The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth and metabolism in response to various environmental inputs, especially amino acids. In fact, the activity of mTORC1 is highly sensitive to changes in amino acid levels. Over past decades, a variety of proteins have been identified as participating in the mTORC1 pathway regulated by amino acids. Classically, the Rag guanosine triphosphatases (GTPases), which reside on the lysosome, transmit amino acid availability to the mTORC1 pathway and recruit mTORC1 to the lysosome upon amino acid sufficiency. Recently, several sensors of leucine, arginine, and S-adenosylmethionine for the amino acid-stimulated mTORC1 pathway have been coming to light. Characterization of these sensors is requisite for understanding how cells adjust amino acid sensing pathways to their different needs. In this review, we summarize recent advances in amino acid sensing mechanisms that regulate mTORC1 activity and highlight these identified sensors that accurately transmit specific amino acid signals to the mTORC1 pathway.
Amino Acids/chemistry* ; Animals ; Arginine/chemistry* ; Cell Membrane/metabolism* ; GTP Phosphohydrolases/metabolism* ; Gene Expression Regulation ; Golgi Apparatus/metabolism* ; Humans ; Leucine/chemistry* ; Lysosomes/metabolism* ; Mechanistic Target of Rapamycin Complex 1/metabolism* ; Methionine/chemistry* ; S-Adenosylmethionine/chemistry* ; Signal Transduction ; TOR Serine-Threonine Kinases/metabolism*

OBJECTIVETo study the protective impact of tea polyphenols (TP) on the injury of fibrinolytic functions induced by high-methionine dietary in rats.

METHODS50 male Wistar rats were divided by stratified based on body weight into 5 groups with 10 in each group: namely control group, model group, low-dose TP group, medium-dose TP group and high-dose TP group. The rats in model group and TP groups were fed with 3% methionine dietary, control group rats with routine diet. In addition, rats in low-dose, medium-dose and high-dose TP groups were treated with TP at 50, 100 and 200 mg/kg dosage respectively by gavages every day, control group and model group rats were given with same amount distilled water. The animals were sacrificed after 8 weeks. The levels of tissue-type plasminogen activator (t-PA) and type-1 plasminogen activator inhibitor (PAI-1) in plasma were determined by ELISA assays, mRNA levels of t-PA and PAI-1 in aortic arch were detected by RT-PCR, t-PA and PAI-1 expression in aortic arch were detected by immunohistochemistry strept-avidin-biotin complex (SABC).

RESULTSAfter experiment, the t-PA expression of aortic arch in control group, model group, low-dose TP group, medium-dose TP group and high-dose TP group were 133.03 ± 10.14, 95.46 ± 11.08, 111.97 ± 11.91, 130.23 ± 10.80, 139.39 ± 9.41 (F = 14.15, P < 0.01), respectively, and the PAI-1 expression were 90.91 ± 8.67, 166.76 ± 12.18, 139.63 ± 12.71, 134.66 ± 13.19, 109.49 ± 10.82 (F = 31.44, P < 0.01). The t-PA concentration of plasma were (10.69 ± 1.26), (6.13 ± 0.92), (8.56 ± 1.19), (9.69 ± 0.92), (11.97 ± 1.08) ng/ml, respectively (F = 41.98, P < 0.01), and the PAI-1 concentration of plasma were (6.31 ± 0.81), (16.98 ± 1.27), (11.39 ± 0.82), (8.46 ± 0.67), (8.08 ± 0.91) ng/ml, respectively (F = 207.74, P < 0.01). The mRNA levels of t-PA in aortic arch were 1.12 ± 0.02, 0.75 ± 0.14, 1.01 ± 0.09, 0.95 ± 0.08, 1.05 ± 0.13 (F = 5.77, P < 0.05), and the mRNA levels of PAI-1 in aortic arch were 1.25 ± 0.11, 1.74 ± 0.06, 1.23 ± 0.05, 1.09 ± 0.14, 1.23 ± 0.04 (F = 23.56, P < 0.01).

CONCLUSIONThe results indicate that TP seems to have regulatory function on transcription and protein levels of t-PA and PAI-1, in addition to maintaining the balance between PAI-1 and t-PA and healing the injury of fibrinolytic functions in rats induced by high-methionine dietary.

Animals ; Diet ; Fibrinolysis ; drug effects ; Male ; Methionine ; adverse effects ; Plasminogen Activator Inhibitor 1 ; blood ; Polyphenols ; pharmacology ; Rats ; Rats, Wistar ; Tea ; chemistry ; Tissue Plasminogen Activator ; blood