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Ferreira PA. Personal essay of a rookie's journey with Bill Pak and his legacy: tales and perspectives on PI-PLC, NorpA and cyclophilin, NinaA - William L. Pak, PhD., 1932-2023: in memoriam. J Neurogenet 2024:1-10. [PMID: 38913811 DOI: 10.1080/01677063.2024.2366455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2024] [Accepted: 05/30/2024] [Indexed: 06/26/2024]
Abstract
The neurogenetics and vision community recently mourned William L. Pak, PhD, whose pioneering work spearheaded the genetic, electrophysiological, and molecular bases of biological processes underpinning vision. This essay provides a historical background to the daunting challenges and personal experiences that carved the path to seminal findings. It also reflects on the intellectual framework, mentoring philosophy, and inspirational legacy of Bill Pak's research. An emphasis and perspectives are placed on the discoveries and implications to date of the phosphatidylinositol-specific phospholipase C (PI-PLC), NorpA, and the cyclophilin, NinaA of the fruit fly, Drosophila melanogaster, and their respective mammalian homologues, PI-PLCβ4, and cyclophilin-related protein, Ran-binding protein 2 (Ranbp2) in critical biological processes and diseases of photoreceptors and other neurons.
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Affiliation(s)
- Paulo A Ferreira
- Departments of Ophthalmology and Pathology, Duke University Medical Center, Durham, North Carolina, USA
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Gutorov R, Katz B, Peters M, Minke B. Membrane lipid modulations by methyl-β-cyclodextrin uncouple the Drosophila light-activated phospholipase C from TRP and TRPL channel gating. J Biol Chem 2024; 300:105484. [PMID: 37992804 PMCID: PMC10770611 DOI: 10.1016/j.jbc.2023.105484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 11/05/2023] [Accepted: 11/14/2023] [Indexed: 11/24/2023] Open
Abstract
Sterols are hydrophobic molecules, known to cluster signaling membrane-proteins in lipid rafts, while methyl-β-cyclodextrin (MβCD) has been a major tool for modulating membrane-sterol content for studying its effect on membrane proteins, including the transient receptor potential (TRP) channels. The Drosophila light-sensitive TRP channels are activated downstream of a G-protein-coupled phospholipase Cβ (PLC) cascade. In phototransduction, PLC is an enzyme that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) generating diacylglycerol, inositol-tris-phosphate, and protons, leading to TRP and TRP-like (TRPL) channel openings. Here, we studied the effects of MβCD on Drosophila phototransduction using electrophysiology while fluorescently monitoring PIP2 hydrolysis, aiming to examine the effects of sterol modulation on PIP2 hydrolysis and the ensuing light-response in the native system. Incubation of photoreceptor cells with MβCD dramatically reduced the amplitude and kinetics of the TRP/TRPL-mediated light response. MβCD also suppressed PLC-dependent TRP/TRPL constitutive channel activity in the dark induced by mitochondrial uncouplers, but PLC-independent activation of the channels by linoleic acid was not affected. Furthermore, MβCD suppressed a constitutively active TRP mutant-channel, trpP365, suggesting that TRP channel activity is a target of MβCD action. Importantly, whole-cell voltage-clamp measurements from photoreceptors and simultaneously monitored PIP2-hydrolysis by translocation of fluorescently tagged Tubby protein domain, from the plasma membrane to the cytosol, revealed that MβCD virtually abolished the light response when having little effect on the light-activated PLC. Together, MβCD uncoupled TRP/TRPL channel gating from light-activated PLC and PIP2-hydrolysis suggesting the involvement of distinct nanoscopic lipid domains such as lipid rafts and PIP2 clusters in TRP/TRPL channel gating.
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Affiliation(s)
- Rita Gutorov
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Ben Katz
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Maximilian Peters
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel
| | - Baruch Minke
- Faculty of Medicine, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University, Jerusalem, Israel.
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Rhodes-Mordov E, Brandwine-Shemmer T, Zaguri R, Gutorov R, Peters M, Minke B. Diacylglycerol Activates the Drosophila Light Sensitive Channel TRPL Expressed in HEK Cells. Int J Mol Sci 2023; 24:ijms24076289. [PMID: 37047261 PMCID: PMC10093889 DOI: 10.3390/ijms24076289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 03/20/2023] [Accepted: 03/24/2023] [Indexed: 03/30/2023] Open
Abstract
Physiological activation by light of the Drosophila TRP and TRP-like (TRPL) channels requires the activation of phospholipase Cβ (PLC). The hydrolysis of phosphatidylinositol 4,5, bisphosphate (PIP2) by PLC is a crucial step in the still-unclear light activation, while the generation of Diacylglycerol (DAG) by PLC seems to be involved. In this study, we re-examined the ability of a DAG analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) to activate the TRPL channels expressed in HEK cells. Unlike previous studies, we added OAG into the cytosol via a patch-clamp pipette and observed robust activation of the expressed TRPL channels. However, TRPL channel activation was much slower than the physiologically activated TRPL by light. Therefore, we used a picosecond-fast optically activated DAG analogue, OptoDArG. Inactive OptoDArG was added into the intracellular solution with the patch-clamp pipette, and it slowly accumulated on the surface membrane of the recorded HEK cell in the dark. A fast application of intense UV light to the recorded cell resulted in a robust and relatively fast TRPL-dependent current that was greatly accelerated by the constitutively active TRPLF557I pore-region mutation. However, this current of the mutant channel was still considerably slower than the native light-induced TRPL current, suggesting that DAG alone is not sufficient for TRPL channel activation under physiological conditions.
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Transient receptor potential (TRP) channels in the Manila clam (Ruditapes philippinarum): Characterization and expression patterns of the TRP gene family under heat stress in Manila clams based on genome-wide identification. Gene 2023; 854:147112. [PMID: 36513188 DOI: 10.1016/j.gene.2022.147112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 11/25/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022]
Abstract
In this study, we identified a total of 40 transient receptor potential genes (RpTRP) in Manila clam by genome-wide identification and classified them into four categories (TRPV, TRPA, TRPM, TRPC) based on gene structure and subfamily relationships. The protein length of RpTRP genes ranges from 281 amino acids to 1601 amino acids. Molecular weight and theoretical PI values range from 182.82 kDa to 32.43 kDa, respectively, with PI values between 5.17 and 9.25. By comparing the expression profiles of TRP genes during heat stress in Manila clams at different latitudes, we found that most genes in the TRP gene family were up-regulated in expression during heat challenge. Therefore, we determined that TRP genes have an important role in the heat stress of Manila clams. This work provides a basis for further studies on the molecular mechanisms of TRP-mediated heat tolerance in Manila clam and for explaining differences in heat tolerance in Manila clam at different latitudes through key differential TRP genes at the molecular level.
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Minke B, Pak WL. The light-activated TRP channel: the founding member of the TRP channel superfamily. J Neurogenet 2022; 36:55-64. [PMID: 36217603 DOI: 10.1080/01677063.2022.2121824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The Drosophila light-activated Transient Receptor Potential (TRP) channel is the founding member of a large and diverse family of channel proteins. The Drosophila TRP (dTRP) channel, which generates the electrical response to light has been investigated in a great detail two decades before the first mammalian TRP channel was discovered. Thus, dTRP is unique among members of the TRP channel superfamily because its physiological role and the enzymatic cascade underlying its activation are established. In this article we outline the research leading to elucidation of dTRP as the light activated channel and focus on a major physiological property of the dTRP channel, which is indirect activation via a cascade of enzymatic reactions. These detailed pioneering studies, based on the genetic dissection approach, revealed that light activation of the Drosophila TRP channel is mediated by G-Protein-Coupled Receptor (GPCR)-dependent enzymatic cascade, in which phospholipase C β (PLC) is a crucial component. This physiological mechanism of Drosophila TRP channel activation was later found in mammalian TRPC channels. However, the initial studies on the mammalian TRPV1 channel indicated that it is activated directly by capsaicin, low pH and hot temperature (>42 °C). This mechanism of activation was apparently at odds with the activation mechanism of the TRPC channels in general and the Drosophila light activated TRP/TRPL channels in particular, which are target of a GPCR-activated PLC cascade. Subsequent studies have indicated that under physiological conditions TRPV1 is also target of a GPCR-activated PLC cascade in the generation of inflammatory pain. The Drosophila light-activated TRP channel is still a useful experimental paradigm because its physiological function as the light-activated channel is known, powerful genetic techniques can be applied to its further analysis, and signaling molecules involved in the activation of these channels are available.
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Affiliation(s)
- Baruch Minke
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC), Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - William L Pak
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
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Chen M, Liu J, Luo H, Duan C, Gao G, Yang H. Increase in membrane surface expression and phosphorylation of TRPC3 related to olfactory dysfunction in α-synuclein transgenic mice. J Cell Mol Med 2022; 26:5008-5020. [PMID: 36029194 PMCID: PMC9549507 DOI: 10.1111/jcmm.17524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 08/05/2022] [Accepted: 08/10/2022] [Indexed: 11/28/2022] Open
Abstract
Olfactory impairment is an initial non-motor symptom of Parkinson's disease that causes the deposition of aggregated α-synuclein (α-syn) in olfactory neurons. Transient receptor potential canonical (TRPC) channels are a diverse group of non-selective Ca2+ entry channels involved in the progression or pathogenesis of PD via Ca2+ homeostatic regulation. However, the relationship between TRPC and α-syn pathology in an olfactory system remains unclear. To address this issue, we assessed the olfactory function in α-syn transgenic mice. In contrast with control mice, the transgenic mice exhibited impaired olfaction, TRPC3 activation and apoptotic neuronal cell death in the olfactory system. Similar results were observed in primary cultures of olfactory neurons, that is TRPC3 activation, increasing intracellular Ca2+ concentration and apoptotic cell death in the α-syn-overexpressed neurons. These changes were significantly attenuated by TRPC3 knockdown. Therefore, our findings suggest that TRPC3 activation and calcium dyshomeostasis play a key role in α-syn-induced olfactory dysfunction in mice.
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Affiliation(s)
- Min Chen
- Department of Neurobiology School of Basic Medical Sciences, Key Laboratory of Neural Regeneration and Repair, Center for Parkinson's Disease, Key Laboratory for Neurodegenerative Diseases of the Ministry of Education, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China.,Guangxi Neurological Disease Clinical Research Center, Laboratory of Neuroscience, Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Jia Liu
- Department of Neurobiology School of Basic Medical Sciences, Key Laboratory of Neural Regeneration and Repair, Center for Parkinson's Disease, Key Laboratory for Neurodegenerative Diseases of the Ministry of Education, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Hanjiang Luo
- Guangxi Neurological Disease Clinical Research Center, Laboratory of Neuroscience, Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Chunli Duan
- Department of Neurobiology School of Basic Medical Sciences, Key Laboratory of Neural Regeneration and Repair, Center for Parkinson's Disease, Key Laboratory for Neurodegenerative Diseases of the Ministry of Education, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Ge Gao
- Department of Neurobiology School of Basic Medical Sciences, Key Laboratory of Neural Regeneration and Repair, Center for Parkinson's Disease, Key Laboratory for Neurodegenerative Diseases of the Ministry of Education, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Hui Yang
- Department of Neurobiology School of Basic Medical Sciences, Key Laboratory of Neural Regeneration and Repair, Center for Parkinson's Disease, Key Laboratory for Neurodegenerative Diseases of the Ministry of Education, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
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Hodge BA, Meyerhof GT, Katewa SD, Lian T, Lau C, Bar S, Leung NY, Li M, Li-Kroeger D, Melov S, Schilling B, Montell C, Kapahi P. Dietary restriction and the transcription factor clock delay eye aging to extend lifespan in Drosophila Melanogaster. Nat Commun 2022; 13:3156. [PMID: 35672419 PMCID: PMC9174495 DOI: 10.1038/s41467-022-30975-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 05/24/2022] [Indexed: 01/15/2023] Open
Abstract
Many vital processes in the eye are under circadian regulation, and circadian dysfunction has emerged as a potential driver of eye aging. Dietary restriction is one of the most robust lifespan-extending therapies and amplifies circadian rhythms with age. Herein, we demonstrate that dietary restriction extends lifespan in Drosophila melanogaster by promoting circadian homeostatic processes that protect the visual system from age- and light-associated damage. Altering the positive limb core molecular clock transcription factor, CLOCK, or CLOCK-output genes, accelerates visual senescence, induces a systemic immune response, and shortens lifespan. Flies subjected to dietary restriction are protected from the lifespan-shortening effects of photoreceptor activation. Inversely, photoreceptor inactivation, achieved via mutating rhodopsin or housing flies in constant darkness, primarily extends the lifespan of flies reared on a high-nutrient diet. Our findings establish the eye as a diet-sensitive modulator of lifespan and indicates that vision is an antagonistically pleiotropic process that contributes to organismal aging.
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Affiliation(s)
- Brian A Hodge
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA.
| | - Geoffrey T Meyerhof
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
- Neuroscience Research Institute and Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Subhash D Katewa
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
- NGM Biopharmaceuticals, 333 Oyster Point Blvd, South San Francisco, CA, 94080, USA
| | - Ting Lian
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
- Sichuan Agricultural University, 46 Xinkang Rd, Yucheng District, Ya'an, Sichuan, China
| | - Charles Lau
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
| | - Sudipta Bar
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
| | - Nicole Y Leung
- Neuroscience Research Institute and Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, 94305, USA
- Department of Neurobiology, Stanford University, Stanford, CA, 94305, USA
| | - Menglin Li
- Neuroscience Research Institute and Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - David Li-Kroeger
- Department of Neurology, Baylor College of Medicine, Houston, TX, 77096, USA
| | - Simon Melov
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
| | - Birgit Schilling
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA
| | - Craig Montell
- Neuroscience Research Institute and Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Pankaj Kapahi
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA, 94945, USA.
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Combined drug triads for synergic neuroprotection in retinal degeneration. Biomed Pharmacother 2022; 149:112911. [DOI: 10.1016/j.biopha.2022.112911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 03/28/2022] [Accepted: 03/29/2022] [Indexed: 11/23/2022] Open
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Shieh BH, Nuzum L, Kristaponyte I. Exploring Excitotoxicity and Regulation of a Constitutively Active TRP Ca 2+ Channel in Drosophila. Fly (Austin) 2020; 15:8-27. [PMID: 33200658 DOI: 10.1080/19336934.2020.1851586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Unregulated Ca2+ influx affects intracellular Ca2+ homoeostasis, which may lead to neuronal death. In Drosophila, following the activation of rhodopsin the TRP Ca2+ channel is open to mediate the light-dependent depolarization. A constitutively active TRP channel triggers the degeneration of TrpP365 /+ photoreceptors. To explore retinal degeneration, we employed a multidisciplinary approach including live imaging using GFP tagged actin and arrestin 2. Importantly, we demonstrate that the major rhodopsin (Rh1) was greatly reduced before the onset of rhabdomere degeneration; a great reduction of Rh1 affects the maintenance of rhabdomere leading to degeneration of photoreceptors. TrpP365 /+ also led to the up-regulation of CaMKII, which is beneficial as suppression of CaMKII accelerated retinal degeneration. We explored the regulation of TRP by investigating the genetic interaction between TrpP365 /+ and mutants affecting the turnover of diacylglycerol (DAG). We show a loss of phospholipase C in norpAP24 exhibited a great reduction of the DAG content delayed degeneration of TrpP365 /+ photoreceptors. In contrast, knockdown or mutations in DAG lipase (InaE) that is accompanied by slightly reduced levels of most DAG but an increased level of DAG 34:1, exacerbated retinal degeneration of TrpP365 /+. Together, our findings support the notion that DAG plays a role in regulating TRP. Interestingly, DAG lipase is likely required during photoreceptor development as TrpP365 /+; inaEN125 double mutants contained severely degenerated rhabdomeres.
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Affiliation(s)
- Bih-Hwa Shieh
- Department of Pharmacology, Center for Molecular Neuroscience and Vanderbilt Vision Research Center, Vanderbilt University , Nashville, TN, USA
| | - Lucinda Nuzum
- Department of Pharmacology, Center for Molecular Neuroscience and Vanderbilt Vision Research Center, Vanderbilt University , Nashville, TN, USA
| | - Inga Kristaponyte
- Department of Pharmacology, Center for Molecular Neuroscience and Vanderbilt Vision Research Center, Vanderbilt University , Nashville, TN, USA
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de Morais MC, de Souza JV, da Silva Maia Bezerra Filho C, Dolabella SS, de Sousa DP. Trypanocidal Essential Oils: A Review. Molecules 2020; 25:molecules25194568. [PMID: 33036315 PMCID: PMC7583723 DOI: 10.3390/molecules25194568] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/07/2020] [Accepted: 09/08/2020] [Indexed: 12/22/2022] Open
Abstract
Trypanosomiases are diseases caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans, this includes Chagas disease and African trypanosomiasis. There are few therapeutic options, and there is low efficacy to clinical treatment. Therefore, the search for new drugs for the trypanosomiasis is urgent. This review describes studies of the trypanocidal properties of essential oils, an important group of natural products widely found in several tropical countries. Seventy-seven plants were selected from literature for the trypanocidal activity of their essential oils. The main chemical constituents and mechanisms of action are also discussed. In vitro and in vivo experimental data show the therapeutic potential of these natural products for the treatment of infections caused by species of Trypanosoma.
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Affiliation(s)
- Mayara Castro de Morais
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900 João Pessoa, Paraíba, Brazil; (M.C.d.M.); (J.V.d.S.); (C.d.S.M.B.F.)
| | - Jucieudo Virgulino de Souza
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900 João Pessoa, Paraíba, Brazil; (M.C.d.M.); (J.V.d.S.); (C.d.S.M.B.F.)
| | - Carlos da Silva Maia Bezerra Filho
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900 João Pessoa, Paraíba, Brazil; (M.C.d.M.); (J.V.d.S.); (C.d.S.M.B.F.)
| | - Silvio Santana Dolabella
- Laboratory of Entomology and Tropical Parasitology, Department of Morphology, Federal University of Sergipe, 49100-000 São Cristóvão, Sergipe, Brazil;
| | - Damião Pergentino de Sousa
- Laboratory of Pharmaceutical Chemistry, Department of Pharmaceutical Sciences, Federal University of Paraíba, 58051-900 João Pessoa, Paraíba, Brazil; (M.C.d.M.); (J.V.d.S.); (C.d.S.M.B.F.)
- Correspondence: ; Tel.: +55-83-3216-7347
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Gaspar P, Almudi I, Nunes MDS, McGregor AP. Human eye conditions: insights from the fly eye. Hum Genet 2018; 138:973-991. [PMID: 30386938 DOI: 10.1007/s00439-018-1948-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 10/20/2018] [Indexed: 12/22/2022]
Abstract
The fruit fly Drosophila melanogaster has served as an excellent model to study and understand the genetics of many human diseases from cancer to neurodegeneration. Studying the regulation of growth, determination and differentiation of the compound eyes of this fly, in particular, have provided key insights into a wide range of diseases. Here we review the regulation of the development of fly eyes in light of shared aspects with human eye development. We also show how understanding conserved regulatory pathways in eye development together with the application of tools for genetic screening and functional analyses makes Drosophila a powerful model to diagnose and characterize the genetics underlying many human eye conditions, such as aniridia and retinitis pigmentosa. This further emphasizes the importance and vast potential of basic research to underpin applied research including identifying and treating the genetic basis of human diseases.
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Affiliation(s)
- Pedro Gaspar
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK
| | - Isabel Almudi
- Centro Andaluz de Biología del Desarrollo, CSIC/ Universidad Pablo de Olavide, Carretera de Utrera Km1, 41013, Sevilla, Spain
| | - Maria D S Nunes
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK
| | - Alistair P McGregor
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP, UK.
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12
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A Single Residue Mutation in the Gα q Subunit of the G Protein Complex Causes Blindness in Drosophila. G3-GENES GENOMES GENETICS 2018; 8:363-371. [PMID: 29158337 PMCID: PMC5765363 DOI: 10.1534/g3.117.300340] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Heterotrimeric G proteins play central roles in many signaling pathways, including the phototransduction cascade in animals. However, the degree of involvement of the G protein subunit Gαq is not clear since animals with previously reported strong loss-of-function mutations remain responsive to light stimuli. We recovered a new allele of Gαq in Drosophila that abolishes light response in a conventional electroretinogram assay, and reduces sensitivity in whole-cell recordings of dissociated cells by at least five orders of magnitude. In addition, mutant eyes demonstrate a rapid rate of degeneration in the presence of light. Our new allele is likely the strongest hypomorph described to date. Interestingly, the mutant protein is produced in the eyes but carries a single amino acid change of a conserved hydrophobic residue that has been assigned to the interface of interaction between Gαq and its downstream effector, PLC. Our study has thus uncovered possibly the first point mutation that specifically affects this interaction in vivo.
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13
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Chen X, Hall H, Simpson JP, Leon-Salas WD, Ready DF, Weake VM. Cytochrome b5 protects photoreceptors from light stress-induced lipid peroxidation and retinal degeneration. NPJ Aging Mech Dis 2017; 3:18. [PMID: 29214051 PMCID: PMC5712525 DOI: 10.1038/s41514-017-0019-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/27/2017] [Accepted: 10/31/2017] [Indexed: 01/06/2023] Open
Abstract
Lipid peroxides are generated by oxidative stress in cells, and contribute to ageing and neurodegenerative disease. The eye is at special risk for lipid peroxidation because photoreceptors possess amplified sensory membranes rich in peroxidation-susceptible polyunsaturated fatty acids. Light-induced lipid peroxidation in the retina contributes to retinal degeneration, and lipid peroxidation has been implicated in the progression of age-associated ocular diseases such as age-related macular degeneration (AMD). Here, we show that exposing Drosophila melanogaster to strong blue light induces oxidative stress including lipid peroxidation that results in retinal degeneration. Surprisingly, very young flies are resilient to this acute light stress, suggesting they possess endogenous neuroprotective mechanisms. While lipophilic antioxidants partially suppressed blue light-induced retinal degeneration in older flies, we find that overexpression of cytochrome b5 (Cyt-b5) completely suppressed both blue light-induced lipid peroxidation and retinal degeneration. Our data identify Cyt-b5 as a neuroprotective factor that targets light-induced oxidative damage, particularly lipid peroxidation. Cyt-b5 may function via supporting antioxidant recycling, thereby providing a strategy to prevent oxidative stress in ageing photoreceptors that would be synergistic with dietary antioxidant supplementation. Paradoxically, light is essential for vision, yet it also induces stress that damages the sensitive cells in the eye. Vikki Weake and her team at Purdue University examined how exposure to blue light causes damage to the retina in fruit flies. Blue light causes death of photoreceptors, the light-sensing neurons. Surprisingly, very young flies are resistant to blue light. Increasing levels of a single protein, Cytochrome-b5, mimicked youthful resilience in older flies. Cytochrome-b5 is central to an ancient cellular defense system that protects membranes from oxidative damage. With expansive sensory membranes containing specialized lipids, photoreceptors are especially sensitive to membrane lipid peroxidation, an emerging final common pathway for cell death in aging and disease. Research into preventing lipid peroxidation might help to develop therapies for age-related diseases such as age-related macular degeneration.
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Affiliation(s)
- Xinping Chen
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907 USA.,Present Address: University of Notre Dame, Notre Dame, IN 46556 USA
| | - Hana Hall
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907 USA
| | - Jeffrey P Simpson
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907 USA
| | - Walter D Leon-Salas
- Purdue Polytechnic Institute, Purdue University, West Lafayette, IN 47907 USA
| | - Donald F Ready
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907 USA
| | - Vikki M Weake
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907 USA.,Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907 USA
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14
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Hofmann L, Wang H, Zheng W, Philipp SE, Hidalgo P, Cavalié A, Chen XZ, Beck A, Flockerzi V. The S4---S5 linker - gearbox of TRP channel gating. Cell Calcium 2017; 67:156-165. [PMID: 28416203 DOI: 10.1016/j.ceca.2017.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/03/2017] [Accepted: 04/03/2017] [Indexed: 10/19/2022]
Abstract
Transient receptor potential (TRP) channels are cation channels which participate in a wide variety of physiological processes in organisms ranging from fungi to humans. They fulfill roles in body homeostasis, are sensors for noxious chemicals and temperature in the mammalian somatosensory system and are activated by light stimulated phospholipase C activity in Drosophila or by hypertonicity in yeast. The transmembrane topology of TRP channels is similar to that of voltage-gated cation channels. TRP proteins assemble as tetramers with each subunit containing six transmembrane helices (S1-S6) and intracellular N- and C-termini. Here we focus on the emerging functions of the cytosolic S4-S5 linker on TRP channel gating. Most of this knowledge comes from pathogenic mutations within the S4-S5 linker that alter TRP channel activities. This knowledge has stimulated forward genetic approaches to identify additional residues around this region which are essential for channel gating and is supported, in part, by recent structures obtained for TRPV1, TRPV2, TRPV6, TRPA1, and TRPP2.
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Affiliation(s)
- Laura Hofmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Hongmei Wang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Wang Zheng
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Stephan E Philipp
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Patricia Hidalgo
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Adolfo Cavalié
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Xing-Zhen Chen
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Andreas Beck
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Veit Flockerzi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany.
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15
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Abstract
Ischemic brain damage represents a major source of morbidity and mortality in westernized society and poses a significant financial burden on the health care system. To date, few effective therapies have been realized to treat stroke and once promising avenues such as antiexcitotoxic therapy with NMDA receptor antagonists have not proven clinically useful. Thus, we need to identify new targets for research and therapeutic intervention of the neurodegeneration caused by stroke. Transient receptor potential (TRP) channels are an exciting new family of cation channels that respond to intracellular and extracellular stimuli. Indeed, several members can be induced by oxidative stress and oxygen free radicals. We have recently demonstrated that one member, TRPM7, is an essential mediator of anoxic neuronal death that is activated by oxidative stress, in parallel to excitotoxic signal pathways. Thus, future treatment of ischemic brain injury may need to include strategies that inhibit or modulate TRPM7 activity. Further investigation of the physiology and pathophysiology of TRPM7 and other TRP family members is needed to provide both pharmacological targets and a better understanding of ischemic brain disorders.
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Affiliation(s)
- Michelle M Aarts
- Applied and Interventional Research and Division of Neurosurgery, Toronto Western Research Institute, 399 BathurstStreet, Toronto, Ontario M5T 2S8, Canada
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16
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Huang Z, Ren S, Jiang Y, Wang T. PINK1 and Parkin cooperatively protect neurons against constitutively active TRP channel-induced retinal degeneration in Drosophila. Cell Death Dis 2016; 7:e2179. [PMID: 27054334 PMCID: PMC4855661 DOI: 10.1038/cddis.2016.82] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 03/03/2016] [Accepted: 03/07/2016] [Indexed: 01/28/2023]
Abstract
Calcium has an important role in regulating numerous cellular activities. However, extremely high levels of intracellular calcium can lead to neurotoxicity, a process commonly associated with degenerative diseases. Despite the clear role of calcium cytotoxicity in mediating neuronal cell death in this context, the pathological mechanisms remain controversial. We used a well-established Drosophila model of retinal degeneration, which involves the constitutively active TRPP365 channels, to study calcium-induced neurotoxicity. We found that the disruption of mitochondrial function was associated with the degenerative process. Further, increasing autophagy flux prevented cell death in TrpP365 mutant flies, and this depended on the PINK1/Parkin pathway. In addition, the retinal degeneration process was also suppressed by the coexpression of PINK1 and Parkin. Our results provide genetic evidence that mitochondrial dysfunction has a key role in the pathology of cellular calcium neurotoxicity. In addition, the results demonstrated that maintaining mitochondrial homeostasis via PINK1/Parkin-dependent mitochondrial quality control can potentially alleviate cell death in a wide range of neurodegenerative diseases.
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Affiliation(s)
- Z Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.,National Institute of Biological Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - S Ren
- National Institute of Biological Sciences, Beijing, China.,College of Biological Sciences, China Agricultural University, Beijing, China
| | - Y Jiang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - T Wang
- National Institute of Biological Sciences, Beijing, China
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17
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Reinach PS, Mergler S, Okada Y, Saika S. Ocular transient receptor potential channel function in health and disease. BMC Ophthalmol 2015; 15 Suppl 1:153. [PMID: 26818117 PMCID: PMC4895786 DOI: 10.1186/s12886-015-0135-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Transient receptor potential (TRP) channels sense and transduce environmental stimuli into Ca(2+) transients that in turn induce responses essential for cell function and adaptation. These non-selective channels with variable Ca(2+) selectivity are grouped into seven different subfamilies containing 28 subtypes based on differences in amino acid sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells where they affect a host of stress-induced regulatory responses essential for normal vision maintenance. This article reviews our current knowledge about the expression, function and regulation of TRPs in different eye tissues. We also describe how under certain conditions TRP activation can induce responses that are maladaptive to ocular function. Furthermore, the possibility of an association between TRP mutations and disease is considered. These findings contribute to evidence suggesting that drug targeting TRP channels may be of therapeutic benefit in a clinical setting. We point out issues that must be more extensively addressed before it will be possible to decide with certainty that this is a realistic endeavor. Another possible upshot of future studies is that disease process progression can be better evaluated by profiling changes in tissue specific functional TRP subtype activity as well as their gene and protein expression.
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Affiliation(s)
- Peter S Reinach
- Department of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xuejuan Road, Wenzhou, Zhejiang, 325027, P. R. China.
| | - Stefan Mergler
- Department of Ophthalmology, Charité-University Medicine Berlin, Campus Virchow-Clinic, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Yuka Okada
- Department of Ophthalmology, Wakayama Medical University School of Medicine, Wakayama, Japan.
| | - Shizuya Saika
- Department of Ophthalmology, Wakayama Medical University School of Medicine, Wakayama, Japan.
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18
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Weiss S, Minke B. A new genetic model for calcium induced autophagy and ER-stress in Drosophila photoreceptor cells. Channels (Austin) 2015; 9:14-20. [PMID: 25664921 DOI: 10.4161/19336950.2014.981439] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cytoplasmic Ca2+ overload is known to trigger autophagy and ER-stress. Furthermore, ER-stress and autophagy are commonly associated with degenerative pathologies, but their role in disease progression is still a matter of debate, in part, owing to limitations of existing animal model systems. The Drosophila eye is a widely used model system for studying neurodegenerative pathologies. Recently, we characterized the Drosophila protein, Calphotin, as a cytosolic immobile Ca2+ buffer, which participates in Ca2+ homeostasis in Drosophila photoreceptor cells. Exposure of calphotin hypomorph flies to continuous illumination, which induces Ca2+ influx into photoreceptor cells, resulted in severe Ca2+-dependent degeneration. Here we show that this degeneration is autophagy and ER-stress related. Our studies thus provide a new model in which genetic manipulations trigger changes in cellular Ca2+ distribution. This model constitutes a framework for further investigations into the link between cytosolic Ca2+, ER-stress and autophagy in human disorders and diseases.
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Affiliation(s)
- Shirley Weiss
- a Department of Medical Neurobiology ; Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC); Faculty of Medicine; The Hebrew University ; Jerusalem , Israel
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19
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The GTP- and Phospholipid-Binding Protein TTD14 Regulates Trafficking of the TRPL Ion Channel in Drosophila Photoreceptor Cells. PLoS Genet 2015; 11:e1005578. [PMID: 26509977 PMCID: PMC4624897 DOI: 10.1371/journal.pgen.1005578] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 09/15/2015] [Indexed: 01/04/2023] Open
Abstract
Recycling of signaling proteins is a common phenomenon in diverse signaling pathways. In photoreceptors of Drosophila, light absorption by rhodopsin triggers a phospholipase Cβ-mediated opening of the ion channels transient receptor potential (TRP) and TRP-like (TRPL) and generates the visual response. The signaling proteins are located in a plasma membrane compartment called rhabdomere. The major rhodopsin (Rh1) and TRP are predominantly localized in the rhabdomere in light and darkness. In contrast, TRPL translocates between the rhabdomeral plasma membrane in the dark and a storage compartment in the cell body in the light, from where it can be recycled to the plasma membrane upon subsequent dark adaptation. Here, we identified the gene mutated in trpl translocation defective 14 (ttd14), which is required for both TRPL internalization from the rhabdomere in the light and recycling of TRPL back to the rhabdomere in the dark. TTD14 is highly conserved in invertebrates and binds GTP in vitro. The ttd14 mutation alters a conserved proline residue (P75L) in the GTP-binding domain and abolishes binding to GTP. This indicates that GTP binding is essential for TTD14 function. TTD14 is a cytosolic protein and binds to PtdIns(3)P, a lipid enriched in early endosome membranes, and to phosphatidic acid. In contrast to TRPL, rhabdomeral localization of the membrane proteins Rh1 and TRP is not affected in the ttd14P75L mutant. The ttd14P75L mutation results in Rh1-independent photoreceptor degeneration and larval lethality suggesting that other processes are also affected by the ttd14P75L mutation. In conclusion, TTD14 is a novel regulator of TRPL trafficking, involved in internalization and subsequent sorting of TRPL into the recycling pathway that enables this ion channel to return to the plasma membrane. Protein trafficking in neurons occurs throughout the lifetime of a cell and includes the internalization and redistribution of plasma membrane proteins. Regulated protein trafficking controls the equipment of the plasma membrane with receptors and ion channels and thereby attenuates or enhances neuronal function. Defects in recycling of plasma membrane proteins can cause detrimental neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and Down´s syndrome. In Drosophila photoreceptors, the TRPL ion channel, together with the TRP channel, mediates vision and light-dependently shuttles between an endomembrane storage compartment and the apical plasma membrane. Here, we report the identification of a mutation in the ttd14 gene that inhibits TRPL-trafficking in both directions and also results in photoreceptor degeneration. The TTD14 protein contains a region with weak homology to a PX-domain, which is also found in proteins that sort cargo in the endosome and enable protein recycling. We characterize TTD14 as a new regulator of photoreceptor maintenance and ion channel trafficking that binds to GTP and PtdIns(3)P, a phospholipid enriched in early endosomes.
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20
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Jaiswal M, Haelterman NA, Sandoval H, Xiong B, Donti T, Kalsotra A, Yamamoto S, Cooper TA, Graham BH, Bellen HJ. Impaired Mitochondrial Energy Production Causes Light-Induced Photoreceptor Degeneration Independent of Oxidative Stress. PLoS Biol 2015; 13:e1002197. [PMID: 26176594 PMCID: PMC4503542 DOI: 10.1371/journal.pbio.1002197] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/10/2015] [Indexed: 11/19/2022] Open
Abstract
Two insults often underlie a variety of eye diseases including glaucoma, optic atrophy, and retinal degeneration—defects in mitochondrial function and aberrant Rhodopsin trafficking. Although mitochondrial defects are often associated with oxidative stress, they have not been linked to Rhodopsin trafficking. In an unbiased forward genetic screen designed to isolate mutations that cause photoreceptor degeneration, we identified mutations in a nuclear-encoded mitochondrial gene, ppr, a homolog of human LRPPRC. We found that ppr is required for protection against light-induced degeneration. Its function is essential to maintain membrane depolarization of the photoreceptors upon repetitive light exposure, and an impaired phototransduction cascade in ppr mutants results in excessive Rhodopsin1 endocytosis. Moreover, loss of ppr results in a reduction in mitochondrial RNAs, reduced electron transport chain activity, and reduced ATP levels. Oxidative stress, however, is not induced. We propose that the reduced ATP level in ppr mutants underlies the phototransduction defect, leading to increased Rhodopsin1 endocytosis during light exposure, causing photoreceptor degeneration independent of oxidative stress. This hypothesis is bolstered by characterization of two other genes isolated in the screen, pyruvate dehydrogenase and citrate synthase. Their loss also causes a light-induced degeneration, excessive Rhodopsin1 endocytosis and reduced ATP without concurrent oxidative stress, unlike many other mutations in mitochondrial genes that are associated with elevated oxidative stress and light-independent photoreceptor demise. Some mitochondrial disorders cause blindness through increased oxidative stress. This study shows that in other such disorders, light-activated photoreceptors degenerate because the shortfall in mitochondrial energy production impairs rhodopsin trafficking and induces toxicity. Mitochondrial dysfunction is associated with a number of metabolic and neurological diseases such as Leigh syndrome and progressive blindness. Increased oxidative stress, which is often associated with mitochondrial dysfunction, is thought to be a common cause of disease progression. Here, we identified nuclear genes that encode mitochondrial proteins, whose loss causes the demise of photoreceptor neurons. Contrary to the common idea that this degeneration is triggered by elevated levels of oxidative stress, we find no change in the levels of oxidative stress. We show that activating photoreceptor neurons with light significantly increases energy production, and that this process is required to sustain their activity. Mitochondrial dysfunction impairs this capacity and leads to a premature termination of the light response. This in turn impairs the cycling of the light-sensitive receptor Rhodopsin in photoreceptors, and Rhodopsin accumulates in the cell inducing toxicity. This distinct mechanism of degeneration suggests that different mitochondrial diseases may follow different paths of disease progression and would hence respond differently to treatments.
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Affiliation(s)
- Manish Jaiswal
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Howard Hughes Medical Institute, BCM, Houston, Texas, United States of America
| | - Nele A. Haelterman
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
| | - Hector Sandoval
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Bo Xiong
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
| | - Taraka Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Auinash Kalsotra
- Department of Pathology and Immunology, BCM, Houston, Texas, United States of America
| | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital (TCH), Houston, Texas, United States of America
| | - Thomas A. Cooper
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Department of Pathology and Immunology, BCM, Houston, Texas, United States of America
| | - Brett H. Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
| | - Hugo J. Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, Texas, United States of America
- Howard Hughes Medical Institute, BCM, Houston, Texas, United States of America
- Program in Developmental Biology, BCM, Houston, Texas, United States of America
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital (TCH), Houston, Texas, United States of America
- Department of Neuroscience, BCM, Houston, Texas, United States of America
- * E-mail:
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21
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Voolstra O, Spät P, Oberegelsbacher C, Claussen B, Pfannstiel J, Huber A. Light-dependent phosphorylation of the Drosophila inactivation no afterpotential D (INAD) scaffolding protein at Thr170 and Ser174 by eye-specific protein kinase C. PLoS One 2015; 10:e0122039. [PMID: 25799587 PMCID: PMC4370639 DOI: 10.1371/journal.pone.0122039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 02/09/2015] [Indexed: 12/02/2022] Open
Abstract
Drosophila inactivation no afterpotential D (INAD) is a PDZ domain-containing scaffolding protein that tethers components of the phototransduction cascade to form a supramolecular signaling complex. Here, we report the identification of eight INAD phosphorylation sites using a mass spectrometry approach. PDZ1, PDZ2, and PDZ4 each harbor one phosphorylation site, three phosphorylation sites are located in the linker region between PDZ1 and 2, one site is located between PDZ2 and PDZ3, and one site is located in the N-terminal region. Using a phosphospecific antibody, we found that INAD phosphorylated at Thr170/Ser174 was located within the rhabdomeres of the photoreceptor cells, suggesting that INAD becomes phosphorylated in this cellular compartment. INAD phosphorylation at Thr170/Ser174 depends on light, the phototransduction cascade, and on eye-Protein kinase C that is attached to INAD via one of its PDZ domains.
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Affiliation(s)
- Olaf Voolstra
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
- * E-mail:
| | - Philipp Spät
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Claudia Oberegelsbacher
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Björn Claussen
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Jens Pfannstiel
- Mass Spectrometry Core Facility, Universität Hohenheim, Stuttgart, Germany
| | - Armin Huber
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
- Mass Spectrometry Core Facility, Universität Hohenheim, Stuttgart, Germany
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22
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Abstract
The Drosophila "transient receptor potential" channel is the prototypical TRP channel, belonging to and defining the TRPC subfamily. Together with a second TRPC channel, trp-like (TRPL), TRP mediates the transducer current in the fly's photoreceptors. TRP and TRPL are also implicated in olfaction and Malpighian tubule function. In photoreceptors, TRP and TRPL are localised in the ~30,000 packed microvilli that form the photosensitive "rhabdomere"-a light-guiding rod, housing rhodopsin and the rest of the phototransduction machinery. TRP (but not TRPL) is assembled into multimolecular signalling complexes by a PDZ-domain scaffolding protein (INAD). TRPL (but not TRP) undergoes light-regulated translocation between cell body and rhabdomere. TRP and TRPL are also found in photoreceptor synapses where they may play a role in synaptic transmission. Like other TRPC channels, TRP and TRPL are activated by a G protein-coupled phospholipase C (PLCβ4) cascade. Although still debated, recent evidence indicates the channels can be activated by a combination of PIP2 depletion and protons released by the PLC reaction. PIP2 depletion may act mechanically as membrane area is reduced by cleavage of PIP2's bulky inositol headgroup. TRP, which dominates the light-sensitive current, is Ca(2+) selective (P Ca:P Cs >50:1), whilst TRPL has a modest Ca(2+) permeability (P Ca:P Cs ~5:1). Ca(2+) influx via the channels has profound positive and negative feedback roles, required for the rapid response kinetics, with Ca(2+) rapidly facilitating TRP (but not TRPL) and also inhibiting both channels. In trp mutants, stimulation by light results in rapid depletion of microvillar PIP2 due to lack of Ca(2+) influx required to inhibit PLC. This accounts for the "transient receptor potential" phenotype that gives the family its name and, over a period of days, leads to light-dependent retinal degeneration. Gain-of-function trp mutants with uncontrolled Ca(2+) influx also undergo retinal degeneration due to Ca(2+) cytotoxicity. In vertebrate retina, mice knockout studies suggest that TRPC6 and TRPC7 mediate a PLCβ4-activated transducer current in intrinsically photosensitive retinal ganglion cells, expressing melanopsin. TRPA1 has been implicated as a "photo-sensing" TRP channel in human melanocytes and light-sensitive neurons in the body wall of Drosophila.
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23
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Voolstra O, Bartels JP, Oberegelsbacher C, Pfannstiel J, Huber A. Phosphorylation of the Drosophila transient receptor potential ion channel is regulated by the phototransduction cascade and involves several protein kinases and phosphatases. PLoS One 2013; 8:e73787. [PMID: 24040070 PMCID: PMC3767779 DOI: 10.1371/journal.pone.0073787] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/29/2013] [Indexed: 12/02/2022] Open
Abstract
Protein phosphorylation plays a cardinal role in regulating cellular processes in eukaryotes. Phosphorylation of proteins is controlled by protein kinases and phosphatases. We previously reported the light-dependent phosphorylation of the Drosophila transient receptor potential (TRP) ion channel at multiple sites. TRP generates the receptor potential upon stimulation of the photoreceptor cell by light. An eye-enriched protein kinase C (eye-PKC) has been implicated in the phosphorylation of TRP by in vitro studies. Other kinases and phosphatases of TRP are elusive. Using phosphospecific antibodies and mass spectrometry, we here show that phosphorylation of most TRP sites depends on the phototransduction cascade and the activity of the TRP ion channel. A candidate screen to identify kinases and phosphatases provided in vivo evidence for an involvement of eye-PKC as well as other kinases and phosphatases in TRP phosphorylation.
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Affiliation(s)
- Olaf Voolstra
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Jonas-Peter Bartels
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Claudia Oberegelsbacher
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
| | - Jens Pfannstiel
- The Life Science Center, Universität Hohenheim, Stuttgart, Germany
| | - Armin Huber
- Department of Biosensorics, Institute of Physiology, Universität Hohenheim, Stuttgart, Germany
- The Life Science Center, Universität Hohenheim, Stuttgart, Germany
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24
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Lee J. Drosophila mosaic screen identifies diehard mutants as norpA P24 suppressors. Genes Genomics 2012. [DOI: 10.1007/s13258-012-0097-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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25
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Georgiev P, Toscano S, Nair A, Hardie R, Raghu P. Identification of a suppressor of retinal degeneration in Drosophila photoreceptors. J Neurogenet 2012; 26:338-47. [PMID: 23043643 DOI: 10.3109/01677063.2012.725436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
During sensory transduction, Drosophila photoreceptors experience substantial increases in intracellular Ca(2+) levels ([Ca(2+)](i)). Nevertheless in a number of mutants associated with excessive Ca(2+) influx through transient receptor potential (TRP) channels, Drosophila photoreceptors undergo loss of normal cellular structure manifest as a retinal degeneration. However, the molecular mechanisms that underpin this degeneration process remain unclear. The authors previously isolated a mutant, su(40), that is able to suppress the retinal degeneration seen in photoreceptors from loss-of-function alleles of rdgA that are known to have constitutively active TRP channels. Here the authors report the genetic mapping of su(40) as well the isolation of additional alleles of su(40). Studies of su(40) as well as these new alleles should facilitate the understanding of the mechanisms by which excessive Ca(2+) influx results in retinal degeneration.
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Affiliation(s)
- Plamen Georgiev
- The Inositide laboratory, Babraham Institute, Babraham Research Campus, Cambridge, United Kingdom
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26
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Looking into eyes: rhodopsin pathologies in Drosophila. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:415-23. [PMID: 22183360 DOI: 10.1007/978-1-4614-0631-0_53] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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27
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Lee S, Lee SB, Ramirez P, Byun Y, Kim J, Jeong Y, Baek K, Yoon J. The Drosophila melanogaster retinophilin gene encodes the peripheral membrane protein in photoreceptor cells. Genes Genomics 2012. [DOI: 10.1007/s13258-011-0198-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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28
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Phototransduction in Drosophila. SCIENCE CHINA-LIFE SCIENCES 2012; 55:27-34. [PMID: 22314488 DOI: 10.1007/s11427-012-4272-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 09/12/2011] [Indexed: 10/14/2022]
Abstract
The Drosophila visual transduction is the fastest known G protein-coupled signaling cascade and has been served as a model for understanding the molecular mechanisms of other G protein-coupled signaling cascades. Numbers of components in visual transduction machinery have been identified. Based on the functional characterization of these genes, a model for Drosophila phototransduction has been outlined, including rhodopsin activation, phosphoinoside signaling, and the opening of TRP and TRPL channels. Recently, the characterization of mutants, showing slow termination, revealed the physiological significance and the mechanism of rapid termination of light response.
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29
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Loukin S, Su Z, Kung C. Increased basal activity is a key determinant in the severity of human skeletal dysplasia caused by TRPV4 mutations. PLoS One 2011; 6:e19533. [PMID: 21573172 PMCID: PMC3088684 DOI: 10.1371/journal.pone.0019533] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 04/04/2011] [Indexed: 02/01/2023] Open
Abstract
TRPV4 is a mechanically activated Ca2+-passing channel implicated in the sensing of forces, including those acting on bones. To date, 33 mutations are known to affect human bone development to different extents. The spectrum of these skeletal dysplasias (SD) ranges from dominantly inherited mild brachylomia (BO) to neonatal lethal forms of metatropic dysplasia (MD). Complexities of the results from fluorescence and electrophysiological studies have led to questions on whether channel activity is a good predictor of disease severity. Here we report on a systematic examination of 14 TRPV4 mutant alleles covering the entire SD spectrum. Expressed in Xenopus oocyte and without any stimulation, the wild-type channel had a ∼1% open probability (Po) while those of most of the lethal MD channels approached 100%. All mutant channels had higher basal open probabilities, which limited their further increase by agonist or hypotonicity. The magnitude of this limitation revealed a clear correlation between the degree of over-activity (the molecular phenotype) and the severity of the disease over the entire spectrum (the biological phenotype). Thus, while other factors are at play, our results are consistent with the increased TRPV4 basal activity being a critical determinant of the severity of skeletal dysplasia. We discuss how the channel over-activity may lead to the “gain-of-function” phenotype and speculate that the function of wild-type TRPV4 may be secondary in normal bone development but crucial in an acute process such as fracture repair in the adult.
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Affiliation(s)
- Stephen Loukin
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail:
| | - Zhenwei Su
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- Department of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
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Abstract
This review recounts the early history of Drosophila phototransduction genetics, covering the period between approximately 1966 to 1979. Early in this period, the author felt that there was an urgent need for a new approach in phototransduction research. Through inputs from a number of colleagues, he was led to consider isolating Drosophila mutants that are defective in the electroretinogram. Thanks to the efforts of dedicated associates and technical staff, by the end of this period, he was able to accumulate a large number of such mutants. Particularly important in this effort was the use of the mutant assay protocol based on the "prolonged depolarizing afterpotential." This collection of mutants formed the basis of the subsequent intensive investigations of the Drosophila phototransduction cascade by many investigators.
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Affiliation(s)
- William L Pak
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2054, USA.
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Miller BA, Zhang W. TRP Channels as Mediators of Oxidative Stress. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:531-44. [DOI: 10.1007/978-94-007-0265-3_29] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Abstract
Transient receptor potential (TRP) channels are polymodal cellular sensors involved in a wide variety of cellular processes, mainly by changing membrane voltage and increasing cellular Ca(2+). This review outlines in detail the history of the founding member of the TRP family, the Drosophila TRP channel. The field began with a spontaneous mutation in the trp gene that led to a blind mutant during prolonged intense light. It was this mutant that allowed for the discovery of the first TRP channels. A combination of electrophysiological, biochemical, Ca(2+) measurements, and genetic studies in flies and in other invertebrates pointed to TRP as a novel phosphoinositide-regulated and Ca(2+)-permeable channel. The cloning and sequencing of the trp gene provided its molecular identity. These seminal findings led to the isolation of the first mammalian homologues of the Drosophila TRP channels. We now know that TRP channel proteins are conserved through evolution and are found in most organisms, tissues, and cell-types. The TRP channel superfamily is classified into seven related subfamilies: TRPC, TRPM, TRPV, TRPA, TRPP, TRPML, and TRPN. A great deal is known today about participation of TRP channels in many biological processes, including initiation of pain, thermoregulation, salivary fluid secretion, inflammation, cardiovascular regulation, smooth muscle tone, pressure regulation, Ca(2+) and Mg(2+) homeostasis, and lysosomal function. The native Drosophila photoreceptor cells, where the founding member of the TRP channels superfamily was found, is still a useful preparation to study basic features of this remarkable channel.
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Affiliation(s)
- Baruch Minke
- Department of Medical Neurobiology, The Institute of Medical Research Israel-Canada, The Edmond and Lily Safra Center for Brain Sciences and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine, The Hebrew University, Jerusalem 91120, Israel.
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Kain P, Badsha F, Hussain SM, Nair A, Hasan G, Rodrigues V. Mutants in phospholipid signaling attenuate the behavioral response of adult Drosophila to trehalose. Chem Senses 2010; 35:663-73. [PMID: 20543015 DOI: 10.1093/chemse/bjq055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Drosophila melanogaster, gustatory receptor genes (Grs) encode putative G-protein-coupled receptors (GPCRs) that are expressed in gustatory receptor neurons (GRNs). One of the Gr genes, Gr5a, encodes a receptor for trehalose that is expressed in a subset of GRNs. Although a role for the G protein, Gsα, has been shown in Gr5a-expressing taste neurons, there is the residual responses to trehalose in Gsα mutants which could suggest additional transduction mechanisms. Expression and genetic analysis of the heterotrimeric G-protein subunit, Gq, shown here suggest involvement of this Gα subunit in trehalose perception in Drosophila. A green fluorescent protein reporter of Gq expression is detected in gustatory neurons in the labellum, tarsal segments, and wing margins. Animals heterozygous for dgq mutations and RNA interference-mediated knockdown of dgq showed reduced responses to trehalose in the proboscis extension reflex assay and feeding behavior assay. These defects were rescued by targeted expression of the wild-type dgqα transgene in the GRNs. These data together with observations from other mutants in phospholipid signaling provide insights into the mechanisms of taste transduction in Drosophila.
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Affiliation(s)
- Pinky Kain
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
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Voolstra O, Beck K, Oberegelsbacher C, Pfannstiel J, Huber A. Light-dependent phosphorylation of the drosophila transient receptor potential ion channel. J Biol Chem 2010; 285:14275-84. [PMID: 20215118 PMCID: PMC2863191 DOI: 10.1074/jbc.m110.102053] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 03/04/2010] [Indexed: 11/06/2022] Open
Abstract
The Drosophila phototransduction cascade terminates in the opening of an ion channel, designated transient receptor potential (TRP). TRP has been shown to become phosphorylated in vitro, suggesting regulation of the ion channel through posttranslational modification. However, except for one phosphorylation site, Ser(982), which was analyzed by functional in vivo studies (Popescu, D. C., Ham, A. J., and Shieh, B. H. (2006) J. Neurosci. 26, 8570-8577), nothing is known about the role of TRP phosphorylation in vivo. Here, we report the identification of 21 TRP phosphorylation sites by a mass spectrometry approach. 20 phosphorylation sites are located in the C-terminal portion of the channel, and one site is located near the N terminus. All 21 phosphorylation sites were also identified in the inaC(P209) mutant, indicating that phosphorylation of TRP at these sites occurred independently from the eye-enriched protein kinase C. Relative quantification of phosphopeptides revealed that at least seven phosphorylation sites were predominantly phosphorylated in the light, whereas one site, Ser(936), was predominantly phosphorylated in the dark. We show that TRP phosphorylated at Ser(936) was located in the rhabomere. Light-dependent changes in the phosphorylation state of this site occurred within minutes. The dephosphorylation of TRP at Ser(936) required activation of the phototransduction cascade.
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Affiliation(s)
- Olaf Voolstra
- Department of Biosensorics, Institute of Physiology, Germany.
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Lev S, Zeevi DA, Frumkin A, Offen-Glasner V, Bach G, Minke B. Constitutive activity of the human TRPML2 channel induces cell degeneration. J Biol Chem 2010; 285:2771-82. [PMID: 19940139 PMCID: PMC2807332 DOI: 10.1074/jbc.m109.046508] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/19/2009] [Indexed: 01/01/2023] Open
Abstract
The mucolipin (TRPML) ion channel proteins represent a distinct subfamily of channel proteins within the transient receptor potential (TRP) superfamily of cation channels. Mucolipin 1, 2, and 3 (TRPML1, -2, and -3, respectively) are channel proteins that share high sequence homology with each other and homology in the transmembrane domain with other TRPs. Mutations in the TRPML1 protein are implicated in mucolipidosis type IV, whereas mutations in TRPML3 are found in the varitint-waddler mouse. The properties of the wild type TRPML2 channel are not well known. Here we show functional expression of the wild type human TRPML2 channel (h-TRPML2). The channel is functional at the plasma membrane and characterized by a significant inward rectification similar to other constitutively active TRPML mutant isoforms. The h-TRPML2 channel displays nonselective cation permeability, which is Ca(2+)-permeable and inhibited by low extracytosolic pH but not Ca(2+) regulated. In addition, constitutively active h-TRPML2 leads to cell death by causing Ca(2+) overload. Furthermore, we demonstrate by functional mutation analysis that h-TRPML2 shares similar characteristics and structural similarities with other TRPML channels that regulate the channel in a similar manner. Hence, in addition to overall structure, all three TRPML channels also share common modes of regulation.
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Affiliation(s)
- Shaya Lev
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
| | - David A. Zeevi
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Ayala Frumkin
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Vered Offen-Glasner
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Gideon Bach
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Baruch Minke
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
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Lev S, Minke B. Constitutive activity of TRP channels methods for measuring the activity and its outcome. Methods Enzymol 2010; 484:591-612. [PMID: 21036252 PMCID: PMC3104132 DOI: 10.1016/b978-0-12-381298-8.00029-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
TRP channels participate in many cellular processes including cell death. These channels mediate these effects mainly by changing the cellular concentration of Ca(2+), a prominent cellular second messenger. Measuring the current-voltage relationship and state of activation of TRP channels is of utmost importance for evaluating their contribution to a cellular process within a spatial and temporal context. The study of TRP channels and characterization of their mode of activation will benefit and progress our understanding of each channel's role in specific cellular mechanisms. Many TRP channels exhibit constitutive activity, which is mostly observed in cell-based expression systems. This constitutive activity can lead, in many cases, to cellular degeneration, which can be readily observed morphologically and by biochemical assays. This chapter describes in brief different modes of TRP channel activity and their current-voltage relationships. The chapter outlines methods for visualizing this activity and methods to correlate between TRP channel activity and cell death, and it illustrates mechanisms that prevent cell death in spite of constitutive activity. Finally, it describes methods for qualitatively and quantitatively measuring the accompanied cellular degeneration.
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Myers BR, Saimi Y, Julius D, Kung C. Multiple unbiased prospective screens identify TRP channels and their conserved gating elements. ACTA ACUST UNITED AC 2009; 132:481-6. [PMID: 18955590 PMCID: PMC2571970 DOI: 10.1085/jgp.200810104] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Benjamin R Myers
- Department of Physiology, University of California, San Francisco, CA 94143, USA
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Leung HT, Tseng-Crank J, Kim E, Mahapatra C, Shino S, Zhou Y, An L, Doerge RW, Pak WL. DAG lipase activity is necessary for TRP channel regulation in Drosophila photoreceptors. Neuron 2008; 58:884-96. [PMID: 18579079 DOI: 10.1016/j.neuron.2008.05.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 04/16/2008] [Accepted: 04/29/2008] [Indexed: 12/31/2022]
Abstract
In Drosophila, a phospholipase C-mediated signaling cascade links photoexcitation of rhodopsin to the opening of the TRP/TRPL channels. A lipid product of the cascade, diacylglycerol (DAG) and its metabolite(s), polyunsaturated fatty acids (PUFAs), have both been proposed as potential excitatory messengers. A crucial enzyme in the understanding of this process is likely to be DAG lipase (DAGL). However, DAGLs that might fulfill this role have not been previously identified in any organism. In this work, the Drosophila DAGL gene, inaE, has been identified from mutants that are defective in photoreceptor responses to light. The inaE-encoded protein isoforms show high sequence similarity to known mammalian DAG lipases, exhibit DAG lipase activity in vitro, and are highly expressed in photoreceptors. Analyses of norpA inaE double mutants and severe inaE mutants show that normal DAGL activity is required for the generation of physiologically meaningful photoreceptor responses.
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Affiliation(s)
- Hung-Tat Leung
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2054, USA
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Yeast gain-of-function mutations reveal structure-function relationships conserved among different subfamilies of transient receptor potential channels. Proc Natl Acad Sci U S A 2007; 104:19607-12. [PMID: 18042709 DOI: 10.1073/pnas.0708584104] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transient receptor potential (TRP) channels found in animals, protists, and fungi are primary chemo-, thermo-, or mechanosensors. Current research emphasizes the characteristics of individual channels in each animal TRP subfamily but not the mechanisms common across subfamilies. A forward genetic screen of the TrpY1, the yeast TRP channel, recovered gain-of-function (GOF) mutations with phenotype in vivo and in vitro. Single-channel patch-clamp analyses of these GOF-mutant channels show prominent aberrations in open probability and channel kinetics. These mutations revealed functionally important aromatic amino acid residues in four locations: at the intracellular end of the fifth transmembrane helix (TM5), at both ends of TM6, and at the immediate extension of TM6. These aromatics have counterparts in most TRP subfamilies. The one in TM5 (F380L) aligns precisely with an exceptional Drosophila mutant allele (F550I) that causes constitutive activity in the canonical TRP channel, resulting in rapid and severe retinal degeneration beyond mere loss of phototaxis. Thus, this phenylalanine maintains the balance of various functional states (conformations) of a channel for insect phototransduction as well as one for fungal mechanotransduction. This residue is among a small cluster of phenylalanines found in all known subfamilies of TRP channels. This unique case illustrates that GOF mutations can reveal structure-function principles that can be generalized across different TRP subfamilies. It appears that the conserved aromatics in the four locations have conserved functions in most TRP channels. The possible mechanistic roles of these aromatics and the further use of yeast genetics to dissect TRP channels are discussed.
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Abstract
Calcium signalling system controls majority of cellular reactions. Calcium signals occurring within tightly regulated temporal and spatial domains, govern a host of Ca2(+)-dependent enzymes, which in turn determine specified cellular responses. Generation of Ca2+ signals is achieved through coordinated activity of several families of Ca2+ channels and transporters differentially distributed between intracellular compartments. Cell damage induced by environmental insults or by overstimulation of physiological pathways results in pathological Ca2+ signals, which trigger necrotic or apoptotic cellular death.
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Abstract
The TRP (Transient Receptor Potential) superfamily of cation channels is remarkable in that it displays greater diversity in activation mechanisms and selectivities than any other group of ion channels. The domain organizations of some TRP proteins are also unusual, as they consist of linked channel and enzyme domains. A unifying theme in this group is that TRP proteins play critical roles in sensory physiology, which include contributions to vision, taste, olfaction, hearing, touch, and thermo- and osmosensation. In addition, TRP channels enable individual cells to sense changes in their local environment. Many TRP channels are activated by a variety of different stimuli and function as signal integrators. The TRP superfamily is divided into seven subfamilies: the five group 1 TRPs (TRPC, TRPV, TRPM, TRPN, and TRPA) and two group 2 subfamilies (TRPP and TRPML). TRP channels are important for human health as mutations in at least four TRP channels underlie disease.
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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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Roger J, Goureau O, Sahel JA, Guillonneau X. Use of suppression subtractive hybridization to identify genes regulated by ciliary neurotrophic factor in postnatal retinal explants. Mol Vis 2007; 13:206-19. [PMID: 17327826 PMCID: PMC2610405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE The retinal progenitors are multipotential, and the decision taken by a progenitor to differentiate along a particular path depends on both cell-intrinsic and cell-extrinsic factors. Ciliary neurotrophic factor (CNTF), a member of the interleukin-6 (IL-6) family, added to rat postnatal retinal progenitors inhibits rod photoreceptor cell differentiation, promotes Müller glia genesis and enhances the expression of bipolar neuron markers. We hypothesized that those transcripts regulated during CNTF-influenced retinal differentiation may be involved in the choice of progenitor cell fate. Our aim was to isolate these genes, characterize their expression in the retina, and to subsequently focus on candidates that may promote photoreceptor cell differentiation. METHODS Retinas were cultured in vitro as explants at postnatal day 0 (P0) in the absence or presence of CNTF for six days. Transcripts regulated by CNTF after six days in vitro (DIV) were selected by subtraction suppressive hybridization (SSH) and cloned as two libraries. The UC6 and DC6 libraries contained those genes upregulated and downregulated, respectively, in the presence of CNTF at 6DIV. RESULTS In the first library, UC6, eight clones representing seven different genes were isolated as up-regulated by CNTF. In the DC6 library, 21 clones, representing 17 different genes appeared as down-regulated by CNTF. Genes were classified in six categories, such as protein modification, signal transduction, and regulation of transcription according to the Gene Ontology Annotation. CONCLUSIONS Among the 24 selected genes, our study revealed 11 genes (two upregulated and nine downregulated) potentially involved in CNTF biological effects.
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Affiliation(s)
- Jérôme Roger
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - Olivier Goureau
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - José-Alain Sahel
- INSERM U592, Paris, France,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
| | - Xavier Guillonneau
- INSERM U592, Paris, France,Université Pierre et Marie Curie-Paris 6 UMR-S592, Paris, F-75012
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Nichols CD. Drosophila melanogaster neurobiology, neuropharmacology, and how the fly can inform central nervous system drug discovery. Pharmacol Ther 2006; 112:677-700. [PMID: 16935347 DOI: 10.1016/j.pharmthera.2006.05.012] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Accepted: 05/24/2006] [Indexed: 01/25/2023]
Abstract
Central nervous system (CNS) drug discovery in the post-genomic era is rapidly evolving. Older empirical methods are giving way to newer technologies that include bioinformatics, structural biology, genetics, and modern computational approaches. In the search for new medical therapies, and in particular treatments for disorders of the central nervous system, there has been increasing recognition that identification of a single biological target is unlikely to be a recipe for success; a broad perspective is required. Systems biology is one such approach, and has been increasingly recognized as a very important area of research, as it places specific molecular targets within a context of overall biochemical action. Understanding the complex interactions between the components within a given biological system that lead to modifications in output, such as changes in behavior or development, may be important avenues of discovery to identify new therapies. One avenue to drug discovery that holds tremendous potential is the use of model genetic organisms such as the fruit fly, Drosophila melanogaster. The similarity between mode of drug action, behavior, and gene response in D. melanogaster and mammalian systems, combined with the power of genetics, have recently made the fly a very attractive system to study fundamental neuropharmacological processes relevant to human diseases. The promise that the use of model organisms such as the fly offers is speed, high throughput, and dramatically reduced overall costs that together should result in an enhanced rate of discovery.
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Affiliation(s)
- Charles D Nichols
- Department of Pharmacology and Experimental Therapeutics, LSU Health Sciences Center, 1901 Perdido St., New Orleans, LA 70112, USA.
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Jose AM, Bany IA, Chase DL, Koelle MR. A specific subset of transient receptor potential vanilloid-type channel subunits in Caenorhabditis elegans endocrine cells function as mixed heteromers to promote neurotransmitter release. Genetics 2006; 175:93-105. [PMID: 17057248 PMCID: PMC1774992 DOI: 10.1534/genetics.106.065516] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Transient receptor potential (TRP) channel subunits form homotetramers that function in sensory transduction. Heteromeric channels also form, but their physiological subunit compositions and functions are largely unknown. We found a dominant-negative mutant of the C. elegans TRPV (vanilloid-type) subunit OCR-2 that apparently incorporates into and inactivates OCR-2 homomers as well as heteromers with the TRPV subunits OCR-1 and -4, resulting in a premature egg-laying defect. This defect is reproduced by knocking out all three OCR genes, but not by any single knockout. Thus a mixture of redundant heteromeric channels prevents premature egg laying. These channels, as well as the G-protein G alpha(o), function in neuroendocrine cells to promote release of neurotransmitters that block egg laying until eggs filling the uterus deform the neuroendocrine cells. The TRPV channel OSM-9, previously suggested to be an obligate heteromeric partner of OCR-2 in sensory neurons, is expressed in the neuroendocrine cells but has no detectable role in egg laying. Our results identify a specific set of heteromeric TRPV channels that redundantly regulate neuroendocrine function and show that a subunit combination that functions in sensory neurons is also present in neuroendocrine cells but has no detectable function in these cells.
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Affiliation(s)
- Antony M Jose
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA
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Richard M, Roepman R, Aartsen WM, van Rossum AGSH, den Hollander AI, Knust E, Wijnholds J, Cremers FPM. Towards understanding CRUMBS function in retinal dystrophies. Hum Mol Genet 2006; 15 Spec No 2:R235-43. [PMID: 16987889 DOI: 10.1093/hmg/ddl195] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mutations in the Crumbs homologue 1 (CRB1) gene cause autosomal recessive retinitis pigmentosa (arRP) and autosomal Leber congenital amaurosis (arLCA). The crumbs (crb) gene was originally identified in Drosophila and encodes a large transmembrane protein required for maintenance of apico-basal cell polarity and adherens junction in embryonic epithelia. Human CRB1 and its two paralogues, CRB2 and CRB3, are highly conserved throughout the animal kingdom. Both in Drosophila and in vertebrates, the short intracellular domain of Crb/CRB organizes an evolutionary conserved protein scaffold. Several lines of evidence, obtained both in Drosophila and in mouse, show that loss-of-function of crb/CRB1 or some of its intracellular interactors lead to morphological defects and light-induced degeneration of photoreceptor cells, features comparable to those observed in patients lacking CRB1 function. In this review, we describe how understanding Crb complex function in fly and vertebrate retina enhances our knowledge of basic cell biological processes and might lead to new therapeutic approaches for patients affected with retinal dystrophies caused by mutations in the CRB1 gene.
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Affiliation(s)
- Mélisande Richard
- Institut für Genetik, Heinrich Heine Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
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Abstract
There is a rapidly growing interest in the family of transient receptor potential (TRP) channels because TRP channels are not only important for many sensory systems, but they are crucial components of the function of neurons, epithelial, blood and smooth muscle cells. These facts make TRP channels important targets for treatment of diseases arising from the malfunction of these channels in the above cells and for treatment of inflammatory pain. TRP channels are also important for a growing number of genetic diseases arising from mutations in various types of TRP channels. The Minerva-Gentner Symposium on TRP channels and Ca(2+) signaling, which took place in Eilat, Israel (February 24-28, 2006) has clearly demonstrated that the study of TRP channels is a newly emerging field of biomedicine with prime importance. In the Eilat symposium, investigators who have contributed seminal publications and insight into the TRP field presented their most recent, and in many cases still unpublished, studies. The excellent presentations and excitement generated by them demonstrated that much progress has been achieved. Nevertheless, it was also evident that the field of TRP channels is still in its infancy in comparison to other fields of ion channels, and even the fundamental knowledge of the gating mechanism of TRP channels is still unsolved. The beautiful location of the symposium, together with informal intensive discussions among the participants, contributed to the success of this meeting.
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Affiliation(s)
- Baruch Minke
- Department of Physiology and the Kühne Minerva Center for Studies of Visual Transduction, The Hebrew University of Jerusalem, Jerusalem 91120, Israel.
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Cronin MA, Lieu MH, Tsunoda S. Two stages of light-dependent TRPL-channel translocation in Drosophila photoreceptors. J Cell Sci 2006; 119:2935-44. [PMID: 16787936 DOI: 10.1242/jcs.03049] [Citation(s) in RCA: 281] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transient receptor potential (TRP) channels across species are expressed in sensory receptor cells, and often localized to specialized subcellular sites. In Drosophila photoreceptors, TRP-like (TRPL) channels are localized to the signaling compartment, the rhabdomere, in the dark, and undergo light-induced translocation into the cell body as a mechanism for long-term light-adaptation. We show that translocation of TRPL channels occurs in two distinct stages, first to the neighboring stalk membrane then to the basolateral membrane. In the first stage, light-induced translocation occurs within 5 minutes, whereas the second stage takes over 6 hours. The exclusive apical localization of TRPL channels in the first stage of translocation suggests that channels are released from the rhabdomere and diffuse laterally through the membrane into the adjoining stalk membrane. In the second stage, TRPL channels are localized in the basolateral membrane, implicating a different transport mechanism. Genetic analyses suggest that activation of the other light-activated TRP channel and eye-protein-kinase C (eye-PKC) are both required for the second stage of TRPL translocation in R1 to R6 photoreceptor cells, whereas only phospholipase C (PLC) is required for the first stage. Finally, we show that arrestin2 is required for the rhabdomeric localization and stability of TRPL channels.
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Affiliation(s)
- Michelle A Cronin
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA
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Abstract
The development of our knowledge on the structure, molecular regulation, and cell function on transient receptor potential (TRP) channels has been growing dramatically during the last few years. Many meetings in the past and upcoming events are now focused on TRP channels as general sensor molecules in cell physiology. However, most of the scientists in the field still feel that we are just beginning to understand these truly remarkable proteins, called TRPs, and there is still a long way to go from structure via molecular regulation to cell and organ function. This generally accepted but exciting view about the long road to the understanding of TRPs dominated all presentations given at the 2006 Minerva-Gentner Symposium on TRP channels and calcium signalling, which was held in Eilat, Israel, and was excellently organized by Baruch Minke (Jerusalem, Israel) and supported by Veit Flockerzi (Homburg, Germany).
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Affiliation(s)
- Bernd Nilius
- Laboratory of Physiology, KU Leuven, B-3000 Leuven, Belgium.
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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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