Protein C is synthesized in the liver and measurement of protein C activity aids in the diagnosis of thrombotic disorders and liver disease. The presence of thrombomodulin accelerates activation by several orders of magnitude,[7]:34 and EPCR speeds up activation by a factor of 20. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. 1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio. SAP-C has been primarily described by O'Brien and colleagues as an activator of β-GlcCer degradation by glucosylceramide β-glucosidase (Fig. It can be demonstrated in ∼3% of younger patients with venous thrombosis. Ultimately, SAP-C molecules, inserted into opposing lipid vesicles, clip one another through domain swapping, thus bringing the vesicles close enough for fusion. In addition, proteins released from cells can impede protein C activation, for example eosinophil, which may explain thrombosis in hypereosinophilic heart disease. It is synthesized in the liver and circulates in the plasma. John A. Heit MD, in Consultative Hemostasis and Thrombosis (Third Edition), 2013. [19] In 1982, a family study by Griffin et al. View Protein Structure Function.pdf from BIO 160 at University of Tennessee. Protein C (PC) and protein S (PS) are vitamin K-dependent glycoproteins and essential components of the thrombomodulin (TM)/PC/PS pathway (Suzuki et al., 2004). If a deficiency is identified, additional testing is recommended for classification. Factor VIII, on the other hand, is a cofactor in production of activated Factor X, which in turn converts prothrombin into thrombin. [38]:211s Deletion of the protein C gene in mice causes fetal death around the time of birth. The protein C (PROC) gene is located on the long arm of chromosome 2 (2q13-q14) and contains nine exons spanning 11 kb. [41]:1332 Drotrecogin alfa-activated is a recombinant form of human activated protein C (rhAPC). Research into the clinical use of a recombinant form of human Activated Protein C (rhAPC) known as Drotrecogin alfa-activated, branded Xigris by Eli Lilly and Company, has been surrounded by controversy. In a recent study, clonal populations of B. burgdorferi producing different OspC types were used to infect mice, serum was harvested and then used to screen an immunoblot consisting of a panel of OspC proteins of different phyletic types (Earnhart et al., 2005). Inherited deficiency of SAP-C causes a variant juvenile form of Gaucher disease (type III) with marked storage of β-GlcCer (Christomanou et al., 1989; Matsuda et al., 2004; Schnabel et al., 1991). There are about 20 genes that are up-regulated by protein C, and 20 genes that are down-regulated: the former are generally anti-inflammatory and antiapoptotic pathways, while the latter tend to be proinflammatory and proapoptotic. The incidence and relative risk of both a first lifetime (incident) and recurrent venous thromboembolism are presented in Table 14-3. Homozygous subjects have a risk 80 times higher. [44] Ceprotin is indicated in purpura fulminans and coumarin-induced skin necrosis in people with severe congenital protein C deficiency.[44]. The heavy chain contains the protease domain and the activation petide. Michael P. Gruber, Todd M. Bull, in Clinical Respiratory Medicine (Fourth Edition), 2012. Compared to the other vitamin K-dependent coagulation proteins, protein C has a quite low affinity for the membrane.8, Alexandre Darmoise, ... Florian Winau, in Advances in Immunology, 2010. The amino acid sequence and domain structure are similar to those of the other vitamin K-dependent serine protease precursors, factor VII (Chapter 641) (identity 41%), factor IX (Chapter 640) (identity 38%) and factor X (Chapter 642) (identity 39%). 18 The Gla domain of protein C/APC binds negatively charged phospholipid membranes and also EPCR, both interactions being important for the physiological function of protein C (Figures 1 and 2). Thus, the person's blood clots too readily, and he is perpetually at an increased risk for thrombosis. To a degree, APC's anticoagulant properties are independent of its cytoprotective ones, in that expression of one pathway is not affected by the existence of the other. [8][16]:2383 The nucleotide sequence that codes for human protein C is approximately 11,000 bases long.[8]:4675. Deficiencies of Natural Anticoagulants, Protein C, Protein S, and Antithrombin (2011): A patient focused article on deficiencies in the natural anticoagulants or blood thinner including Protein C and Protein S. Discusses causes, diagnosis, treatment, complications, and testing. [38]:211s, Activated protein C cleaves Plasmodium falciparum histones which are released during infection: cleavage of these histones eliminates their pro inflammatory effects. In an effort to develop a polyvalent OspC vaccine, Baxter Vaccines tested an OspC recombinant protein cocktail consisting of up to 14 full-length OspC proteins of different types. Type I deficiency consists of concordant reduction in both protein C activity and antigen level, and accounts for about 75% of all congenital cases of protein C deficiency. Protein C deficiency is a disorder that increases a person's risk to develop abnormal blood clots due to a deficiency of the Protein C, a protein in the body that prevents blood clotting. Since you are measuring protein C function with the Cryochek Cot C assay, I suspect the elevation may reflect activation, and not necessarily a protein C production increase. It is located on the second chromosome (2q13-q14) and comprises nine exons. A potential approach to solving this problem is to generate a recombinant chimeric protein that consists entirely of protective epitopes from those OspC types associated with disease in humans. However, these formulations did not elicit sufficient antibody titers against the essential type-specific epitopes of each OspC variant included in the vaccine. These analyses demonstrated that the antibody response elicited during early infection is OspC type-specific suggesting that it is the type-specific domains of the protein that are presented at the bacterial cell surface. Both of these actions down-regulate protein C activation. Activated protein C is inhibited by α1-proteinase inhibitor (protein C inhibitor 1) and α2-macroglobulin. The catalytic activity of activated protein C is greatly enhanced by the vitamin K–dependent cofactor protein S. 3 The function of protein S is to inactivate factor Va and factor VIIIa. Thus, whi … Protein C Protein C. Protein C is a vitamin K-dependent proenzyme of a serine protease composed of multiple domains. whereby it was demonstrated that activated protein C prevented coagulopathy and death in baboons infused with lethal concentrations of E. The protein C plasma concentration (65 nmol/L) is about 100-fold lower than the antithrombin plasma concentration (2.5 µmol/L). [16]:2382 The mutation leading to the loss of this cleavage site actually stops APC from effectively inactivating both Factor Va and Factor VIIIa. This reduces leukocyte adhesion and infiltration into tissues, while also limiting damage to underlying tissue. Inherited deficiency of protein C can lead to familial thrombophilia (increased tendency toward thrombosis). APC effects significant down-regulation of p53 and Bax. CRP is secreted by the liver in response to a variety of inflammatory cytokines. Activated leukocytes release these inflammatory mediators during inflammation, inhibiting the creation of both thrombomodulin and EPCR, and inducing their shedding from the endothelial surface. Human protein C is a vitamin K-dependent glycoprotein structurally similar to other vitamin K-dependent proteins affecting blood clotting,[29] such as prothrombin, Factor VII, Factor IX and Factor X. The inclusion of numerous full-length proteins in the vaccine formulation may have resulted in the misdirection of the immune response by presenting immunodominant but nonprotective epitopes. In contrast, amidolytic assays determine the patient's (activated) protein C level by measuring color from a reporter group (p-nitroaniline) released by cleavage of a synthetic (chromogenic) peptide substrate. Other genetic mutations cause APC resistance, but none to the extent that Factor VLeiden does. [33]:26S Cofactors in the inactivation of Factor Va and Factor VIIIa include protein S, Factor V, high-density lipoprotein, anionic phospholipids and glycosphingolipids. Apart from acting as a cofactor for APC, PS also exerts cytoprotective activity by binding to its Tyro, Axl and Mer (TAM) tyrosine kinase receptors on the cell surface (Suleiman et al., 2013). [21]:1216 The half-life of activated protein C is around 15 minutes. Two separate tests for these proteins are often performed together as part of the investigation of a possible excessive clotting disorder. As infection progresses, a broader array of OspC epitopes in widely separated domains of the protein become recognized by the antibody response (Earnhart et al., 2005, 2007). Another is necessary for interacting with thrombomodulin. In contrast, significant symptoms of the deficiency are detectable in 1 in 20,000 individuals. Protein C deficiency is a rare genetic trait that predisposes to thrombotic disease.It was first described in 1981. The activated protein C inhibits factors V and VIII in the reagent and the resultant prolongation of the aPTT-based clotting time is proportional to plasma PC activity. PC clotting assays use a modified APTT reagent incorporating a PC activator... Natural anticoagulants and thrombophilia. Two different subtypes of inherited protein C deficiency have been identified. [9]:3161 Mild protein C deficiency corresponds to plasma levels above 20 IU/dL, but below the normal range. Congenital protein C deficiency is inherited as an autosomal dominant disorder but with variable penetrance; over 160 unique mutations spread throughout the PROC gene have been identified. Soon after this, Seegers recognised Stenflo's discovery was identical with his own. cell-protecting) functions, most of which are known to require EPCR and PAR-1. Michael A. Laffan, Richard A. Manning, in Dacie and Lewis Practical Haematology (Twelfth Edition), 2017. Protein C and protein S work together to prevent your blood from clotting too much. APC inhibits the release of inflammatory-response mediators in leukocytes as well as endothelial cells, by reducing cytokine response, and maybe diminishing systemic inflammatory response, such as is seen in sepsis. Artificially increased functional protein C values may be due to heparin therapy or the presence of direct thrombin inhibitors or factor Xa inhibitors. Inactivation of Factor Va thus practically halts the production of thrombin. Clot-based protein C activity assays have the potential to detect abnormalities caused by mutation within several different protein C domains as well as factor VIII and factor V, whereas amidolytic assays detect only mutation within the catalytic active site.352 However, interfering substances that prolong the baseline clotting time (e.g., heparin, direct thrombin inhibitors, lupus anticoagulant, uremia353) may preclude interpretation of clot-based assays, and high factor VIII levels (as occur with an acute phase reaction) may cause underestimation of protein C activity when measured using APTT-based assays. EPCR enhances PC activation by presenting the PC substrate to the thrombin-TM activation complex (Mohan Rao et al., 2014). The Gla residues bind calcium and are important for the proper folding of the domain. [43]:211 Clinical use of APC has also been proposed for improving the outcome of pancreatic islet transplantation in treating type I diabetes. Type II deficiency is a qualitative defect with reductions in functional levels of protein C but preserved antigenic function. In parallel, SAP-C can directly bind anionic phospholipids to destabilize membranes and to promote the association of β-glucosylceramidase with its lipid substrate for subsequent degradation (Vaccaro et al., 1993). In the absence of warfarin therapy and known medical conditions that result in acquired protein C deficiency, patients with a protein C level less than 55% of normal are very likely to have a genetic abnormality, whereas levels from 55% to 65% normal are consistent with either a deficient state or low normal values. Thus, repeat testing and/or genetic testing is recommended in most populations. It may be inherited or acquired. The levels of protein C antigen in patients with heterozygous deficiency overlap with those in the normal population, which makes it difficult to define the diagnosis in some patients. [7]:35 In humans, protein C is encoded by the PROC gene, which is found on chromosome 2.[8]. However, the function of protein C in the physio-logical regulation of coagulation was not delineated until several years thereafter. Protein C levels are decreased in acute thrombotic events and during therapy with warfarin. In addition, unacceptable reactigenicity was reported (Hanson and Edelman, 2004). Protein C is a glycoprotein that works directly with Protein S to regulate blood clotting. [8]:4673 The protein C zymogen is activated when it binds to thrombin, another protein heavily involved in coagulation, and protein C's activation is greatly promoted by the presence of thrombomodulin and endothelial protein C receptors (EPCRs). [16]:2381 These proteins that APC inactivates, Factor Va and Factor VIIIa, are highly procoagulant cofactors in the generation of thrombin, which is a crucial element in blood clotting; together they are part of the prothrombinase complex. Thus, whi … Studies on both rats and humans have demonstrated that APC reduces endotoxin-induced pulmonary injury and inflammation. [12], Protein C's anticoagulant role in the human body was first noted by Seegers et al. Christopher G. Earnhart, Richard T. Marconi, in Vaccines for Biodefense and Emerging and Neglected Diseases, 2009. While OspC is highly antigenic and can elicit protective antibody responses, the protective range is narrow (Probert and LeFebvre, 1994; Gilmore et al., 1996; Bockenstedt et al., 1997; Probert et al., 1997; Mathiesen et al., 1998; Rousselle et al., 1998; Gilmore and Mbow, 1999; Mbow et al., 1999; Seinost et al., 1999b; Wallich et al., 2001; Jobe et al., 2003; Scheiblhofer et al., 2003; Brown et al., 2005). These include regulating gene expression, anti-inflammatory effects, antiapoptotic effects and protecting endothelial barrier function. C-reactive protein (CRP) is an ancient highly conserved molecule and a member of the pentraxin family of proteins. Protein C was isolated from bovine plasma by Johan Stenflo in 1976 and named C because it was the third protein to elute from DEAE-Sepharose [1]. Abnormal protein C or S that cannot function normally; Abnormal protein S that is cleared more rapidly by the body (Type 3 deficiency) When these mutations occur, they are independent of each other and the mutation is in one or the other gene (protein C or protein S). PC deficiency is rare in healthy populations, with reported incidence of 0.2%–0.4% of unselected subjects. Levels of CRP increase very rapidly in response to trauma, inflammation, and infection and decrease just … Once produced, the activated protein C (APC) cleaves and inactivates factors Va and VIIIa. Family studies may also be useful in confirming a diagnosis of congenital protein C deficiency. PC is converted to its active form, APC, by thrombin bound to TM on the phospholipid surface of endothelial cells, epithelial cells, monocytes or platelets (Esmon and Owen, 1981; Shirai et al., 1988; Knobe et al., 1999; Morser, 2012). This may be done by inflammatory cytokines, such as interleukin-1β (IL-1β ) and tumor necrosis factor-α (TNF-α). The identification of epitopes that are presented by native OspC during the early stages of infection and that elicit bactericidal antibody is an important step towards the design of an effective and broadly protective OspC-based vaccine. However, type I deficiency also is caused by promoter and 5′-untranslated region mutations that disrupt binding of transcription factors, and splice junction and small insertion-deletion mutations that cause premature stop codons. [27] In 2002, Science published an article that first showed protein C activates protease-activated receptor-1 (PAR-1) and this process accounts for the protein's modulation of the immune system. The N-terminal light chain of protein C (155 amino acids; Mr, 21 kDa) functions in calcium and phospholipid binding, protein C activation, and interaction with protein S, and contains the γ-carboxyglutamic acid (Gla)–rich domain and two epidermal growth factor–like domains. The C-terminal (carboxy terminal) heavy chain (250 amino acids; Mr, 41 kDa) contains the serine protease catalytic domain. It may play a role in the protein functions as either a cofactor for activated protein C (APC) or in binding C4BP. The basis for the limited protective range of OspC has been determined to be due to the above described sequence variation.