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Lankford CK, Umino Y, Poria D, Kefalov V, Solessio E, Baker SA. Cone-Driven Retinal Responses Are Shaped by Rod But Not Cone HCN1. J Neurosci 2022; 42:4231-4249. [PMID: 35437278 PMCID: PMC9145265 DOI: 10.1523/jneurosci.2271-21.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 04/01/2022] [Accepted: 04/07/2022] [Indexed: 11/21/2022] Open
Abstract
Signal integration of converging neural circuits is poorly understood. One example is in the retina where the integration of rod and cone signaling is responsible for the large dynamic range of vision. The relative contribution of rods versus cones is dictated by a complex function involving background light intensity and stimulus temporal frequency. One understudied mechanism involved in coordinating rod and cone signaling onto the shared retinal circuit is the hyperpolarization activated current (Ih) mediated by hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels expressed in rods and cones. Ih opposes membrane hyperpolarization driven by activation of the phototransduction cascade and modulates the strength and kinetics of the photoreceptor voltage response. We examined conditional knock-out (KO) of HCN1 from mouse rods using electroretinography (ERG). In the absence of HCN1, rod responses are prolonged in dim light which altered the response to slow modulation of light intensity both at the level of retinal signaling and behavior. Under brighter intensities, cone-driven signaling was suppressed. To our surprise, conditional KO of HCN1 from mouse cones had no effect on cone-mediated signaling. We propose that Ih is dispensable in cones because of the high level of temporal control of cone phototransduction. Thus, HCN1 is required for cone-driven retinal signaling only indirectly by modulating the voltage response of rods to limit their output.SIGNIFICANCE STATEMENT Hyperpolarization gated hyperpolarization-activated cyclic nucleotide-gated 1 (HCN1) channels carry a feedback current that helps to reset light-activated photoreceptors. Using conditional HCN1 knock-out (KO) mice we show that ablating HCN1 from rods allows rods to signal in bright light when they are normally shut down. Instead of enhancing vision this results in suppressing cone signaling. Conversely, ablating HCN1 from cones was of no consequence. This work provides novel insights into the integration of rod and cone signaling in the retina and challenges our assumptions about the role of HCN1 in cones.
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Affiliation(s)
- Colten K Lankford
- Department of Biochemistry and Molecular Biology, University of Iowa, Iowa City, Iowa 52242
| | - Yumiko Umino
- Center for Vision Research, Department of Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Deepak Poria
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697
| | - Vladimir Kefalov
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, California 92697
- Department of Physiology and Biophysics, University of California, Irvine, California 92697
| | - Eduardo Solessio
- Center for Vision Research, Department of Ophthalmology and Visual Sciences, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Sheila A Baker
- Department of Biochemistry and Molecular Biology, University of Iowa, Iowa City, Iowa 52242
- Department of Ophthalmology and Visual Sciences and Institute for Vision Research, University of Iowa, Iowa City, Iowa 52242
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Abstract
An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.
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Affiliation(s)
- Frans Vinberg
- Department of Ophthalmology and Visual Sciences, Washington University in St. Louis;
| | - Vladimir Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University in St. Louis
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Molnar T, Barabas P, Birnbaumer L, Punzo C, Kefalov V, Križaj D. Store-operated channels regulate intracellular calcium in mammalian rods. J Physiol 2012; 590:3465-81. [PMID: 22674725 DOI: 10.1113/jphysiol.2012.234641] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Exposure to daylight closes cyclic nucleotide-gated (CNG) and voltage-operated Ca(2+) -permeable channels in mammalian rods. The consequent lowering of the cytosolic calcium concentration ([Ca(2+)](i)), if protracted, can contribute to light-induced damage and apoptosis in these cells. We here report that mouse rods are protected against prolonged lowering of [Ca(2+)](i) by store-operated Ca(2+) entry (SOCE). Ca(2+) stores were depleted in Ca(2+)-free saline supplemented with the endoplasmic reticulum (ER) sequestration blocker cyclopiazonic acid. Store depletion elicited [Ca(2+)](i) signals that exceeded baseline [Ca(2+)](i) by 5.9 ± 0.7-fold and were antagonized by an inhibitory cocktail containing 2-APB, SKF 96365 and Gd(3+). Cation influx through SOCE channels was sufficient to elicit a secondary activation of L-type voltage-operated Ca2+ entry. We also found that TRPC1, the type 1 canonical mammalian homologue of the Drosophila photoreceptor TRP channel, is predominantly expressed within the outer nuclear layer of the retina. Rod loss in Pde6b(rdl) (rd1), Chx10/Kip1(-/-rdl) and Elovl4(TG2) dystrophic models was associated with ∼70% reduction in Trpc1 mRNA content whereas Trpc1 mRNA levels in rodless cone-full Nrl(-/-) retinas were decreased by ∼50%. Genetic ablation of TRPC1 channels, however, had no effect on SOCE, the sensitivity of the rod phototransduction cascade or synaptic transmission at rod and cone synapses. Thus, we localized two new mechanisms, SOCE and TRPC1, to mammalian rods and characterized the contribution of SOCE to Ca(2+) homeostasis. By preventing the cytosolic [Ca(2+)](i) from dropping too low under sustained saturating light conditions, these signalling pathways may protect Ca(2+)-dependent mechanisms within the ER and the cytosol without affecting normal rod function.
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Affiliation(s)
- Tünde Molnar
- Department of Ophthalmology & Visual Sciences, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
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Imai H, Kefalov V, Sakurai K, Chisaka O, Ueda Y, Onishi A, Morizumi T, Fu Y, Ichikawa K, Nakatani K, Honda Y, Chen J, Yau KW, Shichida Y. Molecular properties of rhodopsin and rod function. J Biol Chem 2007; 282:6677-84. [PMID: 17194706 PMCID: PMC2885910 DOI: 10.1074/jbc.m610086200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal transduction in rod cells begins with photon absorption by rhodopsin and leads to the generation of an electrical response. The response profile is determined by the molecular properties of the phototransduction components. To examine how the molecular properties of rhodopsin correlate with the rod-response profile, we have generated a knock-in mouse with rhodopsin replaced by its E122Q mutant, which exhibits properties different from those of wild-type (WT) rhodopsin. Knock-in mouse rods with E122Q rhodopsin exhibited a photosensitivity about 70% of WT. Correspondingly, their single-photon response had an amplitude about 80% of WT, and a rate of decline from peak about 1.3 times of WT. The overall 30% lower photosensitivity of mutant rods can be explained by a lower pigment photosensitivity (0.9) and the smaller single-photon response (0.8). The slower decline of the response, however, did not correlate with the 10-fold shorter lifetime of the meta-II state of E122Q rhodopsin. This shorter lifetime became evident in the recovery phase of rod cells only when arrestin was absent. Simulation analysis of the photoresponse profile indicated that the slower decline and the smaller amplitude of the single-photon response can both be explained by the shift in the meta-I/meta-II equilibrium of E122Q rhodopsin toward meta-I. The difference in meta-III lifetime between WT and E122Q mutant became obvious in the recovery phase of the dark current after moderate photobleaching of rod cells. Thus, the present study clearly reveals how the molecular properties of rhodopsin affect the amplitude, shape, and kinetics of the rod response.
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Affiliation(s)
- Hiroo Imai
- Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan
| | - Vladimir Kefalov
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Keisuke Sakurai
- Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan
| | - Osamu Chisaka
- Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507, Japan
| | - Yoshiki Ueda
- Department of Ophthalmology and Visual Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Akishi Onishi
- Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan
| | - Takefumi Morizumi
- Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan
| | - Yingbin Fu
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Kazuhisa Ichikawa
- Department of Brain and Bioinformation Science, Kanazawa Institute of Technology, Ishikawa 924-0838, Japan
| | - Kei Nakatani
- Graduate School of Life and Environmental Sciences, University of Tsukuba and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Ibaraki 305-8572, Japan
| | - Yoshihito Honda
- Department of Ophthalmology and Visual Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Jeannie Chen
- The Mary D. Allen Laboratory for Vision Research, Doheny Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - King-Wai Yau
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan
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Kefalov V, Fu Y, Marsh-Armstrong N, Yau KW. Role of visual pigment properties in rod and cone phototransduction. Nature 2003; 425:526-31. [PMID: 14523449 PMCID: PMC2581816 DOI: 10.1038/nature01992] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2003] [Accepted: 08/07/2003] [Indexed: 12/22/2022]
Abstract
Retinal rods and cones share a phototransduction pathway involving cyclic GMP. Cones are typically 100 times less photosensitive than rods and their response kinetics are several times faster, but the underlying mechanisms remain largely unknown. Almost all proteins involved in phototransduction have distinct rod and cone variants. Differences in properties between rod and cone pigments have been described, such as a 10-fold shorter lifetime of the meta-II state (active conformation) of cone pigment and its higher rate of spontaneous isomerization, but their contributions to the functional differences between rods and cones remain speculative. We have addressed this question by expressing human or salamander red cone pigment in Xenopus rods, and human rod pigment in Xenopus cones. Here we show that rod and cone pigments when present in the same cell produce light responses with identical amplification and kinetics, thereby ruling out any difference in their signalling properties. However, red cone pigment isomerizes spontaneously 10,000 times more frequently than rod pigment. This high spontaneous activity adapts the native cones even in darkness, making them less sensitive and kinetically faster than rods. Nevertheless, additional factors are probably involved in these differences.
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Affiliation(s)
- Vladimir Kefalov
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Yingbin Fu
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Nicholas Marsh-Armstrong
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- Kennedy-Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - King-Wai Yau
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Affiliation(s)
- Rosalie K Crouch
- Department of Ophthalmology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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