Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.291
Filtrar
2.
Biomed Res Int ; 2021: 3236892, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34055970

RESUMO

Background: To investigate the chronic photodamage induced by the low-intensity blue light of phones, we carried out a clinical pilot study and established an animal model by irradiating SD rats with a homemade illuminator. Methods: Clinical investigation: A total of 25 clinical medical workers in our hospital were selected and divided into a control group and an observation group according to the daily video terminal use time. Multifocal electrophysiological system (Mf-ERG) was used for retinal functional examination. Animal experiment: A total of sixty SD rats were randomly divided into a control group (n = 6) and an experimental group (n = 54). The experimental rats were divided into nine groups, which were exposed to the blue light illuminator of the simulated cell phone array for different time. The visual electrophysiology of the rats was tested, and changes in structure were observed by H&E staining and transmission electron microscopy. Results: In clinical investigation, macular centers near the concave area retinal photoreceptor cells have reduced amplitude. In animal experiments, the amplitude of photoreceptor cells decreased, the peak time was delayed, and the amplitudes were lower in the experimental groups. H&E staining and transmission electron microscope showed retinal tissue structure and functional damage in experimental groups. Conclusions: Long-term exposure to low-illuminance blue light can cause retinal tissue structure and functional damage, and the chronic damage due to low-illuminance light warrants attention. The clinical registration number is 2018-KY-KS-LHL.


Assuntos
Telefone Celular , Traumatismos Oculares/etiologia , Luz/efeitos adversos , Retinaldeído/efeitos da radiação , Adulto , Animais , Modelos Animais de Doenças , Traumatismos Oculares/patologia , Feminino , Humanos , Masculino , Estimulação Luminosa , Células Fotorreceptoras de Vertebrados/efeitos da radiação , Ratos , Retina/patologia , Retina/efeitos da radiação , Adulto Jovem
3.
Angew Chem Int Ed Engl ; 60(30): 16442-16447, 2021 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-33973334

RESUMO

Channelrhodopsin-2 (ChR2) is a light-gated cation channel and was used to lay the foundations of optogenetics. Its dark state X-ray structure has been determined in 2017 for the wild-type, which is the prototype for all other ChR variants. However, the mechanistic understanding of the channel function is still incomplete in terms of structural changes after photon absorption by the retinal chromophore and in the framework of functional models. Hence, detailed information needs to be collected on the dark state as well as on the different photointermediates. For ChR2 detailed knowledge on the chromophore configuration in the different states is still missing and a consensus has not been achieved. Using DNP-enhanced solid-state MAS NMR spectroscopy on proteoliposome samples, we unambiguously determined the chromophore configuration in the desensitized state, and we show that this state occurs towards the end of the photocycle.


Assuntos
Channelrhodopsins/química , Chlamydomonas reinhardtii/química , Diterpenos/química , Retinaldeído/química , Bases de Schiff/química , Cátions/química , Luz , Espectroscopia de Ressonância Magnética , Processos Fotoquímicos , Fótons , Conformação Proteica
4.
J Biol Chem ; 296: 100259, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33837742

RESUMO

The ability of iron to transfer electrons enables the contribution of this metal to a variety of cellular activities even as the redox properties of iron are also responsible for the generation of hydroxyl radicals (•OH), the most destructive of the reactive oxygen species. We previously showed that iron can promote the oxidation of bisretinoid by generating highly reactive hydroxyl radical (•OH). Now we report that preservation of iron regulation in the retina is not sufficient to prevent iron-induced bisretinoid oxidative degradation when blood iron levels are elevated in liver-specific hepcidin knockout mice. We obtained evidence for the perpetuation of Fenton reactions in the presence of the bisretinoid A2E and visible light. On the other hand, iron chelation by deferiprone was not associated with changes in postbleaching recovery of 11-cis-retinal or dark-adapted ERG b-wave amplitudes indicating that the activity of Rpe65, a rate-determining visual cycle protein that carries an iron-binding domain, is not affected. Notably, iron levels were elevated in the neural retina and retinal pigment epithelial (RPE) cells of Abca4-/- mice. Consistent with higher iron content, ferritin-L immunostaining was elevated in RPE of a patient diagnosed with ABCA4-associated disease and in RPE and photoreceptor cells of Abca4-/- mice. In neural retina of the mutant mice, reduced Tfrc mRNA was also an indicator of retinal iron overload. Thus iron chelation may defend retina when bisretinoid toxicity is implicated in disease processes.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Genes Recessivos , Retinaldeído/metabolismo , Retinoides/metabolismo , Doença de Stargardt/metabolismo , cis-trans-Isomerases/metabolismo , Transportadores de Cassetes de Ligação de ATP/genética , Animais , Camundongos , Camundongos Knockout , Oxirredução , Retinaldeído/genética , Retinoides/genética , Doença de Stargardt/genética , Doença de Stargardt/patologia , cis-trans-Isomerases/genética
5.
Dev Biol ; 476: 68-78, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33774009

RESUMO

Vitamin A deficiency can cause human pathologies that range from blindness to embryonic malformations. This diversity is due to the lack of two major vitamin A metabolites with very different functions: the chromophore 11-cis-retinal (vitamin A aldehyde) is a critical component of the visual pigment that mediates phototransduction, while the signaling molecule all-trans-retinoic acid regulates the development of various tissues and is required for the function of the immune system. Since animals cannot synthesize vitamin A de novo, they must obtain it either as preformed vitamin A from animal products or as carotenoid precursors from plant sources. Due to its essential role in the visual system, acute vitamin A deprivation impairs photoreceptor function and causes night blindness (poor vision under dim light conditions), while chronic deprivation results in retinal dystrophies and photoreceptor cell death. Chronic vitamin A deficiency is the leading cause of preventable childhood blindness according to the World Health Organization. Due to the requirement of vitamin A for retinoic acid signaling in development and in the immune system, vitamin A deficiency also causes increased mortality in children and pregnant women in developing countries. Drosophila melanogaster is an excellent model to study the effects of vitamin A deprivation on the eye because vitamin A is not essential for Drosophila development and chronic deficiency does not cause lethality. Moreover, genetic screens in Drosophila have identified evolutionarily conserved factors that mediate the production of vitamin A and its cellular uptake. Here, we review our current knowledge about the role of vitamin A in the visual system of mammals and Drosophila melanogaster. We compare the molecular mechanisms that mediate the uptake of dietary vitamin A precursors and the metabolism of vitamin A, as well as the consequences of vitamin A deficiency for the structure and function of the eye.


Assuntos
Visão Ocular/fisiologia , Deficiência de Vitamina A/fisiopatologia , Vitamina A/metabolismo , Animais , Drosophila melanogaster/metabolismo , Mamíferos/metabolismo , Células Fotorreceptoras/metabolismo , Retina/metabolismo , Epitélio Pigmentado da Retina/metabolismo , Retinaldeído/metabolismo , Tretinoína/metabolismo , Percepção Visual/fisiologia , Vitamina A/fisiologia , Deficiência de Vitamina A/metabolismo
6.
J Cosmet Dermatol ; 20(9): 2874-2879, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33569865

RESUMO

BACKGROUND: Retinaldehyde is one of the major members of the retinoid family, which has potential skin rejuvenating effects on photoaged skin and has a good safety profile. AIMS: The study aimed to evaluate the efficacy and safety of multilamellar vesicle containing retinaldehyde (MLV-RAL) 0.05% and 0.1% used to treat photoaged skin. PATIENTS AND METHODS: A randomized, prospective, investigator-blinded, split-face comparison study was conducted. We enrolled 23 Korean volunteers who applied MLV-RAL 0.05%/0.1% cream on one randomized side of their face and retinol 0.05%/0.1% cream on the opposite side. Wrinkle depth on both crow's feet was assessed by the Antera 3D system. Skin hydration, elasticity, facial curved length, and dermal density were also evaluated. RESULTS: After an 8-week application, all objective parameters, including wrinkle depth, were significantly improved in both MLV-RAL 0.05%/0.1% and retinol 0.05%/0.1% treated sides. Compared with the retinol-treated side, MLV-RAL-treated side showed a significant improvement of objective assessments except for dermal density. Additionally, there was no adverse event associated with the use of either MLV-RAL 0.05%/0.1% or retinol 0.05%/0.1% cream. CONCLUSION: The application of MLV-RAL 0.05%/0.1% cream improved wrinkle, facial contour, and biophysical parameters associated with skin aging.


Assuntos
Retinaldeído , Envelhecimento da Pele , Humanos , Estudos Prospectivos , Creme para a Pele , Resultado do Tratamento
7.
J Clin Invest ; 131(4)2021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-33586683

RESUMO

The relationship between adiposity and metabolic health is well established. However, very little is known about the fat depot, known as paracardial fat (pCF), located superior to and surrounding the heart. Here, we show that pCF remodels with aging and a high-fat diet and that the size and function of this depot are controlled by alcohol dehydrogenase 1 (ADH1), an enzyme that oxidizes retinol into retinaldehyde. Elderly individuals and individuals with obesity have low ADH1 expression in pCF, and in mice, genetic ablation of Adh1 is sufficient to drive pCF accumulation, dysfunction, and global impairments in metabolic flexibility. Metabolomics analysis revealed that pCF controlled the levels of circulating metabolites affecting fatty acid biosynthesis. Also, surgical removal of the pCF depot was sufficient to rescue the impairments in cardiometabolic flexibility and fitness observed in Adh1-deficient mice. Furthermore, treatment with retinaldehyde prevented pCF remodeling in these animals. Mechanistically, we found that the ADH1/retinaldehyde pathway works by driving PGC-1α nuclear translocation and promoting mitochondrial fusion and biogenesis in the pCF depot. Together, these data demonstrate that pCF is a critical regulator of cardiometabolic fitness and that retinaldehyde and its generating enzyme ADH1 act as critical regulators of adipocyte remodeling in the pCF depot.


Assuntos
Tecido Adiposo/enzimologia , Álcool Desidrogenase/metabolismo , Mitocôndrias Cardíacas/metabolismo , Obesidade/enzimologia , Pericárdio/enzimologia , Tecido Adiposo/patologia , Álcool Desidrogenase/deficiência , Animais , Núcleo Celular/genética , Núcleo Celular/metabolismo , Metabolômica , Camundongos , Camundongos Knockout , Mitocôndrias Cardíacas/genética , Mitocôndrias Cardíacas/patologia , Obesidade/genética , Obesidade/patologia , Pericárdio/patologia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/genética , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Retinaldeído/metabolismo , Transdução de Sinais/genética
8.
Invest Ophthalmol Vis Sci ; 62(2): 1, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33523199

RESUMO

Purpose: Bis-retinoids are a major component of lipofuscin that accumulates in the retinal pigment epithelium (RPE) in aging and age-related macular degeneration (AMD). Although bis-retinoids are known to originate from retinaldehydes required for the light response of photoreceptor cells, the relative contributions of the chromophore, 11-cis retinal, and photoisomerization product, all-trans retinal, are unknown. In photoreceptor outer segments, all-trans retinal, but not 11-cis retinal, is reduced by retinol dehydrogenase 8 (RDH8). Using Rdh8-/- mice, we evaluated the contribution of increased all-trans retinal to the formation and stability of RPE lipofuscin. Methods: Rdh8-/- mice were reared in cyclic-light or darkness for up to 6 months, with selected light-reared cohorts switched to dark-rearing for the final 1 to 8 weeks. The bis-retinoid A2E was measured from chloroform-methanol extracts of RPE-choroid using HPLC-UV/VIS spectroscopy. Lipofuscin fluorescence was measured from whole flattened eyecups (excitation, 488 nm; emission, 565-725 nm). Results: Cyclic-light-reared Rdh8-/- mice accumulated A2E and RPE lipofuscin approximately 1.5 times and approximately 2 times faster, respectively, than dark-reared mice. Moving Rdh8-/- mice from cyclic-light to darkness resulted in A2E levels less than expected to have accumulated before the move. Conclusions: Our findings establish that elevated levels of all-trans retinal present in cyclic-light-reared Rdh8-/- mice, which remain low in wild-type mice, contribute only modestly to RPE lipofuscin formation and accumulation. Furthermore, decreases in A2E levels occurring after moving cyclic-light-reared Rdh8-/- mice to darkness are consistent with processing of A2E within the RPE and the existence of a mechanism that could be a therapeutic target for controlling A2E cytotoxicity.


Assuntos
Lipofuscina/metabolismo , Degeneração Macular/metabolismo , Epitélio Pigmentado da Retina/metabolismo , Retinaldeído/metabolismo , Retinoides/metabolismo , Animais , Cromatografia Líquida de Alta Pressão , Modelos Animais de Doenças , Feminino , Degeneração Macular/patologia , Masculino , Camundongos , Epitélio Pigmentado da Retina/patologia
9.
Phys Chem Chem Phys ; 23(3): 2072-2079, 2021 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-33433533

RESUMO

We carried out the low-temperature Raman measurement of a sodium pump rhodopsin from Indibacter alkaliphilus (IaNaR) and examined the primary structural change for the light-driven Na+ pump. We observed that photoexcitation of IaNaR produced the distorted 13-cis retinal chromophore in the presence of Na+, while the structural distortion was significantly relaxed in the absence of Na+. This structural difference of the chromophore with/without Na+ was attributed to the Na+ binding to the protein, which alters the active site. Using the spectral sensitivity to the ion binding, we found that IaNaR had a second Na+ binding site in addition to the one already specified on the extracellular surface. To date, the Na+ binding has not been considered as a prerequisite for Na+ transport. However, this study provides insight that the protein structural change induced by the ion binding involved the formation of an R108-D250 salt bridge, which has critical importance in the active transport of Na+.


Assuntos
Proteínas de Bactérias/metabolismo , Bacteroidetes/química , Proteínas de Transporte de Cátions/metabolismo , Rodopsinas Microbianas/metabolismo , Sódio/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/efeitos da radiação , Transporte Biológico Ativo , Domínio Catalítico , Proteínas de Transporte de Cátions/química , Proteínas de Transporte de Cátions/genética , Proteínas de Transporte de Cátions/efeitos da radiação , Temperatura Baixa , Cristalografia por Raios X , Diterpenos/química , Conformação Molecular , Mutação , Retinaldeído/química , Rodopsinas Microbianas/química , Rodopsinas Microbianas/genética , Rodopsinas Microbianas/efeitos da radiação , Análise Espectral Raman
10.
Nat Commun ; 12(1): 629, 2021 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-33504778

RESUMO

Many transmembrane receptors have a desensitized state, in which they are unable to respond to external stimuli. The family of microbial rhodopsin proteins includes one such group of receptors, whose inactive or dark-adapted (DA) state is established in the prolonged absence of light. Here, we present high-resolution crystal structures of the ground (light-adapted) and DA states of Archaerhodopsin-3 (AR3), solved to 1.1 Å and 1.3 Å resolution respectively. We observe significant differences between the two states in the dynamics of water molecules that are coupled via H-bonds to the retinal Schiff Base. Supporting QM/MM calculations reveal how the DA state permits a thermodynamic equilibrium between retinal isomers to be established, and how this same change is prevented in the ground state in the absence of light. We suggest that the different arrangement of internal water networks in AR3 is responsible for the faster photocycle kinetics compared to homologs.


Assuntos
Proteínas Arqueais/metabolismo , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Água/química , Cristalografia por Raios X , Elétrons , Ligação de Hidrogênio , Isomerismo , Lipídeos/química , Conformação Molecular , Processamento de Proteína Pós-Traducional , Prótons , Retinaldeído/química , Retinaldeído/metabolismo
11.
J Biol Chem ; 296: 100187, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33334878

RESUMO

The death of photoreceptor cells in dry age-related macular degeneration (AMD) and autosomal recessive Stargardt disease (STGD1) is closely associated with disruption in all-trans-retinal (atRAL) clearance in neural retina. In this study, we reveal that the overload of atRAL leads to photoreceptor degeneration through activating ferroptosis, a nonapoptotic form of cell death. Ferroptosis of photoreceptor cells induced by atRAL resulted from increased ferrous ion (Fe2+), elevated ACSL4 expression, system Xc- inhibition, and mitochondrial destruction. Fe2+ overload, tripeptide glutathione (GSH) depletion, and damaged mitochondria in photoreceptor cells exposed to atRAL provoked reactive oxygen species (ROS) production, which, together with ACSL4 activation, promoted lipid peroxidation and thereby evoked ferroptotic cell death. Moreover, exposure of photoreceptor cells to atRAL activated COX2, a well-accepted biomarker for ferroptosis onset. In addition to GSH supplement, inhibiting either Fe2+ by deferoxamine mesylate salt (DFO) or lipid peroxidation with ferrostatin-1 (Fer-1) protected photoreceptor cells from ferroptosis caused by atRAL. Abca4-/-Rdh8-/- mice exhibiting defects in atRAL clearance is an animal model for dry AMD and STGD1. We observed that ferroptosis was indeed present in neural retina of Abca4-/-Rdh8-/- mice after light exposure. More importantly, photoreceptor atrophy and ferroptosis in light-exposed Abca4-/-Rdh8-/- mice were effectively alleviated by intraperitoneally injected Fer-1, a selective inhibitor of ferroptosis. Our study suggests that ferroptosis is one of the important pathways of photoreceptor cell death in retinopathies arising from excess atRAL accumulation and should be pursued as a novel target for protection against dry AMD and STGD1.


Assuntos
Ferroptose , Peroxidação de Lipídeos , Degeneração Macular/patologia , Células Fotorreceptoras de Vertebrados/patologia , Retinaldeído/análogos & derivados , Animais , Degeneração Macular/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Estresse Oxidativo , Células Fotorreceptoras de Vertebrados/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Retinaldeído/metabolismo , Doença de Stargardt/metabolismo , Doença de Stargardt/patologia
12.
Biochemistry ; 60(1): 6-18, 2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33356167

RESUMO

Rhodopsin is the light receptor required for the function and health of photoreceptor cells. Mutations in rhodopsin can cause misfolding and aggregation of the receptor, which leads to retinal degeneration. Bovine rhodopsin is often used as a model to understand the effect of pathogenic mutations in rhodopsin due to the abundance of structural information on the bovine form of the receptor. It is unclear whether or not the bovine rhodopsin template is adequate in predicting the effect of these mutations occurring in human retinal disease or in predicting the efficacy of therapeutic strategies. To better understand the extent to which bovine rhodopsin can serve as a model, human and bovine P23H rhodopsin mutants expressed heterologously in cells were examined. The aggregation properties and cellular localization of the mutant receptors were determined by Förster resonance energy transfer and confocal microscopy. The potential therapeutic effects of the pharmacological compounds 9-cis retinal and metformin were also examined. Human and bovine P23H rhodopsin mutants exhibited different aggregation properties and responses to the pharmacological compounds tested. These observations would lead to different predictions on the severity of the phenotype and divergent predictions on the benefit of the therapeutic compounds tested. The bovine rhodopsin template does not appear to adequately model the effects of the P23H mutation in the human form of the receptor.


Assuntos
Diterpenos/metabolismo , Metformina/metabolismo , Proteínas Mutantes/química , Mutação , Agregados Proteicos , Retinaldeído/metabolismo , Rodopsina/química , Animais , Bovinos , Humanos , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Rodopsina/genética , Rodopsina/metabolismo
13.
Proc Natl Acad Sci U S A ; 117(50): 32114-32123, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33257550

RESUMO

Fatty acid transport protein 4 (FATP4), a transmembrane protein in the endoplasmic reticulum (ER), is a recently identified negative regulator of the ER-associated retinal pigment epithelium (RPE)65 isomerase necessary for recycling 11-cis-retinal, the light-sensitive chromophore of both rod and cone opsin visual pigments. The role of FATP4 in the disease progression of retinal dystrophies associated with RPE65 mutations is completely unknown. Here we show that FATP4-deficiency in the RPE results in 2.8-fold and 1.7-fold increase of 11-cis- and 9-cis-retinals, respectively, improving dark-adaptation rates as well as survival and function of rods in the Rpe65 R91W knockin (KI) mouse model of Leber congenital amaurosis (LCA). Degradation of S-opsin in the proteasomes, but not in the lysosomes, was remarkably reduced in the KI mouse retinas lacking FATP4. FATP4-deficiency also significantly rescued S-opsin trafficking and M-opsin solubility in the KI retinas. The number of S-cones in the inferior retinas of 4- or 6-mo-old KI;Fatp4 -/- mice was 7.6- or 13.5-fold greater than those in age-matched KI mice. Degeneration rates of S- and M-cones are negatively correlated with expression levels of FATP4 in the RPE of the KI, KI;Fatp4 +/- , and KI;Fatp4 -/- mice. Moreover, the visual function of S- and M-cones is markedly preserved in the KI;Fatp4 -/- mice, displaying an inverse correlation with the FATP4 expression levels in the RPE of the three mutant lines. These findings establish FATP4 as a promising therapeutic target to improve the visual cycle, as well as survival and function of cones and rods in patients with RPE65 mutations.


Assuntos
Proteínas de Transporte de Ácido Graxo/deficiência , Amaurose Congênita de Leber/fisiopatologia , Retina/patologia , Visão Ocular/fisiologia , cis-trans-Isomerases/genética , Animais , Opsinas dos Cones/metabolismo , Modelos Animais de Doenças , Diterpenos/isolamento & purificação , Proteínas de Transporte de Ácido Graxo/genética , Humanos , Amaurose Congênita de Leber/genética , Amaurose Congênita de Leber/patologia , Camundongos , Camundongos Knockout , Mutação , Retina/metabolismo , Retinaldeído/biossíntese , Retinaldeído/isolamento & purificação , cis-trans-Isomerases/metabolismo
14.
Proc Natl Acad Sci U S A ; 117(40): 24867-24875, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32958638

RESUMO

Visual pigment consists of opsin covalently linked to the vitamin A-derived chromophore, 11-cis-retinaldehyde. Photon absorption causes the chromophore to isomerize from the 11-cis- to all-trans-retinal configuration. Continued light sensitivity necessitates the regeneration of 11-cis-retinal via a series of enzyme-catalyzed steps within the visual cycle. During this process, vitamin A aldehyde is shepherded within photoreceptors and retinal pigment epithelial cells to facilitate retinoid trafficking, to prevent nonspecific reactivity, and to conserve the 11-cis configuration. Here we show that redundancy in this system is provided by a protonated Schiff base adduct of retinaldehyde and taurine (A1-taurine, A1T) that forms reversibly by nonenzymatic reaction. A1T was present as 9-cis, 11-cis, 13-cis, and all-trans isomers, and the total levels were higher in neural retina than in retinal pigment epithelium (RPE). A1T was also more abundant under conditions in which 11-cis-retinaldehyde was higher; this included black versus albino mice, dark-adapted versus light-adapted mice, and mice carrying the Rpe65-Leu450 versus Rpe65-450Met variant. Taurine levels paralleled these differences in A1T. Moreover, A1T was substantially reduced in mice deficient in the Rpe65 isomerase and in mice deficient in cellular retinaldehyde-binding protein; in these models the production of 11-cis-retinal is compromised. A1T is an amphiphilic small molecule that may represent a mechanism for escorting retinaldehyde. The transient Schiff base conjugate that the primary amine of taurine forms with retinaldehyde would readily hydrolyze to release the retinoid and thus may embody a pool of 11-cis-retinal that can be marshalled in photoreceptor cells.


Assuntos
Retinaldeído/metabolismo , Taurina/metabolismo , Animais , Humanos , Isomerismo , Luz , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Células Fotorreceptoras/metabolismo , Células Fotorreceptoras/efeitos da radiação , Retina/metabolismo , Retina/efeitos da radiação , Epitélio Pigmentado da Retina/metabolismo , Epitélio Pigmentado da Retina/efeitos da radiação , Retinaldeído/química , Retinoides/química , Retinoides/metabolismo , Taurina/química , cis-trans-Isomerases/metabolismo
15.
Biochem Biophys Res Commun ; 533(3): 262-267, 2020 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-32951839

RESUMO

Microbial rhodopsins comprise an opsin protein with seven transmembrane helices and a retinal as the chromophore. An all-trans retinal is covalently bonded to a lysine residue through the retinal Schiff base (RSB) and stabilized by a negatively charged counterion. The distance between the RSB and counterion is closely related to the light energy absorption. However, in heliorhodopsin-48C12 (HeR-48C12), while E107 acts as the counterion, E107D mutation exhibits an identical absorption spectrum to the wild-type, suggesting that the distance does not affect its absorption spectra. Here we present the 2.6 Å resolution crystal structure of the Thermoplasmatales archaeon HeR E108D mutant, which also has an identical absorption spectrum to the wild-type. The structure revealed that D108 does not form a hydrogen bond with the RSB, and its counterion interaction becomes weaker. Alternatively, the serine cluster, S78, S112, and S238 form a distinct interaction network around the RSB. The absorption spectra of the E to D and S to A double mutants suggested that S112 influences the spectral shift by compensating for the weaker counterion interaction. Our structural and spectral studies have revealed the unique spectral shift mechanism of HeR and clarified the physicochemical properties of HeRs.


Assuntos
Substituição de Aminoácidos , Proteínas Arqueais/química , Retinaldeído/química , Rodopsinas Microbianas/química , Thermoplasmales/química , Proteínas Arqueais/genética , Proteínas Arqueais/metabolismo , Sítios de Ligação , Clonagem Molecular , Cor , Cristalografia por Raios X , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Modelos Moleculares , Mutação , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Retinaldeído/metabolismo , Rodopsinas Microbianas/genética , Rodopsinas Microbianas/metabolismo , Bases de Schiff/química
16.
Photochem Photobiol Sci ; 19(10): 1300-1307, 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-32812970

RESUMO

Retinal, the vitamin A aldehyde, is a potent photosensitizer that plays a major role in light-induced damage to vertebrate photoreceptors. 11-Cis retinal is the light-sensitive chromophore of rhodopsin, the photopigment of vertebrate rod photoreceptors. It is isomerized by light to all-trans, activating rhodopsin and beginning the process of light detection. All-trans retinal is released by activated rhodopsin, allowing its regeneration by fresh 11-cis retinal continually supplied to photoreceptors. The released all-trans retinal is reduced to all-trans retinol in a reaction using NADPH. We have examined the photooxidation mediated by 11-cis and all-trans retinal in single living rod photoreceptors isolated from mouse retinas. Photooxidation was measured with fluorescence imaging from the oxidation of internalized BODIPY C11, a fluorescent dye whose fluorescence changes upon oxidation. We found that photooxidation increased with the concentration of exogenously added 11-cis or all-trans retinal to metabolically compromised rod outer segments that lacked NADPH supply. In dark-adapted metabolically intact rod outer segments with access to NADPH, there was no significant increase in photooxidation following exposure of the cell to light, but there was significant increase following addition of exogenous 11-cis retinal. The results indicate that both 11-cis and all-trans retinal can mediate light-induced damage in rod photoreceptors. In metabolically intact cells, the removal of the all-trans retinal generated by light through its reduction to retinol minimizes all-trans retinal-mediated photooxidation. However, because the enzymatic machinery of the rod outer segment cannot remove 11-cis retinal, 11-cis-retinal-mediated photooxidation may play a significant role in light-induced damage to photoreceptor cells.


Assuntos
Células Fotorreceptoras/química , Retinaldeído/química , Segmento Externo da Célula Bastonete/química , Vitamina A/química , Animais , Camundongos , Camundongos Knockout , Estrutura Molecular , Imagem Óptica , Oxirredução , Processos Fotoquímicos
17.
Sci Rep ; 10(1): 13992, 2020 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-32814821

RESUMO

Retinal proteins play significant roles in light-induced protons/ions transport across the cell membrane. A recent studied retinal protein, gloeobacter rhodopsin (gR), functions as a proton pump, and binds the carotenoid salinixanthin (sal) in addition to the retinal chromophore. We have studied the interactions between the two chromophores as reflected in the circular dichroism (CD) spectrum of gR complex. gR exhibits a weak CD spectrum but following binding of sal, it exhibits a significant enhancement of the CD bands. To examine the CD origin, we have substituted the retinal chromophore of gR by synthetic retinal analogues, and have concluded that the CD bands originated from excitonic interaction between sal and the retinal chromophore as well as the sal chirality induced by binding to the protein. Temperature increase significantly affected the CD spectra, due to vanishing of excitonic coupling. A similar phenomenon of excitonic interaction lose between chromophores was recently reported for a photosynthetic pigment-protein complex (Nature Commmun, 9, 2018, 99). We propose that the excitonic interaction in gR is weaker due to protein conformational alterations. The excitonic interaction is further diminished following reduction of the retinal protonated Schiff base double bond. Furthermore, the intact structure of the retinal ring is necessary for obtaining the excitonic interaction.


Assuntos
Carotenoides/metabolismo , Bombas de Próton/metabolismo , Retinaldeído/metabolismo , Rodopsina/metabolismo , Rodopsinas Microbianas/metabolismo , Carotenoides/química , Cianobactérias/metabolismo , Glicosídeos/química , Glicosídeos/metabolismo , Concentração de Íons de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Ligação Proteica , Conformação Proteica , Bombas de Próton/química , Retina/metabolismo , Retinaldeído/química , Rodopsina/química , Rodopsinas Microbianas/química , Bases de Schiff/química , Estereoisomerismo , Temperatura
18.
Proc Natl Acad Sci U S A ; 117(33): 19629-19638, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32759209

RESUMO

The visual phototransduction cascade begins with a cis-trans photoisomerization of a retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. Visual opsins release their all-trans-retinal chromophore following photoactivation, which necessitates the existence of pathways that produce 11-cis-retinal for continued formation of visual pigments and sustained vision. Proteins in the retinal pigment epithelium (RPE), a cell layer adjacent to the photoreceptor outer segments, form the well-established "dark" regeneration pathway known as the classical visual cycle. This pathway is sufficient to maintain continuous rod function and support cone photoreceptors as well although its throughput has to be augmented by additional mechanism(s) to maintain pigment levels in the face of high rates of photon capture. Recent studies indicate that the classical visual cycle works together with light-dependent processes in both the RPE and neural retina to ensure adequate 11-cis-retinal production under natural illuminances that can span ten orders of magnitude. Further elucidation of the interplay between these complementary systems is fundamental to understanding how cone-mediated vision is sustained in vivo. Here, we describe recent advances in understanding how 11-cis-retinal is synthesized via light-dependent mechanisms.


Assuntos
Retinaldeído/biossíntese , Visão Ocular , Animais , Humanos , Luz , Transdução de Sinal Luminoso , Opsinas/metabolismo , Células Fotorreceptoras Retinianas Cones/metabolismo , Epitélio Pigmentado da Retina/metabolismo , Retinaldeído/química
19.
J Mol Biol ; 432(19): 5378-5389, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32795534

RESUMO

Rhodopsin is the photosensitive protein, which binds to 11-cis-retinal as its chromophore. In the dark, rhodopsin exists as a stable complex between the opsin moiety and 11-cis-retinal. The absorption of a light photon converts 11-cis-retinal to all-trans-retinal and initiates our vision. As a result, the increase in the rate of dark activation of rhodopsin reduces its photosensitivity resulting in night blindness. The mutations, G90D and T94I are night blindness-causing mutations that exhibit completely different physicochemical characteristics associated with the dark activation of rhodopsin, such as a high rate of thermal isomerization of 11-cis-retinal and a slow pigment regeneration. To elucidate the molecular mechanism by which G90D and T94I mutations affect rhodopsin dark activation and regeneration, we performed light-induced difference FTIR spectroscopy on dark and primary photo-intermediate states of G90D and T94I mutants. The FTIR spectra clearly show that both charged G90D and hydrophobic T94I mutants alter the H-bond network at the Schiff base region of the chromophore, which weakens the electrostatic interaction with Glu113 counterion. Our results further show an altered water-mediated H-bond network around the central transmembrane region of mutant rhodopsin, which is reminiscent of the active Meta-II state. This altered water-mediated H-bond network may cause thermal isomerization of the chromophore and facilitate rhodopsin dark activation.


Assuntos
Cegueira Noturna/genética , Rodopsina/genética , Animais , Bovinos , Ligação de Hidrogênio , Isomerismo , Modelos Moleculares , Cegueira Noturna/metabolismo , Mutação Puntual , Conformação Proteica , Retinaldeído/química , Retinaldeído/genética , Retinaldeído/metabolismo , Rodopsina/química , Rodopsina/metabolismo
20.
Bioorg Med Chem Lett ; 30(18): 127421, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32717613

RESUMO

The discovery of how a photon is converted into a chemical signal is one of the most important achievements in the field of vision. A key molecule in this process is the visual chromophore retinal. Several eye diseases are attributed to the abnormal metabolism of retinal in the retina and the retinal pigment epithelium. Also, the accumulation of two toxic retinal derivatives, N-retinylidene-N-retinylethanolamine and the retinal dimer, can damage the retina leading to blindness. RPE65 (Retinal pigment epithelium-specific 65 kDa protein) is one of the central enzymes that regulates the metabolism of retinal and the formation of its toxic metabolites. Its inhibition might decrease the rate of the retina's degeneration by limiting the amount of retinal and its toxic byproducts. Two RPE65 inhibitors, (R)-emixustat and (R)-MB001, were recently developed for this purpose.


Assuntos
Inibidores Enzimáticos/síntese química , Éteres Fenílicos/síntese química , Propanolaminas/síntese química , Degeneração Retiniana/tratamento farmacológico , cis-trans-Isomerases/antagonistas & inibidores , Alcanos/química , Inibidores Enzimáticos/farmacologia , Halogenação , Humanos , Isomerismo , Modelos Moleculares , Conformação Molecular , Preparações Farmacêuticas/síntese química , Éteres Fenílicos/farmacologia , Propanolaminas/farmacologia , Retina/metabolismo , Retinaldeído/análogos & derivados , Retinaldeído/metabolismo , Relação Estrutura-Atividade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...