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Woodard G, Rosado JA, Li H. The physiological role of TRP channels in sleep and circadian rhythm. J Cell Mol Med 2024; 28:e18274. [PMID: 38676362 PMCID: PMC11053353 DOI: 10.1111/jcmm.18274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 10/24/2023] [Accepted: 01/05/2024] [Indexed: 04/28/2024] Open
Abstract
TRP channels, are non-specific cationic channels that are involved in multiple physiological processes that include salivation, cellular secretions, memory extinction and consolidation, temperature, pain, store-operated calcium entry, thermosensation and functionality of the nervous system. Here we choose to look at the evidence that decisively shows how TRP channels modulate human neuron plasticity as it relates to the molecular neurobiology of sleep/circadian rhythm. There are numerous model organisms of sleep and circadian rhythm that are the results of the absence or genetic manipulation of the non-specific cationic TRP channels. Drosophila and mice that have had their TRP channels genetically ablated or manipulated show strong evidence of changes in sleep duration, sleep activity, circadian rhythm and response to temperature, noxious odours and pattern of activity during both sleep and wakefulness along with cardiovascular and respiratory function during sleep. Indeed the role of TRP channels in regulating sleep and circadian rhythm is very interesting considering the parallel roles of TRP channels in thermoregulation and thermal response with concomitant responses in growth and degradation of neurites, peripheral nerves and neuronal brain networks. TRP channels provide evidence of an ability to create, regulate and modify our sleep and circadian rhythm in a wide array of physiological and pathophysiological conditions. In the current review, we summarize previous results and novel recent advances in the understanding of calcium ion entry via TRP channels in different sleep and circadian rhythm conditions. We discuss the role of TRP channels in sleep and circadian disorders.
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Affiliation(s)
- Geoffrey Woodard
- Department of PsychiatryUniformed Services University of Health SciencesBethesdaMarylandUSA
| | - Juan A. Rosado
- Department of PhysiologyUniversity of ExtremaduraCaceresSpain
| | - He Li
- Department of PsychiatryUniformed Services University of Health SciencesBethesdaMarylandUSA
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2
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Chen W, Zhong W, Yu L, Lin X, Xie J, Liu Z. A Drosophila Model Reveals the Potential Role for mtt in Retinal Disease. Int J Mol Sci 2024; 25:899. [PMID: 38255972 PMCID: PMC10815649 DOI: 10.3390/ijms25020899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/03/2024] [Accepted: 01/06/2024] [Indexed: 01/24/2024] Open
Abstract
Congenital stationary night blindness (CSNB) is a genetically heterogeneous inherited retinal disorder, caused by over 300 mutations in 17 different genes. While there are numerous fly models available for simulating ocular diseases, most are focused on mimicking retinitis pigmentosa (RP), with animal models specifically addressing CSNB limited to mammals. Here, we present a CSNB fly model associated with the mtt gene, utilizing RNA interference (RNAi) to silence the mtt gene in fly eyes (homologous to the mammalian GRM6 gene) and construct a CSNB model. Through this approach, we observed significant defects in the eye structure and function upon reducing mtt expression in fly eyes. This manifested as disruptions in the compound eye lens structure and reduced sensitivity to light responses. These results suggest a critical role for mtt in the function of fly adult eyes. Interestingly, we found that the mtt gene is not expressed in the photoreceptor neurons of adult flies but is localized to the inner lamina neurons. In summary, these results underscore the crucial involvement of mtt in fly retinal function, providing a framework for understanding the pathogenic mechanisms of CSNB and facilitating research into potential therapeutic interventions.
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Affiliation(s)
- Wenfeng Chen
- Institute of Life Sciences, College of Biological Science and Engineering, Fuzhou University, Fuzhou 350108, China
| | - Wenmiao Zhong
- Institute of Life Sciences, College of Biological Science and Engineering, Fuzhou University, Fuzhou 350108, China
| | - Lingqi Yu
- Institute of Life Sciences, College of Biological Science and Engineering, Fuzhou University, Fuzhou 350108, China
| | - Xiang Lin
- Institute of Life Sciences, College of Biological Science and Engineering, Fuzhou University, Fuzhou 350108, China
| | - Jiayu Xie
- School of Medicine, Chongqing University, Chongqing 400044, China;
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China
| | - Zhenxing Liu
- State Key Laboratory of Resource Insects, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China
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3
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Karthikeyan R, Davies WI, Gunhaga L. Non-image-forming functional roles of OPN3, OPN4 and OPN5 photopigments. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2023. [DOI: 10.1016/j.jpap.2023.100177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023] Open
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4
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Križaj D, Cordeiro S, Strauß O. Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration. Prog Retin Eye Res 2023; 92:101114. [PMID: 36163161 PMCID: PMC9897210 DOI: 10.1016/j.preteyeres.2022.101114] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 08/03/2022] [Accepted: 08/08/2022] [Indexed: 02/05/2023]
Abstract
Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.
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Affiliation(s)
- David Križaj
- Departments of Ophthalmology, Neurobiology, and Bioengineering, University of Utah, Salt Lake City, USA
| | - Soenke Cordeiro
- Institute of Physiology, Faculty of Medicine, Christian-Albrechts-University Kiel, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a Corporate Member of Freie Universität, Humboldt-University, The Berlin Institute of Health, Berlin, Germany.
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5
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Contreras E, Nobleman AP, Robinson PR, Schmidt TM. Melanopsin phototransduction: beyond canonical cascades. J Exp Biol 2021; 224:273562. [PMID: 34842918 PMCID: PMC8714064 DOI: 10.1242/jeb.226522] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Melanopsin is a visual pigment that is expressed in a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs). It is involved in regulating non-image forming visual behaviors, such as circadian photoentrainment and the pupillary light reflex, while also playing a role in many aspects of image-forming vision, such as contrast sensitivity. Melanopsin was initially discovered in the melanophores of the skin of the frog Xenopus, and subsequently found in a subset of ganglion cells in rat, mouse and primate retinas. ipRGCs were initially thought to be a single retinal ganglion cell population, and melanopsin was thought to activate a single, invertebrate-like Gq/transient receptor potential canonical (TRPC)-based phototransduction cascade within these cells. However, in the 20 years since the discovery of melanopsin, our knowledge of this visual pigment and ipRGCs has expanded dramatically. Six ipRGC subtypes have now been identified in the mouse, each with unique morphological, physiological and functional properties. Multiple subtypes have also been identified in other species, suggesting that this cell type diversity is a general feature of the ipRGC system. This diversity has led to a renewed interest in melanopsin phototransduction that may not follow the canonical Gq/TRPC cascade in the mouse or in the plethora of other organisms that express the melanopsin photopigment. In this Review, we discuss recent findings and discoveries that have challenged the prevailing view of melanopsin phototransduction as a single pathway that influences solely non-image forming functions.
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Affiliation(s)
- Ely Contreras
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA,Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL 60208, USA
| | - Alexis P. Nobleman
- University of Maryland Baltimore County, Department of Biological Sciences, Baltimore, MD 21250, USA,Section on Light and Circadian Rhythms (SLCR), National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Phyllis R. Robinson
- University of Maryland Baltimore County, Department of Biological Sciences, Baltimore, MD 21250, USA,Authors for correspondence (; )
| | - Tiffany M. Schmidt
- Department of Neurobiology, Northwestern University, Evanston, IL 60208, USA,Department of Ophthalmology, Feinberg School of Medicine, Chicago, IL 60611, USA,Authors for correspondence (; )
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Estevez-Fregoso E, Farfán-García ED, García-Coronel IH, Martínez-Herrera E, Alatorre A, Scorei RI, Soriano-Ursúa MA. Effects of boron-containing compounds in the fungal kingdom. J Trace Elem Med Biol 2021; 65:126714. [PMID: 33453473 DOI: 10.1016/j.jtemb.2021.126714] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 12/10/2020] [Accepted: 01/04/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND The number of known boron-containing compounds (BCCs) is increasing due to their identification in nature and innovative synthesis procedures. Their effects on the fungal kingdom are interesting, and some of their mechanisms of action have recently been elucidated. METHODS In this review, scientific reports from relevant chemistry and biomedical databases were collected and analyzed. RESULTS It is notable that several BCC actions in fungi induce social and economic benefits for humans. In fact, boric acid was traditionally used for multiple purposes, but some novel synthetic BCCs are effective antifungal agents, particularly in their action against pathogen species, and some were recently approved for use in humans. Moreover, most reports testing BCCs in fungal species suggest a limiting effect of these compounds on some vital reactions. CONCLUSIONS New BCCs have been synthesized and tested for innovative technological and biomedical emerging applications, and new interest is developing for discovering new strategic compounds that can act as environmental or wood protectors, as well as antimycotic agents that let us improve food acquisition and control some human infections.
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Affiliation(s)
- Elizabeth Estevez-Fregoso
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, Mexico
| | - Eunice D Farfán-García
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, Mexico.
| | - Itzel H García-Coronel
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, Mexico; Unidad de Investigación, Hospital Regional de Alta Especialidad Ixtapaluca, Carretera Federal México-Puebla km 34.5, C.P. 56530, Ixtapaluca, State of Mexico, Mexico
| | - Erick Martínez-Herrera
- Unidad de Investigación, Hospital Regional de Alta Especialidad Ixtapaluca, Carretera Federal México-Puebla km 34.5, C.P. 56530, Ixtapaluca, State of Mexico, Mexico
| | - Alberto Alatorre
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, Mexico
| | - Romulus I Scorei
- BioBoron Research Institute, Dunarii 31B Street, 207465, Podari, Romania
| | - Marvin A Soriano-Ursúa
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón, 11340, Mexico.
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Canonical transient receptor potential channels and their modulators: biology, pharmacology and therapeutic potentials. Arch Pharm Res 2021; 44:354-377. [PMID: 33763843 PMCID: PMC7989688 DOI: 10.1007/s12272-021-01319-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 03/14/2021] [Indexed: 12/17/2022]
Abstract
Canonical transient receptor potential channels (TRPCs) are nonselective, high calcium permeability cationic channels. The TRPCs family includes TRPC1, TRPC2, TRPC3, TRPC4, TRPC5, TRPC6, and TRPC7. These channels are widely expressed in the cardiovascular and nervous systems and exist in many other human tissues and cell types, playing several crucial roles in the human physiological and pathological processes. Hence, the emergence of TRPCs modulators can help investigate these channels’ applications in health and disease. It is worth noting that the TRPCs subfamilies have structural and functional similarities, which presents a significant difficulty in screening and discovering of TRPCs modulators. In the past few years, only a limited number of selective modulators of TRPCs were detected; thus, additional research on more potent and more selective TRPCs modulators is needed. The present review focuses on the striking desired therapeutic effects of TRPCs modulators, which provides intel on the structural modification of TRPCs modulators and further pharmacological research. Importantly, TRPCs modulators can significantly facilitate future studies of TRPCs and TRPCs related diseases.
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Thapak P, Khare P, Bishnoi M, Sharma SS. Neuroprotective Effect of 2-Aminoethoxydiphenyl Borate (2-APB) in Amyloid β-Induced Memory Dysfunction: A Mechanistic Study. Cell Mol Neurobiol 2020; 42:1211-1223. [PMID: 33219878 DOI: 10.1007/s10571-020-01012-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 11/13/2020] [Indexed: 02/08/2023]
Abstract
β-Amyloid (Aβ) peptide is a characteristic feature of Alzheimer's disease (AD) and accumulation of Aβ is associated with loss of synaptic plasticity and neuronal cell death. Aggregation of Aβ initiates numerous molecular signalling pathways leading to oxidative stress, mitochondrial dysfunction as well as an imbalance of calcium ion influx homeostasis. Recently, it has been shown that transient receptor potential melastatin 2 (TRPM2), a non-selective calcium-permeable cation channel has been postulated to play a vital role in the neuronal death, indicating the potential of TRPM2 inhibition in CNS disease. In this study, neuroprotective potential of 2-aminoethoxydiphenyl borate (2-APB), a broad-spectrum calcium channels blocker was investigated in Aβ-induced memory deficits in rats. In addition, effect of 2-APB on TRPM2 channels gene and protein expressions and also on calcium and memory related proteins was investigated in the hippocampus. Intracerebroventricular (I.C.V.) administration of Aβ (Aβ25-35, 10 μg) markedly induced cognitive impairment and upregulation of mRNA and protein expression of TRPM2 in the hippocampus. In addition, AChE activity was also increased in the cortex of the Aβ administered animals. Three-week treatment with 2-APB led to the down-regulation of TRPM2 mRNA and protein expression in the hippocampus and also improved the cognitive functions which was evident from the behavioral parameters. Moreover, 2-APB treatment also increased the calcium and memory associated proteins namely p-CaMKII, p-GSK-3β, p-CREB and PSD-95 in the hippocampus and reduced the mRNA level of calcium buffering proteins and calcineurin A (PPP3CA) in the hippocampus. Furthermore, 2-APB treatment significantly reduced the AChE activity in the cortex. Thus, our findings suggest the neuroprotective effect of 2-APB in Aβ-induced cognitive impairment.
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Affiliation(s)
- Pavan Thapak
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar, Mohali, Punjab, 160062, India
| | - Pragyanshu Khare
- National Agri-Food Biotechnology Institute (NABI), S.A.S. Nagar, Mohali, Punjab, India
| | - Mahendra Bishnoi
- National Agri-Food Biotechnology Institute (NABI), S.A.S. Nagar, Mohali, Punjab, India
| | - Shyam Sunder Sharma
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar, Mohali, Punjab, 160062, India.
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9
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Foster RG, Hughes S, Peirson SN. Circadian Photoentrainment in Mice and Humans. BIOLOGY 2020; 9:biology9070180. [PMID: 32708259 PMCID: PMC7408241 DOI: 10.3390/biology9070180] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 07/03/2020] [Accepted: 07/05/2020] [Indexed: 12/26/2022]
Abstract
Light around twilight provides the primary entrainment signal for circadian rhythms. Here we review the mechanisms and responses of the mouse and human circadian systems to light. Both utilize a network of photosensitive retinal ganglion cells (pRGCs) expressing the photopigment melanopsin (OPN4). In both species action spectra and functional expression of OPN4 in vitro show that melanopsin has a λmax close to 480 nm. Anatomical findings demonstrate that there are multiple pRGC sub-types, with some evidence in mice, but little in humans, regarding their roles in regulating physiology and behavior. Studies in mice, non-human primates and humans, show that rods and cones project to and can modulate the light responses of pRGCs. Such an integration of signals enables the rods to detect dim light, the cones to detect higher light intensities and the integration of intermittent light exposure, whilst melanopsin measures bright light over extended periods of time. Although photoreceptor mechanisms are similar, sensitivity thresholds differ markedly between mice and humans. Mice can entrain to light at approximately 1 lux for a few minutes, whilst humans require light at high irradiance (>100’s lux) and of a long duration (>30 min). The basis for this difference remains unclear. As our retinal light exposure is highly dynamic, and because photoreceptor interactions are complex and difficult to model, attempts to develop evidence-based lighting to enhance human circadian entrainment are very challenging. A way forward will be to define human circadian responses to artificial and natural light in the “real world” where light intensity, duration, spectral quality, time of day, light history and age can each be assessed.
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10
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Ko GYP. Circadian regulation in the retina: From molecules to network. Eur J Neurosci 2020; 51:194-216. [PMID: 30270466 PMCID: PMC6441387 DOI: 10.1111/ejn.14185] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Revised: 08/16/2018] [Accepted: 08/20/2018] [Indexed: 12/14/2022]
Abstract
The mammalian retina is the most unique tissue among those that display robust circadian/diurnal oscillations. The retina is not only a light sensing tissue that relays light information to the brain, it has its own circadian "system" independent from any influence from other circadian oscillators. While all retinal cells and retinal pigment epithelium (RPE) possess circadian oscillators, these oscillators integrate by means of neural synapses, electrical coupling (gap junctions), and released neurochemicals (such as dopamine, melatonin, adenosine, and ATP), so the whole retina functions as an integrated circadian system. Dysregulation of retinal clocks not only causes retinal or ocular diseases, it also impacts the circadian rhythm of the whole body, as the light information transmitted from the retina entrains the brain clock that governs the body circadian rhythms. In this review, how circadian oscillations in various retinal cells are integrated, and how retinal diseases affect daily rhythms.
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Affiliation(s)
- Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas
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11
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Abstract
The pupillary light reflex (PLR) describes the constriction and subsequent dilation of the pupil in response to light as a result of the antagonistic actions of the iris sphincter and dilator muscles. Since these muscles are innervated by the parasympathetic and sympathetic nervous systems, respectively, different parameters of the PLR can be used as indicators for either sympathetic or parasympathetic modulation. Thus, the PLR provides an important metric of autonomic nervous system function that has been exploited for a wide range of clinical applications. Measurement of the PLR using dynamic pupillometry is now an established quantitative, non-invasive tool in assessment of traumatic head injuries. This review examines the more recent application of dynamic pupillometry as a diagnostic tool for a wide range of clinical conditions, varying from neurodegenerative disease to exposure to toxic chemicals, as well as its potential in the non-invasive diagnosis of infectious disease.
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Affiliation(s)
- Charlotte A Hall
- Research Centre for Topical Drug Delivery and Toxicology, University of Hertfordshire, Hatfield SP10 1JX, UK.
| | - Robert P Chilcott
- Research Centre for Topical Drug Delivery and Toxicology, University of Hertfordshire, Hatfield SP10 1JX, UK.
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12
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Detwiler PB. Phototransduction in Retinal Ganglion Cells. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2018; 91:49-52. [PMID: 29599657 PMCID: PMC5872641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The mammalian retina contains a small number of retinal ganglion cells that express melanopsin, a retinal based visual pigment, and generate a depolarizing response to light in the absence of rod and cone driven synaptic input; hence they are referred to as intrinsically photosensitive retinal ganglion cells (ipRGCs). They have been shown to be comprised of a number of sub-types and to provide luminance information that participates primarily in a variety of non-imaging forming visual functions. Here I review what is currently known about the cascade of events that couple the photoisomerization of melanopsin to the opening of a non-selective cation channel. While these events conform in a general sense to the prevailing model for invertebrate phototransduction, in which visual pigment signals through a G protein of the Gq class and a phospholipase C cascade to open a TRPC type ion channel, none of the molecular elements in the melanopsin transduction process have been unequivocally identified. This has given rise to the possibility that the underlying mechanism responsible for intrinsic photosensitivity is not same in all ipRGC sub-types and to the recognition that signal transduction in ipRGCs is more complex than originally thought.
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Affiliation(s)
- Peter B. Detwiler
- University of Washington, School of Medicine, Department of Physiology and Biophysics
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13
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Benedetto MM, Guido ME, Contin MA. Non-Visual Photopigments Effects of Constant Light-Emitting Diode Light Exposure on the Inner Retina of Wistar Rats. Front Neurol 2017; 8:417. [PMID: 28871236 PMCID: PMC5566984 DOI: 10.3389/fneur.2017.00417] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 07/31/2017] [Indexed: 12/31/2022] Open
Abstract
The retina is part of the central nervous system specially adapted to capture light photons and transmit this information to the brain through photosensitive retinal cells involved in visual and non-visual activities. However, excessive light exposure may accelerate genetic retinal diseases or induce photoreceptor cell (PRC) death, finally leading to retinal degeneration (RD). Light pollution (LP) caused by the characteristic use of artificial light in modern day life may accelerate degenerative diseases or promote RD and circadian desynchrony. We have developed a working model to study RD mechanisms in a low light environment using light-emitting diode (LED) sources, at constant or long exposure times under LP conditions. The mechanism of PRC death is still not fully understood. Our main goal is to study the biochemical mechanisms of RD. We have previously demonstrated that constant light (LL) exposure to white LED produces a significant reduction in the outer nuclear layer (ONL) by classical PRC death after 7 days of LL exposure. The PRCs showed TUNEL-positive labeling and a caspase-3-independent mechanism of cell death. Here, we investigate whether constant LED exposure affects the inner-retinal organization and structure, cell survival and the expression of photopigments; in particular we look into whether constant LED exposure causes the death of retinal ganglion cells (RGCs), of intrinsically photosensitive RGCs (ipRGCs), or of other inner-retinal cells. Wistar rats exposed to 200 lx of LED for 2 to 8 days (LL 2 and LL 8) were processed for histological and protein. The results show no differences in the number of nucleus or TUNEL positive RGCs nor inner structural damage in any of LL groups studied, indicating that LL exposure affects ONL but does not produce RGC death. However, the photopigments melanopsin (OPN4) and neuropsin (OPN5) expressed in the inner retina were seen to modify their localization and expression during LL exposure. Our findings suggest that constant light during several days produces retinal remodeling and ONL cell death as well as significant changes in opsin expression in the inner nuclear layer.
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Affiliation(s)
- María M Benedetto
- Facultad de Ciencias Químicas, Departamento de Química Biológica "Dr. Ranwel Caputto", Universidad Nacional de Córdoba, Córdoba, Argentina.,Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Mario E Guido
- Facultad de Ciencias Químicas, Departamento de Química Biológica "Dr. Ranwel Caputto", Universidad Nacional de Córdoba, Córdoba, Argentina.,Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - María A Contin
- Facultad de Ciencias Químicas, Departamento de Química Biológica "Dr. Ranwel Caputto", Universidad Nacional de Córdoba, Córdoba, Argentina.,Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina
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Moraes MN, Mezzalira N, de Assis LVM, Menaker M, Guler A, Castrucci AML. TRPV1 participates in the activation of clock molecular machinery in the brown adipose tissue in response to light-dark cycle. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:324-335. [DOI: 10.1016/j.bbamcr.2016.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 11/07/2016] [Accepted: 11/12/2016] [Indexed: 02/02/2023]
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15
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Retinal gap junctions are involved in rhythmogenesis of neuronal activity at remote locations – Study on infra-slow oscillations in the rat olivary pretectal nucleus. Neuroscience 2016; 339:150-161. [DOI: 10.1016/j.neuroscience.2016.09.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 09/21/2016] [Accepted: 09/21/2016] [Indexed: 12/21/2022]
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16
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Shirzad-Wasei N, DeGrip WJ. Heterologous expression of melanopsin: Present, problems and prospects. Prog Retin Eye Res 2016; 52:1-21. [DOI: 10.1016/j.preteyeres.2016.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/25/2016] [Accepted: 02/01/2016] [Indexed: 12/12/2022]
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Orlowska-Feuer P, Allen AE, Storchi R, Szkudlarek HJ, Lewandowski MH. The contribution of inner and outer retinal photoreceptors to infra-slow oscillations in the rat olivary pretectal nucleus. Eur J Neurosci 2016; 43:823-33. [PMID: 26804179 DOI: 10.1111/ejn.13184] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 01/12/2016] [Accepted: 01/18/2016] [Indexed: 12/28/2022]
Abstract
A subpopulation of olivary pretectal nucleus (OPN) neurons discharges action potentials in an oscillatory manner, with a period of approximately two minutes. This 'infra-slow' oscillatory activity depends on synaptic excitation originating in the retina. Signals from rod-cone photoreceptors reach the OPN via the axons of either classic retinal ganglion cells or intrinsically photosensitive retinal ganglion cells (ipRGCs), which use melanopsin for photon capturing. Although both cell types convey light information, their physiological functions differ considerably. The aim of the present study was to disentangle how rod-cone and melanopsin photoresponses contribute to generation of oscillatory activity. Pharmacological manipulations of specific phototransduction cascades were used whilst recording extracellular single-unit activity in the OPN of anaesthetized rats. The results show that under photopic conditions (bright light), ipRGCs play a major role in driving infra-slow oscillations, as blocking melanopsin phototransmission abolishes or transiently disturbs oscillatory firing of the OPN neurons. On the other hand, blocking rod-cone phototransmission does not change firing patterns in photopic conditions. However, under mesopic conditions (moderate light), when melanopsin phototransmission is absent, blocking rod-cone signalling causes disturbances or even the disappearance of oscillations implying that classic photoreceptors are of greater importance under moderate light. Evidence is provided that all photoreceptors are required for the generation of oscillations in the OPN, although their roles in driving the rhythm are determined by the lighting conditions, consistent with their relative sensitivities. The results further suggest that maintained retinal activity is crucial to observe infra-slow oscillatory activity in the OPN.
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Affiliation(s)
- Patrycja Orlowska-Feuer
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
| | - Annette E Allen
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Riccardo Storchi
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Hanna J Szkudlarek
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
| | - Marian H Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland
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Hughes S, Jagannath A, Rodgers J, Hankins MW, Peirson SN, Foster RG. Signalling by melanopsin (OPN4) expressing photosensitive retinal ganglion cells. Eye (Lond) 2016; 30:247-54. [PMID: 26768919 DOI: 10.1038/eye.2015.264] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 11/23/2015] [Indexed: 12/17/2022] Open
Abstract
Over the past two decades there have been significant advances in our understanding of both the anatomy and function of the melanopsin system. It has become clear that rather than acting as a simple irradiance detector the melanopsin system is in fact far more complicated. The range of behavioural systems known to be influenced by melanopsin activity is increasing with time, and it is now clear that melanopsin contributes not only to multiple non-image forming systems but also has a role in visual pathways. How melanopsin is capable of driving so many different behaviours is unclear, but recent evidence suggests that the answer may lie in the diversity of melanopsin light responses and the functional specialisation of photosensitive retinal ganglion cell (pRGC) subtypes. In this review, we shall overview the current understanding of the melanopsin system, and evaluate the evidence for the hypothesis that individual pRGC subtypes not only perform specific roles, but are functionally specialised to do so. We conclude that while, currently, the available data somewhat support this hypothesis, we currently lack the necessary detail to fully understand how the functional diversity of pRGC subtypes correlates with different behavioural responses, and ultimately why such complexity is required within the melanopsin system. What we are lacking is a cohesive understanding of how light responses differ between the pRGC subtypes (based not only on anatomical classification but also based on their site of innervation); how these diverse light responses are generated, and most importantly how these responses relate to the physiological functions they underpin.
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Affiliation(s)
- S Hughes
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - A Jagannath
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - J Rodgers
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - M W Hankins
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - S N Peirson
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - R G Foster
- Nuffield Laboratory of Ophthalmology (Nuffield Department of Clinical Neurosciences), Sleep and Circadian Neuroscience Institute, University of Oxford, John Radcliffe Hospital, Oxford, UK
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Transient Receptor Potential Canonical 7 (TRPC7), a Calcium (Ca(2+)) Permeable Non-selective Cation Channel. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 898:251-64. [PMID: 27161232 DOI: 10.1007/978-3-319-26974-0_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Transient receptor potential canonical subfamily, member 7 (TRPC7) is the most recently identified member of the TRPC family of Ca(2+)-permeable non-selective cation channels. The gene encoding the TRPC7 channel plasma membrane protein was first cloned from mouse brain. TRPC7 mRNA and protein have been detected in cell types derived from multiple organ systems from various species including humans. Gq-coupled protein receptor activation is the predominant mode of TRPC7 activation. Lipid metabolites involved in the phospholipase C (PLC) signaling pathway, including diacylglycerol (DAG) and its precursor the phosphatidylinositol-4,5-bisphosphate (PIP2), have been shown to be direct regulators of TRPC7 channel. TRPC7 channels have been linked to the regulation of various cellular functions however, the depth of our understanding of TRPC7 channel function and regulation is limited in comparison to other TRP channel family members. This review takes a historical look at our current knowledge of TRPC7 mechanisms of activation and its role in cellular physiology and pathophysiology.
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20
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Poletini MO, Moraes MN, Ramos BC, Jerônimo R, Castrucci AMDL. TRP channels: a missing bond in the entrainment mechanism of peripheral clocks throughout evolution. Temperature (Austin) 2015; 2:522-34. [PMID: 27227072 PMCID: PMC4843991 DOI: 10.1080/23328940.2015.1115803] [Citation(s) in RCA: 260] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 10/10/2015] [Accepted: 10/29/2015] [Indexed: 11/03/2022] Open
Abstract
Circadian rhythm may be understood as a temporal organization that works to orchestrate physiological processes and behavior in a period of approximately 24 h. Because such temporal organization has evolved in the presence of predictable environmental clues, such as day length, tides, seasons, and temperature, the organism has confronted the natural selection in highly precise intervals of opportunities and risks, generating temporal programs and resetting mechanisms, which are well conserved among different taxa of animals. The present review brings some evidence of how these programs may have co-evolved in systems able to deal with 2 or more environmental clues, and how they similarly function in different group of animals, stressing how important temperature and light were to establish the temporal organizations. For example, melanopsin and rhodopsin, photopigments present respectively in circadian and visual photoreceptors, are required for temperature discrimination in Drosophila melanogaster. These pigments may signal light and temperature via activation of cationic membrane channel, named transient-receptor potential channel (TRP). In fact, TRPs have been suggested to function as thermal sensor for various groups of animals. Another example is the clock machinery at the molecular level. A set of very-well conserved proteins, known as clock proteins, function as transcription factors in positive and negative auto-regulatory loops generating circadian changes of their expression, and of clock-controlled genes. Similar molecular machinery is present in organisms as diverse as cyanobacteria (Synechococcus), fungi (Neurospora), insects (Drosophila), and vertebrates including humans.
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Affiliation(s)
- Maristela O Poletini
- Department of Physiology and Biophysics; Institute of Biological Sciences; Federal University of Minas Gerais ; Belo Horizonte, Brazil
| | - Maria Nathália Moraes
- Department of Physiology; Institute of Biosciences; University of Sao Paulo ; São Paulo, Brazil
| | - Bruno César Ramos
- Department of Physiology; Institute of Biosciences; University of Sao Paulo ; São Paulo, Brazil
| | - Rodrigo Jerônimo
- Department of Physiology; Institute of Biosciences; University of Sao Paulo ; São Paulo, Brazil
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Calcium activates the light-dependent conductance in melanopsin-expressing photoreceptors of amphioxus. Proc Natl Acad Sci U S A 2015; 112:7845-50. [PMID: 26056310 DOI: 10.1073/pnas.1420265112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Melanopsin, the photopigment of the "circadian" receptors that regulate the biological clock and the pupillary reflex in mammals, is homologous to invertebrate rhodopsins. Evidence supporting the involvement of phosphoinositides in light-signaling has been garnered, but the downstream effectors that control the light-dependent conductance remain unknown. Microvillar photoreceptors of the primitive chordate amphioxus also express melanopsin and transduce light via phospholipase-C, apparently not acting through diacylglycerol. We therefore examined the role of calcium in activating the photoconductance, using simultaneous, high time-resolution measurements of membrane current and Ca(2+) fluorescence. The light-induced calcium rise precedes the onset of the photocurrent, making it a candidate in the activation chain. Moreover, photolysis of caged Ca elicits an inward current of similar size, time course and pharmacology as the physiological photoresponse, but with a much shorter latency. Internally released calcium thus emerges as a key messenger to trigger the opening of light-dependent channels in melanopsin-expressing microvillar photoreceptors of early chordates.
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22
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Hughes S, Jagannath A, Hankins MW, Foster RG, Peirson SN. Photic regulation of clock systems. Methods Enzymol 2014; 552:125-43. [PMID: 25707275 DOI: 10.1016/bs.mie.2014.10.018] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Circadian rhythms in physiology and behavior provide a selective advantage by enabling organisms to anticipate rhythmic changes in their environment. These rhythms are based upon a molecular clock generated via an intracellular transcriptional-translational feedback loop involving a number of key clock genes. However, to be of practical use, circadian rhythms need to be entrained to the external environment. In mammals, the primary signal for entrainment is light detected by the photoreceptors of the eye. Research on the mechanisms of photic entrainment has identified a novel photoreceptor system in the retina, consisting of photosensitive retinal ganglion cells expressing the photopigment melanopsin. Light input from these retinal photoreceptors reaches the master circadian pacemaker in the suprachiasmatic nuclei (SCN) via the retinohypothalamic tract, where it then interacts with the molecular clock to bring about entrainment. This chapter focuses on the retinal photoreceptors mediating entrainment, and how light information from the retina is transmitted to the SCN, before detailing recent advances in our understanding of how the molecular clock within the SCN is regulated by light input. Finally, the primary assays that have been used to measure photic entrainment are described.
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Affiliation(s)
- Steven Hughes
- Sleep and Circadian Institute (SCNi), Nuffield Department of Clinical Neurosciences (Nuffield Laboratory of Ophthalmology), University of Oxford, Oxford, United Kingdom
| | - Aarti Jagannath
- Sleep and Circadian Institute (SCNi), Nuffield Department of Clinical Neurosciences (Nuffield Laboratory of Ophthalmology), University of Oxford, Oxford, United Kingdom
| | - Mark W Hankins
- Sleep and Circadian Institute (SCNi), Nuffield Department of Clinical Neurosciences (Nuffield Laboratory of Ophthalmology), University of Oxford, Oxford, United Kingdom
| | - Russell G Foster
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
| | - Stuart N Peirson
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
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23
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Fahrenkrug J, Falktoft B, Georg B, Hannibal J, Kristiansen SB, Klausen TK. Phosphorylation of rat melanopsin at Ser-381 and Ser-398 by light/dark and its importance for intrinsically photosensitive ganglion cells (ipRGCs) cellular Ca2+ signaling. J Biol Chem 2014; 289:35482-93. [PMID: 25378407 PMCID: PMC4271233 DOI: 10.1074/jbc.m114.586529] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The G protein-coupled light-sensitive receptor melanopsin is involved in non-image-forming light responses including circadian timing. The predicted secondary structure of melanopsin indicates a long cytoplasmic tail with many potential phosphorylation sites. Using bioinformatics, we identified a number of amino acids with a high probability of being phosphorylated. We generated antibodies against melanopsin phosphorylated at Ser-381 and Ser-398, respectively. The antibody specificity was verified by immunoblotting and immunohistochemical staining of HEK-293 cells expressing rat melanopsin mutated in Ser-381 or Ser-398. Using the antibody recognizing phospho-Ser-381 melanopsin, we demonstrated by immunoblotting and immunohistochemical staining in HEK-293 cells expressing rat melanopsin that the receptor is phosphorylated in this position during the dark and dephosphorylated when light is turned on. On the contrary, we found that melanopsin at Ser-398 was unphosphorylated in the dark and became phosphorylated after light stimulation. The light-induced changes in phosphorylation at both Ser-381 and Ser-398 were rapid and lasted throughout the 4-h experimental period. Furthermore, phosphorylation at Ser-381 and Ser-398 was independent of each other. The changes in phosphorylation were confirmed in vivo by immunohistochemical staining of rat retinas during light and dark. We further demonstrated that mutation of Ser-381 and Ser-398 in melanopsin-expressing HEK-293 cells affected the light-induced Ca2+ response, which was significantly reduced as compared with wild type. Examining the light-evoked Ca2+ response in a melanopsin Ser-381 plus Ser-398 double mutant provided evidence that the phosphorylation events were independent.
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Affiliation(s)
- Jan Fahrenkrug
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Birgitte Falktoft
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Birgitte Georg
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Jens Hannibal
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Sarah B Kristiansen
- From the Department of Clinical Biochemistry, Faculty of Health Sciences, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark and
| | - Thomas K Klausen
- Department of Biology, Faculty of Science, University of Copenhagen, DK-2200 Copenhagen N, Denmark
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24
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Ryskamp DA, Redmon S, Jo AO, Križaj D. TRPV1 and Endocannabinoids: Emerging Molecular Signals that Modulate Mammalian Vision. Cells 2014; 3:914-38. [PMID: 25222270 PMCID: PMC4197638 DOI: 10.3390/cells3030914] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 08/27/2014] [Accepted: 09/05/2014] [Indexed: 01/18/2023] Open
Abstract
Transient Receptor Potential Vanilloid 1 (TRPV1) subunits form a polymodal cation channel responsive to capsaicin, heat, acidity and endogenous metabolites of polyunsaturated fatty acids. While originally reported to serve as a pain and heat detector in the peripheral nervous system, TRPV1 has been implicated in the modulation of blood flow and osmoregulation but also neurotransmission, postsynaptic neuronal excitability and synaptic plasticity within the central nervous system. In addition to its central role in nociception, evidence is accumulating that TRPV1 contributes to stimulus transduction and/or processing in other sensory modalities, including thermosensation, mechanotransduction and vision. For example, TRPV1, in conjunction with intrinsic cannabinoid signaling, might contribute to retinal ganglion cell (RGC) axonal transport and excitability, cytokine release from microglial cells and regulation of retinal vasculature. While excessive TRPV1 activity was proposed to induce RGC excitotoxicity, physiological TRPV1 activity might serve a neuroprotective function within the complex context of retinal endocannabinoid signaling. In this review we evaluate the current evidence for localization and function of TRPV1 channels within the mammalian retina and explore the potential interaction of this intriguing nociceptor with endogenous agonists and modulators.
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Affiliation(s)
- Daniel A Ryskamp
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
| | - Sarah Redmon
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
| | - Andrew O Jo
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
| | - David Križaj
- Department of Ophthalmology & Visual Sciences, Moran Eye Institute, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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25
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Sodhi P, Hartwick ATE. Adenosine modulates light responses of rat retinal ganglion cell photoreceptors througha cAMP-mediated pathway. J Physiol 2014; 592:4201-20. [PMID: 25038240 DOI: 10.1113/jphysiol.2014.276220] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Adenosine is an established neuromodulator in the mammalian retina, with A1 adenosine receptors being especially prevalent in the innermost ganglion cell layer. Activation of A1 receptors causes inhibition of adenylate cyclase, decreases in intracellular cyclic AMP (cAMP) levels and inhibition of protein kinase A (PKA). In this work, our aim was to characterize the effects of adenosine on the light responses of intrinsically photosensitive retinal ganglion cells (ipRGCs) and to determine whether these photoreceptors are subject to neuromodulation through intracellular cAMP-related signalling pathways. Using multielectrode array recordings from postnatal and adult rat retinas, we demonstrated that adenosine significantly shortened the duration of ipRGC photoresponses and reduced the number of light-evoked spikes fired by these neurons. The effects were A1 adenosine receptor-mediated, and the expression of this receptor on melanopsin-containing ipRGCs was confirmed by calcium imaging experiments on isolated cells in purified cultures. While inhibition of the cAMP/PKA pathway by adenosine shortened ipRGC light responses, stimulation of this pathway with compounds such as forskolin had the opposite effect and lengthened the duration of ipRGC spiking. Our findings reveal that the modification of ipRGC photoresponses through a cAMP/PKA pathway is a general feature of rat ganglion cell photoreceptors, and this pathway can be inhibited through activation of A1 receptors by adenosine. As adenosine levels in the retina rise at night, adenosinergic modulation of ipRGCs may serve as an internal regulatory mechanism to limit transmission of nocturnal photic signals by ipRGCs to the brain. Targeting retinal A1 adenosine receptors for ipRGC inhibition represents a potential therapeutic target for sleep disorders and migraine-associated photophobia.
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Affiliation(s)
- Puneet Sodhi
- Department of Neuroscience, Ohio State University, Columbus, OH, 43210, USA
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26
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Hughes S, Jagannath A, Hickey D, Gatti S, Wood M, Peirson SN, Foster RG, Hankins MW. Using siRNA to define functional interactions between melanopsin and multiple G Protein partners. Cell Mol Life Sci 2014; 72:165-79. [PMID: 24958088 PMCID: PMC4282707 DOI: 10.1007/s00018-014-1664-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 05/10/2014] [Accepted: 06/02/2014] [Indexed: 12/13/2022]
Abstract
Melanopsin expressing photosensitive retinal ganglion cells (pRGCs) represent a third class of ocular photoreceptors and mediate a range of non-image forming responses to light. Melanopsin is a G protein coupled receptor (GPCR) and existing data suggest that it employs a membrane bound signalling cascade involving Gnaq/11 type G proteins. However, to date the precise identity of the Gα subunits involved in melanopsin phototransduction remains poorly defined. Here we show that Gnaq, Gna11 and Gna14 are highly co-expressed in pRGCs of the mouse retina. Furthermore, using RNAi based gene silencing we show that melanopsin can signal via Gnaq, Gna11 or Gna14 in vitro, and demonstrate that multiple members of the Gnaq/11 subfamily, including Gna14 and at least Gnaq or Gna11, can participate in melanopsin phototransduction in vivo and contribute to the pupillary light responses of mice lacking rod and cone photoreceptors. This diversity of G protein interactions suggests additional complexity in the melanopsin phototransduction cascade and may provide a basis for generating the diversity of light responses observed from pRGC subtypes.
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Affiliation(s)
- Steven Hughes
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
| | - Aarti Jagannath
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
- F. Hoffman La Roche, RED Research and Development, CNS DTA, Basel, Switzerland
| | - Doron Hickey
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
| | - Silvia Gatti
- F. Hoffman La Roche, RED Research and Development, CNS DTA, Basel, Switzerland
| | - Matthew Wood
- Department of Anatomy, Physiology and Genetics, University of Oxford, Le Gros Clark Building, South Parks Road, Oxford, OX1 3QX UK
| | - Stuart N. Peirson
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
| | - Russell G. Foster
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
| | - Mark W. Hankins
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, OX3 9DU UK
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Zhang X, Trebak M. Transient receptor potential canonical 7: a diacylglycerol-activated non-selective cation channel. Handb Exp Pharmacol 2014; 222:189-204. [PMID: 24756707 DOI: 10.1007/978-3-642-54215-2_8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Transient receptor potential canonical 7 (TRPC7) channel is the seventh member of the mammalian TRPC channel family. TRPC7 mRNA, protein, and channel activity have been detected in many tissues and organs from the mouse, rat, and human. TRPC7 has high sequence homology with TRPC3 and TRPC6, and all three channels are activated by membrane receptors that couple to isoforms of phospholipase C (PLC) and mediate non-selective cation currents. TRPC7, along with TRPC3 and TRPC6, can be activated by direct exogenous application of diacylglycerol (DAG) analogues and by pharmacological maneuvers that increase endogenous DAG in cells. TRPC7 shows distinct properties of activation, such as constitutive activity and susceptibility to negative regulation by extracellular Ca(2+) and by protein kinase C. TRPC7 can form heteromultimers with TRPC3 and TRPC6. Although TRPC7 remains one of the least studied TRPC channel, its role in various cell types and physiological and pathophysiological conditions is beginning to emerge.
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Affiliation(s)
- Xuexin Zhang
- Nanobioscience Constellation, The State University of New York (SUNY), College of Nanoscale Science and Engineering (CNSE), 257 Fuller Road, Albany, NY, 12203, USA
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28
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Narayanan KL, Subramaniam S, Bengston CP, Irmady K, Unsicker K, von Bohlen und Halbach O. Role of transient receptor potential channel 1 (TRPC1) in glutamate-induced cell death in the hippocampal cell line HT22. J Mol Neurosci 2013; 52:425-33. [PMID: 24242951 DOI: 10.1007/s12031-013-0171-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/31/2013] [Indexed: 02/06/2023]
Abstract
Transient receptor potential channel 1 (TRPC1; a cation channel activated by store depletion and/or through an intracellular messenger) is expressed in a variety of tissues, including the brain. To study the physiological function of TRPC1, we investigated the role of endogenously expressed TRPC1 in glutamate-induced cell death, using the murine hippocampal cell line HT22. Knocking down TRPC1 mRNA using TRPC1-shRNA or blocking of TRPC channels using 2-APB (≥200 μM) robustly attenuated glutamate-induced cell death after 24 h of incubation with 5 mM glutamate. Glutamate toxicity in HT22 cells seems to involve metabotropic glutamate receptor mGluR5 since MPEP (2-methyl-6-(phenylethynyl)-pyridine), an mGluR5 antagonist (≥100 μM), abrogated glutamate toxicity. Furthermore, a direct activation of mGluR5 by CHPG [(RS)-chloro-5-hydroxyphenylglycine; 100 μM or 300 μM] promoted HT22 cell death. TRPC1 knock-down markedly reduced CHPG-induced cell death. These observations suggest that glutamate-induced cell death in HT22 cells activates mGluR5 receptors, which significantly increases Ca(2+) influx through TRPC1 channels. TRPC1 knock-down prevented glutamate- and CHPG-induced cell death, suggesting that glutamate-induced toxicity in HT22 cells is mediated through TRPC1 channels and an mGluR5-dependent pathway. Together, this work provides evidence for a novel receptor activation pathway of TRPC1 in glutamate-induced toxicity.
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Affiliation(s)
- K Lakshmi Narayanan
- Department of Neurology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, 02129-4404, USA
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29
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Chen S, Fan Q, Gao X, Wang X, Huang R, Laties AM, Zhang X. Increased expression of the transient receptor potential cation channel 6 gene in patients with primary open-angle glaucoma. Clin Exp Ophthalmol 2013; 41:753-60. [PMID: 23566105 DOI: 10.1111/ceo.12111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Accepted: 02/22/2013] [Indexed: 12/19/2022]
Abstract
BACKGROUND The result of primary open-angle glaucoma is the loss of retinal ganglion cells. Transient receptor potential cation channel 6 is a pressure-related channel that may function in the survival of retinal ganglion cells. The purpose of this study was to evaluate the expression levels of the transient receptor potential cation channel 6 gene in patients with primary open-angle glaucoma. DESIGN Randomization study at Zhongshan Ophthalmic Center in China. PARTICIPANTS 80 primary open-angle glaucoma patients and 75 cataract patients recruited from Zhongshan Ophthalmic Center. METHODS Total RNA was extracted from the leukocytes of the peripheral blood collected. The levels of transient receptor potential cation channel 6-messenger RNA were determined by real-time polymerase chain reaction. Related factors including age, intraocular pressure, optic cup-to-disc ratio and visual field defect were analysed accordingly. MAIN OUTCOME MEASURES Clinical examination and the messenger RNA level. RESULTS The expression level of the transient receptor potential cation channel 6 gene in the leukocytes of primary open-angle glaucoma patients was two times higher when compared with control cataract patients. The gene expression level was also correlated with intraocular pressure and cup-to-disc ratio. Treatment with different anti-glaucoma drugs did not affect the gene expression. CONCLUSIONS Increasing expression levels of the transient receptor potential cation channel 6 gene in the blood accompanies chronic elevation of intraocular pressure in primary open-angle glaucoma and may serve as a genetic biomarker for primary open-angle glaucoma.
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Affiliation(s)
- Shida Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China
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30
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Adaptation to steady light by intrinsically photosensitive retinal ganglion cells. Proc Natl Acad Sci U S A 2013; 110:7470-5. [PMID: 23589882 DOI: 10.1073/pnas.1304039110] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Intrinsically photosensitive retinal ganglion cells (ipRGCs) are recently discovered photoreceptors in the mammalian eye. These photoreceptors mediate primarily nonimage visual functions, such as pupillary light reflex and circadian photoentrainment, which are generally expected to respond to the absolute light intensity. The classical rod and cone photoreceptors, on the other hand, mediate image vision by signaling contrast, accomplished by adaptation to light. Experiments by others have indicated that the ipRGCs do, in fact, light-adapt. We found the same but, in addition, have now quantified this light adaptation for the M1 ipRGC subtype. Interestingly, in incremental-flash-on-background experiments, the ipRGC's receptor current showed a flash sensitivity that adapted in background light according to the Weber-Fechner relation, well known to describe the adaptation behavior of rods and cones. Part of this light adaptation by ipRGCs appeared to be triggered by a Ca(2+) influx, in that the flash response elicited in the absence of extracellular Ca(2+) showed a normal rising phase but a slower decay phase, resulting in longer time to peak and higher sensitivity. There is, additionally, a prominent Ca(2+)-independent component of light adaptation not typically seen in rods and cones or in invertebrate rhabdomeric photoreceptors.
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Turner KL, Sontheimer H. KCa3.1 modulates neuroblast migration along the rostral migratory stream (RMS) in vivo. ACTA ACUST UNITED AC 2013; 24:2388-400. [PMID: 23585521 DOI: 10.1093/cercor/bht090] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
From the subventricular zone (SVZ), neuronal precursor cells (NPCs), called neuroblasts, migrate through the rostral migratory stream (RMS) to become interneurons in the olfactory bulb (OB). Ion channels regulate neuronal migration during development, yet their role in migration through the adult RMS is unknown. To address this question, we utilized Nestin-CreER(T2)/R26R-YFP mice to fluorescently label neuroblasts in the adult. Patch-clamp recordings from neuroblasts reveal K(+) currents that are sensitive to intracellular Ca(2+) levels and blocked by clotrimazole and TRAM-34, inhibitors of intermediate conductance Ca(2+)-activated K(+) (KCa3.1) channels. Immunolabeling and electrophysiology show KCa3.1 expression restricted to neuroblasts in the SVZ and RMS, but absent in OB neurons. Time-lapse confocal microscopy in situ showed inhibiting KCa3.1 prolonged the stationary phase of neuroblasts' saltatory migration, reducing migration speed by over 50%. Both migration and KCa3.1 currents could also be inhibited by blocking Ca(2+) influx via transient receptor potential (TRP) channels, which, together with positive immunostaining for transient receptor potential canonical 1 (TRPC1), suggest that TRP channels are an important Ca(2+) source modulating KCa3.1 activity. Finally, injecting TRAM-34 into Nestin-CreER(T2)/R26R-YFP mice significantly reduced the number of neuroblasts that reached the OB, suggesting an important role for KCa3.1 in vivo. These studies describe a previously unrecognized protein in migration of adult NPCs.
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Affiliation(s)
- Kathryn L Turner
- Department of Neurobiology and Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Harald Sontheimer
- Department of Neurobiology and Center for Glial Biology in Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Fan Q, Huang WB, Zhang XL. TRPC6: an underlying target for human glaucoma. Int J Ophthalmol 2012; 5:523-6. [PMID: 22937518 DOI: 10.3980/j.issn.2222-3959.2012.04.23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Accepted: 07/20/2012] [Indexed: 11/02/2022] Open
Abstract
Glaucoma is one of the leading causes of visual impairment and blindness worldwide. Of known risk factors for glaucoma, an increased in intraocular pressure is most highly correlated with glaucomatous damage. Irrespective of the cause, apoptosis of the retinal ganglion cells is the eventual outcome. It is widely accepted that glaucoma is a neurodegenerative disease that is strongly correlated with central nervous system disorders, such as Alzheimer's disease. These two disorders also share some similarities in pathogenic mechanisms. Recent studies suggest that the transient receptor potential canonical 6 channel could work together with brain-derived neurotrophic factor to promote neuron survival in brain and retina. In this study, we propose that transient receptor potential canonical 6 may contribute to the pathogenesis of human glaucoma and become a potential therapeutic target.
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Affiliation(s)
- Qian Fan
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-sen University, Guangzhou 510060, Guangdong Province, China
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33
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Drosophila TRP channels and animal behavior. Life Sci 2012; 92:394-403. [PMID: 22877650 DOI: 10.1016/j.lfs.2012.07.029] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/09/2012] [Accepted: 07/16/2012] [Indexed: 11/24/2022]
Abstract
Multiple classes of cell surface receptors and ion channels participate in the detection of changes in environmental stimuli, and thereby influence animal behavior. Among the many classes of ion channels, Transient Receptor Potential (TRP) cation channels are notable in contributing to virtually every sensory modality, and in controlling a daunting array of behaviors. TRP channels appear to be conserved in all metazoan organisms including worms, insects and humans. Flies encode 13 TRPs, most of which are expressed and function in sensory neurons, and impact behaviors ranging from phototaxis to thermotaxis, gravitaxis, the avoidance of noxious tastants and smells and proprioception. Multiple diseases result from defects in TRPs, and flies provide an excellent animal model for dissecting the mechanisms underlying "TRPopathies." Drosophila TRPs also function in the sensation of botanically derived insect repellents, and related TRPs in insect pests are potential targets for the development of improved repellents to combat insect-borne diseases.
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Pulido C, Malagón G, Ferrer C, Chen JK, Angueyra JM, Nasi E, Gomez MDP. The light-sensitive conductance of melanopsin-expressing Joseph and Hesse cells in amphioxus. ACTA ACUST UNITED AC 2012; 139:19-30. [PMID: 22200946 PMCID: PMC3250099 DOI: 10.1085/jgp.201110717] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two types of microvillar photoreceptors in the neural tube of amphioxus, an early chordate, sense light via melanopsin, the same photopigment as in “circadian” light detectors of higher vertebrates. Because in amphioxus melanopsin activates a Gq/phospholipase C cascade, like phototransduction in arthropods and mollusks, possible commonalities in the photoconductance were investigated. Unlike other microvillar photoreceptors, reversal of the photocurrent can only be attained upon replacement of extracellular Na+. In addition to Na+, Ca2+ is also permeant, as indicated by the fact that (a) in normal ionic conditions the photocurrent remains inward at Vm > ENa; (b) in Na-free solution a small residual inward photocurrent persists at Vm near resting level, provided that Ca is present; and (c) Vrev exhibits a modest shift with [Ca]o manipulations. The unusual reversal is accounted for by an uncommonly low permeability of the light-dependent channels to K+, as [K]o only marginally affects the photocurrent amplitude and its reversal. Lanthanum and ruthenium red (RuR), two TRP channel antagonists, reversibly suppress the response to photostimulation of moderate intensity; therefore, the melanopsin-initiated cascade may recruit ion channels of the same family as those of rhabdomeric photoreceptors. With brighter lights, blockage declines, so that both La3+ and RuR induce a right shift in the sensitivity curve without a reduction of its asymptote. Nonetheless, an effect on the transduction cascade, rather than the channels, was ruled out on the basis of the voltage dependency of the blockade and the lack of effects of intracellular application of the same substances. The mechanisms of action of these antagonists thus entail a state-dependent blockade, with a higher affinity for the channel in the closed conformation. Collectively, the results indicate a kinship of the light-sensitive channels of amphioxus with those of invertebrate rhabdomeric visual cells and support the representation of this lineage of photoreceptors among chordates.
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Affiliation(s)
- Camila Pulido
- Departamento de Biología, Universidad Nacional de Colombia, Bogotá
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Sand A, Schmidt TM, Kofuji P. Diverse types of ganglion cell photoreceptors in the mammalian retina. Prog Retin Eye Res 2012; 31:287-302. [PMID: 22480975 DOI: 10.1016/j.preteyeres.2012.03.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/16/2012] [Accepted: 03/19/2012] [Indexed: 01/01/2023]
Abstract
Photoreceptors carry out the first step in vision by capturing light and transducing it into electrical signals. Rod and cone photoreceptors efficiently translate photon capture into electrical signals by light activation of opsin-type photopigments. Until recently, the central dogma was that, for mammals, all phototransduction occurred in rods and cones. However, the recent discovery of a novel photoreceptor type in the inner retina has fundamentally challenged this view. These retinal ganglion cells are intrinsically photosensitive and mediate a broad range of physiological responses such as photoentrainment of the circadian clock, light regulation of sleep, pupillary light reflex, and light suppression of melatonin secretion. Intrinsically photosensitive retinal ganglion cells express melanopsin, a novel opsin-based signaling mechanism reminiscent of that found in invertebrate rhabdomeric photoreceptors. Melanopsin-expressing retinal ganglion cells convey environmental irradiance information directly to brain centers such as the hypothalamus, preoptic nucleus, and lateral geniculate nucleus. Initial studies suggested that these melanopsin-expressing photoreceptors were an anatomically and functionally homogeneous population. However, over the past decade or so, it has become apparent that these photoreceptors are distinguishable as individual subtypes on the basis of their morphology, molecular markers, functional properties, and efferent projections. These results have provided a novel classification scheme with five melanopsin photoreceptor subtypes in the mammalian retina, each presumably with differential input and output properties. In this review, we summarize the evidence for the structural and functional diversity of melanopsin photoreceptor subtypes and current controversies in the field.
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Affiliation(s)
- Andrea Sand
- Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church St SE, Minneapolis, MN 55455, USA
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36
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Van Hook MJ, Wong KY, Berson DM. Dopaminergic modulation of ganglion-cell photoreceptors in rat. Eur J Neurosci 2012; 35:507-18. [PMID: 22304466 DOI: 10.1111/j.1460-9568.2011.07975.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A novel class of photoreceptors, the intrinsically photosensitive retinal ganglion cells (ipRGCs), express the photopigment melanopsin and drive non-image-forming responses to light such as circadian photoentrainment, the pupillary light reflex and suppression of nocturnal melatonin production in the pineal. Because dendrites from one subclass of these cells - the M1-type ipRGCs - make presumptive synaptic contacts at sites of dopamine release from dopaminergic amacrine cells, they are prime targets for modulation by dopamine, a neuromodulator implicated in retinal circadian rhythms and light adaptation. In patch-clamp recordings from ipRGCs in intact rat retinas, dopamine attenuated the melanopsin-based photocurrent. We confirmed that this was the result of direct action on ipRGCs by replicating the effect in dissociated ipRGCs that were isolated from influences of other retinal neurons. In these recordings, the D1-family dopamine receptor agonist SKF38393 attenuated the photocurrent, caused a modest depolarization, and reduced the input resistance of ipRGCs. The D2-family agonist quinpirole had no effect on the photocurrent. Single-cell reverse-transcriptase polymerase chain reaction revealed that the majority of ipRGCs tested expressed drd1a, the gene coding for the D1a dopamine receptor. This finding was supported by immunohistochemical localization of D1a receptor protein in melanopsin-expressing ganglion cells. Finally, the adenylate cyclase activator forskolin, applied in combination with the phosphodiesterase inhibitor IBMX (isobutylmethylxanthine), mimicked the effects of SKF38393 on the ipRGC photocurrent, membrane potential and input resistance, consistent with a D1-receptor signaling pathway. These data suggest that dopamine, acting via D1-family receptors, alters the responses of ipRGCs and thus of non-image-forming vision.
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Affiliation(s)
- Matthew J Van Hook
- Department of Neuroscience, Brown University, Box G-LN, Providence, RI, USA
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37
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Siegert S, Cabuy E, Scherf BG, Kohler H, Panda S, Le YZ, Fehling HJ, Gaidatzis D, Stadler MB, Roska B. Transcriptional code and disease map for adult retinal cell types. Nat Neurosci 2012; 15:487-95, S1-2. [PMID: 22267162 DOI: 10.1038/nn.3032] [Citation(s) in RCA: 191] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 12/20/2011] [Indexed: 12/17/2022]
Abstract
Brain circuits are assembled from a large variety of morphologically and functionally diverse cell types. It is not known how the intermingled cell types of an individual adult brain region differ in their expressed genomes. Here we describe an atlas of cell type transcriptomes in one brain region, the mouse retina. We found that each adult cell type expressed a specific set of genes, including a unique set of transcription factors, forming a 'barcode' for cell identity. Cell type transcriptomes carried enough information to categorize cells into morphological classes and types. Several genes that were specifically expressed in particular retinal circuit elements, such as inhibitory neuron types, are associated with eye diseases. The resource described here allows gene expression to be compared across adult retinal cell types, experimenting with specific transcription factors to differentiate stem or somatic cells to retinal cell types, and predicting cellular targets of newly discovered disease-associated genes.
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Affiliation(s)
- Sandra Siegert
- Neural Circuit Laboratories, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
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38
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Abstract
TRP channels have emerged as key biological sensors in vision, taste, olfaction, hearing, and touch. Despite their importance, virtually nothing is known about the folding and transport of TRP channels during biosynthesis. Here, we identify XPORT (exit protein of rhodopsin and TRP) as a critical chaperone for TRP and its G protein-coupled receptor (GPCR), rhodopsin (Rh1). XPORT is a resident ER and secretory pathway protein that interacts with TRP and Rh1, as well as with Hsp27 and Hsp90. XPORT promotes the targeting of TRP to the membrane in Drosophila S2 cells, a finding that provides a critical first step toward solving a longstanding problem in the successful heterologous expression of TRP. Mutations in xport result in defective transport of TRP and Rh1, leading to retinal degeneration. Our results identify XPORT as a molecular chaperone and provide a mechanistic link between TRP channels and their GPCRs during biosynthesis and transport.
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39
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Provencio I, Warthen DM. Melanopsin, the photopigment of intrinsically photosensitive retinal ganglion cells. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/wmts.29] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Melanopsin-expressing amphioxus photoreceptors transduce light via a phospholipase C signaling cascade. PLoS One 2012; 7:e29813. [PMID: 22235344 PMCID: PMC3250494 DOI: 10.1371/journal.pone.0029813] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2011] [Accepted: 12/05/2011] [Indexed: 12/03/2022] Open
Abstract
Melanopsin, the receptor molecule that underlies light sensitivity in mammalian ‘circadian’ receptors, is homologous to invertebrate rhodopsins and has been proposed to operate via a similar signaling pathway. Its downstream effectors, however, remain elusive. Melanopsin also expresses in two distinct light-sensitive cell types in the neural tube of amphioxus. This organism is the most basal extant chordate and can help outline the evolutionary history of different photoreceptor lineages and their transduction mechanisms; moreover, isolated amphioxus photoreceptors offer unique advantages, because they are unambiguously identifiable and amenable to single-cell physiological assays. In the present study whole-cell patch clamp recording, pharmacological manipulations, and immunodetection were utilized to investigate light transduction in amphioxus photoreceptors. A Gq was identified and selectively localized to the photosensitive microvillar membrane, while the pivotal role of phospholipase C was established pharmacologically. The photocurrent was profoundly depressed by IP3 receptor antagonists, highlighting the importance of IP3 receptors in light signaling. By contrast, surrogates of diacylglycerol (DAG), as well as poly-unsaturated fatty acids failed to activate a membrane conductance or to alter the light response. The results strengthen the notion that calcium released from the ER via IP3-sensitive channels may fulfill a key role in conveying - directly or indirectly - the melanopsin-initiated light signal to the photoconductance; moreover, they challenge the dogma that microvillar photoreceptors and phoshoinositide-based light transduction are a prerogative of invertebrate eyes.
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41
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Colley NJ. Retinal degeneration in the fly. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:407-14. [PMID: 22183359 DOI: 10.1007/978-1-4614-0631-0_52] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Many genes are functionally equivalent between flies and humans. In addition, the same, or similar, mutations cause disease in both species. In fact, nearly three-fourths of all human disease genes have related sequences in Drosophila. The fly has a relatively small genome, made up of about 13,600 genes in four pairs of chromosomes. However, despite the dramatic differences in size and apparent complexity between humans and flies--we have less than twice as many genes as a fly--our genome is estimated to be made up of only 20,000-25,000 genes contained in 23 pairs of chromosomes. Therefore, despite the fly's perceived simplicity, or our perceived complexity, our genetic makeup may not be all that different. Its versatility for genetic manipulation and convenience for unraveling fundamental biological processes continue to guarantee the fly a place in the spotlight for unraveling the basis of and therapeutic treatments for human eye diseases.
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Affiliation(s)
- Nansi Jo Colley
- Department of Ophthalmology and Visual Sciences and Department of Genetics, and UW-Eye Research Institute, University of Wisconsin, Madison, WI 53792, USA.
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42
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43
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Abstract
Lower vertebrates have an intrinsically-photosensitive iris and thus a local pupillary light reflex (PLR). In contrast, it has been a dogma that the PLR in mammals generally requires neuronal circuitry connecting the eye and the brain. We report here that an intrinsic component of the PLR is actually widespread in nocturnal and crepuscular mammals. In mouse, this intrinsic PLR requires the visual pigment, melanopsin. It also requires PLCβ4, the vertebrate homolog of the Drosophila NorpA phospholipase C mediating rhabdomeric phototransduction. The Plcβ4−/− genotype, besides removing the intrinsic PLR, also essentially eliminates the intrinsic light response of the M1-subtype of melanopsin-expressing, intrinsically-photosensitive retinal ganglion cells (M1-ipRGCs), by far the most photosensitive ipRGCs and with the largest responses. Ablating in mouse the expression of both TRPC6 and TRPC7, members of the TRP channel superfamily, likewise essentially eliminated the M1-ipRGC light response, but spared the intrinsic PLR. Thus, melanopsin signaling exists in both iris and retina, involving a PLCβ4-mediated pathway that nonetheless diverges in the two locations.
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44
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Gilliam JC, Wensel TG. TRP channel gene expression in the mouse retina. Vision Res 2011; 51:2440-52. [PMID: 22037305 DOI: 10.1016/j.visres.2011.10.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 10/03/2011] [Accepted: 10/03/2011] [Indexed: 10/16/2022]
Abstract
In order to identify candidate cation channels important for retinal physiology, 28 TRP channel genes were surveyed for expression in the mouse retina. Transcripts for all TRP channels were detected by RT-PCR and sequencing. Northern blotting revealed that mRNAs for 12 TRP channel genes are enriched in the retina. The strongest signals were observed for TRPC1, TRPC3, TRPM1, TRPM3, and TRPML1, and clear signals were obtained for TRPC4, TRPM7, TRPP2, TRPV2, and TRPV4. In situ hybridization and immunofluorescence revealed widespread expression throughout multiple retinal layers for TRPC1, TRPC3, TRPC4, TRPML1, PKD1, and TRPP2. Striking localization of enhanced mRNA expression was observed for TRPC1 in the photoreceptor inner segment layer, for TRPM1 in the inner nuclear layer (INL), for TRPM3 in the INL, and for TRPML1 in the outer plexiform and nuclear layers. Strong immunofluorescence signal in cone outer segments was observed for TRPM7 and TRPP2. TRPC5 immunostaining was largely confined to INL cells immediately adjacent to the inner plexiform layer. TRPV2 antibodies stained photoreceptor axons in the outer plexiform layer. Expression of TRPM1 splice variants was strong in the ciliary body, whereas TRPM3 was strongly expressed in the retinal pigmented epithelium.
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Affiliation(s)
- Jared C Gilliam
- Verna and Marrs McLean, Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, United States
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45
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Zhang Z, Reboreda A, Alonso A, Barker PA, Séguéla P. TRPC channels underlie cholinergic plateau potentials and persistent activity in entorhinal cortex. Hippocampus 2011; 21:386-97. [PMID: 20082292 DOI: 10.1002/hipo.20755] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Persistent neuronal activity lasting seconds to minutes has been proposed to allow for the transient storage of memory traces in entorhinal cortex and thus could play a major role in working memory. Nonsynaptic plateau potentials induced by acetylcholine account for persistent firing in many cortical and subcortical structures. The expression of these intrinsic properties in cortical neurons involves the recruitment of a non-selective cation conductance. Despite its functional importance, the identity of the cation channels remains unknown. Here we show that, in layer V of rat medial entorhinal cortex, muscarinic receptor-evoked plateau potentials and persistent firing induced by carbachol require phospholipase C activation, decrease of PIP(2) levels, and permissive intracellular Ca(2+) concentrations. Plateau potentials and persistent activity were suppressed by the generic nonselective cation channel blockers FFA (100 μM) and 2-APB (100 μM), as well as by the TRPC channel blocker SKF-96365 (50 μM). However, plateau potentials were not affected by the TRPV channel blocker ruthenium red (40 μM). The TRPC3/6/7 activator OAG did not induce or enhance persistent firing evoked by carbachol. Voltage clamp recordings revealed a carbachol-activated, nonselective cationic current with a heteromeric TRPC-like phenotype. Moreover, plateau potentials and persistent firing were inhibited by intracellular application of the peptide EQVTTRL that disrupts interactions between the C-terminal domain of TRPC4/5 subunits and associated PDZ proteins. Altogether, our data suggest that TRPC cation channels mediating persistent muscarinic currents significantly contribute to the firing and mnemonic properties of projection neurons in the entorhinal cortex.
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Affiliation(s)
- Zizhen Zhang
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4 Canada
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46
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Schmidt TM, Chen SK, Hattar S. Intrinsically photosensitive retinal ganglion cells: many subtypes, diverse functions. Trends Neurosci 2011; 34:572-80. [PMID: 21816493 DOI: 10.1016/j.tins.2011.07.001] [Citation(s) in RCA: 339] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 06/29/2011] [Accepted: 07/02/2011] [Indexed: 10/18/2022]
Abstract
For decades, rods and cones were thought to be the only photoreceptors in the mammalian retina. However, a population of atypical photoreceptive retinal ganglion cells (RGCs) expresses the photopigment melanopsin and is intrinsically photosensitive (ipRGCs). These ipRGCs are crucial for relaying light information from the retina to the brain to control circadian photoentrainment, pupillary light reflex, and sleep. ipRGCs were initially described as a uniform population involved solely in signaling irradiance for non-image forming functions. Recent work, however, has uncovered that ipRGCs are unexpectedly diverse at the molecular, cellular and functional levels, and could even be involved in image formation. This review summarizes our current understanding of the diversity of ipRGCs and their various roles in modulating behavior.
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Affiliation(s)
- Tiffany M Schmidt
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA.
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Bollimuntha S, Selvaraj S, Singh BB. Emerging roles of canonical TRP channels in neuronal function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:573-93. [PMID: 21290317 DOI: 10.1007/978-94-007-0265-3_31] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ca(2+) signaling in neurons is intimately associated with the regulation of vital physiological processes including growth, survival and differentiation. In neurons, Ca(2+) elicits two major functions. First as a charge carrier, Ca(2+) reveals an indispensable role in information relay via membrane depolarization, exocytosis, and the release of neurotransmitters. Second on a global basis, Ca(2+) acts as a ubiquitous intracellular messenger to modulate neuronal function. Thus, to mediate Ca(2+)-dependent physiological events, neurons engage multiple mode of Ca(2+) entry through a variety of Ca(2+) permeable plasma membrane channels. Here we discuss a subset of specialized Ca(2+)-permeable non-selective TRPC channels and summarize their physiological and pathological role in the context of excitable cells. TRPC channels are predominately expressed in neuronal cells and are activated through complex mechanisms, including second messengers and store depletion. A growing body of evidence suggests a prime contribution of TRPC channels in regulating fundamental neuronal functions. TRPC channels have been shown to be associated with neuronal development, proliferation and differentiation. In addition, TRPC channels have also been suggested to have a potential role in regulating neurosecretion, long term potentiation, and synaptic plasticity. During the past years, numerous seminal discoveries relating TRPC channels to neurons have constantly emphasized on the significant contribution of this group of ion channels in regulating neuronal function. Here we review the major groundbreaking work that has uniquely placed TRPC channels in a pivotal position for governing neuronal Ca(2+) signaling and associated physiological responses.
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Affiliation(s)
- Sunitha Bollimuntha
- Department of Biochemistry and Molecular Biology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58201, USA.
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48
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McDougal DH, Gamlin PD. The influence of intrinsically-photosensitive retinal ganglion cells on the spectral sensitivity and response dynamics of the human pupillary light reflex. Vision Res 2011; 50:72-87. [PMID: 19850061 DOI: 10.1016/j.visres.2009.10.012] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 10/12/2009] [Accepted: 10/13/2009] [Indexed: 11/15/2022]
Abstract
Historically, it was assumed that the light-evoked neural signals driving the human pupillary light reflex (PLR) originated exclusively from rod and cone photoreceptors. However, a novel melanopsin-containing photoreceptive cell class has recently been discovered in the mammalian retina. These intrinsically-photosensitive retinal ganglion cells (ipRGCs) project to the pretectum, the retinorecipient area of the brain responsible for the PLR. This study was therefore designed to examine the relative contribution of rod, cone and the melanopsin photoresponses of ipRGCs to the human PLR. We establish that the melanopsin photoresponse of ipRGCs contributes significantly to the maintenance of half maximal pupilloconstriction in response to light stimuli of 30s or longer, even at low photopic irradiances. Furthermore, we show that the melanopsin photoresponse contributes significantly to three-quarter maximal pupilloconstriction in response to light stimuli as short as 2s. We also demonstrate that cone photoresponses driving pupilloconstriction adapt considerably and contribute little after 30s, but rod photoresponses adapt less and contribute significantly to the maintenance of pupilloconstriction in response to steady-state light stimuli at irradiance levels which are below the threshold of the melanopsin photoresponse.
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Affiliation(s)
- David H McDougal
- Laboratory of Autonomic Neurosciences, Pennington Biomedical Research, Center, 6400 Perkins Road, Baton Rouge, LA 70808, United States
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49
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Perez-Leighton CE, Schmidt TM, Abramowitz J, Birnbaumer L, Kofuji P. Intrinsic phototransduction persists in melanopsin-expressing ganglion cells lacking diacylglycerol-sensitive TRPC subunits. Eur J Neurosci 2011; 33:856-67. [PMID: 21261756 PMCID: PMC3076293 DOI: 10.1111/j.1460-9568.2010.07583.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In mammals, intrinsically photosensitive retinal ganglion cells (ipRGCs) mediate various non-image-forming photic responses, such as circadian photoentrainment, pupillary light reflex and pineal melatonin suppression. ipRGCs directly respond to environmental light by activation of the photopigment melanopsin followed by the opening of an unidentified cation-selective channel. Studies in heterologous expression systems and in the native retina have strongly implicated diacylglycerol-sensitive transient receptor potential channels containing TRPC3, TRPC6 and TRPC7 subunits in melanopsin-evoked depolarization. Here we show that melanopsin-evoked electrical responses largely persist in ipRGCs recorded from early postnatal (P6-P8) and adult (P22-P50) mice lacking expression of functional TRPC3, TRPC6 or TRPC7 subunits. Multielectrode array (MEA) recordings performed at P6-P8 stages under conditions that prevent influences from rod/cone photoreceptors show comparable light sensitivity for the melanopsin-evoked responses in these mutant mouse lines in comparison to wild-type (WT) mice. Patch-clamp recordings from adult mouse ipRGCs lacking TRPC3 or TRPC7 subunits show intrinsic light-evoked responses equivalent to those recorded in WT mice. Persistence of intrinsic light-evoked responses was also noted in ipRGCs lacking TRPC6 subunits, although with significantly smaller magnitudes. These results demonstrate that the melanopsin-evoked depolarization in ipRGCs is not mediated by either TRPC3, TRPC6 or TRPC7 channel subunits alone. They also suggest that the melanopsin signaling pathway includes TRPC6-containing heteromeric channels in mature retinas.
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Affiliation(s)
| | - Tiffany M. Schmidt
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Joel Abramowitz
- Laboratory of Neurobiology, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health
| | - Paulo Kofuji
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Abstract
Pupil size is determined by the interaction of the parasympathetic and the sympathetic nervous system. The parasympathetic system conducts the light reaction with its major center in the dorsal midbrain. The sympathetic nervous system acts either directly on the dilator muscle (peripherally) or centrally by inhibiting the Edinger-Westphal nucleus. Psychosensory reactions are transmitted via the sympathetic system. The afferent input of the light reflex system in humans is characteristically wired, allowing a detailed analysis of a lesion of the afferent input. Even in humans a subgroup of ganglion cells containing melansopsin plays an important role as a light sensor for the pupillary system. To diagnose normal pupillary function, pupils need to be isocoric and react bilaterally equally to light. Anisocoria indicates a problem of the efferent pupillary pathway. Pupillary disorders may involve the afferent pathways (relative afferent pupillary defect) or the efferent pathways. Physiological anisocoria is a harmless condition that has to be distinguished from Horner's syndrome. In this case pharmacological testing with cocaine eye-drops is helpful. Disorders of the parasympathetic system will impair the light response. They include dorsal midbrain syndrome, third-nerve palsy, and tonic pupil. Tonic pupils are mainly idiopathic and do not need imaging. Disorders of the iris, including application of cholinergic agents, need also to be considered in impaired pupillary light reaction.
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Affiliation(s)
- Helmut Wilhelm
- Centre for Ophthalmology, University Eye Hospital, University of Tübingen, Tübingen, Germany.
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