Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombomodulin (TM) is an anionic (pI approximately 4) protein cofactor that promotes thrombin (THR) cleavage of protein C to generate activated protein C (APC), a potent anticoagulant. We find that the cationic platelet alpha-granule protein platelet factor 4 (PF4) stimulates 4-25-fold the cofactor activity of rabbit TM and two differentially glycanated versions of an extracellular domain human TM polypeptide in which the glycosaminoglycan (GAG) is either present (GAG+ TM) or absent (GAG- TM) with an ED50 of 3.3-10 micrograms/ml. No such stimulation occurs in response to beta-thromboglobulin or thrombospondin, or when protein C lacking its gamma-carboxyglutamic acid (Gla) domain is the substrate. Heparin and chondroitin sulfates A and E reverse PF4 stimulation. PF4 minimally affects the Kd for THR but decreases 30-fold (from 8.3 to 0.3 microM) the Km for protein C of APC generation by GAG+ TM. PF4 also strikingly transforms the [Ca2+] dependence profile of rabbit and GAG+ TM to resemble that of GAG- TM. A potential explanation for this is that PF4, like Ca2+, induces heparin-reversible alterations in native (but not Gla-domainless) protein C conformation as assessed by autofluorescence emission analysis. We conclude that PF4 stimulates TM APC generation by interacting electrostatically with both the TM GAG and the protein C Gla domain to enhance markedly the affinity of the THR.TM complex for protein C. By this mechanism, PF4 may play a previously unsuspected role in the physiologic regulation of clotting.
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PMID:Platelet factor 4 stimulates thrombomodulin protein C-activating cofactor activity. A structure-function analysis. 752 87

The diagnosis of thromboembolic diseases is still difficult to establish before the occurrence of the pathological event, although it is now known that they are the result of a progressive alteration of the cardiovascular system. Introduction of new diagnostic tools for the evaluation of the thromboresistance capacity of the body or for the measurement of molecular markers allows the testing of the body defenses against thrombosis which is becoming a routine clinical diagnosis. Antithrombin III (AT III), protein C, protein S, and parameters of fibrinolysis have been recognized to be very important anticoagulant proteins and regulators of thrombin formation and thrombus extension. Furthermore, a normal factor V is necessary for the normal function of the protein C pathway. The presence of a factor V mutation leads to the activated protein C resistance syndrome. However, the major incidence of thrombotic events concerns the overall population. It has been epidemiologically related to the existence of risk factors producing blood activation, which progressively saturates the body's thromboresistance. This period is clinically silent for a long time. The new molecular markers recently introduced can show the existence of a preclinical state of blood activation at the plasma level (fibrinopeptide A, thrombin-antithrombin complexes, modified antithrombin III, fragments 1 + 2 of prothrombin, D-dimer) or at the platelet level (B-thromboglobulin, platelet factor 4, and thrombospondin), and promising developments concern the endothelial level (soluble thrombomodulin). The most universally used blood activation test is the D-dimer assay. This analyte has become very popular in past years for its high sensitivity, its long half-life, and its easy detection directly on citrated plasma. Its negative predictive value (in deep venous thrombosis or pulmonary embolism) as well as its use for monitoring of thrombotic risk in the post-operative period have been well documented clinically. New investigations are initiated to find analytes reflecting endothelial damage, an early platelet activation, or the involvement of blood cells (mainly monocytes and neutrophils) in abnormal processes. It also becomes possible to evaluate directly pathological causes inducing blood activation, such as the presence of antiphospholipid antibodies or other autoimmune antibodies.
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PMID:Thromboembolic diseases: biochemical mechanisms and new possibilities of biological diagnosis. 880 28

C-Mannosylation is a unique form of protein glycosylation, involving the C-glycosidic attachment of a mannosyl residue to the indole moiety of Trp. In the two examples found so far, human RNase 2 and interleukin-12, only the first Trp in the recognition motif WXXW is specifically C-mannosylated. To establish the generality of protein C-mannosylation, and to learn more about its mechanism, the terminal components of the human complement system (C6, C7, C8,and C9), which contain multiple and complex recognition motifs, were examined. Together with C5b they form the cytolytic agent, the membrane attack complex. These are the first proteins that are C-mannosylated on more than one Trp residue as follows: six in C6, four in C7, C8alpha, and C8beta, and two in C9. Thus, from the 113 Trp residues in the complete membrane attack complex, 50 were found to undergo C-mannosylation. The other important finding is that in C6, C7, C8, and C9 Trp residues without a second Trp (or another aromatic residue) at the +3 position can be C-mannosylated. This shows that they must contain an additional C-mannosylation signal. Whether this is encoded in the primary or tertiary structure is presently unknown. Finally, all modified Trp residues are part of the highly conserved core of the thrombospondin type 1 repeats present in these proteins. Since this module has been found in a large number of other proteins, the results suggest further candidates for C-mannosylation.
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PMID:The four terminal components of the complement system are C-mannosylated on multiple tryptophan residues. 1055 39

Thrombospondin-1 (TSP-1) is a multidomain protein that has been implicated in cell adhesion, motility, and growth. Some of these functions have been localized to the three thrombospondin type 1 repeats (TSRs), modules of approximately 60 amino acids in length with conserved Cys and Trp residues. The Trp residues occur in WXXW patterns, which are the recognition motifs for protein C-mannosylation. This modification involves the attachment of an alpha-mannosyl residue to the C-2 atom of the first tryptophan. Analysis of human platelet TSP-1 revealed that Trp-368, -420, -423, and -480 are C-mannosylated. Mannosylation also occurred in recombinant, baculovirally expressed TSR modules from Sf9 and "High Five" cells, contradictory to earlier reports that such cells do not carry out this reaction. In the course of these studies it was appreciated that the TSRs in TSP-1 undergo a second form of unusual glycosylation. By using a novel mass spectrometric approach, it was found that Ser-377, Thr-432, and Thr-489 in the motif CSX(S/T)CG carry the O-linked disaccharide Glc-Fuc-O-Ser/Thr. This is the first protein in which such a disaccharide has been identified, although protein O-fucosylation is well described in epidermal growth factor-like modules. Both C- and O-glycosylations take place on residues that have been implicated in the interaction of TSP-1 with glycosaminoglycans or other cellular receptors.
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PMID:C-mannosylation and O-fucosylation of the thrombospondin type 1 module. 1106 51

The incomplete penetrance of thrombosis in familial protein C deficiency suggests disease occurs when this deficit is combined with additional abnormalities in the hemostatic system. The pattern of inherited thrombophilia in the Vermont II kindred, which is affected by a clinically dominant type I protein C deficiency, provides strong evidence for a second unidentified gene that segregates independently of protein C deficiency and increases susceptibility to thrombosis. To test the second gene hypothesis, thirty-four candidate genes for proteins involved in hemostasis or inflammation were tested as the unknown defect, using highly polymorphic short tandem repeat (STR) markers in an informative subset (n = 31) of the kindred. The genes considered are; alpha-fibrinogen, beta-fibrinogen, gamma-fibrinogen, prothrombin, tissue factor, factor V, protein S, complement component 4 binding protein, factor XI, factor XII, factor XIIIa, factor XIIIb, histidine rich glycoprotein, high molecular weight kininogen, kallikrein, von Willebrands factor, platelet factor 4, thrombospondin, antithrombin III, alpha-1-antitrypsin, thrombomodulin, plasminogen, tissue plasminogen activator, urokinase plasminogen activator, plasminogen activator inhibitor-1, plasminogen activator inhibitor-2, protein C inhibitor, alpha-2-plasmin inhibitor, kallistatin, lipoprotein a, interleukin 6, interleukin 1, cystathionine-beta-synthase, and methylenetetrahydrofolate reductase. Mutations in many of these genes have been previously established as independent risk factors for thrombosis. However, linkage analysis provided no evidence to implicate any of the candidate genes as the second inherited factor that promotes thrombophilia in this kindred.
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PMID:Genetic screening of candidate genes for a prothrombotic interaction with type I protein C deficiency in a large kindred. 1120 93

Physical exercise produces several adaptive changes in skeletal muscle. However, the molecular mechanisms of these effects are poorly understood. We performed serial analysis of gene expression (SAGE) to quantify the global gene expression profile in sedentary and endurance-trained muscle. A total of 10869 SAGE tags was sequenced and represented 4727 genes. The genes most expressed in muscle are mainly involved in contraction and energy metabolism. Thirty-three genes were differentially expressed between endurance athletes and sedentary individuals. Four genes such as myosin binding protein C fast-type, glycogen phosphorylase, and pyruvate kinase were expressed less in endurance athletes, whereas eight genes coding for expressed sequence tag similar to (EST) crystallin alpha B, EST myosin light chain 2, EST surfactant pulmonary-associated protein A1, EST thrombospondin, EST fructose-bisphosphate aldolase A, EST cytochrome oxidase 1, NADH dehydrogenase 3, and G8 protein were up-regulated. Most of the up-regulated tags corresponded to novel genes. On the other hand, different isoforms of fructose-bisphosphate aldolase A were also differentially expressed. The current study underlying the most highly expressed genes allows a better understanding of global muscle characteristics in normal and endurance-trained individuals. Moreover, the current data suggest novel candidate genes that may be responsible for enhanced endurance performance.
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PMID:Serial analysis of gene expression in the skeletal muscle of endurance athletes compared to sedentary men. 1522 64

Activated protein C (APC) has anti-inflammatory and vascular protective effects independent of anticoagulation. We previously identified the prototypical thrombin receptor, protease-activated receptor-1 (PAR1), as part of a novel APC-endothelial cell protein C receptor (EPCR) signaling pathway in endothelial cells. Experiments in wild-type and PAR1(-/-) mice demonstrated that intravenous injection of APC leads to PAR1-dependent gene induction in the lung. The vascular endothelium undergoes profound changes in severe sepsis, the approved therapeutic indication for APC. Similar to PAR1, APC activated PAR2 through canonical cleavage. Although PAR2 was up-regulated in cytokine-stimulated endothelial cells, APC signaling remained PAR1-dependent. Large scale gene expression profiling documented marked differences in both up- and down-regulated genes between APC and thrombin signaling in cytokine-stimulated cells. APC down-regulated transcripts for proapoptotic proteins including p53 and thrombospondin-1, but p53 was unchanged, and thrombospondin was even up-regulated by thrombin. Concordant PAR1-dependent effects on protein levels were found. Thus, by signaling through the same receptor PAR1, APC, and thrombin can exert distinct biological effects in perturbed endothelium. These data may explain how APC can be therapeutically protective through the EPCR-PAR1 signaling despite ongoing thrombin generation due to disseminated intravascular coagulopathy.
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PMID:Protease-activated receptor-1 signaling by activated protein C in cytokine-perturbed endothelial cells is distinct from thrombin signaling. 1576 47

Interstitial cells, inflammatory-immune cells, tubular cells and endothelial cells of the peritubular capillaries have arisen as possible major players of the nephron damage in lupus nephritis. Increased ICAM-1, Von Willebrand factor, soluble endothelial protein C receptors and decreased ADAMS-13 point to a diffuse vascular damage. Albuminuria elicits a rapid generation of hydrogen peroxide in proximal tubular cells along with nuclear factor-kB activation, endothelin-1 and transforming growth factor (TGF-beta1) upregulation. TGF-beta1 enhances epithelial-to-mesenchymal transdifferentiation. Albuminuria also enhances the expression of macrophage chemotactic protein-1 and macrophage inflammatory protein-1alpha, thus leading to increased interstitial inflammation. TGF-beta1 and thrombospondin-1, a putative activator of TGF-beta, induce apoptosis of peritubular capillaries, as well as of glomerular endothelial cells. All these events can be counteracted by hepatocyte growth factor (HGF), which is expressed by the epithelial tubular cells and stimulates the growth of epithelial cells (mitogen), enhances the motility of epithelial cells (motogen), induces renal epithelial tubule regeneration (morphogen) and enhances angiogenesis (angiogen). The balance between TGF-beta1 and HGF could be a key to define the prognostic value of kidney histopathology at baseline and during follow-up, in lupus nephritis. Therapeutic strategies aiming at altering the biological balance in the patients are at hand to test and prove the experimental evidences.
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PMID:Renal interstitial cells, proteinuria and progression of lupus nephritis: new frontiers for old factors. 1853 6

Protein C-mannosylation is the attachment of alpha-mannopyranose to tryptophan via a C-C linkage. This post-translational modification typically occurs within the sequence motif WXXW, which is frequently present in thrombospondin type-1 repeats (TSRs). TSRs are especially numerous in and a defining feature of the ADAMTS superfamily. We investigated the presence and functional significance of C-mannosylation of ADAMTS-like 1/punctin-1, which contains four TSRs (two with predicted C-mannosylation sites), using mass spectrometry, metabolic labeling, site-directed mutagenesis, and expression in C-mannosylation-defective Chinese hamster ovary cell variants. Analysis of tryptic fragments of recombinant human punctin-1 by mass spectrometry identified a peptide derived from TSR1 containing the (36)WDAWGPWSECSRTC(49) sequence of interest modified with two mannose residues and a Glc-Fuc disaccharide (O-fucosylation). Tandem mass spectrometry (MS/MS) and MS/MS/MS analysis demonstrated the characteristic cross-ring cleavage of C-mannose and identified the modified residues as Trp(39) and Trp(42). C-Mannosylation of TSR1 of the related protease ADAMTS5 was also identified. Metabolic labeling of CHO-K1 cells or Lec35.1 cells demonstrated incorporation of d-[2,6-(3)H]mannose in secreted punctin-1 from CHO-K1 cells but not Lec35.1 cells. Quantitation of punctin-1 secretion in Lec35.1 cells versus CHO-K1 cells suggested decreased secretion in Lec35.1 cells. Replacement of mannosylated Trp residues in TSR1 with either Ala or Phe affected punctin secretion efficiency. These data demonstrate that TSR1 from punctin-1 carries C-mannosylation in close proximity to O-linked fucose. Together, these modifications appear to provide a quality control mechanism for punctin-1 secretion.
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PMID:Post-translational modification of thrombospondin type-1 repeats in ADAMTS-like 1/punctin-1 by C-mannosylation of tryptophan. 1967

We analyzed 66 cases of immune-mediated thrombophilia in patients with lymphoma reported in the literature. Sixty-one cases had a lupus anticoagulant, three an antibody to protein S, one to protein C, and one to ADAMTS 13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). Lupus anticoagulants occurred in all histological subtypes of non-Hodgkin lymphoma, except mantle cell lymphoma, MALT (mucosa-associated lymphoid tissue) lymphoma, and angioimmunoblastic T-cell lymphoma, and rarely in Hodgkin lymphoma. The largest number of cases was described in splenic marginal zone and lymphoplasmacytic lymphoma. Lupus anticoagulants were highly associated with immunoglobulin M (IgM) paraproteinemia, autoimmune hemolytic anemia, and immune thrombocytopenia. About half of the patients had thrombotic events (antiphospholipid antibody syndrome). Venous thromboembolism was more than twice as common as arterial thrombosis; 6.5% had a catastrophic antiphospholipid antibody syndrome. The lupus anticoagulant could be eliminated by lymphoma treatment (chemoimmunotherapy or splenectomy) in more than one-third of patients. It is suggested that a search for lupus anticoagulant should be done in all patients with lymphoma, because a diagnosis of lupus anticoagulant may influence the management of lymphomas in some patients.
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PMID:Acquired immune-mediated thrombophilia in lymphoproliferative disorders. 2176 5


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