Urokinase, also known asurokinase-type plasminogen activator (uPA), is aserine protease present in humans and other animals. The human urokinase protein was discovered, but not named, by McFarlane and Pilling in 1947.[5] Urokinase was originally isolated from humanurine, and it is also present in theblood and in theextracellular matrix of many tissues. The primary physiological substrate of this enzyme isplasminogen, which is an inactive form (zymogen) of the serine proteaseplasmin. Activation of plasmin triggers a proteolytic cascade that, depending on the physiological environment, participates inthrombolysis or extracellular matrix degradation. This cascade had been involved in vascular diseases and cancer progression.[6]
Urokinase is encoded in humans by thePLAU gene, which stands for "plasminogen activator, urokinase".[7] The same symbol represents the gene in other animal species.
ThePLAU gene encodes a serine protease (EC3.4.21.73) involved in the degradation of the extracellular matrix and possibly tumor cell migration and proliferation. A specific polymorphism in this gene may be associated with late-onset Alzheimer disease and also with decreased affinity for fibrin-binding. The protein encoded by this gene converts plasminogen to plasmin by specific cleavage of an Arg-Val bond in plasminogen. This gene's proprotein is cleaved at a Lys-Ile bond by plasmin to form a two-chain derivative in which a single disulfide bond connects the amino-terminal A-chain to the catalytically active, carboxy-terminal B-chain. This two-chain derivative is also called HMW-uPA (high molecular weight uPA). HMW-uPA can be further processed into LMW-uPA (low molecular weight uPA) by cleavage of chain A into a short chain A (A1) and an amino-terminal fragment. LMW-uPA is proteolytically active but does not bind to the uPA receptor.[8]
Urokinase is a 411-residueprotein, consisting of threedomains: the serine protease domain (consisting of residues 159–411), thekringle domain (consisting of residues 50-131), and theEGF-like domain (consisting of residues 1-49). The kringle domain and the serine protease domain are connected by an interdomain linker or connecting peptide (consisting of residues 132–158). Urokinase is synthesized as a zymogen form (prourokinase or single-chain urokinase), and is activated by proteolytic cleavage between Lys158 and Ile159. The two resulting chains are kept together by adisulfide bond between Cys148 and Cys279.[9]
In comparison to the mammalian system,zebrafish (Danio rerio) contains twoorthologs of urokinase which have been characterised as zfuPA-a and zfuPA-b. zfuPA-a differs from the mammalian uPA by lacking anexon sequence encoding for theuPAR (urokinase receptor) binding domain; while the zfuPA-b lacks two cysteines of the epidermal growth factor-like domain. zfuPA-b also has no binding activity in fishwhite blood cells or fish cell lines. The uPAR binding in mammalian system is essential for the activity of urokinase and uPAR as it also functions as an adhesion receptor due to its affinity tovitronectin,integrins and other proteases likePAI-1. The lack of the uPAR binding region in zebrafish uPA, suggests that zebrafish uPA functions without uPAR binding.[10]
zfuPA-a and zfuPA-b are poor activators of humanplasminogen, while human uPA is a poor activator ofsalmon plasminogen. With the primary difference between the zebrafish uPA and human uPA being in theEGF domain.[10]
Elevatedexpression levels of urokinase and several other components of theplasminogen activation system are found to be correlated withtumormalignancy. It is believed that the tissue degradation following plasminogen activation facilitates tissue invasion and, thus, contributes tometastasis.[13] Urokinase-type plasminogen activator (uPA) is more commonly associated with cancer progression thantissue plasminogen activator (tPA).[14] This makes uPA an attractivedrug target, and, so,inhibitors have been sought to be used as anticancer agents.[15][16] However, incompatibilities between the human andmurine systems hamper clinical evaluation of these agents. Moreover, urokinase is used by normal cells for tissue remodeling and vessel growth, which necessitates distinguishing cancer-associated urokinase features for specific targeting.[13]
uPAantigen is elevated in breast cancer tissue, which correlates with poor prognosis in breast cancer patients.[14] For this reason, uPA can be used as a diagnostic biomarker in breast cancer.[14]
Through its interaction with theurokinase receptor, urokinase affects several other aspects of cancer biology such as cell adhesion, migration, and cellularmitotic pathways.
As of December 7, 2012, Mesupron (upamostat), a small molecule serine protease inhibitor developed by the WILEX pharmaceutical company, has completed phase II trials.[17] Mesupron appears to be safe when combined with chemotherapeutic drugCapecitabine for the progression-free survival in human breast cancer.[18]
Urokinase is effective for the restoration of flow to intravenous catheters blocked by clotted blood or fibrin (catheter clearance). Catheters are used extensively to administer treatments to patients for such purposes as dialysis, nutrition, antibiotic treatment and cancer treatment. Approximately 25% of catheters become blocked, meaning that affected patients cannot receive treatment until the catheter has been cleared or replaced. Urokinase is also used clinically as athrombolytic agent in the treatment of severe or massivedeep venous thrombosis, peripheral arterial occlusive disease,pulmonary embolism, acutemyocardial infarction (AMI, heart attack), and occludeddialysis cannulas (catheter clearance). It is also administered intrapleurally to improve the drainage of complicated pleural effusions and empyemas. Urokinase is marketed as Kinlytic (formerly Abbokinase) and competes withrecombinant tissue plasminogen activator (e.g., alteplase) as a thrombolytic drug.
All plasminogen activators (urokinase, tPA) catalyze the production of plasmin, which in turn leads to the breakdown of the fibrin mesh structure in blood clots. While there are commonalities in the mode of action for urokinase and tPA, urokinase has some advantages for treatment of peripheral clots (Pulmonary Embolism, Deep Vein Thrombosis, Peripheral arterial occlusive disease).
Unlike tPA, which is activated by binding to the fibrin within clots, urokinase is not sequestered by fibrin and therefore does not specifically attack hemostatic clots. This makes urokinase less likely to break down such hemostatic clots that are essential for ongoing blood vessel repair throughout the body. Dissolution of these “good” clots can lead to serious adverse events through hemorrhagic bleeding. Years of clinical study have confirmed the safety advantage of using urokinase.[19][20] Consequently, urokinase has been preferentially used indeep venous thrombosis and peripheral arterial occlusive disease where it is administered directly to the site of the clot while tPA is preferred in AMI where peripheral bleeding is a secondary consideration.
A revolutionary method for the production of urokinase was patented byEvelyn Nicol in 1976 (U.S. Patent No. 3,930,944). Nicol was believed to be the first African American woman to receive a molecular biology patent.[21]
The presence of afibrinolytic enzyme in human urine was reported in 1947, without a name given for such an enzyme behind its effect.[22] In 1952 a purified form of the enzyme was extracted from human urine and named "urokinase" for "urinary kinase".[23] The full text for this article is lost, and the only citation points to the abstract of a list of papers read at a conference in the same journal.[24] A few other papers on the purification were published independently around the same time. By 1960, it was still unclear whether the activation ofplasminogen has anything to do with a protease, but akinase is thought to play a role regardless.[25]
^"Human PubMed Reference:".National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:".National Center for Biotechnology Information, U.S. National Library of Medicine.
^Degryse B (1 June 2011). "The urokinase receptor system as strategic therapeutic target: challenges for the 21st century".Current Pharmaceutical Design.17 (19):1872–1873.doi:10.2174/138161211796718161.PMID21711231.
^Tang L, Han X (March 2013). "The urokinase plasminogen activator system in breast cancer invasion and metastasis".Biomedicine & Pharmacotherapy.67 (2):179–182.doi:10.1016/j.biopha.2012.10.003.PMID23201006.
^Nagai M, Hiramatsu R, Kanéda T, Hayasuke N, Arimura H, Nishida M, Suyama T (Dec 1985). "Molecular cloning of cDNA coding for human preprourokinase".Gene.36 (1–2):183–188.doi:10.1016/0378-1119(85)90084-8.PMID2415429.
^España F, Berrettini M, Griffin JH (August 1989). "Purification and characterization of plasma protein C inhibitor".Thrombosis Research.55 (3):369–384.doi:10.1016/0049-3848(89)90069-8.PMID2551064.
^Jankun J, Skrzypczak-Jankun E (July 1999). "Molecular basis of specific inhibition of urokinase plasminogen activator by amiloride".Cancer Biochemistry Biophysics.17 (1–2):109–123.PMID10738907.
^Matthews H, Ranson M, Kelso MJ (November 2011). "Anti-tumour/metastasis effects of the potassium-sparing diuretic amiloride: an orally active anti-cancer drug waiting for its call-of-duty?".International Journal of Cancer.129 (9):2051–2061.doi:10.1002/ijc.26156.PMID21544803.S2CID205943879.
^Ouriel K, Gray B, Clair DG, Olin J (March 2000). "Complications associated with the use of urokinase and recombinant tissue plasminogen activator for catheter-directed peripheral arterial and venous thrombolysis".Journal of Vascular and Interventional Radiology.11 (3):295–298.doi:10.1016/S1051-0443(07)61420-1.PMID10735422.
^Cinà CS, Goh RH, Chan J, Kenny B, Evans G, Rawlinson J, Gill G (November 1999). "Intraarterial catheter-directed thrombolysis: urokinase versus tissue plasminogen activator".Annals of Vascular Surgery.13 (6):571–575.doi:10.1007/s100169900300.PMID10541608.S2CID470599.
^Sobel GW, Mohler SR, Jones NW, Dowdy ABC, Guest MM. Urokinase: an activator of plasma profibrinolysin extracted from urine. Am J Physiol 1952; 171: 768-69.
^"Abstracts of Papers Read".American Journal of Physiology. Legacy Content.171 (3):704–781. 30 November 1952.doi:10.1152/ajplegacy.1952.171.3.704.Normal human and dog urine contains fibrinolysin (plasmin) and a potent activator of profibrinolysin (plasminogen). The activator, which we have designated urokinase, can be concentrated and partially purified by acetone or alcohol fractionation methods.
^Celander DR, Guest MM (August 1960). "The biochemistry and physiology of urokinase".The American Journal of Cardiology.6 (2):409–419.doi:10.1016/0002-9149(60)90333-7.PMID13808740.
Ploug M, Gårdsvoll H, Jørgensen TJ, Lønborg Hansen L, Danø K (April 2002). "Structural analysis of the interaction between urokinase-type plasminogen activator and its receptor: a potential target for anti-invasive cancer therapy".Biochemical Society Transactions.30 (2):177–183.doi:10.1042/BST0300177.PMID12023847.
Alfano M, Sidenius N, Blasi F, Poli G (November 2003). "The role of urokinase-type plasminogen activator (uPA)/uPA receptor in HIV-1 infection".Journal of Leukocyte Biology.74 (5):750–756.doi:10.1189/jlb.0403176.PMID12960238.S2CID8526093.
Harbeck N, Kates RE, Gauger K, Willems A, Kiechle M, Magdolen V, Schmitt M (March 2004). "Urokinase-type plasminogen activator (uPA) and its inhibitor PAI-I: novel tumor-derived factors with a high prognostic and predictive impact in breast cancer".Thrombosis and Haemostasis.91 (3):450–456.doi:10.1160/TH03-12-0798.PMID14983219.S2CID19904733.
Gilabert-Estelles J, Ramon LA, España F, Gilabert J, Castello R, Estelles A (2006). "Expression of the fibrinolytic components in endometriosis".Pathophysiology of Haemostasis and Thrombosis.35 (1–2):136–140.doi:10.1159/000093556.PMID16855359.S2CID29270171.
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