RESUMEN
Neurodegeneration in Fragile X-associated tremor/ataxia syndrome (FXTAS) is caused by a CGG trinucleotide repeat expansion in the 5' UTR of FMR1. Expanded CGG repeat RNAs form stable secondary structures, which in turn support repeat-associated non-AUG (RAN) translation to produce toxic peptides. The parameters that impact RAN translation initiation efficiency are not well understood. Here we used a Drosophila melanogaster model of FXTAS to evaluate the role of the eIF4G family of eukaryotic translation initiation factors (EIF4G1, EIF4GII and EIF4G2/DAP5) in modulating RAN translation and CGG repeat-associated toxicity. DAP5 knockdown robustly suppressed CGG repeat-associated toxicity and inhibited RAN translation. Furthermore, knockdown of initiation factors that preferentially associate with DAP5 (such as EIF2ß, EIF3F and EIF3G) also selectively suppressed CGG repeat-induced eye degeneration. In mammalian cellular reporter assays, DAP5 knockdown exhibited modest and cell-type specific effects on RAN translation. Taken together, these data support a role for DAP5 in CGG repeat associated toxicity possibly through modulation of RAN translation.
Asunto(s)
Proteínas de Drosophila , Síndrome del Cromosoma X Frágil , Animales , Drosophila/metabolismo , Temblor/genética , Drosophila melanogaster/metabolismo , Factor 4G Eucariótico de Iniciación/genética , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/genética , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/metabolismo , Síndrome del Cromosoma X Frágil/genética , Expansión de Repetición de Trinucleótido , Ataxia/genética , Mamíferos/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismoRESUMEN
Repeat-associated non-AUG (RAN) translation of expanded repeat-mutation mRNA produces toxic peptides in neurons of patients suffering from neurodegenerative diseases. Recent findings indicate that RAN translation in diverse model systems is not inhibited by cellular stressors that impair global translation through phosphorylation of the alpha subunit of eIF2, the essential eukaryotic translation initiation factor that brings the initiator tRNA to the 40S ribosome. Using in vitro, cell-based and Drosophila models, we examined the role of alternative ternary complex factors that may function in place of eIF2, including eIF2A, eIF2D, DENR and MCTS1. Among these factors, DENR knockdown had the greatest inhibitory effect on RAN translation of expanded GGGGCC and CGG repeat reporters and its reduction improved the survival of Drosophila expressing expanded GGGGCC repeats. Taken together, these data support a role for alternative initiation factors in RAN translation and suggest these may serve as novel therapeutic targets in neurodegenerative disease.
Asunto(s)
Proteínas de Drosophila , Enfermedades Neurodegenerativas , Animales , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Factor 2 Eucariótico de Iniciación/genética , Factor 2 Eucariótico de Iniciación/metabolismo , Factores Eucarióticos de Iniciación/genética , Factores Eucarióticos de Iniciación/metabolismo , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/metabolismo , Biosíntesis de Proteínas/genética , ARN Mensajero/genética , Ribosomas/genética , Ribosomas/metabolismoRESUMEN
The integrated stress response (ISR) is a conserved mechanism by which eukaryotic cells remodel gene expression to adapt to intrinsic and extrinsic stressors rapidly and reversibly. The ISR is initiated when stress-activated protein kinases phosphorylate the major translation initiation factor eukaryotic translation initiation factor 2É (eIF2É), which globally suppresses translation initiation activity and permits the selective translation of stress-induced genes including important transcription factors such as activating transcription factor 4 (ATF4). Translationally repressed messenger RNAs (mRNAs) and noncoding RNAs assemble into cytoplasmic RNA-protein granules and polyadenylated RNAs are concomitantly stabilized. Thus, regulated changes in mRNA translation, stability, and localization to RNA-protein granules contribute to the reprogramming of gene expression that defines the ISR. We discuss fundamental mechanisms of RNA regulation during the ISR and provide an overview of a growing class of genetic disorders associated with mutant alleles of key translation factors in the ISR pathway. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA in Disease and Development > RNA in Disease Translation > Translation Regulation RNA in Disease and Development > RNA in Development.
Asunto(s)
Factor 2 Eucariótico de Iniciación , Transducción de Señal , Factor de Transcripción Activador 4/genética , Factor de Transcripción Activador 4/metabolismo , Factor 2 Eucariótico de Iniciación/genética , Fosforilación , Biosíntesis de Proteínas , Proteínas/metabolismo , ARN Mensajero/metabolismo , Estrés Fisiológico/genéticaRESUMEN
Transcribed CGG repeat expansions cause neurodegeneration in Fragile X-associated tremor/ataxia syndrome (FXTAS). CGG repeat RNAs sequester RNA-binding proteins (RBPs) into nuclear foci and undergo repeat-associated non-AUG (RAN) translation into toxic peptides. To identify proteins involved in these processes, we employed a CGG repeat RNA-tagging system to capture repeat-associated RBPs by mass spectrometry in mammalian cells. We identified several SR (serine/arginine-rich) proteins that interact selectively with CGG repeats basally and under cellular stress. These proteins modify toxicity in a Drosophila model of FXTAS. Pharmacologic inhibition of serine/arginine protein kinases (SRPKs), which alter SRSF protein phosphorylation, localization, and activity, directly inhibits RAN translation of CGG and GGGGCC repeats (associated with C9orf72 ALS/FTD) and triggers repeat RNA retention in the nucleus. Lowering SRPK expression suppressed toxicity in both FXTAS and C9orf72 ALS/FTD model flies, and SRPK inhibitors suppressed CGG repeat toxicity in rodent neurons. Together, these findings demonstrate roles for CGG repeat RNA binding proteins in RAN translation and repeat toxicity and support further evaluation of SRPK inhibitors in modulating RAN translation associated with repeat expansion disorders.
Asunto(s)
Esclerosis Amiotrófica Lateral , Proteínas de Drosophila , Síndrome del Cromosoma X Frágil , Demencia Frontotemporal , Proteínas Serina-Treonina Quinasas , Esclerosis Amiotrófica Lateral/genética , Animales , Proteína C9orf72/genética , Proteína C9orf72/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/genética , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/metabolismo , Síndrome del Cromosoma X Frágil/genética , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Expansión de Repetición de TrinucleótidoRESUMEN
GGGGCC (G4C2) hexanucleotide repeat expansions in the endosomal trafficking gene C9orf72 are the most common genetic cause of ALS and frontotemporal dementia. Repeat-associated non-AUG (RAN) translation of this expansion through near-cognate initiation codon usage and internal ribosomal entry generates toxic proteins that accumulate in patients' brains and contribute to disease pathogenesis. The helicase protein DEAH-box helicase 36 (DHX36-G4R1) plays active roles in RNA and DNA G-quadruplex (G4) resolution in cells. As G4C2 repeats are known to form G4 structures in vitro, we sought to determine the impact of manipulating DHX36 expression on repeat transcription and RAN translation. Using a series of luciferase reporter assays both in cells and in vitro, we found that DHX36 depletion suppresses RAN translation in a repeat length-dependent manner, whereas overexpression of DHX36 enhances RAN translation from G4C2 reporter RNAs. Moreover, upregulation of RAN translation that is typically triggered by integrated stress response activation is prevented by loss of DHX36. These results suggest that DHX36 is active in regulating G4C2 repeat translation, providing potential implications for therapeutic development in nucleotide repeat expansion disorders.
Asunto(s)
Esclerosis Amiotrófica Lateral/patología , Proteína C9orf72/genética , ARN Helicasas DEAD-box/metabolismo , Expansión de las Repeticiones de ADN , G-Cuádruplex , ARN Helicasas/metabolismo , Esclerosis Amiotrófica Lateral/enzimología , Esclerosis Amiotrófica Lateral/genética , Proteína C9orf72/metabolismo , Línea Celular Tumoral , Demencia Frontotemporal/enzimología , Demencia Frontotemporal/genética , Demencia Frontotemporal/patología , Humanos , Biosíntesis de ProteínasRESUMEN
There is a pressing need to increase the rigor of research in the life and biomedical sciences. To address this issue, we propose that communities of 'rigor champions' be established to campaign for reforms of the research culture that has led to shortcomings in rigor. These communities of rigor champions would also assist in the development and adoption of a comprehensive educational platform that would teach the principles of rigorous science to researchers at all career stages.
Asunto(s)
Investigación Biomédica/educación , Investigación Biomédica/métodos , Investigación Biomédica/normas , Proyectos de Investigación/normas , HumanosRESUMEN
Repeat-associated non-AUG (RAN) translation is a noncanonical translation initiation event that occurs at nucleotide-repeat expansion mutations that are associated with several neurodegenerative diseases, including fragile X-associated tremor ataxia syndrome (FXTAS), ALS, and frontotemporal dementia (FTD). Translation of expanded repeats produces toxic proteins that accumulate in human brains and contribute to disease pathogenesis. Consequently, RAN translation constitutes a potentially important therapeutic target for managing multiple neurodegenerative disorders. Here, we adapted a previously developed RAN translation assay to a high-throughput format to screen 3,253 bioactive compounds for inhibition of RAN translation of expanded CGG repeats associated with FXTAS. We identified five diverse small molecules that dose-dependently inhibited CGG RAN translation, while relatively sparing canonical translation. All five compounds also inhibited RAN translation of expanded GGGGCC repeats associated with ALS and FTD. Using CD and native gel analyses, we found evidence that three of these compounds, BIX01294, CP-31398, and propidium iodide, bind directly to the repeat RNAs. These findings provide proof-of-principle supporting the development of selective small-molecule RAN translation inhibitors that act across multiple disease-causing repeats.
Asunto(s)
Esclerosis Amiotrófica Lateral/genética , Ataxia/genética , Síndrome del Cromosoma X Frágil/genética , Temblor/genética , Expansión de Repetición de Trinucleótido/genética , Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Animales , Ataxia/tratamiento farmacológico , Azepinas/farmacología , Azepinas/uso terapéutico , Células Cultivadas , Dicroismo Circular , Expansión de las Repeticiones de ADN/efectos de los fármacos , Expansión de las Repeticiones de ADN/genética , Evaluación Preclínica de Medicamentos , Síndrome del Cromosoma X Frágil/tratamiento farmacológico , Células HEK293 , Humanos , Enfermedades Neurodegenerativas/genética , Propidio/farmacología , Propidio/uso terapéutico , Pirimidinas/farmacología , Pirimidinas/uso terapéutico , Quinazolinas/farmacología , Quinazolinas/uso terapéutico , Ratas , Temblor/tratamiento farmacológico , Expansión de Repetición de Trinucleótido/efectos de los fármacosRESUMEN
A CGG trinucleotide repeat expansion in the 5' UTR of FMR1 causes the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). This repeat supports a non-canonical mode of protein synthesis known as repeat-associated, non-AUG (RAN) translation. The mechanism underlying RAN translation at CGG repeats remains unclear. To identify modifiers of RAN translation and potential therapeutic targets, we performed a candidate-based screen of eukaryotic initiation factors and RNA helicases in cell-based assays and a Drosophila melanogaster model of FXTAS. We identified multiple modifiers of toxicity and RAN translation from an expanded CGG repeat in the context of the FMR1 5'UTR. These include the DEAD-box RNA helicase belle/DDX3X, the helicase accessory factors EIF4B/4H, and the start codon selectivity factors EIF1 and EIF5. Disrupting belle/DDX3X selectively inhibited FMR1 RAN translation in Drosophila in vivo and cultured human cells, and mitigated repeat-induced toxicity in Drosophila and primary rodent neurons. These findings implicate RNA secondary structure and start codon fidelity as critical elements mediating FMR1 RAN translation and identify potential targets for treating repeat-associated neurodegeneration.
Asunto(s)
Ataxia/metabolismo , ARN Helicasas DEAD-box/metabolismo , Proteínas de Drosophila/metabolismo , Factores Eucarióticos de Iniciación/metabolismo , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/metabolismo , Síndrome del Cromosoma X Frágil/metabolismo , Temblor/metabolismo , Animales , Ataxia/genética , Células Cultivadas , ARN Helicasas DEAD-box/genética , Proteínas de Drosophila/genética , Drosophila melanogaster , Factores Eucarióticos de Iniciación/genética , Femenino , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/genética , Síndrome del Cromosoma X Frágil/genética , Células HEK293 , Células HeLa , Humanos , Inmunoprecipitación , Masculino , Fenotipo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Temblor/genéticaRESUMEN
Aberrant translation initiation at non-AUG start codons is associated with multiple cancers and neurodegenerative diseases. Nevertheless, how non-AUG translation may be regulated differently from canonical translation is poorly understood. Here, we used start codon-specific reporters and ribosome profiling to characterize how translation from non-AUG start codons responds to protein synthesis inhibitors in human cells. These analyses surprisingly revealed that translation of multiple non-AUG-encoded reporters and the endogenous GUG-encoded DAP5 (eIF4G2/p97) mRNA is resistant to cycloheximide (CHX), a translation inhibitor that severely slows but does not completely abrogate elongation. Our data suggest that slowly elongating ribosomes can lead to queuing/stacking of scanning preinitiation complexes (PICs), preferentially enhancing recognition of weak non-AUG start codons. Consistent with this model, limiting PIC formation or scanning sensitizes non-AUG translation to CHX. We further found that non-AUG translation is resistant to other inhibitors that target ribosomes within the coding sequence but not those targeting newly initiated ribosomes. Together, these data indicate that ribosome queuing enables mRNAs with poor initiation context-namely, those with non-AUG start codons-to be resistant to pharmacological translation inhibitors at concentrations that robustly inhibit global translation.
Asunto(s)
Codón Iniciador/genética , Resistencia a Múltiples Medicamentos/genética , Ribosomas/genética , Elongación de la Transcripción Genética/efectos de los fármacos , Cicloheximida/farmacología , Factor 4G Eucariótico de Iniciación/genética , Regulación de la Expresión Génica/efectos de los fármacos , Genes Reporteros/genética , Células HEK293 , Células HeLa , Humanos , Inhibidores de la Síntesis de la Proteína/farmacologíaRESUMEN
Neurodegeneration is a central aspect of the early stages of diabetic retinopathy, the primary ocular complication associated with diabetes. While progress has been made to improve the vascular perturbations associated with diabetic retinopathy, there are still no treatment options to counteract the neuroretinal degeneration associated with diabetes. Our previous work suggested that the molecular chaperones α-crystallins could be involved in the pathophysiology of diabetic retinopathy; however, the role and regulation of α-crystallins remained unknown. In the present study, we demonstrated the neuroprotective role of αA-crystallin during diabetes and its regulation by its phosphorylation on residue 148. We further characterized the dual role of αA-crystallin in neurons and glia, its essential role for neuronal survival, and its direct dependence on phosphorylation on this residue. These findings support further evaluation of αA-crystallin as a treatment option to promote neuron survival in diabetic retinopathy and neurodegenerative diseases in general.
Asunto(s)
Cristalinas/metabolismo , Diabetes Mellitus Experimental/complicaciones , Retinopatía Diabética/patología , Retina/patología , Cadena A de alfa-Cristalina/metabolismo , Anciano , Animales , Línea Celular , Cristalinas/genética , Diabetes Mellitus Experimental/inducido químicamente , Retinopatía Diabética/diagnóstico , Retinopatía Diabética/etiología , Electrorretinografía , Células Ependimogliales/metabolismo , Células Ependimogliales/patología , Femenino , Humanos , Masculino , Ratones , Ratones Noqueados , Neuronas/metabolismo , Neuronas/patología , Fosforilación , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Retina/citología , Estreptozocina/toxicidad , Transfección , Cadena A de alfa-Cristalina/genética , Cadena B de alfa-Cristalina/genética , Cadena B de alfa-Cristalina/metabolismoRESUMEN
Repeat-associated non-AUG (RAN) translation allows for unconventional initiation at disease-causing repeat expansions. As RAN translation contributes to pathogenesis in multiple neurodegenerative disorders, determining its mechanistic underpinnings may inform therapeutic development. Here we analyze RAN translation at G4C2 repeat expansions that cause C9orf72-associated amyotrophic lateral sclerosis and frontotemporal dementia (C9RAN) and at CGG repeats that cause fragile X-associated tremor/ataxia syndrome. We find that C9RAN translation initiates through a cap- and eIF4A-dependent mechanism that utilizes a CUG start codon. C9RAN and CGG RAN are both selectively enhanced by integrated stress response (ISR) activation. ISR-enhanced RAN translation requires an eIF2α phosphorylation-dependent alteration in start codon fidelity. In parallel, both CGG and G4C2 repeats trigger phosphorylated-eIF2α-dependent stress granule formation and global translational suppression. These findings support a model whereby repeat expansions elicit cellular stress conditions that favor RAN translation of toxic proteins, creating a potential feed-forward loop that contributes to neurodegeneration.
Asunto(s)
Proteína C9orf72/genética , Enfermedades Neurodegenerativas/genética , Iniciación de la Cadena Peptídica Traduccional/genética , Estrés Fisiológico/genética , Expansión de Repetición de Trinucleótido/genética , Animales , Extractos Celulares , Codón Iniciador/genética , Factor 2 Eucariótico de Iniciación/genética , Factor 2 Eucariótico de Iniciación/metabolismo , Factor 4A Eucariótico de Iniciación/genética , Células HEK293 , Células HeLa , Humanos , Neuronas , Fosforilación/genética , Cultivo Primario de Células , Conejos , Ratas , ReticulocitosRESUMEN
Repeat-associated non-AUG (RAN) translation produces toxic polypeptides from nucleotide repeat expansions in the absence of an AUG start codon and contributes to neurodegenerative disorders such as ALS and fragile X-associated tremor/ataxia syndrome. How RAN translation occurs is unknown. Here we define the critical sequence and initiation factors that mediate CGG repeat RAN translation in the 5' leader of fragile X mRNA, FMR1. Our results reveal that CGG RAN translation is 30%-40% as efficient as AUG-initiated translation, is m(7)G cap and eIF4E dependent, requires the eIF4A helicase, and is strongly influenced by repeat length. However, it displays a dichotomous requirement for initiation site selection between reading frames, with initiation in the +1 frame, but not the +2 frame, occurring at near-cognate start codons upstream of the repeat. These data support a model in which RAN translation at CGG repeats uses cap-dependent ribosomal scanning, yet bypasses normal requirements for start codon selection.
Asunto(s)
Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/biosíntesis , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/genética , Síndrome del Cromosoma X Frágil/genética , Degeneración Nerviosa , Biosíntesis de Proteínas , ARN Mensajero/genética , Repeticiones de Trinucleótidos , Factor 4E Eucariótico de Iniciación/genética , Factor 4E Eucariótico de Iniciación/metabolismo , Síndrome del Cromosoma X Frágil/diagnóstico , Síndrome del Cromosoma X Frágil/patología , Sistema de Lectura Ribosómico , Genes Reporteros , Predisposición Genética a la Enfermedad , Células HeLa , Humanos , Neuronas/metabolismo , Neuronas/patología , Sistemas de Lectura Abierta , Fenotipo , ARN Mensajero/metabolismo , Ribosomas/metabolismo , Sitio de Iniciación de la Transcripción , Transfección , Expansión de Repetición de TrinucleótidoRESUMEN
Nucleotide-repeat expansions underlie a heterogeneous group of neurodegenerative and neuromuscular disorders for which there are currently no effective therapies. Recently, it was discovered that such repetitive RNA motifs can support translation initiation in the absence of an AUG start codon across a wide variety of sequence contexts, and that the products of these atypical translation initiation events contribute to neuronal toxicity. This review examines what we currently know and do not know about repeat associated non-AUG (RAN) translation in the context of established canonical and non-canonical mechanisms of translation initiation. We highlight recent findings related to RAN translation in three repeat expansion disorders: CGG repeats in fragile X-associated tremor ataxia syndrome (FXTAS), GGGGCC repeats in C9orf72 associated amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and CAG repeats in Huntington disease. These studies suggest that mechanistic differences may exist for RAN translation dependent on repeat type, repeat reading frame, and the surrounding sequence context, but that for at least some repeats, RAN translation retains a dependence on some of the canonical translational initiation machinery. This article is part of a Special Issue entitled SI:RNA Metabolism in Disease.
Asunto(s)
Expansión de las Repeticiones de ADN , Enfermedades Neurodegenerativas/genética , Iniciación de la Cadena Peptídica Traduccional , Esclerosis Amiotrófica Lateral/genética , Animales , Ataxia/genética , Dipéptidos/genética , Síndrome del Cromosoma X Frágil/genética , Demencia Frontotemporal/genética , Humanos , Enfermedad de Huntington/genética , Sistemas de Lectura Abierta , Temblor/genéticaRESUMEN
The formation of acellular capillaries in the retina, a hallmark feature of diabetic retinopathy, is caused by apoptosis of endothelial cells and pericytes. The biochemical mechanism of such apoptosis remains unclear. Small heat shock proteins play an important role in the regulation of apoptosis. In the diabetic retina, pro-inflammatory cytokines are upregulated. In this study, we investigated the effects of pro-inflammatory cytokines on small heat shock protein 27 (Hsp27) in human retinal endothelial cells (HREC). In HREC cultured in the presence of cytokine mixtures (CM), a significant downregulation of Hsp27 at the protein and mRNA level occurred, with no effect on HSF-1, the transcription factor for Hsp27. The presence of high glucose (25mM) amplified the effects of cytokines on Hsp27. CM activated indoleamine 2,3-dioxygenase (IDO) and enhanced the production of kynurenine and ROS. An inhibitor of IDO, 1-methyl tryptophan (MT), inhibited the effects of CM on Hsp27. CM also upregulated NOS2 and, consequently, nitric oxide (NO). A NOS inhibitor, L-NAME, and a ROS scavenger blocked the CM-mediated Hsp27 downregulation. While a NO donor in the culture medium did not decrease the Hsp27 content, a peroxynitrite donor and exogenous peroxynitrite did. The cytokines and high glucose-induced apoptosis of HREC were inhibited by MT and L-NAME. Downregulation of Hsp27 by a siRNA treatment promoted apoptosis in HREC. Together, these data suggest that pro-inflammatory cytokines induce the formation of ROS and NO, which, through the formation of peroxynitrite, reduce the Hsp27 content and bring about apoptosis of retinal capillary endothelial cells.
Asunto(s)
Apoptosis/efectos de los fármacos , Citocinas/farmacología , Células Endoteliales/efectos de los fármacos , Proteínas de Choque Térmico HSP27/metabolismo , Western Blotting , Células Cultivadas , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo/efectos de los fármacos , Células Endoteliales/metabolismo , Glucosa/farmacología , Proteínas de Choque Térmico HSP27/genética , Proteínas de Choque Térmico , Humanos , Indolamina-Pirrol 2,3,-Dioxigenasa/antagonistas & inhibidores , Indolamina-Pirrol 2,3,-Dioxigenasa/metabolismo , Mediadores de Inflamación/farmacología , Interferón gamma/farmacología , Interleucina-1beta/farmacología , Chaperonas Moleculares , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/antagonistas & inhibidores , Óxido Nítrico Sintasa de Tipo II/metabolismo , Ácido Peroxinitroso/metabolismo , Ácido Peroxinitroso/farmacología , Interferencia de ARN , Especies Reactivas de Oxígeno/metabolismo , Retina/citología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Triptófano/análogos & derivados , Triptófano/farmacología , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Diabetic retinopathy is the leading cause of vision loss in working-age individuals in the United States and is expected to continue growing with the increased prevalence of diabetes. Streptozotocin-induced hyperglycemia in rats is the most commonly used model for diabetic retinopathy. Previous studies have shown that this model can lead to different inflammatory changes in the retina depending on the strain of rat. Our previous work has shown that crystallin proteins, including members of the alpha- and beta/gamma-crystallin subfamilies, are upregulated in the STZ rat retina. Crystallin proteins have been implicated in a number of cellular processes, such as neuroprotection, non-native protein folding and vascular remodeling. In this current study, we have demonstrated that unlike other strain-dependent changes, such as inflammatory cytokines and growth factor levels, in the STZ rat, the protein upregulation of crystallins is consistent across the Brown Norway, Long-Evans and Sprague-Dawley rat strains in the context of diabetes. Taken together, these data illustrate the potential critical role played by crystallins, and especially alpha-crystallins, in the retina in the context of diabetes.