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Arnold De Loof
Cells are powerful miniature electrophoresis chambers, at least during part of their life cycle. They die at the moment the voltage gradient over their plasma membrane, and their ability to drive a self-generated electric current carried by inorganic ions through themselves irreversibly collapses. Senescence is likely due to the progressive, multifactorial damage to the cell's electrical system. This is the essence of the "Fading electricity theory of aging" (De Loof et al., Aging Res. Rev. 2013;12:58-66)...
2017: Communicative & Integrative Biology
James H Felce, Sarah L Latty, Rachel G Knox, Susan R Mattick, Yuan Lui, Steven F Lee, David Klenerman, Simon J Davis
The organization of Rhodopsin-family G protein-coupled receptors (GPCRs) at the cell surface is controversial. Support both for and against the existence of dimers has been obtained in studies of mostly individual receptors. Here, we use a large-scale comparative study to examine the stoichiometric signatures of 60 receptors expressed by a single human cell line. Using bioluminescence resonance energy transfer- and single-molecule microscopy-based assays, we found that a relatively small fraction of Rhodopsin-family GPCRs behaved as dimers and that these receptors otherwise appear to be monomeric...
September 12, 2017: Cell Reports
Anne Hanneken, Thomas Neikirk, Jennifer Johnson, Masahiro Kono
PURPOSE: To test the hypothesis that delayed dark adaptation in patients with macular degeneration is due to an excess of free unliganded opsin (apo-opsin) and a deficiency of the visual chromophore, 11-cis retinal, in rod outer segments. METHODS: A total of 50 human autopsy eyes were harvested from donors with and without macular degeneration within 2-24 hrs. postmortem. Protocols were developed which permitted dark adaptation of normal human eyes after death and enucleation...
August 2017: Transactions of the American Ophthalmological Society
Hong-Pei Ji, Yu Xiong, Wei-Tao Song, En-Dong Zhang, Zhao-Lin Gao, Fei Yao, Tao Su, Rong-Rong Zhou, Xiao-Bo Xia
Retinal degenerative diseases ultimately result into irreversible photoreceptor death or loss. At present, the most promising treatment for these diseases is cell replacement therapy. Müller glia are the major glia in the retina, displaying cardinal features of retinal progenitor cells, and can be candidate of seed cells for retinal degenerative diseases. Here, mouse retinal Müller glia dissociated and cultured in vitro amplified and were dedifferentiated into Müller glia-derived progenitors (MGDPs), demonstrating expression of stem/progenitor cell markers Nestin, Sox2 and self-renewal capacity...
September 12, 2017: Scientific Reports
Chen D Lu, ByungKun Lee, Julia Schottenhamml, Andreas Maier, Edward N Pugh, James G Fujimoto
Purpose: To examine outer retinal band changes after flash stimulus and subsequent dark adaptation with ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods: Five dark-adapted left eyes of five normal subjects were imaged with 3-μm axial-resolution UHR-OCT during 30 minutes of dark adaptation following 96%, 54%, 23%, and 0% full-field and 54% half-field rhodopsin bleach. We identified the ellipsoid zone inner segment/outer segment (EZ[IS/OS]), cone interdigitation zone (CIZ), rod interdigitation zone (RIZ), retinal pigment epithelium (RPE), and Bruch's membrane (BM) axial positions and generated two-dimensional thickness maps of the EZ(IS/OS) to the four bands...
September 1, 2017: Investigative Ophthalmology & Visual Science
María Guadalupe Herrera-Hernández, Eva Ramon, Cecylia S Lupala, Mercè Tena-Campos, Juan J Pérez, Pere Garriga
Dietary flavonoids exhibit many biologically-relevant functions and can potentially have beneficial effects in the treatment of pathological conditions. In spite of its well known antioxidant properties, scarce structural information is available on the interaction of flavonoids with membrane receptors. Advances in the structural biology of a specific class of membrane receptors, the G protein-coupled receptors, have significantly increased our understanding of drug action and paved the way for developing improved therapeutic approaches...
September 11, 2017: Scientific Reports
Liangliang Ji, Baofu Ma, Qian Meng, Longjie Li, Ke Liu, Deliang Chen
Bacteriorhodopsin has attracted remarkable attention as a photoactive bio-nanomaterial in the last decades. However, its instability in the presence of detergents has restricted the extent to which bacteriorhodopsin may be applied. In this study, we investigated the oligomerization of a eukaryotic light-driven H(+)-pump, Leptosphaeria rhodopsin, using circular dichroism spectroscopy and other biophysical and biochemical methods. Our findings revealed that Leptosphaeria rhodopsin assembled into oligomers in the cell membrane and also in 0...
September 5, 2017: Biochemical and Biophysical Research Communications
Boudjema Imarazene, Aude Andouche, Yann Bassaglia, Pascal-Jean Lopez, Laure Bonnaud-Ponticelli
In metazoans, there is a remarkable diversity of photosensitive structures; their shapes, physiology, optical properties, and development are different. To approach the evolution of photosensitive structures and visual function, cephalopods are particularly interesting organisms due to their most highly centralized nervous system and their camerular eyes which constitute a convergence with those of vertebrates. The eye morphogenesis in numerous metazoans is controlled mainly by a conserved Retinal Determination Gene Network (RDGN) including pax, six, eya, and dac playing also key developmental roles in non-retinal structures and tissues of vertebrates and Drosophila...
2017: Frontiers in Physiology
Muhammad Fairuz Azmi, Norzana Abd Ghafar, Jemaima Che Hamzah, Ng Sook Luan, Chua Kien Hui
OBJECTIVE: The purpose of this study is to investigate whether light-emitting diode (LED) light at different wavelengths can improve wound healing in both diabetic and normal fibroblasts. MATERIALS AND METHODS: Both diabetic and normal fibroblast cell lines were cultured and artificial wounds were created on the cultured cells in petri dishes as a streak line with pipette tips. Then, both cells were separately irradiated with 635 nm (red), 520 nm (green), and 465 nm (blue) LED lights at 0...
August 31, 2017: Wounds: a Compendium of Clinical Research and Practice
Dong Feng, Zhe Chen, Kuang Yang, Shanshan Miao, Bolin Xu, Yunsi Kang, Haibo Xie, Chengtian Zhao
Photoreceptor degeneration can lead to blindness and represents the most common form of neural degenerative disease worldwide. Although many genes involved in photoreceptor degeneration have been identified, the underlying mechanisms remain to be elucidated. Here, we examined photoreceptor development in zebrafish kif3a and kif3b mutants, which affect two subunits of the Kinesin-2 complex. In both mutants, rods degenerated quickly, whereas cones underwent a slow degeneration process. Notably, the photoreceptor defects were considerably more severe in kif3a mutants than in kif3b mutants...
August 30, 2017: Journal of Biological Chemistry
Brent S Wells, Daniela Pistillo, Erin Barnhart, Claude Desplan
Drosophila color vision is achieved by comparing outputs from two types of color-sensitive photoreceptors, R7 and R8. Ommatidia (unit eyes) are classified into two subtypes, known as 'pale' or 'yellow', depending on Rhodopsin expression in R7 and R8. Subtype specification is controlled by a stochastic decision in R7 and instructed to the underlying R8. We find that the Activin receptor Baboon is required in R8 to receive non-redundant signaling from the three Activin ligands, activating the transcription factor dSmad2...
August 30, 2017: ELife
Štěpán Timr, Roman Pleskot, Jan Kadlec, Miriam Kohagen, Aniket Magarkar, Pavel Jungwirth
Recoverin is a neuronal calcium sensor involved in vision adaptation that reversibly associates with cellular membranes via its calcium-activated myristoyl switch. While experimental evidence shows that the myristoyl group significantly enhances membrane affinity of this protein, molecular details of the binding process are still under debate. Here, we present results of extensive molecular dynamics simulations of recoverin in the proximity of a phospholipid bilayer. We capture multiple events of spontaneous membrane insertion of the myristoyl moiety and confirm its critical role in the membrane binding...
August 23, 2017: ACS Central Science
Leonid S Brown, Oliver P Ernst
Retinal-binding proteins, mainly known as rhodopsins, function as photosensors and ion transporters in a wide range of organisms. From halobacterial light-driven proton pump, bacteriorhodopsin, to bovine photoreceptor, visual rhodopsin, they have served as prototypical α-helical membrane proteins in a large number of biophysical studies and aided in the development of many cutting-edge techniques of structural biology and biospectroscopy. In the last decade, microbial and animal rhodopsin families have expanded significantly, bringing into play a number of new interesting structures and functions...
August 24, 2017: Biochimica et Biophysica Acta
Alice Verchère, Wei-Lin Ou, Birgit Ploier, Takefumi Morizumi, Michael A Goren, Peter Bütikofer, Oliver P Ernst, George Khelashvili, Anant K Menon
The retinylidene protein bacteriorhodopsin (BR) is a heptahelical light-dependent proton pump found in the purple membrane of the archaeon Halobacterium salinarum. We now show that when reconstituted into large unilamellar vesicles, purified BR trimers exhibit light-independent lipid scramblase activity, thereby facilitating transbilayer exchange of phospholipids between the leaflets of the vesicle membrane at a rate >10,000 per trimer per second. This activity is comparable to that of recently described scramblases including bovine rhodopsin and fungal TMEM16 proteins...
August 25, 2017: Scientific Reports
Carmen W Dessauer
The G protein-coupled receptor (GPCR) signaling pathways mediating information exchange across the cell membrane are central to a variety of biological processes and therapeutic strategies, but visualizing the molecular-level details of this exchange has been difficult for all but a few GPCR-G protein complexes. A study by Gao et al. now reports new strategies and tools to obtain receptor complexes in a near-native state, revealing insights into the gross conformational features of rhodopsin-transducin interactions and setting the stage for future studies...
August 25, 2017: Journal of Biological Chemistry
Christa Kistenpfennig, Rudi Grebler, Maite Ogueta, Christiane Hermann-Luibl, Matthias Schlichting, Ralf Stanewsky, Pingkalai R Senthilan, Charlotte Helfrich-Förster
Rhodopsin 7 ( Rh7), a new invertebrate Rhodopsin gene, was discovered in the genome of Drosophila melanogaster in 2000, but its function has remained elusive. We generated an Rh7 null mutant ( Rh7(0)) by P element-mediated mutagenesis and found that an absence of Rh7 had significant effects on fly activity patterns during light-dark (LD) cycles: Rh7(0) mutants exhibited less morning activity and a longer siesta than wild-type controls. Consistent with these results, we found that Rh7 appears to be expressed in a few dorsal clock neurons that have been previously implicated in the control of the siesta...
August 1, 2017: Journal of Biological Rhythms
Roly Megaw, Hashem Abu-Arafeh, Melissa Jungnickel, Carla Mellough, Christine Gurniak, Walter Witke, Wei Zhang, Hemant Khanna, Pleasantine Mill, Baljean Dhillon, Alan F Wright, Majlinda Lako, Charles Ffrench-Constant
Mutations in the Retinitis Pigmentosa GTPase Regulator (RPGR) cause X-linked RP (XLRP), an untreatable, inherited retinal dystrophy that leads to premature blindness. RPGR localises to the photoreceptor connecting cilium where its function remains unknown. Here we show, using murine and human induced pluripotent stem cell models, that RPGR interacts with and activates the actin-severing protein gelsolin, and that gelsolin regulates actin disassembly in the connecting cilium, thus facilitating rhodopsin transport to photoreceptor outer segments...
August 16, 2017: Nature Communications
Fatemeh Nasehi, Mohsen Karshenas, Samad Nadri, Ghasem Barati, Ahdiye Salim
Coaxial electrospinning technique was introduced as a flexible and promising technique for the fabrication of core-shell fibrous scaffold from poly ethylene glycol/poly caprolactone (PEG/PCL), where retinal pigmented epithelium-derived factor (PEDF) was encapsulated in the core, for photoreceptor differentiation of conjunctiva mesenchymal stem cells (CJMSCs) seed on scaffolds. The morphology and structure of fibers were characterized using SEM and TEM and photoreceptor differentiation was examined by quantitative real time PCR (qPCR)...
August 10, 2017: Journal of Biomedical Materials Research. Part A
Ala Morshedian, Matthew B Toomey, Gabriel E Pollock, Rikard Frederiksen, Jennifer M Enright, Stephen D McCormick, M Carter Cornwall, Gordon L Fain, Joseph C Corbo
The spectral composition of ambient light varies across both space and time. Many species of jawed vertebrates adapt to this variation by tuning the sensitivity of their photoreceptors via the expression of CYP27C1, an enzyme that converts vitamin A1 into vitamin A2, thereby shifting the ratio of vitamin A1-based rhodopsin to red-shifted vitamin A2-based porphyropsin in the eye. Here, we show that the sea lamprey (Petromyzon marinus), a jawless vertebrate that diverged from jawed vertebrates during the Cambrian period (approx...
July 2017: Royal Society Open Science
H Potter, E Alenciks, K Frazier, A Porter, G S Fraley
Several light sensitive receptors have been described in the avian brain that are thought to regulate the reproductive axis independently from the eyes and pineal gland.Recently, our lab has described the presence of three of these photoneuroendocrine systems in the Pekin duck: opsin, opsin 5, & melanopsin. We set out to test the hypothesis that melanopsin receptive neurons are necessary to maintain seasonal reproductive status along with growth and development in the Pekin drake. To accomplish these goals we first investigated 50-week-old Pekin drakes that were housed in the aviary at Hope College under long day length (18 hrs lights on) conditions in floor pens...
August 4, 2017: General and Comparative Endocrinology
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