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)

Enhanced phosphorylation of the ribosomal protein s6 kinase, p70(s6k), and the translational repressor, 4E-BP1, are associated with either insulin-induced or amino acid-induced protein synthesis. Hyperphosphorylation of p70(s6k) and 4E-BP1 in response to insulin or amino acids is mediated through the mammalian target of rapamycin (mTOR). In several cell lines, mTOR or its downstream targets can be regulated by phosphatidylinositol (PI) 3-kinase; protein kinases A, B, and C; heterotrimeric G-proteins; a PD98059-sensitive kinase or calcium; as well as by amino acids. Regulation by amino acids appears to involve detection of levels of charged t-RNA or t-RNA synthetase activity and is sensitive to inhibition by amino acid alcohols. In the present article, however, we show that the rapamycin-sensitive regulation of 4E-BP1 and p70(s6k) in freshly isolated rat adipocytes is not inhibited by either L-leucinol or L-histidinol. This finding is in agreement with other recent studies from our laboratory suggesting that the mechanism by which amino acids regulate mTOR in freshly isolated adipocytes may be different than the mechanism found in a number of cell lines. Therefore we investigated the possible role of growth factor-regulated and G-protein-regulated signaling pathways in the rapamycin-sensitive, amino acid alcohol-insensitive actions of amino acids on 4E-BP1 phosphorylation. We found, in contrast to previously published results using 3T3-L1 adipocytes or other cell lines, that the increase in 4E-BP1 phosphorylation promoted by amino acids was insensitive to agents that regulate protein kinase A, mobilize calcium, or inhibit protein kinase C. Furthermore, amino acid-induced 4E-BP1 phosphorylation was not blocked by pertussis toxin nor was it mimicked by the G-protein agonists fluoroaluminate or MAS-7. However, amino acids failed to activate either PI 3-kinase, protein kinase B, or mitogen-activated protein kinase and failed to promote tyrosine phosphorylation of cellular proteins, similar to observations made using cell lines. In summary, amino acids appear to use an amino acid alcohol-insensitive mechanism to regulate mTOR in freshly isolated adipocytes. This mechanism is independent of cell-signaling pathways implicated in the regulation of mTOR or its downstream targets in other cells. Overall, our study emphasizes the need for caution when extending results obtained using established cell lines to the differentiated nondividing cells found in most tissues.
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PMID:Assessment of cell-signaling pathways in the regulation of mammalian target of rapamycin (mTOR) by amino acids in rat adipocytes. 1097 80

The pathogenesis of tumour formation in the anterior pituitary has been intensively studied, but the causative mechanisms involved in pituitary cell transformation and tumourigenesis remain elusive. Most pituitary tumours are sporadic, but some arise as a component of genetic syndromes such as the McCune-Albright syndrome, multiple endocrine neoplasia type 1, Carney complex and, the most recently described, a MEN1-like phenotype (MEN4) and pituitary adenoma predisposition syndromes. Some specific genes have been identified that predispose to pituitary neoplasia (GNAS, MEN1, PRKAR1A, CDKN1B and AIP), but these are rarely involved in the pathogenesis of sporadic tumours. Mutations of tumour suppressor genes or oncogenes, as seen in more common cancers, do not seem to play an important role in the great majority of pituitary adenomas. The pituitary tumour transforming gene (PTTG; securin) was the first transforming gene found to be highly expressed in pituitary tumour cells, and seems to play an important role in the process of oncogenesis. Many tumour suppressor genes, especially those involved in the regulation of the cell cycle, are under-expressed, most often by epigenetic modulation - usually promoter hypermethylation - but the regulator of these co-ordinated series of methylations is also unclear. Cell signalling abnormalities have been identified in pituitary tumours, but their genetic basis is unknown. Both Raf/MEK/ERK and PI3K/Akt/mTOR pathways are over-expressed and/or over-activated in pituitary tumours: these pathways share a common root, including initial activation related to the tyrosine kinase receptor, and we speculate that a change to these receptors or their relationship to membrane matrix-related proteins may be an early event in pituitary tumourigenesis.
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PMID:The pathophysiology of pituitary adenomas. 1994 21