scholarly journals On the Wrong Track: Alterations of Ciliary Transport in Inherited Retinal Dystrophies

2021 ◽  
Vol 9 ◽  
Author(s):  
Laura Sánchez-Bellver ◽  
Vasileios Toulis ◽  
Gemma Marfany
Keyword(s):  
Retinal Degeneration ◽  
Outer Segment ◽  
Molecular Mechanisms ◽  
Photoreceptor Cells ◽  
Cellular Functions ◽  
Inherited Disorders ◽  
Inherited Retinal Dystrophies ◽  
Retinal Dystrophies ◽  
Elevated Protein ◽  
And Function

Ciliopathies are a group of heterogeneous inherited disorders associated with dysfunction of the cilium, a ubiquitous microtubule-based organelle involved in a broad range of cellular functions. Most ciliopathies are syndromic, since several organs whose cells produce a cilium, such as the retina, cochlea or kidney, are affected by mutations in ciliary-related genes. In the retina, photoreceptor cells present a highly specialized neurosensory cilium, the outer segment, stacked with membranous disks where photoreception and phototransduction occurs. The daily renewal of the more distal disks is a unique characteristic of photoreceptor outer segments, resulting in an elevated protein demand. All components necessary for outer segment formation, maintenance and function have to be transported from the photoreceptor inner segment, where synthesis occurs, to the cilium. Therefore, efficient transport of selected proteins is critical for photoreceptor ciliogenesis and function, and any alteration in either cargo delivery to the cilium or intraciliary trafficking compromises photoreceptor survival and leads to retinal degeneration. To date, mutations in more than 100 ciliary genes have been associated with retinal dystrophies, accounting for almost 25% of these inherited rare diseases. Interestingly, not all mutations in ciliary genes that cause retinal degeneration are also involved in pleiotropic pathologies in other ciliated organs. Depending on the mutation, the same gene can cause syndromic or non-syndromic retinopathies, thus emphasizing the highly refined specialization of the photoreceptor neurosensory cilia, and raising the possibility of photoreceptor-specific molecular mechanisms underlying common ciliary functions such as ciliary transport. In this review, we will focus on ciliary transport in photoreceptor cells and discuss the molecular complexity underpinning retinal ciliopathies, with a special emphasis on ciliary genes that, when mutated, cause either syndromic or non-syndromic retinal ciliopathies.

scholarly journals Nutraceutical Supplementation Ameliorates Visual Function, Retinal Degeneration, and Redox Status in rd10 Mice

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1033
Author(s):  
Lorena Olivares-González ◽  
Sheyla Velasco ◽  
Isabel Campillo ◽  
David Salom ◽  
Emilio González-García ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Retinal Degeneration ◽  
Antioxidant Properties ◽  
Photoreceptor Cells ◽  
Redox Status ◽  
Inherited Retinal Dystrophies ◽  
Stress Markers ◽  
Retinal Dystrophies ◽  
Progressive Degeneration ◽  
Light Stimuli

Background: Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies characterized by progressive degeneration of photoreceptor cells. Ocular redox status is altered in RP suggesting oxidative stress could contribute to their progression. In this study, we investigated the effect of a mixture of nutraceuticals with antioxidant properties (NUT) on retinal degeneration in rd10 mice, a model of RP. Methods: NUT was orally administered to rd10 mice from postnatal day (PD) 9 to PD18. At PD18 retinal function and morphology were examined by electroretinography (ERG) and histology including TUNEL assay, immunolabeling of microglia, Müller cells, and poly ADP ribose polymers. Retinal redox status was determined by measuring the activity of antioxidant enzymes and some oxidative stress markers. Gene expression of the cytokines IL-6, TNFα, and IL-1β was assessed by real-time PCR. Results: NUT treatment delayed the loss of photoreceptors in rd10 mice partially preserving their electrical responses to light stimuli. Moreover, it ameliorated redox status and reduced inflammation including microglia activation, upregulation of cytokines, reactive gliosis, and PARP overactivation. Conclusions: NUT ameliorated retinal functionality and morphology at early stages of RP in rd10 mice. This formulation could be useful as a neuroprotective approach for patients with RP in the future.

scholarly journals Dysfunction of Heterotrimeric Kinesin-2 in Rod Photoreceptor Cells and the Role of Opsin Mislocalization in Rapid Cell Death

2010 ◽  
Vol 21 (23) ◽  
pp. 4076-4088 ◽  
Author(s):  
Vanda S. Lopes ◽  
David Jimeno ◽  
Kornnika Khanobdee ◽  
Xiaodan Song ◽  
Bryan Chen ◽  
...  
Keyword(s):  
Cell Death ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Photoreceptor Cells ◽  
Cell Loss ◽  
Rod Photoreceptor ◽  
Retinal Degenerations ◽  
Cell Counts ◽  
And Function

Due to extensive elaboration of the photoreceptor cilium to form the outer segment, axonemal transport (IFT) in photoreceptors is extraordinarily busy, and retinal degeneration is a component of many ciliopathies. Functional loss of heterotrimeric kinesin-2, a major anterograde IFT motor, causes mislocalized opsin, followed by rapid cell death. Here, we have analyzed the nature of protein mislocalization and the requirements for the death of kinesin-2-mutant rod photoreceptors. Quantitative immuno EM showed that opsin accumulates initially within the inner segment, and then in the plasma membrane. The light-activated movement of arrestin to the outer segment is also impaired, but this defect likely results secondarily from binding to mislocalized opsin. Unlike some other retinal degenerations, neither opsin–arrestin complexes nor photoactivation were necessary for cell loss. In contrast, reduced rod opsin expression provided enhanced rod and cone photoreceptor survival and function, as measured by photoreceptor cell counts, apoptosis assays, and ERG analysis. The cell death incurred by loss of kinesin-2 function was almost completely negated by Rho−/−. Our results indicate that mislocalization of opsin is a major cause of photoreceptor cell death from kinesin-2 dysfunction and demonstrate the importance of accumulating mislocalized protein per se, rather than specific signaling properties of opsin, stemming from photoactivation or arrestin binding.

scholarly journals Recent progress in research on molecular mechanisms of autophagy in the heart

2015 ◽  
Vol 308 (4) ◽  
pp. H259-H268 ◽  
Author(s):  
Yasuhiro Maejima ◽  
Yun Chen ◽  
Mitsuaki Isobe ◽  
Åsa B. Gustafsson ◽  
Richard N. Kitsis ◽  
...  
Keyword(s):  
Heart Disease ◽  
Molecular Mechanisms ◽  
Therapeutic Potential ◽  
Degradation Process ◽  
Structure And Function ◽  
Cellular Functions ◽  
Evolutionarily Conserved ◽  
And Function ◽  
Cellular Dysfunction

Dysregulation of autophagy, an evolutionarily conserved process for degradation of long-lived proteins and organelles, has been implicated in the pathogenesis of human disease. Recent research has uncovered pathways that control autophagy in the heart and molecular mechanisms by which alterations in this process affect cardiac structure and function. Although initially thought to be a nonselective degradation process, autophagy, as it has become increasingly clear, can exhibit specificity in the degradation of molecules and organelles, such as mitochondria. Furthermore, it has been shown that autophagy is involved in a wide variety of previously unrecognized cellular functions, such as cell death and metabolism. A growing body of evidence suggests that deviation from appropriate levels of autophagy causes cellular dysfunction and death, which in turn leads to heart disease. Here, we review recent advances in understanding the role of autophagy in heart disease, highlight unsolved issues, and discuss the therapeutic potential of modulating autophagy in heart disease.

scholarly journals Sophisticated Gene Regulation for a Complex Physiological System: The Role of Non-coding RNAs in Photoreceptor Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Sabrina Carrella ◽  
Sandro Banfi ◽  
Marianthi Karali
Keyword(s):  
Molecular Mechanisms ◽  
Developmental Process ◽  
Photoreceptor Cells ◽  
Sensory Transduction ◽  
Circular Rnas ◽  
Therapeutic Implications ◽  
Physiological Processes ◽  
Non Coding Rnas ◽  
And Function

Photoreceptors (PRs) are specialized neuroepithelial cells of the retina responsible for sensory transduction of light stimuli. In the highly structured vertebrate retina, PRs have a highly polarized modular structure to accommodate the demanding processes of phototransduction and the visual cycle. Because of their function, PRs are exposed to continuous cellular stress. PRs are therefore under pressure to maintain their function in defiance of constant environmental perturbation, besides being part of a highly sophisticated developmental process. All this translates into the need for tightly regulated and responsive molecular mechanisms that can reinforce transcriptional programs. It is commonly accepted that regulatory non-coding RNAs (ncRNAs), and in particular microRNAs (miRNAs), are not only involved but indeed central in conferring robustness and accuracy to developmental and physiological processes. Here we integrate recent findings on the role of regulatory ncRNAs (e.g., miRNAs, lncRNAs, circular RNAs, and antisense RNAs), and of their contribution to PR pathophysiology. We also outline the therapeutic implications of translational studies that harness ncRNAs to prevent PR degeneration and promote their survival and function.

scholarly journals ARL2BP, a protein linked to retinitis pigmentosa, is needed for normal photoreceptor cilia doublets and outer segment structure

2018 ◽  
Vol 29 (13) ◽  
pp. 1590-1598 ◽  
Author(s):  
Abigail R. Moye ◽  
Ratnesh Singh ◽  
Victoria A. Kimler ◽  
Tanya L. Dilan ◽  
Daniella Munezero ◽  
...  
Keyword(s):  
Retinitis Pigmentosa ◽  
Outer Segment ◽  
Photoreceptor Cells ◽  
Visual Response ◽  
Photoreceptor Degeneration ◽  
Progressive Reduction ◽  
Ciliary Protein ◽  
Vertically Aligned ◽  
And Function

The outer segment (OS) of photoreceptor cells is an elaboration of a primary cilium with organized stacks of membranous disks that contain the proteins needed for phototransduction and vision. Though ciliary formation and function has been well characterized, little is known about the role of cilia in the development of photoreceptor OS. Nevertheless, progress has been made by studying mutations in ciliary proteins, which often result in malformed OSs and lead to blinding diseases. To investigate how ciliary proteins contribute to OS formation, we generated a knockout (KO) mouse model for ARL2BP, a ciliary protein linked to retinitis pigmentosa. The KO mice display an early and progressive reduction in visual response. Before photoreceptor degeneration, we observed disorganization of the photoreceptor OS, with vertically aligned disks and shortened axonemes. Interestingly, ciliary doublet microtubule (MT) structure was also impaired, displaying open B-tubule doublets, paired with loss of singlet MTs. On the basis of results from this study, we conclude that ARL2BP is necessary for photoreceptor ciliary doublet formation and axoneme elongation, which is required for OS morphogenesis and vision.

scholarly journals Localization of peripherin/rds in the disk membranes of cone and rod photoreceptors: relationship to disk membrane morphogenesis and retinal degeneration.

1992 ◽  
Vol 116 (3) ◽  
pp. 659-667 ◽  
Author(s):  
K Arikawa ◽  
L L Molday ◽  
R S Molday ◽  
D S Williams
Keyword(s):  
Plasma Membrane ◽  
Retinal Degeneration ◽  
Outer Segment ◽  
Photoreceptor Cells ◽  
Growth Stages ◽  
Rod Outer Segments ◽  
Rod Photoreceptor ◽  
Outer Segments ◽  
Disk Membrane ◽  
Membrane Morphogenesis

The outer segments of vertebrate rod photoreceptor cells consist of an ordered stack of membrane disks, which, except for a few nascent disks at the base of the outer segment, is surrounded by a separate plasma membrane. Previous studies indicate that the protein, peripherin or peripherin/rds, is localized along the rim of mature disks of rod outer segments. A mutation in the gene for this protein has been reported to be responsible for retinal degeneration in the rds mouse. In the present study, we have shown by immunogold labeling of rat and ground squirrel retinas that peripherin/rds is present in the disk rims of cone outer segments as well as rod outer segments. Additionally, in the basal regions of rod and cone outer segments, where disk morphogenesis occurs, we have found that the distribution of peripherin/rds is restricted to a region that is adjacent to the cilium. Extension of its distribution from the cilium coincides with the formation of the disk rim. These results support the model of disk membrane morphogenesis that predicts rim formation to be a second stage of growth, after the first stage in which the ciliary plasma membrane evaginates to form open nascent disks. The results also indicate how the proteins of the outer segment plasma membrane and the disk membranes are sorted into their separate domains: different sets of proteins may be incorporated into membrane outgrowths during different growth stages of disk morphogenesis. Finally, the presence of peripherin/rds protein in both cone and rod outer segment disks, together with the phenotype of the rds mouse, which is characterized by the failure of both rod and cone outer segment formation, suggest that the same rds gene is expressed in both types of photoreceptor cells.

scholarly journals Pathophysiological Role of K2P Channels in Human Diseases

2021 ◽  
Vol 55 (S3) ◽  
pp. 65-86
Keyword(s):  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Expression Patterns ◽  
Ion Homeostasis ◽  
Human Diseases ◽  
Cellular Functions ◽  
Aberrant Expression ◽  
K2p Channels ◽  
And Function

The family of two-pore domain potassium (K2P) channels is critically involved in central cellular functions such as ion homeostasis, cell development, and excitability. K2P channels are widely expressed in different human cell types and organs. It is therefore not surprising that aberrant expression and function of K2P channels are related to a spectrum of human diseases, including cancer, autoimmune, CNS, cardiovascular, and urinary tract disorders. Despite homologies in structure, expression, and stimulus, the functional diversity of K2P channels leads to heterogeneous influences on human diseases. The role of individual K2P channels in different disorders depends on expression patterns and modulation in cellular functions. However, an imbalance of potassium homeostasis and action potentials contributes to most disease pathologies. In this review, we provide an overview of current knowledge on the role of K2P channels in human diseases. We look at altered channel expression and function, the potential underlying molecular mechanisms, and prospective research directions in the field of K2P channels.

scholarly journals Inhibition of MicroRNA 6937 Delays Photoreceptor and Vision Loss in a Mouse Model of Retinitis Pigmentosa

Pharmaceutics ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 913
Author(s):  
Ander Anasagasti ◽  
Araceli Lara-López ◽  
Santiago Milla-Navarro ◽  
Leire Escudero-Arrarás ◽  
María Rodríguez-Hidalgo ◽  
...  
Keyword(s):  
Mouse Model ◽  
Retinitis Pigmentosa ◽  
Molecular Mechanisms ◽  
Vision Loss ◽  
Outer Nuclear Layer ◽  
Photoreceptor Cells ◽  
Inherited Retinal Dystrophies ◽  
Gene Expression Control ◽  
Inhibit Gene Expression ◽  
Post Transcriptional Regulation

Inherited retinal dystrophies (IRDs) are a group of rare retinal conditions, including retinitis pigmentosa (RP), caused by monogenic mutations in 1 out of more than 250 genes. Despite recent advancements in gene therapy, there is still a lack of an effective treatment for this group of retinal conditions. MicroRNAs (miRNAs) are a class of highly conserved small non-coding RNAs that inhibit gene expression. Control of miRNAs-mediated protein expression has been described as a widely used mechanism for post-transcriptional regulation in many physiological and pathological processes in different organs, including the retina. Our main purpose was to test the hypothesis that modulation of a group of miRNAs can protect photoreceptor cells from death in the rd10 mouse model of retinitis pigmentosa. For this, we incorporated modulators of three miRNAs in adeno-associated viruses (AAVs), which were administered through sub-retinal injections. The results obtained indicate that inhibition of the miR-6937-5p slows down the visual deterioration of rd10 mice, reflected by an increased electroretinogram (ERG) wave response under scotopic conditions and significant preservation of the outer nuclear layer thickness. This work contributes to broadening our knowledge on the molecular mechanisms underlying retinitis pigmentosa and supports the development of novel therapeutic approaches for RP based on miRNA modulation.

SUMO under stress

2008 ◽  
Vol 36 (5) ◽  
pp. 874-878 ◽  
Author(s):  
Denis Tempé ◽  
Marc Piechaczyk ◽  
Guillaume Bossis
Keyword(s):  
Molecular Mechanisms ◽  
Environmental Stresses ◽  
Present Review ◽  
Post Translational Modification ◽  
Cellular Functions ◽  
And Function

During the last decade, SUMOylation has emerged as a central regulatory post-translational modification in the control of the fate and function of proteins. However, how SUMOylation is regulated itself has just started to be delineated. It appears now that SUMO (small ubiquitin-related modifier) conjugation/deconjugation equilibrium is affected by various environmental stresses, including osmotic, hypoxic, heat, oxidative and genotoxic stresses. This regulation occurs either at the level of individual targets, through an interplay between stress-induced phosphorylation and SUMOylation, or via modulation of the conjugation/deconjugation machinery abundance or activity. The present review gives an overview of the connections between stress and SUMOylation, the underlying molecular mechanisms and their effects on cellular functions.

Involvement of the calcium sensor GCAP1 in hereditary cone dystrophies

2010 ◽  
Vol 391 (6) ◽  
Author(s):  
Petra Behnen ◽  
Daniele Dell'Orco ◽  
Karl-Wilhelm Koch
Keyword(s):  
Guanylate Cyclase ◽  
Biochemical Analysis ◽  
Photoreceptor Cells ◽  
Calcium Sensor ◽  
Cone Photoreceptor ◽  
Visual Transduction ◽  
Inherited Retinal Dystrophies ◽  
Retinal Dystrophies ◽  
Cone Cells ◽  
Neuronal Calcium Sensor Protein

Abstract Progressive visual impairment leading to blindness is often associated with inherited retinal dystrophies. These disorders correlate in most cases with mutations in genes that code for proteins of the visual transduction system in rod and cone photoreceptor cells. Recent progress has highlighted the involvement of a neuronal calcium sensor protein that is specifically expressed in rod and cone cells and operates as a guanylate cyclase-activating protein (GCAP). A group of patients suffering from cone or cone-rod dystrophies carry mutations in the GCAP1 gene, and biochemical analysis of GCAP1 function revealed that for most of these mutations GCAP1 exhibits a disturbance in its Ca2+-sensing and its guanylate cyclase-activating properties. Cellular consequences of different GCAP1 mutations are compared and discussed.

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