Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tuberous sclerosis (TS) is a genetic disorder affecting multiple body systems, and resulting from alterations in cell differentiation and proliferation. The disease is characterized by the development of benign hamartomatous tumors: neurofibromas and angiofibromas, located in the skin, central nervous system, mucosas and other organs. Abnormal neural cell migration plays an important role in the neurological dysfunctions found in TS, the predominant features being mental retardation, seizures and behavioral disorders. The condition is produced by mutations in genes TSC1 of chromosome 9q34 and TSC2 of chromosome 16p13.3, and exhibits a dominant autosomal hereditary trait--though 60-70% of cases are sporadic and represent new mutations. The phenotype is highly variable. The prevalence of TS varies between 1/6000 and 1/10,000 live births. The present study reports the case of a 21-year-old male with TS and oral manifestations of the disease. The clinical characteristics are described, along with the diagnostic criteria and the management strategies, with a review of the literature on the disease.
 ...
PMID:Tuberous sclerosis: presentation of a clinical case with oral manifestations. 1261 72

Tuberous sclerosis complex is a tumor suppressor gene syndrome whose manifestations can include seizures, mental retardation, and benign tumors of the brain, skin, heart, and kidneys. Hamartin and tuberin, the products of the TSC1 and TSC2 genes, respectively, form a complex and inhibit signaling by the mammalian target of rapamycin. Here, we demonstrate that endogenous hamartin is threonine-phosphorylated during nocodazole-induced G2/M arrest and during the G2/M phase of a normal cell cycle. In vitro assays showed that cyclin-dependent kinase 1 phosphorylates hamartin at three sites, one of which (Thr417) is in the hamartin-tuberin interaction domain. Tuberin interacts with phosphohamartin, and tuberin expression attenuates the phosphorylation of exogenous hamartin. Hamartin with alanine mutations in the three cyclin-dependent kinase 1 phosphorylation sites increased the inhibition of p70S6 kinase by the hamartin-tuberin complex. These findings support a model in which phosphorylation of hamartin regulates the function of the hamartin-tuberin complex during the G2/M phase of the cell cycle.
 ...
PMID:Cell cycle-regulated phosphorylation of hamartin, the product of the tuberous sclerosis complex 1 gene, by cyclin-dependent kinase 1/cyclin B. 1455 Dec 5

Tuberous Sclerosis Complex (TSC) is an autosomal dominant disorder associated with mutations in TSC1, which codes for hamartin, or TSC2, which codes for tuberin. The brain is one of the most severely affected organs, and CNS lesions include cortical tubers and subependymal giant cell astrocytomas, resulting in mental retardation and seizures. Tuberin and hamartin function together as a complex in mammals and Drosophila. We report here the association of Pam, a protein identified as an interactor of Myc, with the tuberin-hamartin complex in the brain. The C terminus of Pam containing the RING zinc finger motif binds to tuberin. Pam is expressed in embryonic and adult brain as well as in cultured neurons. Pam has two forms in the rat CNS, an approximately 450-kDa form expressed in early embryonic stages and an approximately 350-kDa form observed in the postnatal period. In cortical neurons, Pam co-localizes with tuberin and hamartin in neurites and growth cones. Although Pam function(s) are yet to be defined, the highly conserved Pam homologs, HIW (Drosophila) and RPM-1 (Caenorhabditis elegans), are neuron-specific proteins that regulate synaptic growth. Here we show that HIW can genetically interact with the Tsc1.Tsc2 complex in Drosophila and could negatively regulate Tsc1.Tsc2 activity. Based on genetic studies, HIW has been implicated in ubiquitination, possibly functioning as an E3 ubiquitin ligase through the RING zinc finger domain. Therefore, we hypothesize that Pam, through its interaction with tuberin, could regulate the ubiquitination and proteasomal degradation of the tuberin-hamartin complex particularly in the CNS.
 ...
PMID:Pam and its ortholog highwire interact with and may negatively regulate the TSC1.TSC2 complex. 1455 97

Mutations in either TSC1 or TSC2 cause tuberous sclerosis complex, an autosomal dominant disorder characterized by seizures, mental retardation, and benign tumors of the skin, brain, heart, and kidneys. Homologs for the TSC1 and TSC2 genes have been identified in mouse, rat, Fugu, Drosophila, and in the yeast Schizosaccharomyces pombe. Here we show that S. pombe lacking tsc1+ or tsc2+ have similar phenotypes including decreased arginine uptake, decreased expression of three amino acid permeases, and low intracellular levels of four members of the arginine biosynthesis pathway. Recently, the small GTPase Rheb was identified as a target of the GTPase-activating domain of tuberin in mammalian cells and in Drosophila. We show that the defect in arginine uptake in cells lacking tsc2+ is rescued by the expression of a dominant negative form of rhb1+, the Rheb homolog in S. pombe, but not by expressing wild-type rhb1+. Expression of the tsc2+ gene with a patient-derived mutation within the GAP domain did not rescue the arginine uptake defect in tsc2+ mutant yeast. Taken together, these findings support a model in which arginine uptake is regulated through tsc1+, tsc2+, and rhb1+ in S. pombe and also suggest a role for the Tsc1 and Tsc2 proteins in amino acid biosynthesis and sensing.
 ...
PMID:Tsc1+ and tsc2+ regulate arginine uptake and metabolism in Schizosaccharomyces pombe. 1471 25

Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome with manifestations that can include seizures, mental retardation, autism, and tumors in the brain, retina, kidney, heart, and skin. The products of the TSC1 and TSC2 genes, hamartin and tuberin, respectively, heterodimerize and inhibit the mammalian target of rapamycin (mTOR). We found that tuberin expression increases p42/44 MAPK phosphorylation and B-Raf kinase activity. Short interfering RNA down-regulation of tuberin decreased the p42/44 MAPK phosphorylation and B-Raf activity. Expression of Rheb, the target of the GTPase-activating domain of tuberin, inhibited wild-type B-Raf kinase but not activated forms of B-Raf. The interaction of endogenous Rheb with B-Raf was enhanced by serum and by Ras overexpression. A farnesylation-defective mutant of Rheb co-immunoprecipitated with and inhibited B-Raf but did not activate ribosomal protein S6 kinase, indicating that farnesylation is not required for B-Raf inhibition by Rheb and that B-Raf inhibition and S6 kinase activation are separable activities of Rheb. Consistent with this, inhibition of B-Raf and p42/44 MAPK by Rheb was resistant to rapamycin in contrast to Rheb activation of S6 kinase, which is rapamycin-sensitive. Taken together these data demonstrate that inhibition of B-Raf kinase via Rheb is an mTOR-independent function of tuberin.
 ...
PMID:Regulation of B-Raf kinase activity by tuberin and Rheb is mammalian target of rapamycin (mTOR)-independent. 1515 Feb 71

Tuberous sclerosis (TSC) is an autosomal dominant tumour suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumours characteristically occur in different organs of TSC patients. Typically, highly epileptogenic dysplastic lesions (tubers) composed of abnormal shaped neurones can be detected in the cerebral cortex. Two tumour suppressor genes have been shown to be responsible for this disease: TSC1, encoding hamartin, and TSC2, encoding tuberin. In this study we performed a proteomic approach of two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after ectopic overexpression of human TSC1 or TSC2. We found the protein levels of alpha1-tubulin, protein disulfide isomerase, tropomyosin 3 and 5 and vimentin to be regulated by the two tuberous sclerosis gene products. The here presented findings suggest that deregulation of the control of these target proteins might contribute to the development of tumours in tuberous sclerosis patients. These data provide important new insights into the molecular development of this disease especially since alpha1-tubulin, protein disulfide isomerase and certain tropomyosins have also been implicated in the regulation of neuronal differentiation.
 ...
PMID:Protein levels of alpha1-tubulin, protein disulfide isomerase, tropomyosins and vimentin are regulated by the tuberous sclerosis gene products. 1518 38

Gene deletion studies in mice and in Drosophila have shown that the 40S ribosomal protein S6 Kinases, dS6K in Drosophila and S6K1 and S6K2 in mice are important regulators of cell growth in response to insulin stimulation and nutrition availability. Here we chiefly focus on dS6k and S6K1, whose activities are regulated by an upstream kinase termed the mammalian target of rapamycin (mTOR, or dTOR in Drosophila). Our understanding of the mechanisms regulating the mTOR/S6K1-signalling pathway will be fundamental in determining the mechanisms which control cell growth in response to insulin signalling. Recent findings from this laboratory and others suggests that the tumour suppressor complex made of two proteins TSC1/hamartin and TSC2/tuberin, acts as a negative regulator of mTOR/S6K1 signalling. Mutations in either TSC1 or TSC2 are genetically linked to tuberous sclerosis complex (TSC) syndrome, which can lead to severe pathological consequences, including mental retardation, epilepsy and autism, as well as cardiac, pulmonary and renal failure. Despite a large number of initial reports on the TSC1/TSC2 complex, and the finding that its activity is regulated by protein kinase B (PKB), the direct target of the TSC1/TSC2 inhibitory complex was unknown until recently. Since TSC2 has a GTPase-activating domain, or GAP-like sequence, others and we searched for a small GTP binding protein, which may serve as the target of TSC1/TSC2 inhibitory complex. In our case we took advantage of a genome wide screen in Drosophila for effectors of cell growth and in parallel searched for a small GTPase whose activity is up-regulated in TSC2-deficient cells. The identified gene was a member of the Ras family of GTPases termed Ras homologue enriched in brain or Rheb. Here we review recent findings demonstrating that the TSC1/TSC2 inhibitory complex normally acts on Rheb to mediate mTOR/S6K1-signalling.
 ...
PMID:The mTOR/S6K signalling pathway: the role of the TSC1/2 tumour suppressor complex and the proto-oncogene Rheb. 1556 27

The most devastating complications of tuberous sclerosis complex affect the central nervous system and include epilepsy, mental retardation, autism, and glial tumors. Mutations in one of two genes, TSC1 and TSC2, result in a similar disease phenotype by disrupting the normal interaction of their protein products, hamartin and tuberin, which form a functional signaling complex. Disruption of these genes in the brain results in abnormal cellular differentiation, migration, and proliferation, giving rise to characteristic brain lesions called cortical tubers. Relevant animal models, including conventional and conditional knockout mice, are valuable tools for studying the normal functions of tuberin and hamartin and how disruption of their expression gives rise to the variety of clinical features that characterize tuberous sclerosis complex. In the future, these animals will be invaluable preclinical models for the development of highly specific and efficacious treatments for children affected with tuberous sclerosis complex.
 ...
PMID:Mouse models of tuberous sclerosis complex. 1556 20

The genes, TSC1 on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13.3, encoding tuberin, are responsible for tuberous sclerosis (TSC). TSC is an autosomal dominant tumor suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumors characteristically occur in different organs of TSC patients and are believed to result from defects in cell cycle/cell size control. Hamartin and tuberin form a complex providing a tentative explanation for the similar disease phenotype in TSC patients with mutations in either of these genes. Beside overlap in many features of patients with TSC1 and TSC2 mutations, data accumulated providing evidence for specific clinical differences. In this study, we performed a proteomic approach of two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after ectopic overexpression of human TSC1 or TSC2. We found the protein levels of the calumenin precursor; the complement component 1; heterogeneous nuclear ribonucleoproteins, C1/C2; heterogeneous nuclear ribonucleoprotein, C1-like protein; nascent polypeptide-associated complex-alpha; proteasome subunit alpha type 5; reticulocalbin 1 precursor; translationally-controlled tumor protein; UV excision repair protein, RAD23 homolog B; elongation factor 1-delta; and the eukaryotic initiation factors, eIF-4A-like NUK-34 and eIF-6; to be deregulated upon ectopic TSC gene expression. These findings suggest that deregulation of the control of these new target proteins might contribute to the development of tubers/hamartomas in tuberous sclerosis patients. The data are presented and discussed in the context of the published literature on proteomic approaches for the identification of targets of the TSC genes.
 ...
PMID:The cellular response to ectopic overexpression of the tuberous sclerosis genes, TSC1 and TSC2: a proteomic approach. 1607 35

Tuberous sclerosis (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumors characteristically occur in different organs of TSC patients. The genes, TSC1 on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13.3, encoding tuberin are responsible for TSC. Hamartin and tuberin form a complex providing a tentative explanation for the similar disease phenotype in TSC patients with mutations in either of these genes. Besides overlap in many features of patients with TSC1 and TSC2 mutations, data accumulated provide evidence for specific clinical differences. Here, we performed microarray analyses of the gene expression response to overexpressed TSC1 or TSC2 in HeLa cells. Out of 2400 analysed genes we found 115 genes to be up-regulated > or =2-fold upon ectopic TSC1 overexpression and 284 genes to be up-regulated > or =2-fold via TSC2. Only 34 of these genes were up-regulated by both, TSC1 and TSC2. Whereas only 7 genes were down-regulated > or =2-fold via TSC1, ectopic TSC2 triggered a > or =2-fold down-regulation of 113 genes. Only 3 of these genes were down-regulated by TSC1 and TSC2. This study provides new insights into the cellular roles of TSC proteins and promotes discussion on whether separable functions of these proteins might be associated with the clinical differences of TSC1- and TSC2-associated disease.
 ...
PMID:The tuberous sclerosis genes, TSC1 and TSC2, trigger different gene expression responses. 1621 Dec 38


<< Previous 1 2 3 4 5 6 7 8 Next >>