1
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Rajala RVS, Rajala A. From Insight to Eyesight: Unveiling the Secrets of the Insulin-Like Growth Factor Axis in Retinal Health. Aging Dis 2024; 15:1994-2002. [PMID: 38300646 PMCID: PMC11346401 DOI: 10.14336/ad.2024.0128] [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: 01/01/2024] [Accepted: 01/29/2024] [Indexed: 02/02/2024] Open
Abstract
Insulin-like growth factor-1 (IGF-1) plays a diverse role in the retina, exerting its effects in both normal and diseased conditions. Deficiency of IGF-1 in humans leads to issues such as microcephaly, mental retardation, deafness, and postnatal growth failure. IGF-1 is produced in the retinal pigment epithelium (RPE) and activates the IGF-1 receptor (IGF-1R) in photoreceptor cells. When IGF-1R is absent in rod cells, it results in the degeneration of photoreceptors, emphasizing the neuroprotective function of IGF signaling in these cells. Contrastingly, in neovascular age-related macular degeneration (AMD), there is an overexpression of both IGF-1 and IGF-1R in RPE. The mechanisms behind this altered regulation of IGF-1 in diseased states are currently unknown. This comprehensive review provides recent insights into the role of IGF-1 in the health and disease of the retina, raising several unanswered questions that still need further investigation.
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Affiliation(s)
- Raju V. S. Rajala
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma, USA.
- Physiology, University of Oklahoma Health Sciences Center, Oklahoma, USA.
- Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, USA.
- Dean McGee Eye Institute, Oklahoma, Oklahoma, USA.
| | - Ammaji Rajala
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma, USA.
- Dean McGee Eye Institute, Oklahoma, Oklahoma, USA.
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2
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Ebrahimi M, Thompson P, Lauer AK, Sivaprasad S, Perry G. The retina-brain axis and diabetic retinopathy. Eur J Ophthalmol 2023; 33:2079-2095. [PMID: 37259525 DOI: 10.1177/11206721231172229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Diabetic retinopathy (DR) is a major contributor to permanent vision loss and blindness. Changes in retinal neurons, glia, and microvasculature have been the focus of intensive study in the quest to better understand DR. However, the impact of diabetes on the rest of the visual system has received less attention. There are reports of associations of changes in the visual system with preclinical and clinical manifestations of diabetes. Simultaneous investigation of the retina and the brain may shed light on the mechanisms underlying neurodegeneration in diabetics. Additionally, investigating the links between DR and other neurodegenerative disorders of the brain including Alzheimer's and Parkinson's disease may reveal shared mechanisms for neurodegeneration and potential therapy options.
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Affiliation(s)
- Moein Ebrahimi
- School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Network of Immunity in Infection, Malignancy, and Autoimmunity, Universal Scientific Education and Research Network (USERN), Tehran, Iran
| | - Paul Thompson
- Imaging Genetics Center, Mark and Mary Stevens Institute for Neuroimaging and Informatics, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Andreas K Lauer
- Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA
| | - Sobha Sivaprasad
- National Institute of Health and Care Research Moorfields Biomedical Research Centre, Moorfields Eye Hospital, London, UK
| | - George Perry
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas and San Antonio, San Antonio, TX, USA
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3
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Lantz C, Thorp EB. Metabolism: How removal of damaged cells impacts energy availability in the retina. Curr Biol 2023; 33:R279-R282. [PMID: 37040713 PMCID: PMC10410992 DOI: 10.1016/j.cub.2023.02.044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
Once thought to be a quiescent process, elimination of damaged cells by professional phagocytes is now understood to modulate metabolite availability within tissues. A new study reveals that the retinal pigment epithelium serves as a local source of insulin after engulfment of damaged photoreceptors.
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Affiliation(s)
- Connor Lantz
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
| | - Edward B Thorp
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Feinberg Cardiovascular and Renal Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; The Heart Center, Stanley Manne Children's Research Institute, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA.
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4
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Iker Etchegaray J, Kelley S, Penberthy K, Karvelyte L, Nagasaka Y, Gasperino S, Paul S, Seshadri V, Raymond M, Marco AR, Pinney J, Stremska M, Barron B, Lucas C, Wase N, Fan Y, Unanue E, Kundu B, Burstyn-Cohen T, Perry J, Ambati J, Ravichandran KS. Phagocytosis in the retina promotes local insulin production in the eye. Nat Metab 2023; 5:207-218. [PMID: 36732622 PMCID: PMC10457724 DOI: 10.1038/s42255-022-00728-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 12/16/2022] [Indexed: 02/04/2023]
Abstract
The retina is highly metabolically active, relying on glucose uptake and aerobic glycolysis. Situated in close contact to photoreceptors, a key function of cells in the retinal pigment epithelium (RPE) is phagocytosis of damaged photoreceptor outer segments (POS). Here we identify RPE as a local source of insulin in the eye that is stimulated by POS phagocytosis. We show that Ins2 messenger RNA and insulin protein are produced by RPE cells and that this production correlates with RPE phagocytosis of POS. Genetic deletion of phagocytic receptors ('loss of function') reduces Ins2, whereas increasing the levels of the phagocytic receptor MerTK ('gain of function') increases Ins2 production in male mice. Contrary to pancreas-derived systemic insulin, RPE-derived local insulin is stimulated during starvation, which also increases RPE phagocytosis. Global or RPE-specific Ins2 gene deletion decreases retinal glucose uptake in starved male mice, dysregulates retinal physiology, causes defects in phototransduction and exacerbates photoreceptor loss in a mouse model of retinitis pigmentosa. Collectively, these data identify RPE cells as a phagocytosis-induced local source of insulin in the retina, with the potential to influence retinal physiology and disease.
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Affiliation(s)
- J Iker Etchegaray
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Shannon Kelley
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Kristen Penberthy
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Laura Karvelyte
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Yosuke Nagasaka
- Center for Advanced Vision Science, University of Virginia, Charlottesville, VA, USA
| | - Sofia Gasperino
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Soumen Paul
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Vikram Seshadri
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Michael Raymond
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Ana Royo Marco
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Jonathan Pinney
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
| | - Marta Stremska
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Brady Barron
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Christopher Lucas
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA
- University of Edinburgh, Edinburgh, UK
| | - Nishikant Wase
- Biomolecular Analysis Facility, University of Virginia, Charlottesville, VA, USA
| | - Yong Fan
- Drexel University, Philadelphia, PA, USA
| | - Emil Unanue
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Bijoy Kundu
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, USA
| | - Tal Burstyn-Cohen
- Hadassah Medical School, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Justin Perry
- Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jayakrishna Ambati
- Center for Advanced Vision Science, University of Virginia, Charlottesville, VA, USA
- Ophthalmology, University of Virginia, Charlottesville, VA, USA
| | - Kodi S Ravichandran
- Center for Cell Clearance, University of Virginia, Charlottesville, VA, USA.
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA.
- Hadassah Medical School, Hebrew University of Jerusalem, Jerusalem, Israel.
- VIB/UGent Inflammation Research Centre, and Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
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5
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Rajala A, Teel K, Bhat MA, Batushansky A, Griffin TM, Purcell L, Rajala RVS. Insulin-like growth factor 1 receptor mediates photoreceptor neuroprotection. Cell Death Dis 2022; 13:613. [PMID: 35840554 PMCID: PMC9287313 DOI: 10.1038/s41419-022-05074-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 07/04/2022] [Accepted: 07/06/2022] [Indexed: 01/21/2023]
Abstract
Insulin-like growth factor I (IGF-1) is a neurotrophic factor and is the ligand for insulin-like growth factor 1 receptor (IGF-1R). Reduced expression of IGF-1 has been reported to cause deafness, mental retardation, postnatal growth failure, and microcephaly. IGF-1R is expressed in the retina and photoreceptor neurons; however, its functional role is not known. Global IGF-1 KO mice have age-related vision loss. We determined that conditional deletion of IGF-1R in photoreceptors and pan-retinal cells produces age-related visual function loss and retinal degeneration. Retinal pigment epithelial cell-secreted IGF-1 may be a source for IGF-1R activation in the retina. Altered retinal, fatty acid, and phosphoinositide metabolism are observed in photoreceptor and retinal cells lacking IGF-1R. Our results suggest that the IGF-1R pathway is indispensable for photoreceptor survival, and activation of IGF-1R may be an essential element of photoreceptor and retinal neuroprotection.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Dean McGee Eye Institute, Oklahoma City, OK, 73104, USA
| | - Kenneth Teel
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Dean McGee Eye Institute, Oklahoma City, OK, 73104, USA
| | - Mohd A Bhat
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Dean McGee Eye Institute, Oklahoma City, OK, 73104, USA
| | | | | | - Lindsey Purcell
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Dean McGee Eye Institute, Oklahoma City, OK, 73104, USA
| | - Raju V S Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
- Dean McGee Eye Institute, Oklahoma City, OK, 73104, USA.
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
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6
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Insulin receptor activation by proinsulin preserves synapses and vision in retinitis pigmentosa. Cell Death Dis 2022; 13:383. [PMID: 35444190 PMCID: PMC9021205 DOI: 10.1038/s41419-022-04839-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 04/04/2022] [Accepted: 04/05/2022] [Indexed: 11/23/2022]
Abstract
Synaptic loss, neuronal death, and circuit remodeling are common features of central nervous system neurodegenerative disorders. Retinitis pigmentosa (RP), the leading cause of inherited blindness, is a group of retinal dystrophies characterized by photoreceptor dysfunction and death. The insulin receptor, a key controller of metabolism, also regulates neuronal survival and synaptic formation, maintenance, and activity. Indeed, deficient insulin receptor signaling has been implicated in several brain neurodegenerative pathologies. We present evidence linking impaired insulin receptor signaling with RP. We describe a selective decrease in the levels of the insulin receptor and its downstream effector phospho-S6 in retinal horizontal cell terminals in the rd10 mouse model of RP, as well as aberrant synapses between rod photoreceptors and the postsynaptic terminals of horizontal and bipolar cells. A gene therapy strategy to induce sustained proinsulin, the insulin precursor, production restored retinal insulin receptor signaling, by increasing S6 phosphorylation, without peripheral metabolic consequences. Moreover, proinsulin preserved photoreceptor synaptic connectivity and prolonged visual function in electroretinogram and optomotor tests. These findings point to a disease-modifying role of insulin receptor and support the therapeutic potential of proinsulin in retinitis pigmentosa.
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7
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Pitale PM, Gorbatyuk MS. Diabetic Retinopathy: From Animal Models to Cellular Signaling. Int J Mol Sci 2022; 23:ijms23031487. [PMID: 35163410 PMCID: PMC8835767 DOI: 10.3390/ijms23031487] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 12/24/2022] Open
Abstract
Diabetic retinopathy (DR) is an ocular complication of diabetes mellitus (DM), a metabolic disorder characterized by elevation in blood glucose level. The pathogenesis of DR includes vascular, neuronal, and inflammatory components leading to activation of complex cellular molecular signaling. If untreated, the disease can culminate in vision loss that eventually leads to blindness. Animal models mimicking different aspects of DM complications have been developed to study the development and progression of DR. Despite the significant contribution of the developed DR models to discovering the mechanisms of DR and the recent achievements in the research field, the sequence of cellular events in diabetic retinas is still under investigation. Partially, this is due to the complexity of molecular mechanisms, although the lack of availability of models that adequately mimic all the neurovascular pathobiological features observed in patients has also contributed to the delay in determining a precise molecular trigger. In this review, we provide an update on the status of animal models of DR to help investigators choose an appropriate system to validate their hypothesis. We also discuss the key cellular and physiological events of DR in these models.
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Affiliation(s)
- Priyamvada M. Pitale
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA;
| | - Marina S. Gorbatyuk
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
- Correspondence: ; Tel.: +1-205-934-6762; Fax: +1-205-934-3425
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8
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Teimouri M, Hosseini H, ArabSadeghabadi Z, Babaei-Khorzoughi R, Gorgani-Firuzjaee S, Meshkani R. The role of protein tyrosine phosphatase 1B (PTP1B) in the pathogenesis of type 2 diabetes mellitus and its complications. J Physiol Biochem 2022; 78:307-322. [PMID: 34988903 DOI: 10.1007/s13105-021-00860-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 11/16/2021] [Indexed: 01/16/2023]
Abstract
Insulin resistance, the most important characteristic of the type 2 diabetes mellitus (T2DM), is mostly caused by impairment in the insulin receptor (IR) signal transduction pathway. Protein tyrosine phosphatase 1B (PTP1B), one of the main negative regulators of the IR signaling pathway, is broadly expressed in various cells and tissues. PTP1B decreases the phosphorylation of the IR resulting in insulin resistance in various tissues. The evidence for the physiological role of PTP1B in regulation of metabolic pathways came from whole-body PTP1B-knockout mice. Whole-body and tissue-specific PTP1B-knockout mice showed improvement in adiposity, insulin resistance, and glucose tolerance. In addition, the key role of PTP1B in the pathogenesis of T2DM and its complications was further investigated in mice models of PTP1B deficient/overexpression. In recent years, targeting PTP1B using PTP1B inhibitors is being considered an attractive target to treat T2DM. PTP1B inhibitors improve the sensitivity of the insulin receptor and have the ability to cure insulin resistance-related diseases. We herein summarized the biological functions of PTP1B in different tissues in vivo and in vitro. We also describe the effectiveness of potent PTP1B inhibitors as pharmaceutical agents to treat T2DM.
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Affiliation(s)
- Maryam Teimouri
- Department of Clinical Biochemistry, School of Allied Medical Sciences, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Hossein Hosseini
- Department of Clinical Biochemistry, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Zahra ArabSadeghabadi
- Department of Clinical Sciences, Faculty of Veterinary Science, Bu-Ali Sina University, Hamedan, Iran
| | - Reyhaneh Babaei-Khorzoughi
- Department of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Sattar Gorgani-Firuzjaee
- Department of Medical Laboratory Sciences, School of Allied Health Medicine, AJA University of Medical Sciences, Tehran, Iran
| | - Reza Meshkani
- Department of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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9
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Ipp E. Diabetic Retinopathy and Insulin Insufficiency: Beta Cell Replacement as a Strategy to Prevent Blindness. Front Endocrinol (Lausanne) 2021; 12:734360. [PMID: 34912295 PMCID: PMC8667804 DOI: 10.3389/fendo.2021.734360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 09/28/2021] [Indexed: 12/02/2022] Open
Abstract
Diabetic retinopathy (DR) is a potentially devastating complication of diabetes because it puts patients at risk of blindness. Diabetes is a common cause of blindness in the U.S. and worldwide and is dramatically increasing in global prevalence. Thus new approaches are needed to prevent this dreaded complication. There is extensive data that indicates beta cell secretory failure is a risk factor for DR, independent of its influence on glycemic control. This perspective article will provide evidence for insufficient endogenous insulin secretion as an important factor in the development of DR. The areas of evidence discussed are: (a) Presence of insulin receptors in the retina, (b) Clinical studies that show an association of beta cell insufficiency with DR, (c) Treatment with insulin in type 2 diabetes, a marker for endogenous insulin deficiency, is an independent risk factor for DR, (d) Recent clinical studies that link DR with an insulin deficient form of type 2 diabetes, and (e) Beta cell replacement studies that demonstrate endogenous insulin prevents progression of DR. The cumulative data drive our conclusion that beta cell replacement will have an important role in preventing DR and/or mitigating its severity in both type 1 diabetes and insulinopenic type 2 diabetes.
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Affiliation(s)
- Eli Ipp
- Department of Medicine, The Lundquist Institute at Harbor-University of California Los Angeles (UCLA) Medical Center, Torrance, CA, United States
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10
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Wei C, Li Y, Feng X, Hu Z, Paquet-Durand F, Jiao K. RNA Biological Characteristics at the Peak of Cell Death in Different Hereditary Retinal Degeneration Mutants. Front Genet 2021; 12:728791. [PMID: 34777465 PMCID: PMC8586524 DOI: 10.3389/fgene.2021.728791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/21/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: The present work investigated changes in the gene expression, molecular mechanisms, and pathogenesis of inherited retinal degeneration (RD) in three different disease models, to identify predictive biomarkers for their varied phenotypes and to provide a better scientific basis for their diagnosis, treatment, and prevention. Methods: Differentially expressed genes (DEGs) between retinal tissue from RD mouse models obtained during the photoreceptor cell death peak period (Pde6b rd1 at post-natal (PN) day 13, Pde6b rd10 at PN23, Prph rd2 at PN29) and retinal tissue from C3H wild-type mice were identified using Illumina high-throughput RNA-sequencing. Co-expression gene modules were identified using a combination of GO and KEGG enrichment analyses and gene co-expression network analysis. CircRNA-miRNA-mRNA network interactions were studied by genome-wide circRNA screening. Results: Pde6b rd1 , Pde6b rd10 , and Prph rd2 mice had 1,926, 3,096, and 375 DEGs, respectively. Genes related to ion channels, stress, inflammatory processes, tumor necrosis factor (TNF) production, and microglial cell activation were up-regulated, while genes related to endoplasmic reticulum regulation, metabolism, and homeostasis were down-regulated. Differential expression of transcription factors and non-coding RNAs generally implicated in other human diseases was detected (e.g., glaucoma, diabetic retinopathy, and inherited retinal degeneration). CircRNA-miRNA-mRNA network analysis indicated that these factors may be involved in photoreceptor cell death. Moreover, excessive cGMP accumulation causes photoreceptor cell death, and cGMP-related genes were generally affected by different pathogenic gene mutations. Conclusion: We screened genes and pathways related to photoreceptor cell death. Additionally, up-stream regulatory factors, such as transcription factors and non-coding RNA and their interaction networks were analyzed. Furthermore, RNAs involved in RD were functionally annotated. Overall, this study lays a foundation for future studies on photoreceptor cell death mechanisms.
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Affiliation(s)
- Chunling Wei
- Kunming Medical University, Kunming, China.,Department of Ophthalmology, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, China
| | - Yan Li
- Department of Ophthalmology, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, China.,Key Laboratory of Yunnan Province, Yunnan Eye Institute, Kunming, China
| | - Xiaoxiao Feng
- Department of Ophthalmology, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, China.,Key Laboratory of Yunnan Province, Yunnan Eye Institute, Kunming, China
| | - Zhulin Hu
- Department of Ophthalmology, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, China.,Key Laboratory of Yunnan Province, Yunnan Eye Institute, Kunming, China
| | - François Paquet-Durand
- Institute for Ophthalmic Research, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Kangwei Jiao
- Department of Ophthalmology, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, China.,Key Laboratory of Yunnan Province, Yunnan Eye Institute, Kunming, China
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11
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Tonade D, Kern TS. Photoreceptor cells and RPE contribute to the development of diabetic retinopathy. Prog Retin Eye Res 2021; 83:100919. [PMID: 33188897 PMCID: PMC8113320 DOI: 10.1016/j.preteyeres.2020.100919] [Citation(s) in RCA: 88] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 10/27/2020] [Accepted: 10/31/2020] [Indexed: 12/26/2022]
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.
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Affiliation(s)
- Deoye Tonade
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Timothy S Kern
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA; Veterans Administration Medical Center Research Service, Cleveland, OH, USA; Gavin Herbert Eye Institute, University of California Irvine, Irvine, CA, USA; Veterans Administration Medical Center Research Service, Long Beach, CA, USA.
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12
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Rajala RVS, McCauley A, Rajala R, Teel K, Rajala A. Regulation of Phosphoinositide Levels in the Retina by Protein Tyrosine Phosphatase 1B and Growth Factor Receptor-Bound Protein 14. Biomolecules 2021; 11:biom11040602. [PMID: 33921658 PMCID: PMC8073254 DOI: 10.3390/biom11040602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 04/09/2021] [Accepted: 04/15/2021] [Indexed: 11/16/2022] Open
Abstract
Protein tyrosine kinases and protein phosphatases play a critical role in cellular regulation. The length of a cellular response depends on the interplay between activating protein kinases and deactivating protein phosphatases. Protein tyrosine phosphatase 1B (PTP1B) and growth factor receptor-bound protein 14 (Grb14) are negative regulators of receptor tyrosine kinases. However, in the retina, we have previously shown that PTP1B inactivates insulin receptor signaling, whereas phosphorylated Grb14 inhibits PTP1B activity. In silico docking of phosphorylated Grb14 and PTP1B indicate critical residues in PTP1B that may mediate the interaction. Phosphoinositides (PIPs) are acidic lipids and minor constituents in the cell that play an important role in cellular processes. Their levels are regulated by growth factor signaling. Using phosphoinositide binding protein probes, we observed increased levels of PI(3)P, PI(4)P, PI(3,4)P2, PI(4,5)P2, and PI(3,4,5)P3 in PTP1B knockout mouse retina and decreased levels of these PIPs in Grb14 knockout mouse retina. These observations suggest that the interplay between PTP1B and Grb14 can regulate PIP metabolism.
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Affiliation(s)
- Raju V. S. Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.M.); (K.T.); (A.R.)
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
- Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
- Correspondence: ; Tel.: +1-405-271-8255; Fax: +1-405-271-8128
| | - Austin McCauley
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.M.); (K.T.); (A.R.)
- Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
| | - Rahul Rajala
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA;
- Cardiovascular Biology Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Kenneth Teel
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.M.); (K.T.); (A.R.)
- Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
| | - Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA; (A.M.); (K.T.); (A.R.)
- Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
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13
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Abstract
The field of phosphoinositide signaling has expanded significantly in recent years. Phosphoinositides (also known as phosphatidylinositol phosphates or PIPs) are universal signaling molecules that directly interact with membrane proteins or with cytosolic proteins containing domains that directly bind phosphoinositides and are recruited to cell membranes. Through the activities of phosphoinositide kinases and phosphoinositide phosphatases, seven distinct phosphoinositide lipid molecules are formed from the parent molecule, phosphatidylinositol. PIP signals regulate a wide range of cellular functions, including cytoskeletal assembly, membrane budding and fusion, ciliogenesis, vesicular transport, and signal transduction. Given the many excellent reviews on phosphoinositide kinases, phosphoinositide phosphatases, and PIPs in general, in this review, we discuss recent studies and advances in PIP lipid signaling in the retina. We specifically focus on PIP lipids from vertebrate (e.g., bovine, rat, mouse, toad, and zebrafish) and invertebrate (e.g., Drosophila, horseshoe crab, and squid) retinas. We also discuss the importance of PIPs revealed from animal models and human diseases, and methods to study PIP levels both in vitro and in vivo. We propose that future studies should investigate the function and mechanism of activation of PIP-modifying enzymes/phosphatases and further unravel PIP regulation and function in the different cell types of the retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology, Physiology, and Cell Biology, and Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104.
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14
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Abstract
Based on clinical findings, diabetic retinopathy (DR) has traditionally been defined as a retinal microvasculopathy. Retinal neuronal dysfunction is now recognized as an early event in the diabetic retina before development of overt DR. While detrimental effects of diabetes on the survival and function of inner retinal cells, such as retinal ganglion cells and amacrine cells, are widely recognized, evidence that photoreceptors in the outer retina undergo early alterations in diabetes has emerged more recently. We review data from preclinical and clinical studies demonstrating a conserved reduction of electrophysiological function in diabetic retinas, as well as evidence for photoreceptor loss. Complementing in vivo studies, we discuss the ex vivo electroretinography technique as a useful method to investigate photoreceptor function in isolated retinas from diabetic animal models. Finally, we consider the possibility that early photoreceptor pathology contributes to the progression of DR, and discuss possible mechanisms of photoreceptor damage in the diabetic retina, such as enhanced production of reactive oxygen species and other inflammatory factors whose detrimental effects may be augmented by phototransduction.
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Sundar JC, Munezero D, Bryan-Haring C, Saravanan T, Jacques A, Ramamurthy V. Rhodopsin signaling mediates light-induced photoreceptor cell death in rd10 mice through a transducin-independent mechanism. Hum Mol Genet 2020; 29:394-406. [PMID: 31925423 PMCID: PMC7015845 DOI: 10.1093/hmg/ddz299] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 11/22/2019] [Accepted: 12/02/2019] [Indexed: 01/08/2023] Open
Abstract
Retinitis pigmentosa (RP) is a debilitating blinding disease affecting over 1.5 million people worldwide, but the mechanisms underlying this disease are not well understood. One of the common models used to study RP is the retinal degeneration-10 (rd10) mouse, which has a mutation in Phosphodiesterase-6b (Pde6b) that causes a phenotype mimicking the human disease. In rd10 mice, photoreceptor cell death occurs with exposure to normal light conditions, but as demonstrated in this study, rearing these mice in dark preserves their retinal function. We found that inactivating rhodopsin signaling protected photoreceptors from degeneration suggesting that the pathway activated by this G-protein-coupled receptor is causing light-induced photoreceptor cell death in rd10 mice. However, inhibition of transducin signaling did not prevent the loss of photoreceptors in rd10 mice reared under normal light conditions implying that the degeneration caused by rhodopsin signaling is not mediated through its canonical G-protein transducin. Inexplicably, loss of transducin in rd10 mice also led to photoreceptor cell death in darkness. Furthermore, we found that the rd10 mutation in Pde6b led to a reduction in the assembled PDE6αβγ2 complex, which was corroborated by our data showing mislocalization of the γ subunit. Based on our findings and previous studies, we propose a model where light activates a non-canonical pathway mediated by rhodopsin but independent of transducin that sensitizes cyclic nucleotide gated channels to cGMP and causes photoreceptor cell death. These results generate exciting possibilities for treatment of RP patients without affecting their vision or the canonical phototransduction cascade.
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Affiliation(s)
- Jesse C Sundar
- Departments of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
| | - Daniella Munezero
- Departments of Ophthalmology and Visual Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
| | - Caitlyn Bryan-Haring
- Departments of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
| | - Thamaraiselvi Saravanan
- Departments of Ophthalmology and Visual Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
| | - Angelica Jacques
- Departments of Ophthalmology and Visual Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
| | - Visvanathan Ramamurthy
- Departments of Biochemistry, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
- Departments of Ophthalmology and Visual Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
- Departments of Neuroscience, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, WV 26505, USA
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16
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Rajala A, Rajala RVS. A non-canonical rhodopsin-mediated insulin receptor signaling pathway in retinal photoreceptor neurons. Cell Biol Int 2020; 44:1020-1027. [PMID: 31889373 DOI: 10.1002/cbin.11299] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/28/2019] [Indexed: 01/08/2023]
Abstract
We previously reported a ligand-independent and rhodopsin-dependent insulin receptor (IR) neuroprotective signaling pathway in both rod and cone photoreceptor cells, which is activated through protein-protein interaction. Our previous studies were performed with either retina or isolated rod or cone outer segment preparations and the expression of IR signaling proteins were examined. The isolation of outer segments with large portions of the attached inner segments is a technical challenge. Optiprep™ density gradient medium has been used to isolate the cells and subcellular organelles, Optiprep™ is a non-ionic iodixanol-based medium with a density of 1.320 g/mL. We employed this method to examine the expression of IR and its signaling proteins, and activation of one of the downstream effectors of the IR in isolated photoreceptor cells. Identification of the signaling complexes will be helpful for therapeutic targeting in disease conditions.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma, OK, 73104, USA.,Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma City, OK, 73104, USA
| | - Raju V S Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma, OK, 73104, USA.,Department of Physiology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma, OK, 73104, USA.,Department of Cell Biology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma, OK, 73104, USA.,Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd, Oklahoma City, OK, 73104, USA
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17
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Rajala RVS. Therapeutic Benefits from Nanoparticles: The Potential Significance of Nanoscience in Retinal Degenerative Diseases. JOURNAL OF MOLECULAR BIOLOGY & THERAPEUTICS 2019; 1:44-55. [PMID: 34528026 PMCID: PMC8439377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Several nanotechnology podiums have gained remarkable attention in the area of medical sciences, including diagnostics and treatment. In the past decade, engineered multifunctional nanoparticles have served as drug and gene carriers. The most important aspect of translating nanoparticles from the bench to bedside is safety. These nanoparticles should not elicit any immune response and should not be toxic to humans or the environment. Lipid-based nanoparticles have been shown to be the least toxic for in vivo applications, and significant progress has been made in gene and drug delivery employing lipid-based nanoassemblies. Several excellent reviews and reports discuss the general use and application of lipid-based nanoparticles; our review focuses on the application of lipid-based nanoparticles for the treatment of ocular diseases, and recent advances in and updates on their use.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology, Physiology and Cell Biology, University of Oklahoma Health Sciences Center, Dean McGee Eye Institute, Oklahoma City, OK 73104, USA
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18
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Tarchick MJ, Cutler AH, Trobenter TD, Kozlowski MR, Makowski ER, Holoman N, Shao J, Shen B, Anand-Apte B, Samuels IS. Endogenous insulin signaling in the RPE contributes to the maintenance of rod photoreceptor function in diabetes. Exp Eye Res 2018; 180:63-74. [PMID: 30543793 DOI: 10.1016/j.exer.2018.11.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 11/19/2018] [Accepted: 11/20/2018] [Indexed: 01/01/2023]
Abstract
In diabetes, there are two major physiological aberrations: (i) Loss of insulin signaling due to absence of insulin (type 1 diabetes) or insulin resistance (type 2 diabetes) and (ii) increased blood glucose levels. The retina has a high proclivity to damage following diabetes, and much of the pathology seen in diabetic retinopathy has been ascribed to hyperglycemia and downstream cascades activated by increased blood glucose. However, less attention has been focused on the direct role of insulin on retinal physiology, likely due to the fact that uptake of glucose in retinal cells is not insulin-dependent. The retinal pigment epithelium (RPE) is instrumental in maintaining the structural and functional integrity of the retina. Recent studies have suggested that RPE dysfunction is a precursor of, and contributes to, the development of diabetic retinopathy. To evaluate the role of insulin on RPE cell function directly, we generated a RPE specific insulin receptor (IR) knockout (RPEIRKO) mouse using the Cre-loxP system. Using this mouse, we sought to determine the impact of insulin-mediated signaling in the RPE on retinal function under physiological control conditions as well as in streptozotocin (STZ)-induced diabetes. We demonstrate that loss of RPE-specific IR expression resulted in lower a- and b-wave electroretinogram amplitudes in diabetic mice as compared to diabetic mice that expressed IR on the RPE. Interestingly, RPEIRKO mice did not exhibit significant differences in the amplitude of the RPE-dependent electroretinogram c-wave as compared to diabetic controls. However, loss of IR-mediated signaling in the RPE reduced levels of reactive oxygen species and the expression of pro-inflammatory cytokines in the retina of diabetic mice. These results imply that IR-mediated signaling in the RPE regulates photoreceptor function and may play a role in the generation of oxidative stress and inflammation in the retina in diabetes.
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Affiliation(s)
- Matthew J Tarchick
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Alecia H Cutler
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Timothy D Trobenter
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Michael R Kozlowski
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Emily R Makowski
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Nicholas Holoman
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Jianning Shao
- Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Bailey Shen
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Bela Anand-Apte
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA; Department of Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
| | - Ivy S Samuels
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, USA; Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH, USA.
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19
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de Pablo F, Hernández-Sánchez C, de la Rosa EJ. The Prohormone Proinsulin as a Neuroprotective Factor: Past History and Future Prospects. Front Mol Neurosci 2018; 11:426. [PMID: 30534050 PMCID: PMC6275302 DOI: 10.3389/fnmol.2018.00426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 11/02/2018] [Indexed: 01/22/2023] Open
Abstract
Proinsulin was first identified as the primary translation product of the insulin gene in Donald Steiner’s laboratory in 1967, and was the first prohormone to be isolated and sequenced. While its role as an insulin precursor has been extensively studied in the field of endocrinology, the bioactivity of the proinsulin molecule itself has received much less attention. Insulin binds to isoforms A and B of the insulin receptor (IR) with high affinity. Proinsulin, in contrast, binds with high affinity only to IR-A, which is present in the nervous system, among other tissues and elicits antiapoptotic and neuroprotective effects in the developing and postnatal nervous system. Proinsulin specifically exerts neuroprotection in the degenerating retina in mouse and rat models of retinitis pigmentosa (RP), delaying photoreceptor and vision loss after local administration in the eye or systemic (intramuscular) administration of an adeno-associated viral (AAV) vector that induces constitutive proinsulin release. AAV-mediated proinsulin expression also decreases the expression of neuroinflammation markers in the hippocampus and sustains cognitive performance in a mouse model of precocious brain senescence. We have therefore proposed that proinsulin should be considered a functionally distinct member of the insulin superfamily. Here, we briefly review the legacy of Steiner’s research, the neural expression of proinsulin, and the tissue expression patterns and functional characteristics of IR-A. We discuss the neuroprotective activity of proinsulin and its potential as a therapeutic tool in neurodegenerative conditions of the central nervous system, particularly in retinal dystrophies.
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Affiliation(s)
- Flora de Pablo
- 3D Lab, Development, Differentiation and Degeneration, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CIB/CSIC), Madrid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain
| | - Catalina Hernández-Sánchez
- 3D Lab, Development, Differentiation and Degeneration, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CIB/CSIC), Madrid, Spain.,Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), ISCIII, Madrid, Spain
| | - Enrique J de la Rosa
- 3D Lab, Development, Differentiation and Degeneration, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas (CIB/CSIC), Madrid, Spain
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20
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Role of neuritin in retinal ganglion cell death in adult mice following optic nerve injury. Sci Rep 2018; 8:10132. [PMID: 29973613 PMCID: PMC6031618 DOI: 10.1038/s41598-018-28425-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 06/21/2018] [Indexed: 12/31/2022] Open
Abstract
Neuritin is a small extracellular protein that plays important roles in the process of neural development, synaptic plasticity, and neural cell survival. Here we investigated the function of neuritin in a mouse model of optic nerve injury (ONI). ONI induced upregulation of neuritin mRNA in the retina of WT mice. The retinal structure and the number of retinal ganglion cells (RGCs) were normal in adult neuritin knockout (KO) mice. In vivo retinal imaging and histopathological analyses demonstrated that RGC death and inner retinal degeneration following ONI were more severe in neuritin KO mice. Immunoblot analyses revealed that ONI-induced phosphorylation of Akt and ERK were suppressed in neuritin KO mice. Our findings suggest that neuritin has neuroprotective effects following ONI and may be useful for treatment of posttraumatic complication.
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21
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Jiang Y, Liu L, Steinle JJ. miRNA15a regulates insulin signal transduction in the retinal vasculature. Cell Signal 2018; 44:28-32. [PMID: 29339083 DOI: 10.1016/j.cellsig.2018.01.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/10/2018] [Accepted: 01/11/2018] [Indexed: 02/06/2023]
Abstract
We previously reported that tumor necrosis factor alpha (TNFα) could inhibit insulin signal transduction in retinal cells. We recently found that miR15a/16 also reduced TNFα in retinal endothelial cells (REC) and in vascular specific miR15a/16 knockout mice. Since in silico programs suggested that miR15a could directly bind the insulin receptor, we wanted to determine whether miR15a altered insulin signal transduction. We used a luciferase-based binding assay to determine whether miR15a directly bound the insulin receptor. We then used Western blotting, ELISA, and qPCR to investigate whether miR15a altered insulin signaling proteins in REC and in both miR15a/16 endothelial cell knockout and overexpressing mice. We also treated some REC with resveratrol to determine if resveratrol could increase miR15a expression, since resveratrol is protective to the diabetic retina. We found that miR15a directly bound the 3'UTR of the insulin receptor. Treatment with resveratrol increased miR15a expression in REC grown in high glucose. While total insulin receptor levels were not altered, insulin signal transduction was reduced in REC grown in high glucose and was restored with treatment with resveratrol. miR15a knockout mice had reduced insulin receptor phosphorylation and Akt2 levels, with increased insulin receptor substrate 1 (IRS-1) phosphorylation on serine 307, a site known to inhibit insulin signaling. In contrast, overexpression of miR15a increased insulin signal transduction. Taken together, these data suggest that miR15a binds the insulin receptor and indirectly regulates insulin receptor actions. It also offers an additional mechanism by which resveratrol is protective to the diabetic retina.
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Affiliation(s)
- Youde Jiang
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Li Liu
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, United States
| | - Jena J Steinle
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, United States; Department of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, United States.
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22
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Activation of oncogenic tyrosine kinase signaling promotes insulin receptor-mediated cone photoreceptor survival. Oncotarget 2018; 7:46924-46942. [PMID: 27391439 PMCID: PMC5216914 DOI: 10.18632/oncotarget.10447] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/26/2016] [Indexed: 01/18/2023] Open
Abstract
In humans, daylight vision is primarily mediated by cone photoreceptors. These cells die in age-related retinal degenerations. Prolonging the life of cones for even one decade would have an enormous beneficial effect on usable vision in an aging population. Photoreceptors are postmitotic, but shed 10% of their outer segments daily, and must synthesize the membrane and protein equivalent of a proliferating cell each day. Although activation of oncogenic tyrosine kinase and inhibition of tyrosine phosphatase signaling is known to be essential for tumor progression, the cellular regulation of this signaling in postmitotic photoreceptor cells has not been studied. In the present study, we report that a novel G-protein coupled receptor–mediated insulin receptor (IR) signaling pathway is regulated by non-receptor tyrosine kinase Src through the inhibition of protein tyrosine phosphatase IB (PTP1B). We demonstrated the functional significance of this pathway through conditional deletion of IR and PTP1B in cones, in addition to delaying the death of cones in a mouse model of cone degeneration by activating the Src. This is the first study demonstrating the molecular mechanism of a novel signaling pathway in photoreceptor cells, which provides a window of opportunity to save the dying cones in retinal degenerative diseases.
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23
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Abstract
Dysfunctional insulin signalling is a causative factor in type-2 diabetes. While insulin signal transduction has been well investigated in many tissues, less is known in retinal tissues. We have previously reported that toll-like receptor 4 (TLR4) is involved in retinal damage in diabetes. We used TLR4 retinal Müller cell-specific knockout mice and Müller cells in culture to investigate the effects of loss of TLR4 on Müller cell insulin signal transduction. Loss of TLR4 in the mouse retinal Müller cells led to increased insulin receptor and Akt phosphorylation, with reduced insulin receptor substrate 1 (IRS-1) phosphorylation on serine 307, which was associated with reduced cleavage of caspase 3. In retinal Müller cells grown in high glucose, insulin signal transduction was impaired, but these responses were reduced with cells were transfected with TLR4 siRNA. Taken together, the data suggest that TLR4 regulates insulin signal transduction in retinal Müller cells.
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Affiliation(s)
- Li Liu
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit MI
| | - Jena J. Steinle
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit MI
- Department of Ophthalmology, Wayne State University School of Medicine, Detroit MI
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24
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Neuroprotective Strategy in Retinal Degeneration: Suppressing ER Stress-Induced Cell Death via Inhibition of the mTOR Signal. Int J Mol Sci 2017; 18:ijms18010201. [PMID: 28106827 PMCID: PMC5297831 DOI: 10.3390/ijms18010201] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/13/2017] [Accepted: 01/16/2017] [Indexed: 12/11/2022] Open
Abstract
The retina is a specialized sensory organ, which is essential for light detection and visual formation in the human eye. Inherited retinal degenerations are a heterogeneous group of eye diseases that can eventually cause permanent vision loss. UPR (unfolded protein response) and ER (endoplasmic reticulum) stress plays an important role in the pathological mechanism of retinal degenerative diseases. mTOR (the mammalian target of rapamycin) kinase, as a signaling hub, controls many cellular processes, covering protein synthesis, RNA translation, ER stress, and apoptosis. Here, the hypothesis that inhibition of mTOR signaling suppresses ER stress-induced cell death in retinal degenerative disorders is discussed. This review surveys knowledge of the influence of mTOR signaling on ER stress arising from misfolded proteins and genetic mutations in retinal degenerative diseases and highlights potential neuroprotective strategies for treatment and therapeutic implications.
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25
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Spencer WJ, Pearring JN, Salinas RY, Loiselle DR, Skiba NP, Arshavsky VY. Progressive Rod-Cone Degeneration (PRCD) Protein Requires N-Terminal S-Acylation and Rhodopsin Binding for Photoreceptor Outer Segment Localization and Maintaining Intracellular Stability. Biochemistry 2016; 55:5028-37. [PMID: 27509380 PMCID: PMC5513659 DOI: 10.1021/acs.biochem.6b00489] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The light-sensing outer segments of photoreceptor cells harbor hundreds of flattened membranous discs containing the visual pigment, rhodopsin, and all the proteins necessary for visual signal transduction. PRCD (progressive rod-cone degeneration) protein is one of a few proteins residing specifically in photoreceptor discs, and the only one with completely unknown function. The importance of PRCD is highlighted by its mutations that cause photoreceptor degeneration and blindness in canine and human patients. Here we report that PRCD is S-acylated at its N-terminal cysteine and anchored to the cytosolic surface of disc membranes. We also showed that mutating the S-acylated cysteine to tyrosine, a common cause of blindness in dogs and a mutation found in affected human families, causes PRCD to be completely mislocalized from the photoreceptor outer segment. We next undertook a proteomic search for PRCD-interacting partners in disc membranes and found that it binds rhodopsin. This interaction was confirmed by reciprocal precipitation and co-chromatography experiments. We further demonstrated this interaction to be critically important for supporting the intracellular stability of PRCD, as the knockout of rhodopsin caused a drastic reduction in the photoreceptor content of PRCD. These data reveal the cause of photoreceptor disease in PRCD mutant dogs and implicate rhodopsin to be involved in PRCD's unknown yet essential function in photoreceptors.
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Affiliation(s)
- William J. Spencer
- Department of Pharmacology, Duke University, Durham, NC 27710
- Department of Ophthalmology, Duke University, Durham, NC 27710
| | | | - Raquel Y. Salinas
- Department of Pharmacology, Duke University, Durham, NC 27710
- Department of Ophthalmology, Duke University, Durham, NC 27710
| | | | | | - Vadim Y. Arshavsky
- Department of Pharmacology, Duke University, Durham, NC 27710
- Department of Ophthalmology, Duke University, Durham, NC 27710
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26
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McKeown AS, Pitale PM, Kraft TW. Signalling beyond photon absorption: extracellular retinoids and growth factors modulate rod photoreceptor sensitivity. J Physiol 2016; 594:1841-54. [PMID: 26691896 DOI: 10.1113/jp271650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 12/18/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We propose that the end product of chromophore bleaching in rod photoreceptors, all-trans retinol, is part of a feedback loop that increases the sensitivity of the phototransduction cascade in rods. A previously described light-induced hypersensitivity in rods, termed adaptive potentiation, is reduced by exogenously applied all-trans retinol but not all-trans retinal. This potentiation is produced by insulin-like growth factor-1, whose binding proteins are located in the extracellular matrix, even in our isolated retina preparation after removal of the retinal pigmented epithelium. Simple modelling suggests that the light stimuli used in the present study will produce sufficient all-trans retinol within the interphotoreceptor matrix to explain the potentiation effect. ABSTRACT Photoreceptors translate the absorption of photons into electrical signals for propagation through the visual system. Mammalian photoreceptor signalling has largely been studied in isolated cells, and such studies have necessarily avoided the complex environment of supportive proteins that surround the photoreceptors. The interphotoreceptor matrix (IPM) contains an array of proteins that aid in both structural maintenance and cellular homeostasis, including chromophore turnover. In signalling photon absorption, the chromophore 11-cis retinal is first isomerized to all-trans retinal, followed by conversion to all-trans retinol (ROL) for removal from the photoreceptor. Interphotoreceptor retinoid-binding protein (IRBP) is the most abundant protein in the IPM, and it promotes the removal of bleached chromophores and recycling in the nearby retinal pigment epithelium. By studying the light responses of isolated mouse retinas, we demonstrate that ROL can act as a feedback signal onto photoreceptors that influences the sensitivity of phototransduction. In addition to IRBP, the IPM also contains insulin-like growth factor-1 (IGF-1) and its associated binding proteins, although their functions have not yet been described. We demonstrate that extracellular application of physiological concentrations of IGF-1 can increase rod photoreceptor sensitivity in mammalian retinas. We also determine that chromophores and growth factors can limit the range of a newly described form of photoreceptor light adaptation. Finally, fluorescent antibodies demonstrate the presence of IRBP and IGFBP-3 in isolated retinas. A simple model of the formation and release of ROL into the extracellular space quantitatively describes this novel feedback loop.
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Affiliation(s)
| | | | - Timothy W Kraft
- Department of Vision Sciences.,Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
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27
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German OL, Agnolazza DL, Politi LE, Rotstein NP. Light, lipids and photoreceptor survival: live or let die? Photochem Photobiol Sci 2015. [PMID: 26204250 DOI: 10.1039/c5pp00194c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Due to its constant exposure to light and its high oxygen consumption the retina is highly sensitive to oxidative damage, which is a common factor in inducing the death of photoreceptors after light damage or in inherited retinal degenerations. The high content of docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, has been suggested to contribute to this sensitivity. DHA is crucial for developing and preserving normal visual function. However, further roles of DHA in the retina are still controversial. Current data support that it can tilt the scale either towards degeneration or survival of retinal cells. DHA peroxidation products can be deleterious to the retina and might lead to retinal degeneration. However, DHA has also been shown to act as, or to be the source of, a survival molecule that protects photoreceptors and retinal pigment epithelium cells from oxidative damage. We have established that DHA protects photoreceptors from oxidative stress-induced apoptosis and promotes their differentiation in vitro. DHA activates the retinoid X receptor (RXR) and the ERK/MAPK pathway, thus regulating the expression of anti and pro-apoptotic proteins. It also orchestrates a diversity of signaling pathways, modulating enzymatic pathways that control the sphingolipid metabolism and activate antioxidant defense mechanisms to promote photoreceptor survival and development. A deeper comprehension of DHA signaling pathways and context-dependent behavior is required to understand its dual functions in retinal physiology.
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Affiliation(s)
- Olga Lorena German
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur (UNS)-CONICET, Bahía Blanca, Buenos Aires, Argentina.
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Transgenic Mice Overexpressing Serum Retinol-Binding Protein Develop Progressive Retinal Degeneration through a Retinoid-Independent Mechanism. Mol Cell Biol 2015; 35:2771-89. [PMID: 26055327 DOI: 10.1128/mcb.00181-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 06/01/2015] [Indexed: 12/19/2022] Open
Abstract
Serum retinol-binding protein 4 (RBP4) is the sole specific transport protein for retinol in the blood, but it is also an adipokine with retinol-independent, proinflammatory activity associated with obesity, insulin resistance, type 2 diabetes, and cardiovascular disease. Moreover, two separate studies reported that patients with proliferative diabetic retinopathy have increased serum RBP4 levels compared to patients with mild or no retinopathy, yet the effect of increased levels of RBP4 on the retina has not been studied. Here we show that transgenic mice overexpressing RBP4 (RBP4-Tg mice) develop progressive retinal degeneration, characterized by photoreceptor ribbon synapse deficiency and subsequent bipolar cell loss. Ocular retinoid and bisretinoid levels are normal in RBP4-Tg mice, demonstrating that a retinoid-independent mechanism underlies retinal degeneration. Increased expression of pro-interleukin-18 (pro-IL-18) mRNA and activated IL-18 protein and early-onset microglia activation in the retina suggest that retinal degeneration is driven by a proinflammatory mechanism. Neither chronic systemic metabolic disease nor other retinal insults are required for RBP4 elevation to promote retinal neurodegeneration, since RBP4-Tg mice do not have coincident retinal vascular pathology, obesity, dyslipidemia, or hyperglycemia. These findings suggest that elevation of serum RBP4 levels could be a risk factor for retinal damage and vision loss in nondiabetic as well as diabetic patients.
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Ma S, Venkatesh A, Langellotto F, Le YZ, Hall MN, Rüegg MA, Punzo C. Loss of mTOR signaling affects cone function, cone structure and expression of cone specific proteins without affecting cone survival. Exp Eye Res 2015; 135:1-13. [PMID: 25887293 DOI: 10.1016/j.exer.2015.04.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/01/2015] [Accepted: 04/09/2015] [Indexed: 10/23/2022]
Abstract
Cones are the primary photoreceptor (PR) cells responsible for vision in humans. They are metabolically highly active requiring phosphoinositide 3-kinase (PI3K) activity for long-term survival. One of the downstream targets of PI3K is the kinase mammalian target of rapamycin (mTOR), which is a key regulator of cell metabolism and growth, integrating nutrient availability and growth factor signals. Both PI3K and mTOR are part of the insulin/mTOR signaling pathway, however if mTOR is required for long-term PR survival remains unknown. This is of particular interest since deregulation of this pathway in diabetes results in reduced PR function before the onset of any clinical signs of diabetic retinopathy. mTOR is found in two distinct complexes (mTORC1 & mTORC2) that are characterized by their unique accessory proteins RAPTOR and RICTOR respectively. mTORC1 regulates mainly cell metabolism in response to nutrient availability and growth factor signals, while mTORC2 regulates pro-survival mechanisms in response to growth factors. Here we analyze the effect on cones of loss of mTORC1, mTORC2 and simultaneous loss of mTORC1 & mTORC2. Interestingly, neither loss of mTORC1 nor mTORC2 affects cone function or survival at one year of age. However, outer and inner segment morphology is affected upon loss of either complex. In contrast, concurrent loss of mTORC1 and mTORC2 leads to a reduction in cone function without affecting cone viability. The data indicates that PI3K mediated pro-survival signals diverge upstream of both mTOR complexes in cones, suggesting that they are independent of mTOR activity. Furthermore, the data may help explain why PR function is reduced in diabetes, which can lead to deregulation of both mTOR complexes simultaneously. Finally, although mTOR is a key regulator of cell metabolism, and PRs are metabolically highly active, the data suggests that the role of mTOR in regulating the metabolic transcriptome in healthy cones is minimal.
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Affiliation(s)
- Shan Ma
- Tianjin Medical University Eye Hospital, No. 251 Fu Kang Road, Nankai District, Tianjin 300384, PR China; Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
| | - Aditya Venkatesh
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
| | - Fernanda Langellotto
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
| | - Yun Z Le
- Department of Medicine Endocrinology, University of Oklahoma Health Sciences Center, BSEB 302G, 941 S L Young Blvd., Oklahoma City 73104, USA.
| | - Michael N Hall
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
| | - Markus A Rüegg
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
| | - Claudio Punzo
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
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Gupta VK, Rajala A, Rajala RVS. Non-canonical regulation of phosphatidylinositol 3-kinase gamma isoform activity in retinal rod photoreceptor cells. Cell Commun Signal 2015; 13:7. [PMID: 25644171 PMCID: PMC4326362 DOI: 10.1186/s12964-015-0087-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 01/20/2015] [Indexed: 12/31/2022] Open
Abstract
Background Phosphatidylinositol 3-Kinases (PI3Ks) are a family of lipid kinases that phosphorylate the D3-hydroxyls of the inositol ring of phosphoinositides, and are responsible for coordinating a diverse range of cellular functions. A canonical pathway of activation of PI3Ks through the interaction of RA-domain with Ras proteins has been well established. In retinal photoreceptors, we have identified a non-canonical pathway of PI3Kγ activation through the interaction of its RA-domain with a putative Ras-like domain (RLD) in alpha subunit of cyclic nucleotide-gated channel (CNGA1) in retinal rod photoreceptors. Results The interaction between PI3Kγ and CNGA1 does not appear to play a role in regulation of CNG channel activity, but PI3Kγ uses CNGA1 as an anchoring module to achieve close proximity to its substrate to generate D3-phosphoinositides. Conclusions Our studies suggest a functional non-canonical PI3Kγ activation in retinal rod photoreceptor cells.
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Effect of knocking down the insulin receptor on mouse rod responses. Sci Rep 2015; 5:7858. [PMID: 25598343 PMCID: PMC4297982 DOI: 10.1038/srep07858] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 12/18/2014] [Indexed: 12/12/2022] Open
Abstract
Previous experiments have shown that the insulin receptor (IR) is expressed in mammalian rods and contributes to the protection of photoreceptors during bright-light exposure. The role of the insulin receptor in the production of the light response is however unknown. We have used suction-electrode recording to examine the responses of rods after conditionally knocking down the insulin receptor. Our results show that these IR knock-down rods have an accelerated decay of the light response and a small decrease in sensitivity by comparison to littermate WT rods. Our results indicate that the insulin receptor may have some role in controlling the rate of rod response decay, but they exclude a major role of the insulin receptor pathway in phototransduction.
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Abstract
Although photoreceptors account for most of the mass and metabolic activity of the retina, their role in the pathogenesis of diabetic retinopathy has been largely overlooked. Recent studies suggest that photoreceptors might play a critical role in the diabetes-induced degeneration of retinal capillaries, and thus can no longer be ignored. The present review summarizes diabetes-induced alterations in photoreceptor structure and function, and provides a rationale for further study of a role of photoreceptors in the pathogenesis of the retinopathy.
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Affiliation(s)
- Timothy S Kern
- Case Western Reserve University, Department of Medicine and Center for Diabetes Research Cleveland, Ohio, USA ; Veterans Administration Medical Center Research Service 151 Cleveland, Ohio, USA
| | - Bruce A Berkowitz
- Wayne State University School of Medicine, Departments of Anatomy and Cell Biology and Ophthalmology Detroit, Michigan, USA
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Rajala RVS, Rajala A, Morris AJ, Anderson RE. Phosphoinositides: minor lipids make a major impact on photoreceptor cell functions. Sci Rep 2014; 4:5463. [PMID: 24964953 PMCID: PMC4071336 DOI: 10.1038/srep05463] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/11/2014] [Indexed: 11/09/2022] Open
Abstract
Activation of the phosphoinositide (PI) cycle generates the second messengers that control various aspects of cellular signaling. We have previously shown that two PI cycle enzymes, type II phosphatidylinositol 5-phosphate 4-kinase (PIPK IIα) and phosphoinositide 3-kinase (PI3K), are activated through light stimulation. In our earlier studies, we measured enzyme activities, instead of directly measuring the products, due to lack of sensitive analytical techniques. Cells have very low levels of PIs, compared to other lipids, so special techniques and sensitive analytical instruments are necessary for their identification and quantification. There are also other considerations, such as different responses in different cell types, which may complicate quantification of PIs. For example, although light activated PIPK IIα, there was no increase in PI-4,5-P2 measured by liquid chromatography–mass spectrometry (LC/MS) This discrepancy is due to the heterogeneous nature of the retina, which is composed of various cell types. In this study, we examined PI generation in situ using immunohistochemistry with specific PI antibodies. PIs were generated in specific retinal cell layers, suggesting that analyzing PIs from the total retina by LC/MS underscores the significance. This suggests that PI-specific antibodies are useful tools to study the cell-specific regulation of PIs in the retina.
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Affiliation(s)
- Raju V S Rajala
- 1] Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [2] Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [3] Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [4] Dean McGee Eye Institute, Oklahoma City, OK
| | - Ammaji Rajala
- 1] Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [2] Dean McGee Eye Institute, Oklahoma City, OK
| | - Andrew J Morris
- Division of Cardiovascular Medicine, University of Kentucky College of Medicine, Lexington, KY
| | - Robert E Anderson
- 1] Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [2] Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK [3] Dean McGee Eye Institute, Oklahoma City, OK
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Abcouwer SF, Gardner TW. Diabetic retinopathy: loss of neuroretinal adaptation to the diabetic metabolic environment. Ann N Y Acad Sci 2014; 1311:174-90. [PMID: 24673341 DOI: 10.1111/nyas.12412] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Diabetic retinopathy (DR) impairs vision of patients with type 1 and type 2 diabetes, associated with vascular dysfunction and occlusion, retinal edema, hemorrhage, and inappropriate growth of new blood vessels. The recent success of biologic treatments targeting vascular endothelial growth factor (VEGF) demonstrates that treating the vascular aspects in the later stages of the disease can preserve vision in many patients. It would also be highly desirable to prevent the onset of the disease or arrest its progression at a stage preceding the appearance of overt microvascular pathologies. The progression of DR is not necessarily linear but may follow a series of steps that evolve over the course of multiple years. Abundant data suggest that diabetes affects the entire neurovascular unit of the retina, with an early loss of neurovascular coupling, gradual neurodegeneration, gliosis, and neuroinflammation occurring before observable vascular pathologies. In this article, we consider the pathology of DR from the point of view that diabetes causes measurable dysfunctions in the complex integral network of cell types that produce and maintain human vision.
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Affiliation(s)
- Steven F Abcouwer
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, Michigan
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35
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Sundermeier TR, Vinberg F, Mustafi D, Bai X, Kefalov VJ, Palczewski K. R9AP overexpression alters phototransduction kinetics in iCre75 mice. Invest Ophthalmol Vis Sci 2014; 55:1339-47. [PMID: 24526444 DOI: 10.1167/iovs.13-13564] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Determine the impact of rod photoreceptor-specific expression of Cre recombinase on the kinetics of phototransduction in the mouse eye and identify changes in gene expression that underlie any observed phenotypic differences. METHODS Transretinal ERG and single-cell suction electrode recordings were used to measure the kinetics of phototransduction in a mouse line exhibiting rod photoreceptor-specific Cre recombinase expression, and the results were compared with those from control non-Cre-expressing littermates. Gene expression changes were evaluated using RNA sequencing transcriptome analysis. The pattern of expression of Rgs9bp was determined by mapping sequencing reads to the mouse genome and performing 3'-rapid amplification of cDNA ends (3'-RACE). RESULTS Expression of the rod-specific iCre75 transgene was accompanied by accelerated phototransduction inactivation, likely due to overexpression of the Rgs9bp gene, which encodes the Rgs9 anchor protein (R9AP). R9AP upregulation stabilized the RGS9 GAP complex, altering phototransduction kinetics. 3'-Race identified an abundant, unexpected Rgs9bp-Prm1 fusion mRNA in Cre-expressing mouse retinas, which was determined to be derived from a second transgene present in the iCre75 line. CONCLUSIONS Here we report the presence of a second, R9AP-expressing transgene in the iCre75 mouse line, leading to altered kinetics of phototransduction. These results highlight an important caveat that must be considered when utilizing this mouse line for rod photoreceptor-specific gene loss of function studies.
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Alves CH, Pellissier LP, Wijnholds J. The CRB1 and adherens junction complex proteins in retinal development and maintenance. Prog Retin Eye Res 2014; 40:35-52. [PMID: 24508727 DOI: 10.1016/j.preteyeres.2014.01.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 01/21/2014] [Accepted: 01/27/2014] [Indexed: 12/30/2022]
Abstract
The early developing retinal neuroepithelium is composed of multipotent retinal progenitor cells that differentiate in a time specific manner, giving rise to six major types of neuronal and one type of glial cells. These cells migrate and organize in three distinct nuclear layers divided by two plexiform layers. Apical and adherens junction complexes have a crucial role in this process by the establishment of polarity and adhesion. Changes in these complexes disturb the spatiotemporal aspects of retinogenesis, leading to retinal degeneration resulting in mild or severe impairment of retinal function and vision. In this review, we summarize the mouse models for the different members of the apical and adherens junction protein complexes and describe the main features of their retinal phenotypes. The knowledge acquired from the different mutant animals for these proteins corroborate their importance in retina development and maintenance of normal retinal structure and function. More recently, several studies have tried to unravel the connection between the apical proteins, important cellular signaling pathways and their relation in retina development. Still, the mechanisms by which these proteins function remain largely unknown. Here, we hypothesize how the mammalian apical CRB1 complex might control retinogenesis and prevents onset of Leber congenital amaurosis or retinitis pigmentosa.
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Affiliation(s)
- Celso Henrique Alves
- Department of Neuromedical Genetics, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105 BA Amsterdam, The Netherlands
| | - Lucie P Pellissier
- Department of Neuromedical Genetics, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105 BA Amsterdam, The Netherlands
| | - Jan Wijnholds
- Department of Neuromedical Genetics, The Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW), Meibergdreef 47, 1105 BA Amsterdam, The Netherlands.
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Forkwa TK, Neumann ID, Tamm ER, Ohlmann A, Reber SO. Short-term psychosocial stress protects photoreceptors from damage via corticosterone-mediated activation of the AKT pathway. Exp Neurol 2014; 252:28-36. [DOI: 10.1016/j.expneurol.2013.11.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 11/09/2013] [Accepted: 11/14/2013] [Indexed: 01/22/2023]
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Rajala RVS, Rajala A. Neuroprotective role of protein tyrosine phosphatase-1B in rod photoreceptor neurons. Protein Cell 2013; 4:890-2. [PMID: 24203758 PMCID: PMC4114312 DOI: 10.1007/s13238-013-3063-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, 73104, USA,
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Rajala A, Gupta VK, Anderson RE, Rajala RVS. Light activation of the insulin receptor regulates mitochondrial hexokinase. A possible mechanism of retinal neuroprotection. Mitochondrion 2013; 13:566-76. [PMID: 23993956 DOI: 10.1016/j.mito.2013.08.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 08/03/2013] [Accepted: 08/15/2013] [Indexed: 12/23/2022]
Abstract
The serine/threonine kinase Akt has been shown to mediate the anti-apoptotic activity through hexokinase (HK)-mitochondria interaction. We previously reported that Akt activation in retinal rod photoreceptor cells is mediated through the light-dependent insulin receptor (IR)/PI3K pathway. Our data indicate that light-induced activation of IR/PI3K/Akt results in the translocation of HK-II to mitochondria. We also found that PHLPPL, a serine/threonine phosphatase, enhanced the binding of HK-II to mitochondria. We found a mitochondrial targeting signal in PHLPPL and our study suggests that Akt translocation to mitochondria could be mediated through PHLPPL. Our results suggest that the light-dependent IR/PI3K/Akt pathway regulates hexokinase-mitochondria interaction in photoreceptors. Down-regulation of IR signaling has been associated with ocular diseases of retinitis pigmentosa, diabetic retinopathy, and Leber Congenital Amaurosis-type 2, and agents that enhance the binding interaction between hexokinase and mitochondria may have therapeutic potential against these ocular diseases.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK 73104, USA
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Rajala A, Dighe R, Agbaga MP, Anderson RE, Rajala RVS. Insulin receptor signaling in cones. J Biol Chem 2013; 288:19503-15. [PMID: 23673657 DOI: 10.1074/jbc.m113.469064] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In humans, age-related macular degeneration and diabetic retinopathy are the most common disorders affecting cones. In retinitis pigmentosa (RP), cone cell death precedes rod cell death. Systemic administration of insulin delays the death of cones in RP mouse models lacking rods. To date there are no studies on the insulin receptor signaling in cones; however, mRNA levels of IR signaling proteins are significantly higher in cone-dominant neural retina leucine zipper (Nrl) knock-out mouse retinas compared with wild type rod-dominant retinas. We previously reported that conditional deletion of the p85α subunit of phosphoinositide 3-kinase (PI3K) in cones resulted in age-related cone degeneration, and the phenotype was not rescued by healthy rods, raising the question of why cones are not protected by the rod-derived cone survival factors. Interestingly, systemic administration of insulin has been shown to delay the death of cones in mouse models of RP lacking rods. These observations led to the hypothesis that cones may have their own endogenous neuroprotective pathway, or rod-derived cone survival factors may be signaled through cone PI3K. To test this hypothesis we generated p85α(-/-)/Nrl(-/-) double knock-out mice and also rhodopsin mutant mice lacking p85α and examined the effect of the p85α subunit of PI3K on cone survival. We found that the rate of cone degeneration is significantly faster in both of these models compared with respective mice with competent p85α. These studies suggest that cones may have their own endogenous PI3K-mediated neuroprotective pathway in addition to the cone viability survival signals derived from rods.
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Affiliation(s)
- Ammaji Rajala
- Department of Ophthalmology, University of Oklahoma Health Sciences Center and Dean A McGee Eye Institute, Oklahoma City, Oklahoma 73104, USA
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41
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Desbuquois B, Carré N, Burnol AF. Regulation of insulin and type 1 insulin-like growth factor signaling and action by the Grb10/14 and SH2B1/B2 adaptor proteins. FEBS J 2013. [PMID: 23190452 DOI: 10.1111/febs.12080] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The effects of insulin and type 1 insulin-like growth factor (IGF-1) on metabolism, growth and survival are mediated by their association with specific receptor tyrosine kinases, which results in both receptor and substrate phosphorylation. Phosphotyrosine residues on receptors and substrates provide docking sites for signaling proteins containing SH2 (Src homology 2) domains, including molecular adaptors. This review focuses on the regulation of insulin/IGF-1 signaling and action by two adaptor families with a similar domain organization: the growth factor receptor-bound proteins Grb7/10/14 and the SH2B proteins. Both Grb10/14 and SH2B1/B2 associate with the activation loop of insulin/IGF-1 receptors through their SH2 domains, but association of Grb10/14 also involves their unique BPS domain. Consistent with Grb14 binding as a pseudosubstrate to the kinase active site, insulin/IGF-induced activation of receptors and downstream signaling pathways in cultured cells is inhibited by Grb10/14 adaptors, but is potentiated by SH2B1/B2 adaptors. Accordingly, Grb10 and Grb14 knockout mice show improved insulin/IGF sensitivity in vivo, and, for Grb10, overgrowth and increased skeketal muscle and pancreatic β-cell mass. Conversely, SH2B1-depleted mice display insulin and IGF-1 resistance, with peripheral depletion leading to reduced adiposity and neuronal depletion leading to obesity through associated leptin resistance. Grb10/14 and SH2B1 adaptors also modulate insulin/IGF-1 action by interacting with signaling components downstream of receptors and exert several tissue-specific effects. The identification of Grb10/14 and SH2B1 as physiological regulators of insulin signaling and action, together with observations that variants at their gene loci are associated with obesity and/or insulin resistance, highlight them as potential therapeutic targets for these conditions.
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Affiliation(s)
- Bernard Desbuquois
- Institut Cochin, Départment d'Endocrinologie, Métabolisme et Cancer, Université Paris-Descartes, Institut National de la Santé et de la Recherche Médicale, Unité 1016, et Centre National de la Recherche Scientifique, Unité Mixte de Recherche, Paris, France
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Abstract
Photoreceptor cyclic nucleotide gated (CNG) channels are critical elements in phototransduction and light adaptation. Here we report that insulin receptor (IR), an integral membrane protein, directly phosphorylates the CNGA1 subunit of CNG channels that in turn affects the function of these channels negatively. The IR phosphorylates Tyr(498) and Tyr(503) residues on CNGA1 that are situated at the membrane-cytoplasmic interface. The IR tyrosine kinase activity is essential for the inhibition of CNG channel. To maintain the channels in an off state, it is necessary not only to have a precise balance of the cGMP levels but also to have a control on the cGMP sensitivity of the CNG channels itself. In this study, we observed that the channel opens at a lower concentration of cGMP in IR(-/-) mice. These studies suggest that IR regulates the modulation of CNG channel activity in vivo.
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Affiliation(s)
- Vivek K Gupta
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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Fernández-Sánchez L, Lax P, Isiegas C, Ayuso E, Ruiz JM, de la Villa P, Bosch F, de la Rosa EJ, Cuenca N. Proinsulin slows retinal degeneration and vision loss in the P23H rat model of retinitis pigmentosa. Hum Gene Ther 2012; 23:1290-300. [PMID: 23017108 DOI: 10.1089/hum.2012.067] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Proinsulin has been characterized as a neuroprotective molecule. In this work we assess the therapeutic potential of proinsulin on photoreceptor degeneration, synaptic connectivity, and functional activity of the retina in the transgenic P23H rat, an animal model of autosomal dominant retinitis pigmentosa (RP). P23H homozygous rats received an intramuscular injection of an adeno-associated viral vector serotype 1 (AAV1) expressing human proinsulin (hPi+) or AAV1-null vector (hPi-) at P20. Levels of hPi in serum were determined by enzyme-linked immunosorbent assay (ELISA), and visual function was evaluated by electroretinographic (ERG) recording at P30, P60, P90, and P120. Preservation of retinal structure was assessed by immunohistochemistry at P120. Human proinsulin was detected in serum from rats injected with hPi+ at all times tested, with average hPi levels ranging from 1.1 nM (P30) to 1.4 nM (P120). ERG recordings showed an amelioration of vision loss in hPi+ animals. The scotopic b-waves were significantly higher in hPi+ animals than in control rats at P90 and P120. This attenuation of visual deterioration correlated with a delay in photoreceptor degeneration and the preservation of retinal cytoarchitecture. hPi+ animals had 48.7% more photoreceptors than control animals. Presynaptic and postsynaptic elements, as well as the synaptic contacts between photoreceptors and bipolar or horizontal cells, were preserved in hPi+ P23H rats. Furthermore, in hPi+ rat retinas the number of rod bipolar cell bodies was greater than in control rats. Our data demonstrate that hPi expression preserves cone and rod structure and function, together with their contacts with postsynaptic neurons, in the P23H rat. These data strongly support the further development of proinsulin-based therapy to counteract retinitis pigmentosa.
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Affiliation(s)
- Laura Fernández-Sánchez
- Department of Physiology, Genetics and Microbiology, University of Alicante, E-03080 Alicante, Spain
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Rask-Madsen C, Kahn CR. Tissue-specific insulin signaling, metabolic syndrome, and cardiovascular disease. Arterioscler Thromb Vasc Biol 2012; 32:2052-9. [PMID: 22895666 DOI: 10.1161/atvbaha.111.241919] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Impaired insulin signaling is central to development of the metabolic syndrome and can promote cardiovascular disease indirectly through development of abnormal glucose and lipid metabolism, hypertension, and a proinflammatory state. However, insulin's action directly on vascular endothelium, atherosclerotic plaque macrophages, and in the heart, kidney, and retina has now been described, and impaired insulin signaling in these locations can alter progression of cardiovascular disease in the metabolic syndrome and affect development of microvascular complications of diabetes mellitus. Recent advances in our understanding of the complex pathophysiology of insulin's effects on vascular tissues offer new opportunities for preventing these cardiovascular disorders.
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Affiliation(s)
- Christian Rask-Madsen
- Joslin Diabetes Center, Harvard Medical School, One Joslin Place, Boston, MA 02215, USA
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Malaguarnera R, Sacco A, Voci C, Pandini G, Vigneri R, Belfiore A. Proinsulin binds with high affinity the insulin receptor isoform A and predominantly activates the mitogenic pathway. Endocrinology 2012; 153:2152-63. [PMID: 22355074 DOI: 10.1210/en.2011-1843] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proinsulin is generally regarded as an inactive prohormone because of its low metabolic activity. However, proinsulin appears to regulate embryo development in animal models. In this study, we evaluated whether proinsulin may differentially bind to and activate the two insulin receptor (IR) isoforms (IR-A and IR-B), because IR-A is a relatively low-specificity receptor that is prevalent in fetal and cancer cells and is able to mediate the growth effects of IGF-II. Mouse R(-) fibroblasts devoid of IGF-I receptor (IGF-IR) and stably transfected with cDNA encoding either human IR-A or IR-B (R(-) /IR-A and R(-) /IR-B cells) were used. Three human cancer cell lines were also studied. We found that proinsulin stimulated phosphorylation of IR-A with an EC(50) of 4.5 ± 0.6 nm and displaced [(125)I]insulin from IR-A with a similar EC(50). In contrast, proinsulin EC(50) values for stimulation of IR-B phosphorylation and for [(125)I]insulin displacement from IR-B were approximately 7-fold higher. Proinsulin did not bind or activate IGF-IR or IR/IGF-IR hybrids. Via IR-A, proinsulin activated the ERK/p70S6K pathway to a similar degree as insulin but elicited a weaker Akt response. Despite its low metabolic activity, proinsulin was almost equipotent as insulin in inducing cell proliferation and migration in cells expressing various IR-A levels. In conclusion, proinsulin is a selective IR-A ligand and may induce biological effects through this IR isoform.
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Affiliation(s)
- Roberta Malaguarnera
- Department of Health, Endocrinology, University of Catanzaro, Campus Universitario, località Germaneto, 88100 Catanzaro, Italy
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Basavarajappa DK, Gupta VK, Rajala RVS. Protein tyrosine phosphatase 1B: a novel molecular target for retinal degenerative diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 723:829-34. [PMID: 22183413 DOI: 10.1007/978-1-4614-0631-0_106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Protein tyrosine phosphatase 1B (PTP1B) is considered as a major negative regulator of insulin receptor (IR) signaling. IR signaling in retina has been demonstrated to be neuroprotective. Photoreceptor specific deletion of PTP1B results in enhanced retinal IR-mediated neuroprotection indicating the importance of PTP1B as a negative regulator in the retina. Elevated levels of retinal PTP1B activity has been observed in mice lacking retinal pigment epithelium (Rpe65-/-), a mouse model of leber congenital amaurosis (LCA-type 2), retinitis pigmentosa and diabetic retinopathy animal models. This enhanced PTP1B activity could down regulate the IR signaling which may contribute to the death of photoreceptor neurons and ultimately lead to retinal degenerations. The potential therapeutic agents that specifically reduce or inhibit the PTP1B activity could be beneficial in protecting or delaying the photoreceptor cell death in the retinal degenerative diseases.
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Affiliation(s)
- Devaraj K Basavarajappa
- Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA
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Punzo C, Xiong W, Cepko CL. Loss of daylight vision in retinal degeneration: are oxidative stress and metabolic dysregulation to blame? J Biol Chem 2011; 287:1642-8. [PMID: 22074929 PMCID: PMC3265845 DOI: 10.1074/jbc.r111.304428] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Retinitis pigmentosa is characterized by loss of night vision, followed by complete blindness. Over 40 genetic loci for retinitis pigmentosa have been identified in humans, primarily affecting photoreceptor structure and function. The availability of excellent animal models allows for a mechanistic characterization of the disease. Metabolic dysregulation and oxidative stress have been found to correlate with the loss of vision, particularly in cones, the type of photoreceptors that mediate daylight and color vision. The evidence that these problems actually cause loss of vision and potential therapeutic approaches targeting them are discussed.
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Affiliation(s)
- Claudio Punzo
- Department of Ophthalmology and Gene Therapy Center, University of Massachusetts Medical School, Worcester, Massachusetts 01606, USA
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Abstract
The importance of phosphoinositides (phosphorylated phosphatidyl inositol derivatives, PIs) for normal cellular function cannot be overstated. Although they represent a small fraction of the total phospholipid within the cell, they are essential regulators of many cellular functions. They direct membrane trafficking by functioning as recruitment factors for vesicular trafficking components, they can modulate ion channel activity through direct binding within cellular membranes, and their hydrolysis generates second messenger signaling molecules. Despite an explosion of information regarding the importance of these lipids in cellular biology, their precise roles in vertebrate retinal photoreceptors has not been established. This review summarizes the literature on potential roles for different phosphoinositides and their regulators in vertebrate rods and cones. A brief description of the importance of PI signaling in other photosensitive cells is also presented. The highly specialized functions of the vertebrate photoreceptor, combined with the established importance of phosphoinositides, promise significant future discoveries in this field.
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Affiliation(s)
- Susan E Brockerhoff
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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Ivanovic I, Allen DT, Dighe R, Le YZ, Anderson RE, Rajala RVS. Phosphoinositide 3-kinase signaling in retinal rod photoreceptors. Invest Ophthalmol Vis Sci 2011; 52:6355-62. [PMID: 21730346 DOI: 10.1167/iovs.10-7138] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PURPOSE Phosphoinositide 3-kinase (PI3K) consists of a p110 catalytic protein and a p85α regulatory protein, required for the stabilization and localization of p110-PI3K activity. The biological significance of PI3K was investigated in vertebrate rod photoreceptors by deleting its regulatory p85α protein and examining its role in photoreceptor structure, function, and protein trafficking. METHODS Mice that expressed Cre recombinase in rods were bred to mice with a floxed p85α (pik3r1) regulatory subunit of PI3K to generate a conditional deletion of pik3r1 in rods. Functional and structural changes were determined by ERG and morphometric analysis, respectively. PI3K activity was measured in retinal homogenates immunoprecipitated with an anti-PY antibody. Akt activation was determined by Western blot analysis with a pAkt antibody. RESULTS Light-induced stress increased PI3K activity in retinal immunoprecipitates and phosphorylation of Akt. There was no effect of pik3r1 deletion on retinal structure. However, twin flash electroretinography revealed a slight delay in recovery kinetics in pik3r1 knockout (KO) mice compared with wild-type controls. The movement of arrestin in the pik3r1 KO mice was slower than that in the wild-type mouse retinas at 5 minutes of exposure to light. At 10 minutes of exposure, the ROS localization of arrestin was almost identical between the wild-type and pik3r1 KO mice. CONCLUSIONS The results provide the first direct evidence that rods use PI3K-generated phosphoinositides for photoreceptor function. The lack of phenotype in pik3r1 KO rod photoreceptors suggests a redundant role in controlling PIP(3) synthesis.
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Affiliation(s)
- Ivana Ivanovic
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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Phosphorylated Grb14 is an endogenous inhibitor of retinal protein tyrosine phosphatase 1B, and light-dependent activation of Src phosphorylates Grb14. Mol Cell Biol 2011; 31:3975-87. [PMID: 21791607 DOI: 10.1128/mcb.05659-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Growth factor receptor-bound protein 14 (Grb14) is an adapter protein implicated in receptor tyrosine kinase signaling. Grb14(-/-) studies highlight both the positive and negative roles of Grb14 in receptor tyrosine kinase signaling in a tissue-specific manner. In this study, we made a novel finding that Grb14 inhibits the activity of PTP1B, the major negative regulator of insulin receptor (IR) signaling, in a phosphorylation-regulated manner. Phosphorylation of Tyr-347 in the BPS domain of Grb14 is critical for interaction with PTP1B, resulting in the competitive inhibition of PTP1B activity. We also found that rhodopsin-regulated Src kinase activation in retina leads to the phosphorylation of Grb14. Further, ablation of Grb14 resulted in significantly elevated retinal PTP1B activity in vivo. PTP1B is known to be regulated by oxidation, glutathionylation, phosphorylation, and SUMOlyation, and our study for the first time demonstrates the inhibition of PTP1B activity in vivo by protein molecule Grb14 in a tissue-specific manner.
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