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Green SL, Silvester E, Dworkin S, Shakya M, Klein A, Lowe R, Datta K, Holland A. Molecular variations to the proteome of zebrafish larvae induced by environmentally relevant copper concentrations. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 272:106963. [PMID: 38776608 DOI: 10.1016/j.aquatox.2024.106963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 05/14/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Contaminants are increasingly accumulating in aquatic environments and biota, with potential adverse effects on individual organisms, communities and ecosystems. However, studies that explore the molecular changes in fish caused by environmentally relevant concentrations of metals, such as copper (Cu), are limited. This study uses embryos of the model organism zebrafish (Danio rerio) to investigate effect of Cu on the proteome and amino acid (AA) composition of fish. Wild-type embryos at 24 h post-fertilisation were exposed to Cu (2 µg L-1 to 120 µg L-1) for 96 h and the number of healthy larvae were determined based on larvae that had hatched and did not display loss of equilibrium (LOE). The effect concentrations where Cu caused a 10 % (EC10) or 50 % (EC50) decrease in the number of healthy larvae were calculated as 3.7 µg L-1 and 10.9 µg L-1, respectively. Proteomics analysis of embryos exposed to the EC10 and EC50 concentrations of Cu revealed the proteome to differ more strongly after 48 h than 96 h, suggesting the acclimatisation of some larvae. Exposure to excess Cu caused differentially expressed proteins (DEPs) involved in oxidative stress, mitochondrial respiration, and neural transduction as well as the modulation of the AAs (Proline, Glycine and Alanine). This is the first study to suggest that LOE displayed by Cu-stressed fish may involve the disruption to GABAergic proteins and the calcium-dependent inhibitory neurotransmitter GABA. Moreover, this study highlights that proteomics and AA analysis can be used to identify potential biomarkers for environmental monitoring.
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Affiliation(s)
- Sarah L Green
- Department of Environment and Genetics, La Trobe University, 133 Mckoy Street, West Wodonga, Albury-Wodonga Campus, Victoria 3690, Australia.
| | - Ewen Silvester
- Department of Environment and Genetics, La Trobe University, 133 Mckoy Street, West Wodonga, Albury-Wodonga Campus, Victoria 3690, Australia
| | - Sebastian Dworkin
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora Campus, Victoria, Australia
| | - Manisha Shakya
- School of Environmental and Rural Science, Faculty of Science, Agriculture, Business and Law, University of New England, Armidale, New South Wales, Australia
| | - Annaleise Klein
- Australian Synchrotron, ANSTO, 800 Blackburn Road, Clayton, Victoria 3168, Australia
| | - Rohan Lowe
- Proteomics and Metabolomics Platform, La Trobe University, Bundoora Campus, Victoria, Australia
| | - Keshava Datta
- Proteomics and Metabolomics Platform, La Trobe University, Bundoora Campus, Victoria, Australia
| | - Aleicia Holland
- Department of Environment and Genetics, La Trobe University, 133 Mckoy Street, West Wodonga, Albury-Wodonga Campus, Victoria 3690, Australia
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Nguyen MN, Chakraborty D, Rao SR, Onysk A, Radkiewicz M, Surmacz L, Swiezewska E, Soubeyrand E, Akhtar TA, Kraft TW, Sherry DM, Fliesler SJ, Pittler SJ. A Dhdds K42E knock-in RP59 mouse model shows inner retina pathology and defective synaptic transmission. Cell Death Dis 2023; 14:420. [PMID: 37443173 PMCID: PMC10345138 DOI: 10.1038/s41419-023-05936-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 06/07/2023] [Accepted: 06/29/2023] [Indexed: 07/15/2023]
Abstract
Retinitis pigmentosa (RP) defines a group of hereditary progressive rod-cone degenerations that exhibit a common phenotype caused by variants in over 70 genes. While most variants in the dehydrodolichyl diphosphate synthase (DHDDS) gene result in syndromic abnormalities, some variants cause non-syndromic RP (RP59). DHDDS encodes one subunit of the enzyme cis-prenyltransferase (CPT), which is required for the synthesis of dolichol (Dol), that is a necessary protein glycosylation cofactor. We previously reported the creation and initial characterization of a knock-in (KI) mouse model harboring the most prevalent RP59-associated DHDDS variant (K42E) to understand how defects in DHDDS lead to retina-specific pathology. This model exhibited no profound retinal degeneration, nor protein N-glycosylation defects. Here, we report that the Dol isoprenylogue species in retina, liver, and brain of the K42E mouse model are statistically shorter than in the corresponding tissues of age-matched controls, as reported in blood and urine of RP59 patients. Retinal transcriptome analysis demonstrated elevation of many genes encoding proteins involved in synaptogenesis and synaptic function. Quantitative retinal cell layer thickness measurements demonstrated a significant reduction in the inner nuclear layer (INL) and total retinal thickness (TRT) beginning at postnatal (PN) ∼2 months, progressively increasing to PN 18-mo. Histological analysis revealed cell loss in the INL, outer plexiform layer (OPL) disruption, and ectopic localization of outer nuclear layer (ONL) nuclei into the OPL of K42E mutant retinas, relative to controls. Electroretinograms (ERGs) of mutant mice exhibited reduced b-wave amplitudes beginning at PN 1-mo, progressively declining through PN 18-mo, without appreciable a-wave attenuation, relative to controls. Our results suggest that the underlying cause of DHDDS K42E variant driven RP59 retinal pathology is defective synaptic transmission from outer to inner retina.
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Affiliation(s)
- Mai N Nguyen
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Dibyendu Chakraborty
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sriganesh Ramachandra Rao
- Research Service, VA Western New York Healthcare System, Buffalo, NY, 14215, USA
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, Buffalo, NY, 14203, USA
| | - Agnieszka Onysk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Mariusz Radkiewicz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Liliana Surmacz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Ewa Swiezewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, 02106, Poland
| | - Eric Soubeyrand
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada
| | - Tariq A Akhtar
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada
| | - Timothy W Kraft
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - David M Sherry
- Departments of Cell Biology, Neurosurgery, and Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Steven J Fliesler
- Research Service, VA Western New York Healthcare System, Buffalo, NY, 14215, USA
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, The State University of New York, University at Buffalo, Buffalo, NY, 14203, USA
| | - Steven J Pittler
- Department of Optometry and Vision Science, Vision Science Research Center, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
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Ding RF, Yu Q, Liu K, Du J, Yin HJ, Ji ZL. Gene network analyses unveil possible molecular basis underlying drug-induced glaucoma. BMC Med Genomics 2021; 14:109. [PMID: 33874942 PMCID: PMC8056654 DOI: 10.1186/s12920-021-00960-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 04/07/2021] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Drug-induced glaucoma (DIG) is a kind of serious adverse drug reaction that can cause irreversible blindness. Up-to-date, the molecular mechanism of DIG largely remains unclear yet due to the medical complexity of glaucoma onset. METHODS In this study, we conducted data mining of tremendous historical adverse drug events and genome-wide drug-regulated gene signatures to identify glaucoma-associated drugs. Upon these drugs, we carried out serial network analyses, including the weighted gene co-expression network analysis (WGCNA), to illustrate the gene interaction network underlying DIG. Furthermore, we applied pathogenic risk assessment to discover potential biomarker genes for DIG. RESULTS As the results, we discovered 13 highly glaucoma-associated drugs, a glaucoma-related gene network, and 55 glaucoma-susceptible genes. These genes likely played central roles in triggering DIGs via an integrative mechanism of phototransduction dysfunction, intracellular calcium homeostasis disruption, and retinal ganglion cell death. Further pathogenic risk analysis manifested that a panel of nine genes, particularly OTOF gene, could serve as potential biomarkers for early-onset DIG prognosis. CONCLUSIONS This study elucidates the possible molecular basis underlying DIGs systematically for the first time. It also provides prognosis clues for early-onset glaucoma and thus assists in designing better therapeutic regimens.
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Affiliation(s)
- Ruo-Fan Ding
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China
| | - Qian Yu
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China
| | - Ke Liu
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China
| | - Juan Du
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China
| | - Hua-Jun Yin
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China
| | - Zhi-Liang Ji
- State Key Laboratory of Stress Cell Biology, School of Life Sciences, Xiamen University, Xiamen, 361102, Fujian, People's Republic of China.
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Identification of a CNGB1 Frameshift Mutation in a Han Chinese Family with Retinitis Pigmentosa. Optom Vis Sci 2019; 95:1155-1161. [PMID: 30451805 DOI: 10.1097/opx.0000000000001305] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
SIGNIFICANCE Retinitis pigmentosa (RP) is a severe hereditary retinal disorder characterized by progressive degeneration of rod and cone photoreceptors. This study identified a novel frameshift mutation, c.385delC, p.(L129WfsTer148), in the cyclic nucleotide-gated channel beta 1 (CNGB1) gene of a consanguineous Han Chinese family with autosomal recessive RP (arRP). This expands the spectrum of CNGB1 gene variants in RP cases and possibly refines future genetic counseling. PURPOSE The present study sought to identify potential pathogenetic gene mutations in a five-generation consanguineous Han Chinese family with RP. METHODS Two members of a five-generation consanguineous Han Chinese pedigree with arRP and 100 normal individuals were enrolled in this study. Exome sequencing was performed on the 70-year-old male proband from a consanguineous family to screen potential pathogenic mutations according to the American College of Medical Genetics and Genomics for the interpretation of sequence variants. Sanger sequencing was performed on the proband, the proband's unaffected son, and 100 normal individuals to verify the disease-causing mutation. RESULTS A novel frameshift mutation, c.385delC, p.(L129WfsTer148), with homozygous status in the CNGB1 gene was identified in the proband of the family with arRP, and the mutation with heterozygous status was carried by the asymptomatic son. CONCLUSIONS The c.385delC (p.(L129WfsTer148)) mutation in the CNGB1 gene screened by exome sequencing is probably responsible for the RP phenotype in this family. The result expands the spectrum of CNGB1 gene variants in RP cases and possibly refines future genetic counseling.
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Morshedian A, Woodruff ML, Fain GL. Role of recoverin in rod photoreceptor light adaptation. J Physiol 2018; 596:1513-1526. [PMID: 29435986 DOI: 10.1113/jp275779] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 02/01/2018] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Recoverin is a small molecular-weight, calcium-binding protein in rod outer segments that can modulate the rate of rhodopsin phosphorylation. We describe two additional and perhaps more important functions during photoreceptor light adaptation. Recoverin influences the rate of change of adaptation. In wild-type rods, sensitivity and response integration time adapt with similar time constants of 150-200 ms. In Rv-/- rods lacking recoverin, sensitivity declines faster and integration time is already shorter and not significantly altered. During steady light exposure, rod circulating current slowly increases during a time course of tens of seconds, gradually extending the operating range of the rod. In Rv-/- rods, this mechanism is deleted, steady-state currents are already larger and rods saturate at brighter intensities. We propose that recoverin modulates spontaneous and light-activated phophodiesterase-6, the phototransduction effector enzyme, to increase sensitivity in dim light but improve responsiveness to change in brighter illumination. ABSTRACT Recoverin is a small molecular-weight, calcium-binding protein in rod outer segments that binds to G-protein receptor kinase 1 and can alter the rate of rhodopsin phosphorylation. A change in phosphorylation should change the lifetime of light-activated rhodopsin and the gain of phototransduction, but deletion of recoverin has little effect on the sensitivity of rods either in the dark or in dim-to-moderate background light. We describe two additional functions perhaps of greater physiological significance. (i) When the ambient intensity increases, sensitivity and integration time decrease in wild-type (WT) rods with similar time constants of 150-200 ms. Recoverin is part of the mechanism controlling this process because, in Rv-/- rods lacking recoverin, sensitivity declines more rapidly and integration time is already shorter and not further altered. (ii) During steady light exposure, WT rod circulating current slowly increases during a time course of tens of seconds, gradually extending the operating range of the rod. In Rv-/- rods, this mechanism is also deleted, steady-state currents are already larger and rods saturate at brighter intensities. We argue that neither (i) nor (ii) can be caused by modulation of rhodopsin phosphorylation but may instead be produced by direct modulation of phophodiesterase-6 (PDE6), the phototransduction effector enzyme. We propose that recoverin in dark-adapted rods keeps the integration time long and the spontaneous PDE6 rate relatively high to improve sensitivity. In background light, the integration time is decreased to facilitate detection of change and motion and the spontaneous PDE6 rate decreases to augment the rod working range.
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Affiliation(s)
- Ala Morshedian
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA, USA.,Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA, USA
| | - Michael L Woodruff
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA, USA
| | - Gordon L Fain
- Department of Integrative Biology and Physiology, UCLA, Los Angeles, CA, USA.,Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA, USA
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miR-183/96 plays a pivotal regulatory role in mouse photoreceptor maturation and maintenance. Proc Natl Acad Sci U S A 2017; 114:6376-6381. [PMID: 28559309 DOI: 10.1073/pnas.1618757114] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
MicroRNAs (miRNAs) are known to be essential for retinal maturation and functionality; however, the role of the most abundant miRNAs, the miR-183/96/182 cluster (miR-183 cluster), in photoreceptor cells remains unclear. Here we demonstrate that ablation of two components of the miR-183 cluster, miR-183 and miR-96, significantly affects photoreceptor maturation and maintenance in mice. Morphologically, early-onset dislocated cone nuclei, shortened outer segments and thinned outer nuclear layers are observed in the miR-183/96 double-knockout (DKO) mice. Abnormal photoreceptor responses, including abolished photopic electroretinography (ERG) responses and compromised scotopic ERG responses, reflect the functional changes in the degenerated retina. We further identify Slc6a6 as the cotarget of miR-183 and miR-96. The expression level of Slc6a6 is significantly higher in the DKO mice than in the wild-type mice. In contrast, Slc6a6 is down-regulated by adeno-associated virus-mediated overexpression of either miR-183 or miR-96 in wild-type mice. Remarkably, both silencing and overexpression of Slc6a6 in the retina are detrimental to the electrophysiological activity of the photoreceptors in response to dim light stimuli. We demonstrate that miR-183/96-mediated fine-tuning of Slc6a6 expression is indispensable for photoreceptor maturation and maintenance, thereby providing insight into the epigenetic regulation of photoreceptors in mice.
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DeRamus ML, Stacks DA, Zhang Y, Huisingh CE, McGwin G, Pittler SJ. GARP2 accelerates retinal degeneration in rod cGMP-gated cation channel β-subunit knockout mice. Sci Rep 2017; 7:42545. [PMID: 28198469 PMCID: PMC5309851 DOI: 10.1038/srep42545] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/09/2017] [Indexed: 12/20/2022] Open
Abstract
The Cngb1 locus-encoded β-subunit of rod cGMP-gated cation channel and associated glutamic acid rich proteins (GARPs) are required for phototransduction, disk morphogenesis, and rod structural integrity. To probe individual protein structure/function of the GARPs, we have characterized several transgenic mouse lines selectively restoring GARPs on a Cngb1 knockout (X1−/−) mouse background. Optical coherence tomography (OCT), light and transmission electron microscopy (TEM), and electroretinography (ERG) were used to analyze 6 genotypes including WT at three and ten weeks postnatal. Comparison of aligned histology/OCT images demonstrated that GARP2 accelerates the rate of degeneration. ERG results are consistent with the structural analyses showing the greatest attenuation of function when GARP2 is present. Even 100-fold or more overexpression of GARP1 could not accelerate degeneration as rapidly as GARP2, and when co-expressed GARP1 attenuated the structural and functional deficits elicited by GARP2. These results indicate that the GARPs are not fully interchangeable and thus, likely have separate and distinct functions in the photoreceptor. We also present a uniform murine OCT layer naming nomenclature system that is consistent with human retina layer designations to standardize murine OCT, which will facilitate data evaluation across different laboratories.
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Affiliation(s)
- Marci L DeRamus
- Departments of Optometry and Vision Science, University of Alabama at Birmingham, 1670 University Blvd, VH 375, Birmingham, AL 35294-0019, USA
| | - Delores A Stacks
- Departments of Optometry and Vision Science, University of Alabama at Birmingham, 1670 University Blvd, VH 375, Birmingham, AL 35294-0019, USA
| | - Youwen Zhang
- Departments of Optometry and Vision Science, University of Alabama at Birmingham, 1670 University Blvd, VH 375, Birmingham, AL 35294-0019, USA
| | - Carrie E Huisingh
- Department of Ophthalmology, University of Alabama at Birmingham, 700 18th Street South, Suite 609, Birmingham, AL 35294, USA
| | - Gerald McGwin
- Department of Epidemiology, University of Alabama at Birmingham, Ryals Public Health Building, 1665 University Boulevard, Birmingham, AL 35294, USA
| | - Steven J Pittler
- Departments of Optometry and Vision Science, University of Alabama at Birmingham, 1670 University Blvd, VH 375, Birmingham, AL 35294-0019, USA
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Chakraborty D, Conley SM, Pittler SJ, Naash MI. Role of RDS and Rhodopsin in Cngb1-Related Retinal Degeneration. Invest Ophthalmol Vis Sci 2016; 57:787-97. [PMID: 26934134 PMCID: PMC4777275 DOI: 10.1167/iovs.15-18516] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Rod photoreceptor outer segment (OS) morphogenesis, structural integrity, and proper signal transduction rely on critical proteins found in the different OS membrane domains (e.g., plasma, disc, and disc rim membrane). Among these key elements are retinal degeneration slow (RDS, also known as peripherin-2), rhodopsin, and the beta subunit of the cyclic nucleotide gated channel (CNGB1a), which have been found to interact in a complex. The purpose of this study was to evaluate the potential interplay between these three proteins by examining retinal disease phenotypes in animal models expressing varying amounts of CNGB1a, rhodopsin, and RDS. Methods Outer segment trafficking, retinal function, and photoreceptor structure were evaluated using knockout mouse lines. Results Eliminating Cngb1 and reducing RDS leads to additive defects in RDS expression levels and rod electroretinogram (ERG) function, (e.g., Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−) but not to additive defects in rod ultrastructure. These additive effects also manifested in cone function: Photopic ERG responses were significantly lower in the Cngb1−/−/rds+/− versus rds+/− or Cngb1−/−, suggesting that eliminating Cngb1 can accelerate the cone degeneration that usually presents later in the rds+/−. This was not the case with rhodopsin; reducing rhodopsin levels in concert with eliminating CNGB1a did not lead to phenotypes more severe than those observed in the Cngb1 knockout alone. Conclusions These data support a role for RDS as the core component of a multiprotein plasma membrane-rim-disc complex that has both a structural role in photoreceptor OS formation and maintenance and a functional role in orienting proteins for optimal signal transduction.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Steven J Pittler
- Department of Vision Sciences, School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
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Goldberg AFX, Moritz OL, Williams DS. Molecular basis for photoreceptor outer segment architecture. Prog Retin Eye Res 2016; 55:52-81. [PMID: 27260426 DOI: 10.1016/j.preteyeres.2016.05.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/27/2016] [Accepted: 05/29/2016] [Indexed: 01/11/2023]
Abstract
To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ∼10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained.
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Affiliation(s)
- Andrew F X Goldberg
- Eye Research Institute, Oakland University, 417 Dodge Hall, Rochester, MI, 48309, USA.
| | - Orson L Moritz
- Department of Ophthalmology & Visual Sciences, University of British Columbia, Vancouver, BC, Canada
| | - David S Williams
- Department of Ophthalmology and Jules Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, USA
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Chakraborty D, Conley SM, DeRamus ML, Pittler SJ, Naash MI. Varying the GARP2-to-RDS Ratio Leads to Defects in Rim Formation and Rod and Cone Function. Invest Ophthalmol Vis Sci 2016; 56:8187-98. [PMID: 26720471 DOI: 10.1167/iovs.15-17785] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
PURPOSE The beta subunit of the rod cyclic nucleotide gated channel B1 (CNGB1) contains a proline/glutamic acid-rich N-terminal domain (GARP), which is also present in rods as a non-membrane-bound protein (GARP1/2). GARP2 and CNGB1 bind to retinal degeneration slow (RDS), which is present in the rims of rod and cone outer segment (OS) layers. Here we focus on the importance of RDS/GARP complexes in OS morphogenesis and stability. METHODS Retinal structure, function, and biochemistry were assessed in GARP2-Tg transgenic mice crossed onto rds+/+, rds+/-, and rds-/- genetic backgrounds. RESULTS GARP2 expression decreased in animals with reduced RDS levels. Overexpression of GARP2 led to abnormalities in disc stacking in GARP2-Tg/rds+/+ and the accumulation of abnormal vesicular structures in GARP2-Tg/rds+/- OS, as well as alterations in RDS-ROM-1 complex formation. These abnormalities were associated with diminished scotopic a- and b-wave amplitudes in GARP2-Tg mice on both the rds+/+ and rds+/- backgrounds. In addition, severe defects in cone function were observed in GARP2-Tg mice on all RDS backgrounds. CONCLUSIONS Our results indicate that overexpression of GARP2 significantly exacerbates the defects in rod function associated with RDS haploinsufficiency and leads to further abnormalities in OS ultrastructure. These data also suggest that GARP2 expression in cones can be detrimental to cones. RDS/GARP interactions remain under investigation but are critical for both OS structure and function.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Cell Biology University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Shannon M Conley
- Department of Cell Biology University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Marci L DeRamus
- Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Steven J Pittler
- Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, United States
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Asteriti S, Cangiano L. Slow light response kinetics in rods points towards a perturbation of the normal cellular milieu. J Physiol 2016; 593:2975-6. [PMID: 26123098 DOI: 10.1113/jp270504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Sabrina Asteriti
- Department of Translational Research, University of Pisa, Via San Zeno 31, 56123, Pisa, Italy
| | - Lorenzo Cangiano
- Department of Translational Research, University of Pisa, Via San Zeno 31, 56123, Pisa, Italy.
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Koch KW, Dell'Orco D. Protein and Signaling Networks in Vertebrate Photoreceptor Cells. Front Mol Neurosci 2015; 8:67. [PMID: 26635520 PMCID: PMC4646965 DOI: 10.3389/fnmol.2015.00067] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/26/2015] [Indexed: 01/10/2023] Open
Abstract
Vertebrate photoreceptor cells are exquisite light detectors operating under very dim and bright illumination. The photoexcitation and adaptation machinery in photoreceptor cells consists of protein complexes that can form highly ordered supramolecular structures and control the homeostasis and mutual dependence of the secondary messengers cyclic guanosine monophosphate (cGMP) and Ca2+. The visual pigment in rod photoreceptors, the G protein-coupled receptor rhodopsin is organized in tracks of dimers thereby providing a signaling platform for the dynamic scaffolding of the G protein transducin. Illuminated rhodopsin is turned off by phosphorylation catalyzed by rhodopsin kinase (GRK1) under control of Ca2+-recoverin. The GRK1 protein complex partly assembles in lipid raft structures, where shutting off rhodopsin seems to be more effective. Re-synthesis of cGMP is another crucial step in the recovery of the photoresponse after illumination. It is catalyzed by membrane bound sensory guanylate cyclases (GCs) and is regulated by specific neuronal Ca2+-sensor proteins called guanylate cyclase-activating proteins (GCAPs). At least one GC (ROS-GC1) was shown to be part of a multiprotein complex having strong interactions with the cytoskeleton and being controlled in a multimodal Ca2+-dependent fashion. The final target of the cGMP signaling cascade is a cyclic nucleotide-gated (CNG) channel that is a hetero-oligomeric protein located in the plasma membrane and interacting with accessory proteins in highly organized microdomains. We summarize results and interpretations of findings related to the inhomogeneous organization of signaling units in photoreceptor outer segments.
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Affiliation(s)
- Karl-Wilhelm Koch
- Department of Neurosciences, Biochemistry Group, University of Oldenburg Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry and Center for BioMedical Computing (CBMC), University of Verona Verona, Italy
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