Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retinitis pigmentosa is an incurable retinal disease that leads to blindness. One puzzling aspect concerns the progression of the disease. Although most mutations that cause retinitis pigmentosa are in rod photoreceptor-specific genes, cone photoreceptors also die as a result of such mutations. To understand the mechanism of non-autonomous cone death, we analyzed four mouse models harboring mutations in rod-specific genes. We found changes in the insulin/mammalian target of rapamycin pathway that coincided with the activation of autophagy during the period of cone death. We increased or decreased the insulin level and measured the survival of cones in one of the models. Mice that were treated systemically with insulin had prolonged cone survival, whereas depletion of endogenous insulin had the opposite effect. These data suggest that the non-autonomous cone death in retinitis pigmentosa could, at least in part, be a result of the starvation of cones.
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PMID:Stimulation of the insulin/mTOR pathway delays cone death in a mouse model of retinitis pigmentosa. 1910 41

Retinal degenerations such as retinitis pigmentosa (RP) lead to rod death due to apoptotic cell death, initiated by mutations in retinal genes that encode proteins with crucial photoreceptors functions. The mechanism(s) of cone death have remained elusive until this study. Using a combination of animal models of human RP, Affymetrix expression array studies, RT-PCR and immunohistochemical analyses, Punzo et al. determined that cone death is due to nutritional deficiencies, starration, and autophagy driven by the insulin/mTOR pathway. These novel and exciting seights also provide alternative avenues for therapeutic interventions for cone rescue.
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PMID:Why do cone photoreceptors die in rod-specific forms of retinal degenerations? 1994 21

The HERC gene family encodes proteins with two characteristic domains: HECT and RCC1-like. Proteins with HECT domains have been described to function as ubiquitin ligases, and those that contain RCC1-like domains have been reported to function as GTPases regulators. These two activities are essential in a number of important cellular processes such as cell cycle, cell signaling, and membrane trafficking. Mutations affecting these domains have been found associated with retinitis pigmentosa, amyotrophic lateral sclerosis, and cancer. In humans, six HERC genes have been reported which encode two subgroups of HERC proteins: large (HERC1-2) and small (HERC3-6). The giant HERC1 protein was the first to be identified. It has been involved in membrane trafficking and cell proliferation/growth through its interactions with clathrin, M2-pyruvate kinase, and TSC2 proteins. Mutations affecting other members of the HERC family have been found to be associated with sterility and growth retardation. Here, we report the characterization of a recessive mutation named tambaleante, which causes progressive Purkinje cell degeneration leading to severe ataxia with reduced growth and lifespan in homozygous mice aged over two months. We mapped this mutation in mouse chromosome 9 and then performed positional cloning. We found a G<-->A transition at position 1448, causing a Gly to Glu substitution (Gly483Glu) in the highly conserved N-terminal RCC1-like domain of the HERC1 protein. Successful transgenic rescue, with either a mouse BAC containing the normal copy of Herc1 or with the human HERC1 cDNA, validated our findings. Histological and biochemical studies revealed extensive autophagy associated with an increase of the mutant protein level and a decrease of mTOR activity. Our observations concerning this first mutation in the Herc1 gene contribute to the functional annotation of the encoded E3 ubiquitin ligase and underline the crucial and unexpected role of this protein in Purkinje cell physiology.
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PMID:Progressive Purkinje cell degeneration in tambaleante mutant mice is a consequence of a missense mutation in HERC1 E3 ubiquitin ligase. 2004 Dec 18

There is an urgent need for therapies for retinal diseases; retinitis pigmentosa sufferers have no treatment options available and those targeted at other retinopathies have shown limited effectiveness. The process of programmed cell death or apoptosis although complex, remains a possible target for the treatment of retinal diseases. Having identified apoptosis in the vertebrate retina in populations of immature neurons as an essential part of development it was proposed that re-activation of these developmental cell death pathways might provide insight into the death mechanisms operating in retinal diseases. However, the discovery that numerous factors initiate and mediate the apoptotic cascade in mature photoreceptors has resulted in a relatively untargeted approach to examining and arresting apoptosis in the retina. In the last 5 years, mouse models have been treated with a diverse range of drugs or factors including anti-oxidants, growth factors, steroid hormones, calcium/calpain inhibitors and tetracycline antibiotics. Therefore to draw a unifying theme from these broad research areas is challenging. However, this review focusses on two targets which are currently under investigation, reactive oxygen species and mammalian target of rapamycin, drawing together the common themes of these research areas.
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PMID:Preventing retinal apoptosis--is there a common therapeutic theme? 2236 79

Slow, progressive rod degeneration followed by cone death leading to blindness is the pathological signature of all forms of human retinitis pigmentosa (RP). Therapeutic schemes based on intraocular delivery of neuroprotective agents prolong the lifetime of photoreceptors and have reached the stage of clinical trial. The success of these approaches depends upon optimization of chronic supply and appropriate combination of factors. Environmental enrichment (EE), a novel neuroprotective strategy based on enhanced motor, sensory and social stimulation, has already been shown to exert beneficial effects in animal models of various disorders of the CNS, including Alzheimer and Huntington disease. Here we report the results of prolonged exposure of rd10 mice, a mutant strain undergoing progressive photoreceptor degeneration mimicking human RP, to such an enriched environment from birth. By means of microscopy of retinal tissue, electrophysiological recordings, visual behaviour assessment and molecular analysis, we show that EE considerably preserves retinal morphology and physiology as well as visual perception over time in rd10 mutant mice. We find that protective effects of EE are accompanied by increased expression of retinal mRNAs for CNTF and mTOR, both factors known as instrumental to photoreceptor survival. Compared to other rescue approaches used in similar animal models, EE is highly effective, minimally invasive and results into a long-lasting retinal protection. These results open novel perspectives of research pointing to environmental strategies as useful tools to extend photoreceptor survival.
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PMID:Environmental enrichment extends photoreceptor survival and visual function in a mouse model of retinitis pigmentosa. 2320 20

The UPR is activated in the mouse retina expressing misfolded T17M rhodopsin (RHO) during autosomal dominant retinitis pigmentosa (ADRP) progression. Therefore, the goal of this study is to validate the UPR-induced caspase-7 as a new therapeutic target that modulates the UPR, reduces the level of apoptosis and protects the ADRP retina from retinal degeneration and light-induced damage. Mice were analyzed using ERG, SD-OCT and histology to determine the role of caspase-7 ablation. The results of these experiments demonstrate the significant preservation of photoreceptors and their function in T17M RHO CASP-7 retinas from P30 to P90 compared with control mice. These mice were also protected from the light-induced decline in the ERG responses and apoptosis. The RNA and protein analyses of T17M RHO+Csp7-siRNA, Tn+Csp7-siRNA 661W cells and T17M RHO CASP-7 retinas revealed that caspase-7 ablation reprograms the UPR and reduces JNK-induced apoptosis. This reduction is believed to occur through the downregulation of the mTOR and Hif1a proteins. In addition, decline in activated PARP1 was detected in T17M RHO CASP-7 retina. Altogether, our findings indicate that the targeting of caspase-7 in T17M RHO mice could be a feasible therapeutic strategy for advanced stages of ADRP.
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PMID:Caspase-7 ablation modulates UPR, reprograms TRAF2-JNK apoptosis and protects T17M rhodopsin mice from severe retinal degeneration. 2347 May 35

We previously reported activation of the unfolded protein response (UPR) in P23H rhodopsin (RHO) retinas with autosomal dominant retinitis pigmentosa (ADRP). Knowing that the UPR can trigger Ca(2+) release from the endoplasmic reticulum and regulate cellular signaling we examined the level of Ca(2+)-regulated proteins. We also looked for changes in the expression of Bcl2 family proteins, autophagy proteins and the mTOR/AKT pathways, as well as for the induction of mitochondria-associated apoptosis in the P23H RHO retina. Our data demonstrated that the elevation of calpain and caspase-12 activity was concomitantly observed with a decrease in the BCL2-XL/BAX ratio and an increase in mTor levels in the P23H-3 RHO retina suggesting a vulnerability of P23H RHO photoreceptors to apoptosis. The translocation of BAX to the mitochondria, as well as the release of cytochrome C and AIF into the cytosol supports this conclusion and indicates the involvement of mitochondria-induced apoptosis in the progression of ADRP. The level of autophagy proteins in general was found to be decreased in the P21-P30 P23H RHO retina. Injections of rapamycin, however, protected the P23H RHO rod photoreceptors from experiencing physiological decline. Despite this fact, the downregulation of mTOR did not alter the level of autophagy proteins. Our results imply that in addition to activation of the UPR during ADRP progression, photoreceptors also experience alterations in major proapoptotic pathways.
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PMID:Modulation of cellular signaling pathways in P23H rhodopsin photoreceptors. 2437 35

Retinitis pigmentosa (RP) is an inherited photoreceptor degenerative disorder that results in blindness. The disease is often caused by mutations in genes that are specific to rod photoreceptors; however, blindness results from the secondary loss of cones by a still unknown mechanism. Here, we demonstrated that the mammalian target of rapamycin complex 1 (mTORC1) is required to slow the progression of cone death during disease and that constitutive activation of mTORC1 in cones is sufficient to maintain cone function and promote long-term cone survival. Activation of mTORC1 in cones enhanced glucose uptake, retention, and utilization, leading to increased levels of the key metabolite NADPH. Moreover, cone death was delayed in the absence of the NADPH-sensitive cell death protease caspase 2, supporting the contribution of reduced NADPH in promoting cone death. Constitutive activation of mTORC1 preserved cones in 2 mouse models of RP, suggesting that the secondary loss of cones is caused mainly by metabolic deficits and is independent of a specific rod-associated mutation. Together, the results of this study address a longstanding question in the field and suggest that activating mTORC1 in cones has therapeutic potential to prolong vision in RP.
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PMID:Activated mTORC1 promotes long-term cone survival in retinitis pigmentosa mice. 2579 15

Understanding the mechanisms that contribute to secondary cone photoreceptor loss in retinitis pigmentosa (RP) is critical to devise strategies to prolong vision in this neurodegenerative disease. We previously showed that constitutive activation of the mammalian target of rapamycin complex 1 (mTORC1), by loss of its negative regulator the tuberous sclerosis complex protein 1 (Tsc1; also known as Hamartin), was sufficient to promote robust survival of nutrient-stressed cones in two mouse models of RP by improving glucose uptake and utilization. However, while cone protection remained initially stable for several weeks, eventually cone loss resumed. Here we show that loss of Tsc1 in the cones of RP mice causes a defect in autophagy, leading to the accumulation of ubiquitinated aggregates. We demonstrate that this defect was not due to an inhibition of autophagy initiation, but due to an accumulation of autolysosomes, suggesting a defect in the end-stage of the process causing an amino-acid shortage in cones, thereby hampering long-term cone survival. Because cells with TSC loss fail to completely inhibit mTORC1 and properly activate autophagy in the absence of amino acids, we sporadically administered the mTORC1 inhibitor rapamycin, which was sufficient to correct the defects seen in cones, further enhancing the efficiency of cone survival mediated by Tsc1 loss. Concordantly, activation of mTORC1 by loss of the phosphatase and tensin homolog (Pten) did not affect autophagy and amino-acid metabolism, leading to a more sustained long-term protection of cones. As loss of Pten, which in cones results in less robust mTORC1 activation when compared with loss of Tsc1, still affords long-term cone survival, therapeutic interventions with mTORC1 activators or gene therapy with selected mTORC1 targets that improve glucose metabolism are potential strategies to delay vision loss in patients with RP.
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PMID:TSC but not PTEN loss in starving cones of retinitis pigmentosa mice leads to an autophagy defect and mTORC1 dissociation from the lysosome. 2736 97

Retinitis pigmentosa (RP) is one of the leading causes of adult blindness and has no established therapy. We have shown that valosin-containing protein (VCP) modulators, Kyoto University Substances (KUSs), ameliorated abnormally low ATP levels by inhibiting the ATPase of VCP, thereby protected several types of cells, including retinal neurons, from cell death-inducing insults. In this study, we found that KUS121, one of the VCP modulators, effectively protects photoreceptors both morphologically and functionally, in two animal models of retinal degeneration, rd12 mice and RP rabbits with a rhodopsin (Pro347Leu) mutation. In rd12 mice, KUS121 suppressed the loss of photoreceptors, not only rods but also cones, as well as the visual function deterioration. Significant protective effects existed even when the medication was started in later stages of the disease. In RP rabbits, KUS121 suppressed thinning of the outer nuclear layer and maintained visual function. In the retinas treated with KUS121, suppression of endoplasmic reticulum stress, activation of mammalian target of rapamycin and suppression of disease-associated apoptosis were evident. The ability of KUS121 to protect photoreceptors, especially cones, even in later stages of the disease may contribute to the preservation of central vision in RP patients, which is important for quality of vision.
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PMID:Neuoroprotective efficacies by KUS121, a VCP modulator, on animal models of retinal degeneration. 2750 4


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