Plasmin-dependent elimination of the growth-factor-like domain in urokinase causes its rapid cellular uptake and degradation

Role of Fibrinolytic Enzymes in Anti-Thrombosis Therapy

Thrombosis, a major cause of deaths in this modern era responsible for 31% of all global deaths reported by WHO in 2017, is due to the aggregation of fibrin in blood vessels which leads to myocardial infarction or other cardiovascular diseases (CVDs). Classical agents such as anti-platelet, anti-coagulant drugs or other enzymes used for thrombosis treatment at present could leads to unwanted side effects including bleeding complication, hemorrhage and allergy. Furthermore, their high cost is a burden for patients, especially for those from low and middle-income countries. Hence, there is an urgent need to develop novel and low-cost drugs for thrombosis treatment. Fibrinolytic enzymes, including plasmin like proteins such as proteases, nattokinase, and lumbrokinase, as well as plasminogen activators such as urokinase plasminogen activator, and tissue-type plasminogen activator, could eliminate thrombi with high efficacy rate and do not have significant drawbacks by directly degrading the fibrin. Furthermore, they could be produced with high-yield and in a cost-effective manner from microorganisms as well as other sources. Hence, they have been considered as potential compounds for thrombosis therapy. Herein, we will discuss about natural mechanism of fibrinolysis and thrombus formation, the production of fibrinolytic enzymes from different sources and their application as drugs for thrombosis therapy.

Urokinase Plasminogen Activator: A Potential Thrombolytic Agent for Ischaemic Stroke

Stroke continues to be one of the leading causes of mortality and morbidity worldwide. Restoration of cerebral blood flow by recombinant plasminogen activator (rtPA) with or without mechanical thrombectomy is considered the most effective therapy for rescuing brain tissue from ischaemic damage, but this requires advanced facilities and highly skilled professionals, entailing high costs, thus in resource-limited contexts urokinase plasminogen activator (uPA) is commonly used as an alternative. This literature review summarises the existing studies relating to the potential clinical application of uPA in ischaemic stroke patients. In translational studies of ischaemic stroke, uPA has been shown to promote nerve regeneration and reduce infarct volume and neurological deficits. Clinical trials employing uPA as a thrombolytic agent have replicated these favourable outcomes and reported consistent increases in recanalisation, functional improvement and cerebral haemorrhage rates, similar to those observed with rtPA. Single-chain zymogen pro-urokinase (pro-uPA) and rtPA appear to be complementary and synergistic in their action, suggesting that their co-administration may improve the efficacy of thrombolysis without affecting the overall risk of haemorrhage. Large clinical trials examining the efficacy of uPA or the combination of pro-uPA and rtPA are desperately required to unravel whether either therapeutic approach may be a safe first-line treatment option for patients with ischaemic stroke. In light of the existing limited data, thrombolysis with uPA appears to be a potential alternative to rtPA-mediated reperfusive treatment due to its beneficial effects on the promotion of revascularisation and nerve regeneration.

Transforming growth factor-β, matrix metalloproteinases, and urokinase-type plasminogen activator interaction in the cancer epithelial to mesenchymal transition

Transforming growth factor-β (TGF-β) is a pleiotropic factor that acts as a tumor suppressor in the early stages, while it exerts tumor promoting activities in advanced stages of cancer development. One of the hallmarks of cancer progression is the capacity of cancer cells to migrate and invade surrounding tissues with subsequent metastasis to different organs. Matrix metalloproteinases (MMPs) together with urokinase-type plasminogen activator (uPA) and its receptor (uPAR), whose main original function described is the proteolytic degradation of the extracellular matrix, play key cellular roles in the enhancement of cell malignancy during cancer progression. TGF-β tightly regulates the expression of several MMPs and uPA/uPAR in cancer cells, which in return can participate in TGF-β activation, thus contributing to tumor malignancy. TGF-β is one of the master factors in the induction of cancer-associated epithelial to mesenchymal transition (EMT), and recently both MMPs and uPA/uPAR have also been shown to be implicated in the cancer-associated EMT process. In this review, we analyze the main molecular mechanisms underlying MMPs and uPA/uPAR regulation by TGF-β, as well as their mutual implication in the development of EMT in cancer cells. Developmental Dynamics 247:382-395, 2018. © 2017 Wiley Periodicals, Inc.

Transforming growth factor-Beta and urokinase-type plasminogen activator: dangerous partners in tumorigenesis-implications in skin cancer

Transforming growth factor-beta (TGF-β) is a pleiotropic factor, with several different roles in health and disease. TGF-β has been postulated as a dual factor in tumor progression, since it represses epithelial tumor development in early stages, whereas it stimulates tumor progression in advanced stages. During tumorigenesis, cancer cells acquire the capacity to migrate and invade surrounding tissues and to metastasize different organs. The urokinase-type plasminogen activator (uPA) system, comprising uPA, the uPA cell surface receptor, and plasminogen-plasmin, is involved in the proteolytic degradation of the extracellular matrix and regulates key cellular events by activating intracellular signal pathways, which together allow cancer cells to survive, thus, enhancing cell malignance during tumor progression. Due to their importance, uPA and its receptor are tightly transcriptionally regulated in normal development, but are deregulated in cancer, when their activity and expression are related to further development of cancer. TGF-β regulates uPA expression in cancer cells, while uPA, by plasminogen activation, may activate the secreted latent TGF-β, thus, producing a pernicious cycle which contributes to the enhancement of tumor progression. Here we review the specific roles and the interplay between TGF-β and uPA system in cancer cells and their implication in skin cancer.

Fibulin-5 binds urokinase-type plasminogen activator and mediates urokinase-stimulated β1-integrin-dependent cell migration

uPA (urokinase-type plasminogen activator) stimulates cell migration through multiple pathways, including formation of plasmin and extracellular metalloproteinases, and binding to the uPAR (uPA receptor; also known as CD87), integrins and LRP1 (low-density lipoprotein receptor-related protein 1) which activate intracellular signalling pathways. In the present paper we report that uPA-mediated cell migration requires an interaction with fibulin-5. uPA stimulates migration of wild-type MEFs (mouse embryonic fibroblasts) (Fbln5+/+ MEFs), but has no effect on fibulin-5-deficient (Fbln5-/-) MEFs. Migration of MEFs in response to uPA requires an interaction of fibulin-5 with integrins, as MEFs expressing a mutant fibulin-5 incapable of binding integrins (Fbln(RGE/RGE) MEFs) do not migrate in response to uPA. Moreover, a blocking anti-(human β1-integrin) antibody inhibited the migration of PASMCs (pulmonary arterial smooth muscle cells) in response to uPA. Binding of uPA to fibulin-5 generates plasmin, which excises the integrin-binding N-terminal cbEGF (Ca2+-binding epidermal growth factor)-like domain, leading to loss of β1-integrin binding. We suggest that uPA promotes cell migration by binding to fibulin-5, initiating its cleavage by plasmin, which leads to its dissociation from β1-integrin and thereby unblocks the capacity of integrin to facilitate cell motility.

Regulation of arterial remodeling and angiogenesis by urokinase-type plasminogen activatorThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue)

A wide variety of disorders are associated with an imbalance in the plasminogen activator system, including inflammatory diseases, atherosclerosis, intimal hyperplasia, the response mechanism to vascular injury, and restenosis. Urokinase-type plasminogen activator (uPA) is a multifunctional protein that in addition to its fibrinolytic and matrix degradation capabilities also affects growth factor bioavailability, cytokine modulation, receptor shedding, cell migration and proliferation, phenotypic modulation, protein expression, and cascade activation of proteases, inhibitors, receptors, and modulators. uPA is the crucial protein for neointimal growth and vascular remodeling. Moreover, it was recently shown to be implicated in the stimulation of angiogenesis, which makes it a promising multipurpose therapeutic target. This review is focused on the mechanisms by which uPA can regulate arterial remodeling, angiogenesis, and cell migration and proliferation after arterial injury and the means by which it modulates gene expression in vascular cells. The role of domain specificity of urokinase in these processes is also discussed.

Nuclear translocation of urokinase-type plasminogen activator

Urokinase-type plasminogen activator (uPA) participates in diverse (patho)physiological processes through intracellular signaling events that affect cell adhesion, migration, and proliferation, although the mechanisms by which these occur are only partially understood. Here we report that upon cell binding and internalization, single-chain uPA (scuPA) translocates to the nucleus within minutes. Nuclear translocation does not involve proteolytic activation or degradation of scuPA. Neither the urokinase receptor (uPAR) nor the low-density lipoprotein-related receptor (LRP) is required for nuclear targeting. Rather, translocation involves the binding of scuPA to the nucleocytoplasmic shuttle protein nucleolin through a region containing the kringle domain. RNA interference and mutational analysis demonstrate that nucleolin is required for the nuclear transport of scuPA. Furthermore, nucleolin is required for the induction smooth muscle alpha-actin (alpha-SMA) by scuPA. These data reveal a novel pathway by which uPA is rapidly translocated to the nucleus where it might participate in regulating gene expression.

Structural basis of interaction between urokinase-type plasminogen activator and its receptor

Recent studies indicate that binding of the urokinase-type plasminogen activator (uPA) to its high-affinity receptor (uPAR) orchestrates uPAR interactions with other cellular components that play a pivotal role in diverse (patho-)physiological processes, including wound healing, angiogenesis, inflammation, and cancer metastasis. However, notwithstanding the wealth of biochemical data available describing the activities of uPAR, little is known about the exact mode of uPAR/uPA interactions or the presumed conformational changes that accompany uPA/uPAR engagement. Here, we report the crystal structure of soluble urokinase plasminogen activator receptor (suPAR), which contains the three domains of the wild-type receptor but lacks the cell-surface anchoring sequence, in complex with the amino-terminal fragment of urokinase-type plasminogen activator (ATF), at the resolution of 2.8 A. We report the 1.9 A crystal structure of free ATF. Our results provide a structural basis, represented by conformational changes induced in uPAR, for several published biochemical observations describing the nature of uPAR/uPA interactions and provide insight into mechanisms that may be responsible for the cellular responses induced by uPA binding.

Production and purification of urokinase: A comprehensive review

An increased emphasis on prevention of fatalities due to thrombovascular disorders is broadening opportunities for several cardiovascular agents, especially plasminogen activators, for preventing strokes and heart attacks. Hence, urokinase, as one of the most potent plasminogen activators is attracting a great deal of attention. Developments in cell lines and bioprocess technology have made it possible to produce urokinase from in vitro cell culture. Attempts are now underway to enhance urokinase production from cell culture through media manipulation, bioreactor cultivation, and innovative purification techniques. Downstream processing also poses an intricate problem due to the complexity of cell culture extracts, susceptibility of urokinase to autocatalytic and proteolytic degradation and due to the presence of plasminogen activator inhibitors in the culture media. Hence, enhancing cellular productivity and downstream product recovery continue to be major challenges as discussed in this review. Furthermore, an approach for integrated upstream and downstream processing is needed to develop an economically viable technology. In the present review the emerging trends in urokinase production and purification have been discussed in detail.

The kringle domain of urokinase-type plasminogen activator potentiates LPS-induced neutrophil activation through interaction with {alpha}V{beta}3 integrins

Urokinase plasminogen activator (uPA) is a serine protease that catalyzes the conversion of plasminogen to plasmin. In addition, uPA has been shown to have proinflammatory properties, particularly in potentiating lipopolysaccharide (LPS)-induced neutrophil responses. To explore the mechanisms by which uPA exerts these effects, we examined the ability of specific uPA domains to increase cytokine expression in murine and human neutrophils stimulated with LPS. Whereas the addition of intact uPA to neutrophils cultured with LPS increased mRNA and protein levels of interleukin-1beta, macrophage-inflammatory protein-2, and tumor necrosis factor alpha, deletion of the kringle domain (KD) from uPA resulted in loss of these potentiating effects. Addition of purified uPA KD to LPS-stimulated neutrophils increased cytokine expression to a degree comparable with that produced by single-chain uPA. Inclusion of the arginine-glycine-aspartic but not the arginine-glycine-glutamic peptide to neutrophil cultures blocked uPA kringle-induced potentiation of proinflammatory responses, demonstrating that interactions between the KD and integrins were involved. Antibodies to alpha(V) or beta(3) integrins or to the combination of alpha(V)beta(3) prevented uPA kringle-induced enhancement of expression of proinflammatory cytokines and also of adhesion of neutrophils to the uPA KD. These results demonstrate that the KD of uPA, through interaction with alpha(V)beta(3) integrins, potentiates neutrophil activation.

Activation of p38 MAP-kinase and caldesmon phosphorylation are essential for urokinase-induced human smooth muscle cell migration

We have explored intracellular pathways involved in the urokinase type plasminogen activator (urokinase or uPA)-stimulated migration of human airway smooth muscle cells (hAWSMC). Using a set of uPA mutants we found that protease activity, growth factor-like and kringle domains of uPA differentially contribute to activation of p42/p44erk1,2 and p38 MAP-kinases. Consistent with our earlier data [Mukhina et al., J. Biol. Chem. 275 (2000), 16450-16458], the kringle domain of uPA was sufficient and required to stimulate cell motility. Here we report that uPA mutants containing the kringle domain specifically activate the p38 MAP-kinase pathway and actomyosin by increasing phosphorylation of the critical Ser-19 on the myosin regulatory light chain and MAP-kinase sites of the actin-associated regulatory protein caldesmon. While pharmacological inhibition of p38 MAP-kinase activation did not affect myosin light chain phosphorylation, it blocked the increase in caldesmon phosphorylation and uPA-stimulated migration of hAWSMC on a collagen-coated surface. We conclude that activation of p38 MAP-kinase and downstream phosphorylation of non-muscle caldesmon is essential for urokinase-stimulated smooth muscle cell migration.