Padova, Italy
| | - Rudi Grebler
- Neurobiology and Genetics, Biocenter, Theodor-Boveri-Institute, University of Würzburg, Würzburg, Germany
| | - Rodolfo Costa
- Department of Biology, University of Padova, Padova, Italy
| | | | - Charlotte Helfrich-Förster
- Neurobiology and Genetics, Biocenter, Theodor-Boveri-Institute, University of Würzburg, Würzburg, Germany
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11
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Pellikka M, Tepass U. Unique cell biological profiles of retinal disease-causing missense mutations in the polarity protein Crumbs. J Cell Sci 2017; 130:2147-2158. [PMID: 28515229 DOI: 10.1242/jcs.197178] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 05/11/2017] [Indexed: 01/09/2023] Open
Abstract
Mutations in human crumbs 1 (CRB1) are a major cause of retinal diseases that lead to blindness. CRB1 is a transmembrane protein found in the inner segment of photoreceptor cells (PRCs) and the apical membrane of Müller glia. The function of the extracellular region of CRB1 is poorly understood, although more than 80 disease-causing missense mutations have been mapped to it. We have recreated four of these mutations, affecting different extracellular domains, in Drosophila Crumbs (Crb). Crb regulates epithelial polarity and growth, and contributes to PRC differentiation and survival. The mutant Crb isoforms showed a remarkable diversity in protein abundance, subcellular distribution and ability to rescue the lack of endogenous Crb, elicit a gain-of-function phenotype or promote PRC degeneration. Interestingly, although expression of mutant isoforms led to a substantial rescue of the developmental defects seen in crb mutants, they accelerated PRC degeneration compared to that seen in retinas that lacked Crb, indicating that the function of Crb in cellular differentiation and cell survival depends on distinct molecular pathways. Several Crb mutant proteins accumulated abnormally in the rhabdomere and affected rhodopsin trafficking, suggesting that abnormal rhodopsin physiology contributes to Crb/CRB1-associated retinal degeneration.
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Affiliation(s)
- Milena Pellikka
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, M5S 3G5, Canada
| | - Ulrich Tepass
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, M5S 3G5, Canada
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Raval MH, Quintero OA, Weck ML, Unrath WC, Gallagher JW, Cui R, Kachar B, Tyska MJ, Yengo CM. Impact of the Motor and Tail Domains of Class III Myosins on Regulating the Formation and Elongation of Actin Protrusions. J Biol Chem 2016; 291:22781-22792. [PMID: 27582493 PMCID: PMC5077211 DOI: 10.1074/jbc.m116.733741] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 08/29/2016] [Indexed: 11/06/2022] Open
Abstract
Class III myosins (MYO3A and MYO3B) are proposed to function as transporters as well as length and ultrastructure regulators within stable actin-based protrusions such as stereocilia and calycal processes. MYO3A differs from MYO3B in that it contains an extended tail domain with an additional actin-binding motif. We examined how the properties of the motor and tail domains of human class III myosins impact their ability to enhance the formation and elongation of actin protrusions. Direct examination of the motor and enzymatic properties of human MYO3A and MYO3B revealed that MYO3A is a 2-fold faster motor with enhanced ATPase activity and actin affinity. A chimera in which the MYO3A tail was fused to the MYO3B motor demonstrated that motor activity correlates with formation and elongation of actin protrusions. We demonstrate that removal of individual exons (30-34) in the MYO3A tail does not prevent filopodia tip localization but abolishes the ability to enhance actin protrusion formation and elongation in COS7 cells. Interestingly, our results demonstrate that MYO3A slows filopodia dynamics and enhances filopodia lifetime in COS7 cells. We also demonstrate that MYO3A is more efficient than MYO3B at increasing formation and elongation of stable microvilli on the surface of cultured epithelial cells. We propose that the unique features of MYO3A, enhanced motor activity, and an extended tail with tail actin-binding motif, allow it to play an important role in stable actin protrusion length and ultrastructure maintenance.
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Affiliation(s)
- Manmeet H Raval
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033
| | - Omar A Quintero
- the Department of Biology, University of Richmond, Richmond, Virginia 23173
| | - Meredith L Weck
- the Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - William C Unrath
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033
| | - James W Gallagher
- the Department of Biology, Lincoln University, Philadelphia, Pennsylvania 19104, and
| | - Runjia Cui
- the Laboratory of Cell Structure and Dynamics, NIDCD, National Institutes of Health, Bethesda, Maryland 20892
| | - Bechara Kachar
- the Laboratory of Cell Structure and Dynamics, NIDCD, National Institutes of Health, Bethesda, Maryland 20892
| | - Matthew J Tyska
- the Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Christopher M Yengo
- From the Department of Cellular and Molecular Physiology, Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033,
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13
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Gurevich VV, Gurevich EV. Arrestins: Critical Players in Trafficking of Many GPCRs. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:1-14. [PMID: 26055052 DOI: 10.1016/bs.pmbts.2015.02.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Arrestins specifically bind active phosphorylated G protein-coupled receptors (GPCRs). Receptor binding induces the release of the arrestin C-tail, which in non-visual arrestins contains high-affinity binding sites for clathrin and its adaptor AP2. Thus, serving as a physical link between the receptor and key components of the internalization machinery of the coated pit is the best-characterized function of non-visual arrestins in GPCR trafficking. However, arrestins also regulate GPCR trafficking less directly by orchestrating their ubiquitination and deubiquitination. Several reports suggest that arrestins play additional roles in receptor trafficking. Non-visual arrestins appear to be required for the recycling of internalized GPCRs, and the mechanisms of their function in this case remain to be elucidated. Moreover, visual and non-visual arrestins were shown to directly bind N-ethylmaleimide-sensitive factor, an important ATPase involved in vesicle trafficking, but neither molecular details nor the biological role of these interactions is clear. Considering how many different proteins arrestins appear to bind, we can confidently expect the elucidation of additional trafficking-related functions of these versatile signaling adaptors.
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Affiliation(s)
- Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA.
| | - Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
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Battelle BA, Kempler KE, Parker AK, Gaddie CD. Opsin1-2, G(q)α and arrestin levels at Limulus rhabdoms are controlled by diurnal light and a circadian clock. ACTA ACUST UNITED AC 2013; 216:1837-49. [PMID: 23393287 DOI: 10.1242/jeb.083519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dark and light adaptation in photoreceptors involve multiple processes including those that change protein concentrations at photosensitive membranes. Light- and dark-adaptive changes in protein levels at rhabdoms have been described in detail in white-eyed Drosophila maintained under artificial light. Here we tested whether protein levels at rhabdoms change significantly in the highly pigmented lateral eyes of wild-caught Limulus polyphemus maintained in natural diurnal illumination and whether these changes are under circadian control. We found that rhabdomeral levels of opsins (Ops1-2), the G protein activated by rhodopsin (G(q)α) and arrestin change significantly from day to night and that nighttime levels of each protein at rhabdoms are significantly influenced by signals from the animal's central circadian clock. Clock input at night increases Ops1-2 and G(q)α and decreases arrestin levels at rhabdoms. Clock input is also required for a rapid decrease in rhabdomeral Ops1-2 beginning at sunrise. We found further that dark adaptation during the day and the night are not equivalent. During daytime dark adaptation, when clock input is silent, the increase of Ops1-2 at rhabdoms is small and G(q)α levels do not increase. However, increases in Ops1-2 and G(q)α at rhabdoms are enhanced during daytime dark adaptation by treatments that elevate cAMP in photoreceptors, suggesting that the clock influences dark-adaptive increases in Ops1-2 and G(q)α at Limulus rhabdoms by activating cAMP-dependent processes. The circadian regulation of Ops1-2 and G(q)α levels at rhabdoms probably has a dual role: to increase retinal sensitivity at night and to protect photoreceptors from light damage during the day.
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Affiliation(s)
- Barbara-Anne Battelle
- The Whitney Laboratory for Marine Bioscience, 9505 Ocean Shore Blvd, St Augustine, FL 32080-8610, USA.
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Regulation of arrestin translocation by Ca2+ and myosin III in Drosophila photoreceptors. J Neurosci 2012; 32:9205-16. [PMID: 22764229 DOI: 10.1523/jneurosci.0924-12.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Upon illumination several phototransduction proteins translocate between cell body and photosensory compartments. In Drosophila photoreceptors arrestin (Arr2) translocates from cell body to the microvillar rhabdomere down a diffusion gradient created by binding of Arr2 to photo-isomerized metarhodopsin. Translocation is profoundly slowed in mutants of key phototransduction proteins including phospholipase C (PLC) and the Ca(2+)-permeable transient receptor potential channel (TRP), but how the phototransduction cascade accelerates Arr2 translocation is unknown. Using real-time fluorescent imaging of Arr2-green fluorescent protein translocation in dissociated ommatidia, we show that translocation is profoundly slowed in Ca(2+)-free solutions. Conversely, in a blind PLC mutant with ∼100-fold slower translocation, rapid translocation was rescued by the Ca(2+) ionophore, ionomycin. In mutants lacking NINAC (calmodulin [CaM] binding myosin III) in the cell body, translocation remained rapid even in Ca(2+)-free solutions. Immunolabeling revealed that Arr2 in the cell body colocalized with NINAC in the dark. In intact eyes, the impaired translocation found in trp mutants was rescued in ninaC;trp double mutants. Nevertheless, translocation following prolonged dark adaptation was significantly slower in ninaC mutants, than in wild type: a difference that was reflected in the slow decay of the electroretinogram. The results suggest that cytosolic NINAC is a Ca(2+)-dependent binding target for Arr2, which protects Arr2 from immobilization by a second potential sink that sequesters and releases arrestin on a much slower timescale. We propose that rapid Ca(2+)/CaM-dependent release of Arr2 from NINAC upon Ca(2+) influx accounts for the acceleration of translocation by phototransduction.
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Montell C. Drosophila visual transduction. Trends Neurosci 2012; 35:356-63. [PMID: 22498302 DOI: 10.1016/j.tins.2012.03.004] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 03/06/2012] [Accepted: 03/11/2012] [Indexed: 11/26/2022]
Abstract
Visual transduction in the Drosophila compound eye functions through a pathway that couples rhodopsin to phospholipase C (PLC) and the opening of transient receptor potential (TRP) channels. This cascade differs from phototransduction in mammalian rods and cones, but is remarkably similar to signaling in mammalian intrinsically photosensitive retinal ganglion cells (ipRGCs). In this review, I focus on recent advances in the fly visual system, including the discovery of a visual cycle and insights into the machinery and mechanisms involved in generating a light response in photoreceptor cells.
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Affiliation(s)
- Craig Montell
- Departments of Biological Chemistry and Neuroscience, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Raghu P, Yadav S, Mallampati NBN. Lipid signaling in Drosophila photoreceptors. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1154-65. [PMID: 22487656 DOI: 10.1016/j.bbalip.2012.03.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 03/20/2012] [Accepted: 03/22/2012] [Indexed: 11/19/2022]
Abstract
Drosophila photoreceptors are sensory neurons whose primary function is the transduction of photons into an electrical signal for forward transmission to the brain. Photoreceptors are polarized cells whose apical domain is organized into finger like projections of plasma membrane, microvilli that contain the molecular machinery required for sensory transduction. The development of this apical domain requires intense polarized membrane transport during development and it is maintained by post developmental membrane turnover. Sensory transduction in these cells involves a high rate of G-protein coupled phosphatidylinositol 4,5 bisphosphate [PI(4,5)P(2)] hydrolysis ending with the activation of ion channels that are members of the TRP superfamily. Defects in this lipid-signaling cascade often result in retinal degeneration, which is a consequence of the loss of apical membrane homeostasis. In this review we discuss the various membrane transport challenges of photoreceptors and their regulation by ongoing lipid signaling cascades in these cells. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Padinjat Raghu
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bellary Road, Banglore 560065, India.
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Minke B. The history of the prolonged depolarizing afterpotential (PDA) and its role in genetic dissection of Drosophila phototransduction. J Neurogenet 2012; 26:106-17. [PMID: 22428622 DOI: 10.3109/01677063.2012.666299] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In invertebrate photoreceptors, the photopigment exhibits a long-lived and physiologically active photoproduct, called metarhodopsin (M). The long life of invertebrate M implies that under physiological conditions, M and the original pigment state rhodopsin, R, are in photoequilibrium. In many invertebrates, the absorption spectra of R and M states are different, allowing large photopigment conversion between R and M states. These net pigment molecules conversions between R and M are the basis of the prolonged depolarizing afterpotential (PDA) phenomenology, which is the main subject of this review. A large net conversion of R to M disrupts phototransduction termination at the photopigment level, which in turn results in sustained excitation long after the light is turned off. Throughout this period, the photoreceptors are partially desensitized and are insensitive (or less sensitive) to subsequent test lights. In Drosophila, the PDA tests the maximal capacity of the photoreceptor cell to maintain excitation for an extended period and is strictly dependent on the presence of high concentrations of rhodopsin and the transient receptor potential (TRP) channels. Therefore, it detects even minor defects in rhodopsin or TRP biogenesis and easily scores deficient replenishment of phototransduction components, which results in temporary desensitization of the phototransduction process. Indeed, the introduction and use of PDA to screen for phototransduction-defective Drosophila mutants by Pak and colleagues yielded a plethora of new and most interesting visual mutants. Remarkably, to this day, the PDA mutants that Pak and his colleagues isolated are the main source of mutants for analysis of the Drosophila visual system.
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Affiliation(s)
- Baruch Minke
- Department of Medical Neurobiology, The Institute of Medical Research Israel-Canada, Faculty of Medicine and the Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University , Jerusalem , Israel.
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Abstract
Drosophila photoreceptors (R cells) are an extreme instance of sensory membrane amplification via apical microvilli, a widely deployed and deeply conserved operation of polarized epithelial cells. Developmental rotation of R cell apices aligns rhabdomere microvilli across the optical axis and enables enormous membrane expansion in a new, proximal distal dimension. R cell ectoplasm, the specialized cortical cytoplasm abutting the rhabdomere is likewise enormously amplified. Ectoplasm is dominated by the actin-rich terminal web, a conserved operational domain of the ancient vesicle-transport motor, Myosin V. R cells harness Myosin V to move two distinct cargoes, the biosynthetic traffic that builds the rhabdomere during development, and the migration of pigment granules that mediates the adaptive "longitudinal pupil" in adults, using two distinct Rab proteins. Ectoplasm further shapes a distinct cortical endosome compartment, the subrhabdomeral cisterna (SRC), vital to normal cell function. Reticulon, a protein that promotes endomembrane curvature, marks the SRC. R cell visual arrestin 2 (Arr2) is predominantly cytoplasmic in dark-adapted photoreceptors but on illumination it translocates to the rhabdomere, where it quenches ongoing photosignaling by binding to activated metarhodopsin. Arr2 translocation is "powered" by diffusion; a motor is not required to move Arr2 and ectoplasm does not obstruct its rapid diffusion to the rhabdomere.
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Affiliation(s)
- Hongai Xia
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Lieu MH, Vallejos MJ, Michael E, Tsunoda S. Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors. PLoS One 2012; 7:e31622. [PMID: 22363689 PMCID: PMC3282777 DOI: 10.1371/journal.pone.0031622] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 01/16/2012] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere), TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels. METHODOLOGY/PRINCIPAL FINDINGS We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content. CONCLUSIONS/SIGNIFICANCE Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a light-dependent anchor in the rhabdomere.
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Affiliation(s)
- Minh-Ha Lieu
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Maximiliano J. Vallejos
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Emily Michael
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Susan Tsunoda
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
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Van Hook MJ, Wong KY, Berson DM. Dopaminergic modulation of ganglion-cell photoreceptors in rat. Eur J Neurosci 2012; 35:507-18. [PMID: 22304466 DOI: 10.1111/j.1460-9568.2011.07975.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A novel class of photoreceptors, the intrinsically photosensitive retinal ganglion cells (ipRGCs), express the photopigment melanopsin and drive non-image-forming responses to light such as circadian photoentrainment, the pupillary light reflex and suppression of nocturnal melatonin production in the pineal. Because dendrites from one subclass of these cells - the M1-type ipRGCs - make presumptive synaptic contacts at sites of dopamine release from dopaminergic amacrine cells, they are prime targets for modulation by dopamine, a neuromodulator implicated in retinal circadian rhythms and light adaptation. In patch-clamp recordings from ipRGCs in intact rat retinas, dopamine attenuated the melanopsin-based photocurrent. We confirmed that this was the result of direct action on ipRGCs by replicating the effect in dissociated ipRGCs that were isolated from influences of other retinal neurons. In these recordings, the D1-family dopamine receptor agonist SKF38393 attenuated the photocurrent, caused a modest depolarization, and reduced the input resistance of ipRGCs. The D2-family agonist quinpirole had no effect on the photocurrent. Single-cell reverse-transcriptase polymerase chain reaction revealed that the majority of ipRGCs tested expressed drd1a, the gene coding for the D1a dopamine receptor. This finding was supported by immunohistochemical localization of D1a receptor protein in melanopsin-expressing ganglion cells. Finally, the adenylate cyclase activator forskolin, applied in combination with the phosphodiesterase inhibitor IBMX (isobutylmethylxanthine), mimicked the effects of SKF38393 on the ipRGC photocurrent, membrane potential and input resistance, consistent with a D1-receptor signaling pathway. These data suggest that dopamine, acting via D1-family receptors, alters the responses of ipRGCs and thus of non-image-forming vision.
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Affiliation(s)
- Matthew J Van Hook
- Department of Neuroscience, Brown University, Box G-LN, Providence, RI, USA
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22
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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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Ivanovic I, Allen DT, Dighe R, Le YZ, Anderson RE, Rajala RVS. Phosphoinositide 3-kinase signaling in retinal rod photoreceptors. Invest Ophthalmol Vis Sci 2011; 52:6355-62. [PMID: 21730346 DOI: 10.1167/iovs.10-7138] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PURPOSE Phosphoinositide 3-kinase (PI3K) consists of a p110 catalytic protein and a p85α regulatory protein, required for the stabilization and localization of p110-PI3K activity. The biological significance of PI3K was investigated in vertebrate rod photoreceptors by deleting its regulatory p85α protein and examining its role in photoreceptor structure, function, and protein trafficking. METHODS Mice that expressed Cre recombinase in rods were bred to mice with a floxed p85α (pik3r1) regulatory subunit of PI3K to generate a conditional deletion of pik3r1 in rods. Functional and structural changes were determined by ERG and morphometric analysis, respectively. PI3K activity was measured in retinal homogenates immunoprecipitated with an anti-PY antibody. Akt activation was determined by Western blot analysis with a pAkt antibody. RESULTS Light-induced stress increased PI3K activity in retinal immunoprecipitates and phosphorylation of Akt. There was no effect of pik3r1 deletion on retinal structure. However, twin flash electroretinography revealed a slight delay in recovery kinetics in pik3r1 knockout (KO) mice compared with wild-type controls. The movement of arrestin in the pik3r1 KO mice was slower than that in the wild-type mouse retinas at 5 minutes of exposure to light. At 10 minutes of exposure, the ROS localization of arrestin was almost identical between the wild-type and pik3r1 KO mice. CONCLUSIONS The results provide the first direct evidence that rods use PI3K-generated phosphoinositides for photoreceptor function. The lack of phenotype in pik3r1 KO rod photoreceptors suggests a redundant role in controlling PIP(3) synthesis.
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Affiliation(s)
- Ivana Ivanovic
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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Gurevich VV, Hanson SM, Song X, Vishnivetskiy SA, Gurevich EV. The functional cycle of visual arrestins in photoreceptor cells. Prog Retin Eye Res 2011; 30:405-30. [PMID: 21824527 DOI: 10.1016/j.preteyeres.2011.07.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/20/2011] [Accepted: 07/21/2011] [Indexed: 01/14/2023]
Abstract
Visual arrestin-1 plays a key role in the rapid and reproducible shutoff of rhodopsin signaling. Its highly selective binding to light-activated phosphorylated rhodopsin is an integral part of the functional perfection of rod photoreceptors. Structure-function studies revealed key elements of the sophisticated molecular mechanism ensuring arrestin-1 selectivity and paved the way to the targeted manipulation of the arrestin-1 molecule to design mutants that can compensate for congenital defects in rhodopsin phosphorylation. Arrestin-1 self-association and light-dependent translocation in photoreceptor cells work together to keep a constant supply of active rhodopsin-binding arrestin-1 monomer in the outer segment. Recent discoveries of arrestin-1 interaction with other signaling proteins suggest that it is a much more versatile signaling regulator than previously thought, affecting the function of the synaptic terminals and rod survival. Elucidation of the fine molecular mechanisms of arrestin-1 interactions with rhodopsin and other binding partners is necessary for the comprehensive understanding of rod function and for devising novel molecular tools and therapeutic approaches to the treatment of visual disorders.
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Affiliation(s)
- Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, 2200 Pierce Ave, PRB, Rm 417D, Nashville, TN 37232, USA.
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Satoh AK, Xia H, Yan L, Liu CH, Hardie RC, Ready DF. Arrestin translocation is stoichiometric to rhodopsin isomerization and accelerated by phototransduction in Drosophila photoreceptors. Neuron 2010; 67:997-1008. [PMID: 20869596 PMCID: PMC2946946 DOI: 10.1016/j.neuron.2010.08.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2010] [Indexed: 11/19/2022]
Abstract
Upon illumination, visual arrestin translocates from photoreceptor cell bodies to rhodopsin and membrane-rich photosensory compartments, vertebrate outer segments or invertebrate rhabdomeres, where it quenches activated rhodopsin. Both the mechanism and function of arrestin translocation are unresolved and controversial. In dark-adapted photoreceptors of the fruitfly Drosophila, confocal immunocytochemistry shows arrestin (Arr2) associated with distributed photoreceptor endomembranes. Immunocytochemistry and live imaging of GFP-tagged Arr2 demonstrate rapid reversible translocation to stimulated rhabdomeres in stoichiometric proportion to rhodopsin photoisomerization. Translocation is very rapid in normal photoreceptors (time constant <10 s) and can also be resolved in the time course of electroretinogram recordings. Genetic elimination of key phototransduction proteins, including phospholipase C (PLC), Gq, and the light-sensitive Ca2+-permeable TRP channels, slows translocation by 10- to 100-fold. Our results indicate that Arr2 translocation in Drosophila photoreceptors is driven by diffusion, but profoundly accelerated by phototransduction and Ca2+ influx.
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Affiliation(s)
- Akiko K. Satoh
- Department of Biological Sciences, Graduate School of Science, Nagoya University, Nagoya, 466-8601, Japan
| | - Hongai Xia
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
| | - Limin Yan
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB2 3DY, UK
| | - Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB2 3DY, UK
| | - Roger C. Hardie
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB2 3DY, UK
| | - Donald F. Ready
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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Quintero OA, Moore JE, Unrath WC, Manor U, Salles FT, Grati M, Kachar B, Yengo CM. Intermolecular autophosphorylation regulates myosin IIIa activity and localization in parallel actin bundles. J Biol Chem 2010; 285:35770-82. [PMID: 20826793 DOI: 10.1074/jbc.m110.144360] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Myosin IIIa (Myo3A) transports cargo to the distal end of actin protrusions and contains a kinase domain that is thought to autoregulate its activity. Because Myo3A tends to cluster at the tips of actin protrusions, we investigated whether intermolecular phosphorylation could regulate Myo3A biochemical activity, cellular localization, and cellular function. Inactivation of Myo3A 2IQ kinase domain with the point mutation K50R did not alter maximal ATPase activity, whereas phosphorylation of Myo3A 2IQ resulted in reduced maximal ATPase activity and actin affinity. The rate and degree of Myo3A 2IQ autophosphorylation was unchanged by the presence of actin but was found to be dependent upon Myo3A 2IQ concentration within the range of 0.1 to 1.2 μm, indicating intermolecular autophosphorylation. In cultured cells, we observed that the filopodial tip localization of Myo3A lacking the kinase domain decreased when co-expressed with kinase-active, full-length Myo3A. The cellular consequence of reduced Myo3A tip localization was decreased filopodial density along the cell periphery, identifying a novel cellular function for Myo3A in mediating the formation and stability of actin-based protrusions. Our results suggest that Myo3A motor activity is regulated through a mechanism involving concentration-dependent autophosphorylation. We suggest that this regulatory mechanism plays an essential role in mediating the transport and actin bundle formation/stability functions of Myo3A.
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Affiliation(s)
- Omar A Quintero
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, Pennsylvania 17033, USA
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Lange K. Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signaling system at the cell periphery. J Cell Physiol 2010; 226:896-927. [PMID: 20607764 DOI: 10.1002/jcp.22302] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Elsaesser R, Kalra D, Li R, Montell C. Light-induced translocation of Drosophila visual Arrestin2 depends on Rac2. Proc Natl Acad Sci U S A 2010; 107:4740-5. [PMID: 20176938 PMCID: PMC2842041 DOI: 10.1073/pnas.0906386107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Photoreceptor cells are remarkable in their ability to adjust their sensitivity to light over a wide range of intensities. Rapid termination of the photoresponse is achieved in part by shuttling proteins in and out of the light-transducing compartment of the photoreceptor cells. One protein that undergoes light-dependent translocation is the rhodopsin regulatory protein arrestin. However, the mechanisms coupling rhodopsin to arrestin movement are poorly understood. Here we show that light-dependent shuttling of the major arrestin in Drosophila photoreceptor cells, Arrestin2 (Arr2), occurs independently of known elements of the phototransduction cascade. Disruptions of the trimeric G protein, phospholipase Cbeta, the TRP channel, or the Na(+)/Ca(2+) exchanger did not influence Arr2 localization. Rather, we found that loss of the small GTPase Rac2 severely impaired Arr2 movement and prolonged the termination of the photoresponse. Our findings demonstrate that light-induced translocation of Arr2 occurs through a noncanonical rhodopsin/Rac2 pathway, which is distinct from the classical phototransduction cascade.
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Affiliation(s)
- Rebecca Elsaesser
- Center for Sensory Biology, Departments of Biological Chemistry and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Deepak Kalra
- Center for Sensory Biology, Departments of Biological Chemistry and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ruoxia Li
- Center for Sensory Biology, Departments of Biological Chemistry and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Craig Montell
- Center for Sensory Biology, Departments of Biological Chemistry and Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
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Katz B, Minke B. Drosophila photoreceptors and signaling mechanisms. Front Cell Neurosci 2009; 3:2. [PMID: 19623243 PMCID: PMC2701675 DOI: 10.3389/neuro.03.002.2009] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Accepted: 05/11/2009] [Indexed: 01/10/2023] Open
Abstract
Fly eyes have been a useful biological system in which fundamental principles of sensory signaling have been elucidated. The physiological optics of the fly compound eye, which was discovered in the Musca, Calliphora and Drosophila flies, has been widely exploited in pioneering genetic and developmental studies. The detailed photochemical cycle of bistable photopigments has been elucidated in Drosophila using the genetic approach. Studies of Drosophila phototransduction using the genetic approach have led to the discovery of novel proteins crucial to many biological processes. A notable example is the discovery of the inactivation no afterpotential D scaffold protein, which binds the light-activated channel, its activator the phospholipase C and it regulator protein kinase C. An additional protein discovered in the Drosophila eye is the light-activated channel transient receptor potential (TRP), the founding member of the diverse and widely spread TRP channel superfamily. The fly eye has thus played a major role in the molecular identification of processes and proteins with prime importance.
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Affiliation(s)
- Ben Katz
- Department of Physiology, Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine, The Hebrew UniversityJerusalem, Israel
| | - Baruch Minke
- Department of Physiology, Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine, The Hebrew UniversityJerusalem, Israel
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30
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Delpire E. The mammalian family of sterile 20p-like protein kinases. Pflugers Arch 2009; 458:953-67. [PMID: 19399514 DOI: 10.1007/s00424-009-0674-y] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Accepted: 04/15/2009] [Indexed: 12/12/2022]
Abstract
Twenty-eight kinases found in mammalian genomes share similarity to the budding yeast kinase Ste20p. This review article examines the biological function of these mammalian Ste20 kinases. Some of them have conserved the Ste20p function of transducing extracellular signals to mitogen-activated kinases. Others affect ion transport, cell cycle, cytoskeleton organization, and program cell death. A number of molecular details involved in the activation of the kinases are discussed including autophosphorylation, substrate recognition, autoinhibition, dimerization, and substrate binding.
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Affiliation(s)
- Eric Delpire
- Department of Anesthesiology, Vanderbilt University Medical Center, T-4202 MCN 1161 21st Avenue South, Nashville, TN 37232-2520, USA.
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31
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Wang Z, Edwards JG, Riley N, Provance DW, Karcher R, Li XD, Davison IG, Ikebe M, Mercer JA, Kauer JA, Ehlers MD. Myosin Vb mobilizes recycling endosomes and AMPA receptors for postsynaptic plasticity. Cell 2008; 135:535-48. [PMID: 18984164 DOI: 10.1016/j.cell.2008.09.057] [Citation(s) in RCA: 361] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 07/16/2008] [Accepted: 09/09/2008] [Indexed: 10/21/2022]
Abstract
Learning-related plasticity at excitatory synapses in the mammalian brain requires the trafficking of AMPA receptors and the growth of dendritic spines. However, the mechanisms that couple plasticity stimuli to the trafficking of postsynaptic cargo are poorly understood. Here we demonstrate that myosin Vb (MyoVb), a Ca2+-sensitive motor, conducts spine trafficking during long-term potentiation (LTP) of synaptic strength. Upon activation of NMDA receptors and corresponding Ca2+ influx, MyoVb associates with recycling endosomes (REs), triggering rapid spine recruitment of endosomes and local exocytosis in spines. Disruption of MyoVb or its interaction with the RE adaptor Rab11-FIP2 abolishes LTP-induced exocytosis from REs and prevents both AMPA receptor insertion and spine growth. Furthermore, induction of tight binding of MyoVb to actin using an acute chemical genetic strategy eradicates LTP in hippocampal slices. Thus, Ca2+-activated MyoVb captures and mobilizes REs for AMPA receptor insertion and spine growth, providing a mechanistic link between the induction and expression of postsynaptic plasticity.
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Affiliation(s)
- Zhiping Wang
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA; Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
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32
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Primary processes in sensory cells: current advances. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2008; 195:1-19. [PMID: 19011871 DOI: 10.1007/s00359-008-0389-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2008] [Revised: 10/25/2008] [Accepted: 10/25/2008] [Indexed: 12/20/2022]
Abstract
In the course of evolution, the strong and unremitting selective pressure on sensory performance has driven the acuity of sensory organs to its physical limits. As a consequence, the study of primary sensory processes illustrates impressively how far a physiological function can be improved if the survival of a species depends on it. Sensory cells that detect single-photons, single molecules, mechanical motions on a nanometer scale, or incredibly small fluctuations of electromagnetic fields have fascinated physiologists for a long time. It is a great challenge to understand the primary sensory processes on a molecular level. This review points out some important recent developments in the search for primary processes in sensory cells that mediate touch perception, hearing, vision, taste, olfaction, as well as the analysis of light polarization and the orientation in the Earth's magnetic field. The data are screened for common transduction strategies and common transduction molecules, an aspect that may be helpful for researchers in the field.
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33
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Reidel B, Goldmann T, Giessl A, Wolfrum U. The translocation of signaling molecules in dark adapting mammalian rod photoreceptor cells is dependent on the cytoskeleton. ACTA ACUST UNITED AC 2008; 65:785-800. [PMID: 18623243 DOI: 10.1002/cm.20300] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In vertebrate rod photoreceptor cells, arrestin and the visual G-protein transducin move between the inner segment and outer segment in response to changes in light. This stimulus dependent translocation of signalling molecules is assumed to participate in long term light adaptation of photoreceptors. So far the cellular basis for the transport mechanisms underlying these intracellular movements remains largely elusive. Here we investigated the dependency of these movements on actin filaments and the microtubule cytoskeleton of photoreceptor cells. Co-cultures of mouse retina and retinal pigment epithelium were incubated with drugs stabilizing and destabilizing the cytoskeleton. The actin and microtubule cytoskeleton and the light dependent distribution of signaling molecules were subsequently analyzed by light and electron microscopy. The application of cytoskeletal drugs differentially affected the cytoskeleton in photoreceptor compartments. During dark adaptation the depolymerization of microtubules as well as actin filaments disrupted the translocation of arrestin and transducin in rod photoreceptor cells. During light adaptation only the delivery of arrestin within the outer segment was impaired after destabilization of microtubules. Movements of transducin and arrestin required intact cytoskeletal elements in dark adapting cells. However, diffusion might be sufficient for the fast molecular movements observed as cells adapt to light. These findings indicate that different molecular translocation mechanisms are responsible for the dark and light associated translocations of arrestin and transducin in rod photoreceptor cells.
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Affiliation(s)
- Boris Reidel
- Department of Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg University of Mainz, Germany
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34
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Liu CH, Satoh AK, Postma M, Huang J, Ready DF, Hardie RC. Ca2+-dependent metarhodopsin inactivation mediated by calmodulin and NINAC myosin III. Neuron 2008; 59:778-89. [PMID: 18786361 DOI: 10.1016/j.neuron.2008.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 06/03/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
Phototransduction in flies is the fastest known G protein-coupled signaling cascade, but how this performance is achieved remains unclear. Here, we investigate the mechanism and role of rhodopsin inactivation. We determined the lifetime of activated rhodopsin (metarhodopsin = M( *)) in whole-cell recordings from Drosophila photoreceptors by measuring the time window within which inactivating M( *) by photoreisomerization to rhodopsin could suppress responses to prior illumination. M( *) was inactivated rapidly (tau approximately 20 ms) under control conditions, but approximately 10-fold more slowly in Ca2+-free solutions. This pronounced Ca2+ dependence of M( *) inactivation was unaffected by mutations affecting phosphorylation of rhodopsin or arrestin but was abolished in mutants of calmodulin (CaM) or the CaM-binding myosin III, NINAC. This suggests a mechanism whereby Ca2+ influx acting via CaM and NINAC accelerates the binding of arrestin to M( *). Our results indicate that this strategy promotes quantum efficiency, temporal resolution, and fidelity of visual signaling.
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Affiliation(s)
- Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge CB23DY, UK
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35
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Slepak VZ, Hurley JB. Mechanism of light-induced translocation of arrestin and transducin in photoreceptors: interaction-restricted diffusion. IUBMB Life 2008; 60:2-9. [PMID: 18379987 DOI: 10.1002/iub.7] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Many signaling proteins change their location within cells in response to external stimuli. In photoreceptors, this phenomenon is remarkably robust. The G protein of rod photoreceptors and rod transducin concentrates in the outer segments (OS) of these neurons in darkness. Within approximately 30 minutes after illumination, rod transducin redistributes throughout all of the outer and inner compartments of the cell. Visual arrestin concurrently relocalises from the inner compartments to become sequestered primarily within the OS. In the past several years, the question of whether these proteins are actively moved by molecular motors or whether they are redistributed by simple diffusion has been extensively debated. This review focuses on the most essential works in the area and concludes that the basic principle driving this protein movement is diffusion. The directionality and light dependence of this movement is achieved by the interactions of arrestin and transducin with their spatially restricted binding partners.
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Affiliation(s)
- Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL, USA.
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36
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Hanson SM, Vishnivetskiy SA, Hubbell WL, Gurevich VV. Opposing effects of inositol hexakisphosphate on rod arrestin and arrestin2 self-association. Biochemistry 2007; 47:1070-5. [PMID: 18161994 DOI: 10.1021/bi7021359] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The robust cooperative formation of rod arrestin tetramers has been well-established, whereas the ability of other members of the arrestin family to self-associate remains controversial. Here, we used purified arrestins and multi-angle light scattering to quantitatively compare the propensity of the four mammalian arrestin subtypes to self-associate. Both non-visual and cone arrestins only form oligomers at very high non-physiological concentrations. However, inositol hexakisphosphate (IP6), a fairly abundant form of inositol in the cytoplasm, greatly facilitates self-association of arrestin2. Arrestin2 self-association equilibrium constants in the presence of 100 microM IP6 suggest that an appreciable proportion could exist in an oligomeric state but only in intracellular compartments where its concentration is 5-10-fold higher than average. In contrast to arrestin2, IP6 inhibits self-association of rod arrestin, indicating that the structure of these two tetramers in solution is likely different.
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Affiliation(s)
- Susan M Hanson
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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37
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Sanxaridis PD, Cronin MA, Rawat SS, Waro G, Acharya U, Tsunoda S. Light-induced recruitment of INAD-signaling complexes to detergent-resistant lipid rafts in Drosophila photoreceptors. Mol Cell Neurosci 2007; 36:36-46. [PMID: 17689976 PMCID: PMC2034437 DOI: 10.1016/j.mcn.2007.05.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 05/19/2007] [Accepted: 05/31/2007] [Indexed: 12/01/2022] Open
Abstract
Here, we reveal a novel feature of the dynamic organization of signaling components in Drosophila photoreceptors. We show that the multi-PDZ protein INAD and its target proteins undergo light-induced recruitment to detergent-resistant membrane (DRM) rafts. Reduction of ergosterol, considered to be a key component of lipid rafts in Drosophila, resulted in a loss of INAD-signaling complexes associated with DRM fractions. Genetic analysis demonstrated that translocation of INAD-signaling complexes to DRM rafts requires activation of the entire phototransduction cascade, while constitutive activation of the light-activated channels resulted in recruitment of complexes to DRM rafts in the dark. Mutations affecting INAD and TRP showed that PDZ4 and PDZ5 domains of INAD, as well as the INAD-TRP interaction, are required for translocation of components to DRM rafts. Finally, selective recruitment of phosphorylated, and therefore activatable, eye-PKC to DRM rafts suggests that DRM domains are likely to function in signaling, rather than trafficking.
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Affiliation(s)
| | - Michelle A. Cronin
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
| | - Satinder S. Rawat
- Program is Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA
| | - Girma Waro
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
| | - Usha Acharya
- Program is Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA
| | - Susan Tsunoda
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA
- *Address correspondence to: Susan Tsunoda, Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, Telephone: 617-358-1756, FAX: 617-353-8484,
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38
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Rosenzweig DH, Nair KS, Wei J, Wang Q, Garwin G, Saari JC, Chen CK, Smrcka AV, Swaroop A, Lem J, Hurley JB, Slepak VZ. Subunit dissociation and diffusion determine the subcellular localization of rod and cone transducins. J Neurosci 2007; 27:5484-94. [PMID: 17507570 PMCID: PMC2655354 DOI: 10.1523/jneurosci.1421-07.2007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Activation of rod photoreceptors by light induces a massive redistribution of the heterotrimeric G-protein transducin. In darkness, transducin is sequestered within the membrane-enriched outer segments of the rod cell. In light, it disperses throughout the entire neuron. We show here that redistribution of rod transducin by light requires activation, but it does not require ATP. This observation rules out participation of molecular motors in the redistribution process. In contrast to the light-stimulated redistribution of rod transducin in rods, cone transducin in cones does not redistribute during activation. Remarkably, when cone transducin is expressed in rods, it does undergo light-stimulated redistribution. We show here that the difference in subcellular localization of activated rod and cone G-proteins correlates with their affinity for membranes. Activated rod transducin releases from membranes, whereas activated cone transducin remains bound to membranes. A synthetic peptide that dissociates G-protein complexes independently of activation facilitates dispersion of both rod and cone transducins within the cells. This peptide also facilitates detachment of both G-proteins from the membranes. Together, these results show that it is the dissociation state of transducin that determines its localization in photoreceptors. When rod transducin is stimulated, its subunits dissociate, leave outer segment membranes, and equilibrate throughout the cell. Cone transducin subunits do not dissociate during activation and remain sequestered within the outer segment. These findings indicate that the subunits of some heterotrimeric G-proteins remain associated during activation in their native environments.
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Affiliation(s)
- Derek H. Rosenzweig
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - K. Saidas Nair
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, Florida 33136
| | | | - Qiang Wang
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Greg Garwin
- Ophthalmology, University of Washington, Seattle, Washington 98195
| | - John C. Saari
- Ophthalmology, University of Washington, Seattle, Washington 98195
| | - Ching-Kang Chen
- Department of Biochemistry, Virginia Commonwealth University, Richmond, Virginia 23284
| | - Alan V. Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14603
| | - Anand Swaroop
- Departments of Ophthalmology and Visual Sciences, and Human Genetics, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Janis Lem
- Molecular Cardiology Research Institute, Tufts–New England Medical Center, Boston, Massachusetts 02111
| | | | - Vladlen Z. Slepak
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, Florida 33136
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39
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Swardfager W, Mitchell J. Purification of visual arrestin from squid photoreceptors and characterization of arrestin interaction with rhodopsin and rhodopsin kinase. J Neurochem 2007; 101:223-31. [PMID: 17394465 DOI: 10.1111/j.1471-4159.2006.04364.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Invertebrate visual signal transduction involves photoisomerization of rhodopsin, activating a guanine nucleotide binding protein (G protein) of the G(q) class, iG(q), which stimulates a phospholipase C, increasing intracellular Ca2+. Arrestin binding to photoactivated rhodopsin is a key mechanism of desensitization. We have previously reported the cloning of a retina-specific arrestin cDNA from Loligo pealei displaying 56-64% sequence similarity to other reported arrestin sequences. Here, we report the purification of the 55-kDa squid visual arrestin. Purified squid visual arrestin is able to inhibit light-activated GTPase activity dose-dependently in arrestin-depleted rhabdomeric membranes and associate with the membrane in a light-dependent manner. Membrane association can be partially inhibited by inositol 1,2,3,4,5,6-hexakisphosphate (IP6), a soluble analog of the membrane lipid phosphatidylinositol 3,4,5-triphosphate. In reconstitution assays, we demonstrate arrestin phosphorylation by squid rhodopsin kinase, a novel function among the G protein-coupled receptor kinase family. Phosphorylation of purified arrestin requires squid rhodopsin kinase, membranes, light-activation, and the presence of Ca2+. This is the first large-scale purification of an invertebrate arrestin and biochemical demonstration of arrestin function in the invertebrate visual system.
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Affiliation(s)
- Walter Swardfager
- Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada
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40
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Wang T, Montell C. Phototransduction and retinal degeneration in Drosophila. Pflugers Arch 2007; 454:821-47. [PMID: 17487503 DOI: 10.1007/s00424-007-0251-1] [Citation(s) in RCA: 215] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 03/05/2007] [Indexed: 01/05/2023]
Abstract
Drosophila visual transduction is the fastest known G-protein-coupled signaling cascade and has therefore served as a genetically tractable animal model for characterizing rapid responses to sensory stimulation. Mutations in over 30 genes have been identified, which affect activation, adaptation, or termination of the photoresponse. Based on analyses of these genes, a model for phototransduction has emerged, which involves phosphoinoside signaling and culminates with opening of the TRP and TRPL cation channels. Many of the proteins that function in phototransduction are coupled to the PDZ containing scaffold protein INAD and form a supramolecular signaling complex, the signalplex. Arrestin, TRPL, and G alpha(q) undergo dynamic light-dependent trafficking, and these movements function in long-term adaptation. Other proteins play important roles either in the formation or maturation of rhodopsin, or in regeneration of phosphatidylinositol 4,5-bisphosphate (PIP2), which is required for the photoresponse. Mutation of nearly any gene that functions in the photoresponse results in retinal degeneration. The underlying bases of photoreceptor cell death are diverse and involve mechanisms such as excessive endocytosis of rhodopsin due to stable rhodopsin/arrestin complexes and abnormally low or high levels of Ca2+. Drosophila visual transduction appears to have particular relevance to the cascade in the intrinsically photosensitive retinal ganglion cells in mammals, as the photoresponse in these latter cells appears to operate through a remarkably similar mechanism.
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Affiliation(s)
- Tao Wang
- Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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41
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Abstract
Upon their discovery, beta-arrestins 1 and 2 were named for their capacity to sterically hinder the G protein coupling of agonist-activated seven-transmembrane receptors, ultimately resulting in receptor desensitization. Surprisingly, recent evidence shows that beta-arrestins can also function to activate signaling cascades independently of G protein activation. By serving as multiprotein scaffolds, the beta-arrestins bring elements of specific signaling pathways into close proximity. beta-Arrestin regulation has been demonstrated for an ever-increasing number of signaling molecules, including the mitogen-activated protein kinases ERK, JNK, and p38 as well as Akt, PI3 kinase, and RhoA. In addition, investigators are discovering new roles for beta-arrestins in nuclear functions. Here, we review the signaling capacities of these versatile adapter molecules and discuss the possible implications for cellular processes such as chemotaxis and apoptosis.
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Affiliation(s)
- Scott M DeWire
- Howard Hughes Medical Institute and Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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42
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Nash ZA, Naash MI. Light/dark translocation of alphatransducin in mouse photoreceptor cells expressing G90D mutant opsin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 572:125-31. [PMID: 17249565 PMCID: PMC2793175 DOI: 10.1007/0-387-32442-9_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- Zack A Nash
- Cell Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., Oklahoma City, OK 73104, USA
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43
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Smith WC, Peterson JJ, Orisme W, Dinculescu A. Arrestin translocation in rod photoreceptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 572:455-64. [PMID: 17249609 PMCID: PMC2977922 DOI: 10.1007/0-387-32442-9_63] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Affiliation(s)
- W Clay Smith
- Department of Ophthalmology, University of Florida, Gainesville, FL 32610-0284, USA.
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44
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Kempler K, Tóth J, Yamashita R, Mapel G, Robinson K, Cardasis H, Stevens S, Sellers JR, Battelle BA. Loop 2 of limulus myosin III is phosphorylated by protein kinase A and autophosphorylation. Biochemistry 2007; 46:4280-93. [PMID: 17367164 PMCID: PMC2580675 DOI: 10.1021/bi062112u] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Little is known about the functions of class III unconventional myosins although, with an N-terminal kinase domain, they are potentially both signaling and motor proteins. Limulus myosin III is particularly interesting because it is a phosphoprotein abundant in photoreceptors that becomes more heavily phosphorylated at night by protein kinase A. This enhanced nighttime phosphorylation occurs in response to signals from an endogenous circadian clock and correlates with dramatic changes in photoreceptor structure and function. We seek to understand the role of Limulus myosin III and its phosphorylation in photoreceptors. Here we determined the sites that become phosphorylated in Limulus myosin III and investigated its kinase, actin binding, and myosin ATPase activities. We show that Limulus myosin III exhibits kinase activity and that a major site for both protein kinase A and autophosphorylation is located within loop 2 of the myosin domain, an important actin binding region. We also identify the phosphorylation of an additional protein kinase A and autophosphorylation site near loop 2, and a predicted phosphorylation site within loop 2. We show that the kinase domain of Limulus myosin III shares some pharmacological properties with protein kinase A, and that it is a potential opsin kinase. Finally, we demonstrate that Limulus myosin III binds actin but lacks ATPase activity. We conclude that Limulus myosin III is an actin-binding and signaling protein and speculate that interactions between actin and Limulus myosin III are regulated by both second messenger mediated phosphorylation and autophosphorylation of its myosin domain within and near loop 2.
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Affiliation(s)
- Karen Kempler
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Judit Tóth
- Department of Biochemistry, Eötvös Loránd University Pázmány P.s. 1/c. Budapest 1117, Hungary
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Roxanne Yamashita
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Gretchen Mapel
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Kimberly Robinson
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
| | - Helene Cardasis
- Proteomics Core of the ICBR, University of Florida, Gainesville 32010
- Department of Chemistry, University of Florida, Gainesville 32010
| | - Stanley Stevens
- Proteomics Core of the ICBR, University of Florida, Gainesville 32010
| | - James R. Sellers
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-1762
| | - Barbara-Anne Battelle
- Whitney Laboratory for Marine Bioscience and the Department of Neuroscience, University of Florida, St. Augustine 32080
- CORRESPONDING AUTHOR: Barbara-Anne Battelle, Whitney Laboratory for Marine Bioscience, University of Florida, 9505 Ocean Shore Blvd. St. Augustine, FL 32080. Tel. 904-461-4022; Fax 904-461-008;
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45
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Rey M, Valenzuela-Fernández A, Urzainqui A, Yáñez-Mó M, Pérez-Martínez M, Penela P, Mayor F, Sánchez-Madrid F. Myosin IIA is involved in the endocytosis of CXCR4 induced by SDF-1alpha. J Cell Sci 2007; 120:1126-33. [PMID: 17327270 DOI: 10.1242/jcs.03415] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endocytosis of chemokine receptors regulates signal transduction initiated by chemokines, but the molecular mechanisms underlying this process are not fully defined. In this work, we assessed the involvement of the motor protein nonmuscle myosin heavy chain IIA (MIIA) in the endocytosis of CXCR4 induced by SDF-1alpha (also known as CXCL12) in T lymphocytes. Overexpression of the C-terminal half of MIIA inhibited the ligand-induced endocytosis of CXCR4, but not that of transferrin receptor. Targeting MIIA either by silencing its expression with small interfering RNA (siRNA) or by blebbistatin treatment also inhibited endocytosis of CXCR4. Inhibition of endocytosis of CXCR4 by targeting endogenous MIIA resulted in an increased migration of T cells induced by SDF-1alpha, and in the inhibition of the HIV-1-Env antifusogenic activity of this chemokine. Coimmunoprecipitation and protein-protein binding studies demonstrated that MIIA interacts with both the cytoplasmic tail of CXCR4 and beta-arrestin. Moreover, SDF-1alpha promotes a rapid MIIA-beta-arrestin dissociation. Our data reveal a novel role for MIIA in CXCR4 endocytosis, which involves its dynamic association with beta-arrestin and highlights the role of endogenous MIIA as a regulator of CXCR4 internalization and, therefore, the onset of SDF-1alpha signaling.
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Affiliation(s)
- Mercedes Rey
- Servicio de Inmunología, Hospital Universitario de la Princesa, Diego de León, 62, 28006 Madrid, Spain
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46
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Dosé AC, Ananthanarayanan S, Moore JE, Burnside B, Yengo CM. Kinetic mechanism of human myosin IIIA. J Biol Chem 2006; 282:216-31. [PMID: 17074769 DOI: 10.1074/jbc.m605964200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin IIIA is specifically expressed in photoreceptors and cochlea and is important for the phototransduction and hearing processes. In addition, myosin IIIA contains a unique N-terminal kinase domain and C-terminal tail actin-binding motif. We examined the kinetic properties of baculovirus expressed human myosin IIIA containing the kinase, motor, and two IQ domains. The maximum actin-activated ATPase rate is relatively slow (k(cat) = 0.77 +/- 0.08 s(-1)), and high actin concentrations are required to fully activate the ATPase rate (K(ATPase) = 34 +/- 11 microm). However, actin co-sedimentation assays suggest that myosin III has a relatively high steady-state affinity for actin in the presence of ATP (K(actin) approximately 7 microm). The rate of ATP binding to the motor domain is quite slow both in the presence and absence of actin (K(1)k(+2) = 0.020 and 0.001 microm(-1).s(-1), respectively). The rate of actin-activated phosphate release is more than 100-fold faster (85 s(-1)) than the k(cat), whereas ADP release in the presence of actin follows a two-step mechanism (7.0 and 0.6 s(-1)). Thus, our data suggest a transition between two actomyosin-ADP states is the rate-limiting step in the actomyosin III ATPase cycle. Our data also suggest the myosin III motor spends a large fraction of its cycle in an actomyosin ADP state that has an intermediate affinity for actin (K(d) approximately 5 microm). The long lived actomyosin-ADP state may be important for the ability of myosin III to function as a cellular transporter and actin cross-linker in the actin bundles of sensory cells.
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Affiliation(s)
- Andréa C Dosé
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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Schneider ME, Dosé AC, Salles FT, Chang W, Erickson FL, Burnside B, Kachar B. A new compartment at stereocilia tips defined by spatial and temporal patterns of myosin IIIa expression. J Neurosci 2006; 26:10243-52. [PMID: 17021180 PMCID: PMC6674622 DOI: 10.1523/jneurosci.2812-06.2006] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Class III myosins are motor proteins that contain an N-terminal kinase domain and a C-terminal actin-binding domain. We show that myosin IIIa, which has been implicated in nonsyndromic progressive hearing loss, is localized at stereocilia tips. Myosin IIIa progressively accumulates during stereocilia maturation in a thimble-like pattern around the stereocilia tip, distinct from the cap-like localization of myosin XVa and the shaft localization of myosin Ic. Overexpression of deletion mutants for functional domains of green fluorescent protein (GFP)-myosin IIIa shows that the motor domain, but not the actin-binding tail domain, is required for stereocilia tip localization. Deletion of the kinase domain produces stereocilia elongation and bulging of the stereocilia tips. The thimble-like localization and the influence myosin IIIa has on stereocilia shape reveal a previously unrecognized molecular compartment at the distal end of stereocilia, the site of actin polymerization as well as operation of the mechanoelectrical transduction apparatus.
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Affiliation(s)
- Mark E. Schneider
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
| | - Andréa C. Dosé
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, and
| | - Felipe T. Salles
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
| | - Weise Chang
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
| | - Floyd L. Erickson
- Department of Biological Sciences, Salisbury University, Salisbury, Maryland 21801
| | - Beth Burnside
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, and
| | - Bechara Kachar
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892
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Kambara T, Komaba S, Ikebe M. Human myosin III is a motor having an extremely high affinity for actin. J Biol Chem 2006; 281:37291-301. [PMID: 17012748 DOI: 10.1074/jbc.m603823200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin IIIA is expressed in photoreceptor cells and thought to play a critical role in phototransduction processes, yet its function on a molecular basis is largely unknown. Here we clarified the kinetic mechanism of the ATPase cycle of human myosin IIIA. The steady-state ATPase activity was markedly activated approximately 10-fold with very low actin concentration. The rate of ADP off from actomyosin IIIA was 10 times greater than the overall cycling rate, thus not a rate-determining step. The rate constant of the ATP hydrolysis step of the actin-dissociated form was very slow, but the rate was markedly accelerated by actin binding. The dissociation constant of the ATP-bound form of myosin IIIA from actin is submicromolar, which agrees well with the low K(actin). These results indicate that ATP hydrolysis predominantly takes place in the actin-bound form for actomyosin IIIA ATPase reaction. The obtained K(actin) was much lower than the previously reported one, and we found that the autophosphorylation of myosin IIIA dramatically increased the K(actin), whereas the V(max) was unchanged. Our kinetic model indicates that both the actin-attached hydrolysis and the P(i) release steps determine the overall cycle rate of the dephosphorylated form. Although the stable steady-state intermediates of actomyosin IIIA ATPase reaction are not typical strong actin-binding intermediates, the affinity of the stable intermediates for actin is much higher than conventional weak actin binding forms. The present results suggest that myosin IIIA can spend a majority of its ATP hydrolysis cycling time on actin.
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Affiliation(s)
- Taketoshi Kambara
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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Meyer NE, Joel-Almagor T, Frechter S, Minke B, Huber A. Subcellular translocation of the eGFP-tagged TRPL channel in Drosophila photoreceptors requires activation of the phototransduction cascade. J Cell Sci 2006; 119:2592-603. [PMID: 16735439 PMCID: PMC1945099 DOI: 10.1242/jcs.02986] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Signal-mediated translocation of transient receptor potential (TRP) channels is a novel mechanism to fine tune a variety of signaling pathways including neuronal path finding and Drosophila photoreception. In Drosophila phototransduction the cation channels TRP and TRP-like (TRPL) are the targets of a prototypical G protein-coupled signaling pathway. We have recently found that the TRPL channel translocates between the rhabdomere and the cell body in a light-dependent manner. This translocation modifies the ion channel composition of the signaling membrane and induces long-term adaptation. However, the molecular mechanism underlying TRPL translocation remains unclear. Here we report that eGFP-tagged TRPL expressed in the photoreceptor cells formed functional ion channels with properties of the native channels, whereas TRPL-eGFP translocation could be directly visualized in intact eyes. TRPL-eGFP failed to translocate to the cell body in flies carrying severe mutations in essential phototransduction proteins, including rhodopsin, Galphaq, phospholipase Cbeta and the TRP ion channel, or in proteins required for TRP function. Our data, furthermore, show that the activation of a small fraction of rhodopsin and of residual amounts of the Gq protein is sufficient to trigger TRPL-eGFP internalization. In addition, we found that endocytosis of TRPL-eGFP occurs independently of dynamin, whereas a mutation of the unconventional myosin III, NINAC, hinders complete translocation of TRPL-eGFP to the cell body. Altogether, this study revealed that activation of the phototransduction cascade is mandatory for TRPL internalization, suggesting a critical role for the light induced conductance increase and the ensuing Ca2+ -influx in the translocation process. The critical role of Ca2+ influx was directly demonstrated when the light-induced TRPL-eGFP translocation was blocked by removing extracellular Ca2+.
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Affiliation(s)
- Nina E. Meyer
- Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Tamar Joel-Almagor
- Department of Physiology and The Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Shahar Frechter
- Department of Physiology and The Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Baruch Minke
- Department of Physiology and The Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
| | - Armin Huber
- Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany
- *Author for correspondence (e-mail: )
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Satoh AK, Ready DF. Arrestin1 mediates light-dependent rhodopsin endocytosis and cell survival. Curr Biol 2006; 15:1722-33. [PMID: 16213818 DOI: 10.1016/j.cub.2005.08.064] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 08/29/2005] [Accepted: 08/31/2005] [Indexed: 11/23/2022]
Abstract
BACKGROUND Arrestins are pivotal, multifunctional organizers of cell responses to GPCR stimulation, including cell survival and cell death. In Drosophila norpA and rdgC mutants, endocytosis of abnormally stable complexes of rhodopsin (Rh1) and fly photoreceptor Arrestin2 (Arr2) triggers cell death, implicating Rh1/Arr2-bearing endosomes in pro-cell death signaling, potentially via arrestin-mediated GPCR activation of effector kinase pathways. In order to further investigate arrestin function in photoreceptor physiology and survival, we studied Arr2's partner photoreceptor arrestin, Arr1, in developing and adult Drosophila compound eyes. RESULTS We report that Arr1, but not Arr2, is essential for normal, light-induced rhodopsin endocytosis. Also distinct from Arr2, Arr1 is essential for light-independent photoreceptor survival. Photoreceptor cell death caused by loss of Arr1 is strongly suppressed by coordinate loss of Arr2. We further find that Rh1 C-terminal phosphorylation is essential for light-induced endocytosis and also for translocation of Arr1, but not Arr2, from dark-adapted photoreceptor cytoplasm to photosensory membrane rhabdomeres. In contrast to a previous report, we do not find a requirement for photoreceptor myosin kinase NINAC in Arr1 or Arr2 translocation. CONCLUSIONS The two Drosophila photoreceptor arrestins mediate distinct and essential cell pathways downstream of rhodopsin activation. We propose that Arr1 mediates an endocytotic cell-survival activity, scavenging phosphorylated rhodopsin and thereby countering toxic Arr2/Rh1 accumulation; elimination of toxic Arr2/Rh1 in double mutants could thus rescue arr1 mutant photoreceptor degeneration.
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Affiliation(s)
- Akiko K Satoh
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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