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Soluble Mediators of Cellular Cooperation: The Cytokines
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Receptor. The IL-8R (CDw128, gene on chromosome 2) has a structure different from most other cytokine receptors. This molecule has seven transmembrane α-helices and has been grouped in the rhodopsin receptor family (see below and Table 7–VI). IL-8R are very dense on the neutrophil surface, about 20,000 per cell. In contrast, T cells only express approximately 300 IL-8R per cell.
The vitamins
Published in Geoffrey P. Webb, Nutrition, 2019
Rhodopsin is the light-sensitive pigment in the rod cells of the retina. It is comprised of 11-cis retinal (the chromophore) and a protein called opsin. Within the eye, all trans retinol (vitamin A) is converted by enzymes to 11-cis retinal and this binds spontaneously with opsin to form rhodopsin. Light induces isomerisation of the 11-cis retinal in rhodopsin to all trans retinal, and this causes the opsin and retinal to dissociate and the pigment to become bleached. It is this light-induced cis-to-trans isomerisation that generates the nervous impulses that we perceive as vision. Enzymes in the eye then regenerate 11-cis retinal and thus rhodopsin (summarised in Figure 15.2).
Medical retina
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
A condition that is characterized by photoreceptor dysfunction (rods, then cones) and progressive atrophy/degeneration of retinal tissue. Most commonly due to a mutation in the rhodopsin gene in the long arm of chromosome 3. Inheritance can be AD (most common, least severe), AR or XL inheritance (worst prognosis).
The light-activated TRP channel: the founding member of the TRP channel superfamily
Published in Journal of Neurogenetics, 2022
The Pak lab (O’Tousa et al., 1985) and the Rubin lab (Zuker, Cowman, & Rubin, 1985) had earlier cloned the gene encoding the majority class (R1-6) of Drosophila rhodopsin. Although its overall sequence similarity to mammalian rhodopsin was fairly modest (36%), it had all the hall-marks of a rhodopsin protein, including seven transmembrane domains, the presumed chromophore attachment site (a lysine residue near the middle of the seventh transmembrane domain) and potential phosphorylation sites near the C-terminus. Rhodopsin is an archetypal G-protein coupled receptor (GPCR). Since strong norpA alleles abolish the receptor potential, they were led to the inevitable conclusion that GPCR (rhodopsin)-mediated stimulation of PI-PLC is necessary for the light-activated opening of phototransduction channels. This molecular study thus provided compelling evidence for the biochemical and electrophysiological data that demonstrated coupling of photoexcited rhodopsin to Gq-mediated PIP2 hydrolysis in the fly retina (Figure 1, (Devary et al., 1987)).
Quantitative autofluorescence: Review of Current Technical Aspects and Applications in Chorioretinal Disease
Published in Seminars in Ophthalmology, 2021
Iris Deitch, Kevin Ferenchak, John B. Miller
There are several factors that affect the AF signal. Clarity of ocular media is important, and crystalline lenses are highly fluorescent and can reduce the quality of images. Features of the retina and RPE that affect the AF signal include macular pigments, melanin and rhodopsin. Pigments concentrated in the macula lutea include three yellow carotenoids (xanthophylls); lutein, zeaxanthin and meso-zeaxanthin.14 Exhibiting a strong absorption in blue light, the macular pigments are responsible for the foveal hypoflourescence seen at the foveal center of normal subjects. RPE melanin is generally located apically in the lipofuscin granules of the RPE cell and therefore attenuates the fluorescence at all wavelengths, particularly in the fovea where the RPE is thicker. Rhodopsin is a visual pigment concentrated in rod photoreceptor outer segments. It absorbs the excitation beam and thus decreases AF.15 The ocular fundus also exhibits a faint AF under near IR-excitation. Near-infrared (IR) FAF imaging uses long wavelengths (at 790 nm) to excite molecules other than lipofuscin. Topographic distribution and observations in selected clinical cases suggest that melanin or components related to melanin are responsible for the observed AF.16
Antisense oligonucleotide therapeutics in clinical trials for the treatment of inherited retinal diseases
Published in Expert Opinion on Investigational Drugs, 2020
Kanmin Xue, Robert E. MacLaren
Mutations in the rhodopsin gene (RHO) account for over 25% of autosomal dominant retinitis pigmentosa (adRP). Due to a suspected founder effect, around 10% of RHO-associated adRP are due to a C-to-A transversion in codon 23 of RHO, which causes a Pro-23-His single amino acid change [30,31]. The misfolded RHO proteins expressed from the mutant allele appear to accumulate in the endoplasmic reticulum, leading to pro-apoptotic stress responses and a toxic dominant negative effect on rod photoreceptors [32]. Due to the dominant nature of most RHO mutations, the disease is not amenable to standard adeno-associated viral (AAV) vector-mediated gene augmentation therapy even though the RHO gene is under 1.5 kb. However, a ‘block and replace’ therapeutic strategy involving co-expression of an inhibitory shRNA against RHO and a codon-modified cDNA of RHO resistant to the shRNA has shown early success in a canine model of RHO-adRP [33].