Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The individual contributions of glycoprotein Ib (GPIb) and the seven transmembrane domain receptor (STDR) to increases in platelet [Ca2+]i induced by alpha-thrombin or the tethered ligand peptide (TLP; SFLLRNPNDKYEPF) have been determined in control platelets, in platelets where the thrombin binding site on GPIb was blocked with the monoclonal antibodies TM60 and LJ-Ib10, in platelets where access of thrombin to the STDR was blocked by polyclonal antipeptide antibodies, and in Bernard-Soulier platelets which constitutively lack GPIb. Curve-fitting analyses (LIGAND) showed that binding of PPACK-thrombin and alpha-thrombin to the moderate-affinity site was not detected in the best-fit model in the presence of anti-STDR antibodies although with alpha-thrombin there was also decreased binding at the high-affinity site. Conversely, TM60 blocked binding of alpha-thrombin to the high-affinity site but also decreased binding at the moderate affinity site. Separately, either TM60 or anti-TNA (150 micrograms/mL) reduced thrombin (0.5 nM)-induced elevations in [Ca2+]i to 50% of control values, but Ca2+ elevations were essentially abrogated (4.2 +/- 5%) when the two were added in combination. [Ca2+]i dose-response curves for alpha-thrombin were curvilinear and were only 50% of controls in the presence of anti-GPIb or anti-STDR antibodies at up to 10 nM alpha-thrombin, with their greatest sensitivity being below 2 nM. With Bernard-Soulier platelets, changes in [Ca2+]i were not detectable at < or = 0.5 nM alpha-thrombin but were also 50% of controls at 5-10 nM alpha-thrombin. [Ca2+]i responses to TLP (1-100 microM) of antibody-blocked platelets were identical to those of controls whereas responses were approximately 50% of controls in Bernard-Soulier platelets. The rate of increase in [Ca2+]i in controls was twice that seen in antibody-blocked platelets and about 5-fold greater than in Bernard-Soulier platelets. These results demonstrate that both GPIb and the STDR are required to ensure the optimal rate and extent of platelet activation over a range of alpha-thrombin concentrations (0.3-10 nM) and that the STDR corresponds to the previously described moderate-affinity thrombin receptor.
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PMID:Contributions of glycoprotein Ib and the seven transmembrane domain receptor to increases in platelet cytoplasmic [Ca2+] induced by alpha-thrombin. 854 72

We examined the effects of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF alpha) on the expression of proteolytically activated thrombin receptor (PATR) in human umbilical vein endothelial cells (HUVEC). PATR mRNA and protein levels were measured in confluent HUVEC monolayers after challenge with TNF alpha. Northern analysis indicated that TNF alpha treatment resulted in 2- to 3-fold decrease in PATR mRNA in a time- and dose-dependent manner. PATR mRNA level returned to the control level within 6 hr. The nuclear run-on assay indicated that the decreased mRNA signal was due to reduction in the transcription rate. Immunoblotting experiments indicated that the decrease in expression of PATR protein followed in time the decrease in mRNA; the lowest level of protein expression was achieved at 22 hr after TNF alpha treatment. PATR protein returned to basal value within 40 hr after TNA alpha challenge. To assess alterations in endothelial cell function after TNF alpha treatment, we measured thrombin-induced increase in cytosolic Ca2+ ([Ca2+]i) and the cell shape change (measured by decrease in electrical impedance of endothelial cell monolayer). In HUVEC treated with TNF alpha (100 U/ml for 22 hr), the rise in [Ca2+]i after thrombin challenge was approximately 2-fold less than in control thrombin-treated cells. The decrease in electrical impedance of HUVEC monolayers in response to thrombin after TNF alpha treatment was also significantly reduced. However, the rise in [Ca2+]i in response to histamine was not altered by TNF alpha pretreatment. In conclusion, TNF alpha exposure of endothelial cells decreased both mRNA and protein expression of PATR, which explain the decreased activation of thrombin generated signals after the TNF alpha exposure.
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PMID:Tumor necrosis factor decreases thrombin receptor expression in endothelial cells. 860 Jan 59

The synthesis of 4'-methoxymethyl threofuranosyl (4'-MOM-TNA) thymidine and derived oligomers of the G-rich thrombin-binding aptameric (TBA) sequence is reported. The G-quadruplex stability, anticoagulation activity, and the enzymatic stability of these oligomers bearing the 2'-3'-phosphodiester backbone as single substitutions in the loop regions are studied. Amongst all the oligomers, TBA-7T bearing the 4'-MOM-TNA unit at the T7 position formed a quadruplex with the highest thermal stability. It also resulted in enhanced anticlotting activity that allowed a one-third reduction in the dose, relative to TBA. Further, TBA-7T exhibited enhanced nuclease resistance properties to both endo- and exonucleases.
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PMID:Methoxymethyl Threofuranosyl Thymidine (4'-MOM-TNA-T) at the T7 Position of the Thrombin-Binding Aptamer Boosts Anticoagulation Activity, Thermal Stability, and Nuclease Resistance. 3195 96

Upon activation, platelets release a host of soluble and vesicular signals, collectively termed the "platelet releasate" (PR). The contents of this PR play a significant role in haemostasis, inflammation, and pathologic sequelae. Despite this, proteomic studies investigating the PR in coronary artery disease have not been performed. Here, we undertook a comparative label-free quantitative (LFQ) proteomic profiling of the 1 U/ml thrombin-induced PR from 13 acute coronary syndrome vs. 14 stable angina pectoris patients using a tandem mass spectrometry approach. Data are available via ProteomeXchange with identifier PXD009356. 318 PR proteins were identified across both cohorts with 9 proteins found to be differentially released, including tetranectin (CLEC3B), protein disulfide-isomerase-A3 (PDIA3), coagulation factor V (F5), and fibronectin (FN1). Strikingly, these 9 differential proteins were all associated with the gene ontology cellular component term "extracellular vesicle" and reduced levels of EVs were detected in the corresponding plasma of ST-segment elevation myocardial infarction (STEMI) patients. Network analysis revealed 3 proteins either reduced (F5; FN1) or absent (CLEC3B) in the PR of STEMI patients that are strongly connected to both the clotting cascade and major druggable targets on platelets. This moderated proteomic signature may prove useful for non-invasive risk assessment of the progression of coronary artery disease. These data further contribute to the growing evidence-base of using the platelet releasate as a predictor of pathological state and disease severity.
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PMID:Comparative Platelet Releasate Proteomic Profiling of Acute Coronary Syndrome versus Stable Coronary Artery Disease. 3267 Oct 99