Role Of Plasminogen Activator Research Articles

C-terminal lysine residues enhance plasminogen activation by inducing conformational flexibility and stabilization of activator complex of staphylokinase with plasmin

Staphylokinase (SAK), a potent fibrin-specific plasminogen activator secreted by Staphylococcus aureus, carries a pair of lysine at the carboxy-terminus that play a key role in plasminogen activation. The underlaying mechanism by which C-terminal lysins of SAK modulate its function remains unknown. This study has been undertaken to unravel role of C-terminal lysins of SAK in plasminogen activation. While deletion of C-terminal lysins (Lys135, Lys136) drastically impaired plasminogen activation by SAK, addition of lysins enhanced its catalytic activity 2–2.5-fold. Circular dichroism analysis revealed that C-terminally modified mutants of SAK carry significant changes in their beta sheets and secondary structure. Structure models and RING (residue interaction network generation) studies indicated that the deletion of lysins has conferred extensive topological alterations in SAK, disrupting vital interactions at the interface of SAK.plasmin complex, thereby leading significant impairment in its functional activity. In contrast, addition of lysins at the C-terminus enhanced its conformational flexibility, creating a stronger coupling at the interface of SAK.plasmin complex and making it more efficient for plasminogen activation. Taken together, these studies provided new insights on the role of C-terminal lysins in establishment of precise intermolecular interactions of SAK with the plasmin for the optimal function of activator complex.

Commentary on “Elevated plasma levels of plasminogen activator inhibitor‐1 are associated with risk of future incident venous thromboembolism”: A new role for plasminogen activator inhibitor‐1—An inhibitor of fibrinolysis predicts future venous thromboembolic events and links them to obesity

Commentary on “Elevated plasma levels of plasminogen activator inhibitor‐1 are associated with risk of future incident venous thromboembolism”: A new role for plasminogen activator inhibitor‐1—An inhibitor of fibrinolysis predicts future venous thromboembolic events and links them to obesity

The Plasminogen Activator System, Glucocorticoid, and Mineralocorticoid Receptors in the Primate Endometrium During Artificial Menstrual Cycles.

As a key mechanism in fibrinolysis and tissue remodeling, the plasminogen activator system has been suggested in the process of endometrial shedding and tissue remodeling. Previous studies have explored the role of estrogen, progesterone, and androgen receptors as well as elements of the renin-angiotensin-aldosterone system in shaping the morphology of the endometrium. This study investigates the distribution and concentrations of the mineralocorticoid receptor, glucocorticoid receptor, tissue plasminogen activator, urokinase plasminogen activator, and plasminogen activator inhibitor-1 within the endometrial stroma, glandular, and endothelial cells of the primate endometrium during artificial menstrual cycles. Our immunohistochemistry quantification shows mineralocorticoid and glucocorticoid receptors are ubiquitously distributed within the macaque endometrium with their patterns of expression following similar fluctuations to urokinase and tissue plasminogen activators particularly within the endometrial vasculature. These proteins are present in endometrial vasculature in high levels during the proliferative phase, decreasing levels during the secretory phase followed by rising levels in the menstrual phase. These similarities could suggest overlapping pathways and interactions between the plasminogen activator system and the steroid receptors within the endometrium. Given the anti-inflammatory properties of glucocorticoids and the role of plasminogen activators in endometrial breakdown, the glucocorticoid receptor may be contributing to stabilizing the endometrium by regulating plasminogen activators during the proliferative phase and menstruation. Furthermore, given the anti-mineralocorticoid properties of certain anti-androgenic progestins and their reduced unscheduled uterine bleeding patterns, the mineralocorticoid receptor may be involved in unscheduled endometrial bleeding.

Role of plasminogen activator inhibitor-1 in the diagnosis and prognosis of patients with Parkinson's disease.

Parkinson's disease is a neurodegenerative disease that frequently results in memory disorders, cognitive decline and dementia. Previous studies have reported that plasminogen activator inhibitor-1 (PAI-1) serves an important role in cardiovascular disease risk, adiposity, insulin resistance and inflammation. However, the role of PAI-1 in diagnosis and prognosis of patients with Parkinson's disease following deep brain stimulation (DBS) has not reported, to the best of our knowledge. Therefore, the purpose of the present study was to investigate the clinical significance of PAI-1 in patients with Parkinson's disease. Plasma PAI-1 levels were measured in 102 patients with Parkinson's disease who underwent DBS. It was demonstrated that plasma PAI-1 levels were significantly increased in patients with Parkinson's disease compared with healthy individuals (P<0.01). Patients with Parkinson's disease received DBS presented significantly improved cognitive competence compared with controls (P<0.01). DBS significantly decreased plasma PAI-1 levels in patients with Parkinson's disease compared with controls (P<0.05). It was also observed that plasma PAI-1 levels were significantly negatively associated with cognitive function for patients with Parkinson's disease (P<0.01). In conclusion, these findings demonstrated that the degree of Parkinson's disease severity is positively associated with circulating levels of plasma PAI-1 levels, which suggests that PAI-1 may be a potential diagnostic and prognostic marker for patients with Parkinson's disease.

Activators of tissue and urokinase types plasminogen in basal cell skin cancer.

e22220 Background: Researches have demonstrated the role of plasminogen activators in processes of progression in various neoplasms. However, the contemporary authors give little coverage to this i...

A Role of Plasminogen Activators in Animal Reproductive Cells and Organs

A Role of Plasminogen Activators in Animal Reproductive Cells and Organs

Effect of Glycated LDL on Monocyte Adhesion on Vascular Endothelial Cells: Role of Plasminogen Activator Inhibitor‐1

Diabetes accelerates the development of atherosclerotic cardiovascular diseases. Inflammation on endothelium plays a key role in atherosclerosis. Monocyte adhesion is the earliest event of vascular inflammation. Elevated levels of glycated low density lipoprotein (gLDL) were detected in diabetic patients. We previously demonstrated that gLDL increased the expression of plasminogen activator inhibitor‐1 (PAI‐1) in vascular endothelial cells (EC). PAI‐1 is the physiological inhibitor of tissue and urokinase activators, and a marker of inflammation and endothelial dysfunction. The results of the present study demonstrated that pre‐incubation with gLDL significantly increased the adhesion of THP‐1 monocytes on the surface of cultured human umbilical vein EC (HUVEC) with a peak at 100 μg/ml for 6 h. Transfection of short interference RNA (siRNA) for PAI‐1 to EC prevented gLDL‐induced monocyte adhesion on EC. Scrumble siRNA did not inhibit gLDL‐induced monocyte adhesion on EC. Increased monocyte adhesion on aorta was detected in leptin receptor‐deficient (db/db) diabetic mice. The results of the present study suggest that diabetes‐associated metabolic disorders may promote the adhesion of monocytes to vascular endothelium, and PAI‐1 is required for glyLDL‐induced monocyte adhesion to vascular EC (supported by CDA and CIHR).

Fertilization outcome could be regulated by binding of oviductal plasminogen to oocytes and by releasing of plasminogen activators during interplay between gametes

To detect plasminogen and plasminogen activators (PA) in oviduct and oocytes and to clarify the role of the plasminogen/plasmin system on mammalian fertilization. Experimental prospective study. Mammalian reproduction research laboratory. Oviducts and ovaries from porcine and bovine females were collected at slaughterhouse. A total of 52 oviducts and 2,292 oocytes were used. Boar and bull ejaculated spermatozoa were also used. Plasminogen concentration in oviductal fluid (OF) through the cycle was measured. Immunolocalization of plasminogen and PAs in oocytes was carried out before and after fertilization. Porcine and bovine oocytes were in vitro fertilized, with plasminogen and plasmin added to the culture medium at different concentrations. Plasminogen concentration in OF. Plasminogen and PAs immunolocalization in oocytes. Penetration and monospermy rates, number of spermatozoa in the ooplasma and on the zona pellucida (ZP) after IVF. Oviductal fluid contains about 92 μg/mL of plasminogen. The mature oocyte shows immunoreactivity toward plasminogen and toward PAs on its oolemma and ZP. After fertilization, plasminogen and PAs immunolabeling decreases in the oocyte, suggesting its conversion into plasmin. When exogenous plasminogen is added to the IVF medium, sperm entry into the oocyte is hampered, suggesting that the role of plasminogen activation during fertilization is to reduce the number of (or to select) penetrating spermatozoa. The plasminogen/plasmin system is activated during gamete interaction and regulates the sperm entry into the oocyte.

(Patho)physiological consequences of interactions of amyloid-β with cellular and non-cellular proteins; the role of “The Crossbeta Pathway”.

Misfolding is an inherent and potentially problematic property of proteins. Misfolded proteins tend to aggregate and the deposition of aggregated proteins, termed amyloid, is associated with a variety of highly debilitating diseases known as amyloidoses, which includes Alzheimer's disease. In Alzheimer's disease amyloid-ß is considered to contribute to disease pathology. However, how amyloid-ß is normally cleared on the one hand, and how amyloid-ß induces cellular toxicity on the other end remains still unclear. First, several misfolded proteins with amyloid properties, including amyloid-ß, were tested in vitro for their ability to activate tPA-mediated plasminogen activation and FXII-mediated prekallikrein activation. Second, known FXII-activation surfaces were tested for their ability to form amyloid-like properties. Third, plasma of amyloidosis patients were analyzed for the presence of products of tPA and FXII activation. Fourth, the role of plasminogen activation on the effect of amyloid-ß on neurons was studied. A unique characteristic of misfolding in protein aggregation is the formation of crossbeta structure. In recent years we have identified proteins, including two homologous proteases, factor XII (FXII) and tissue-type plasminogen activator (tPA) that specifically recognize misfolded proteins, including amyloid-ß. Factor XII was known as initiator of the contact system, an enzymatic cascade in blood that was known to become activated when blood contacts ‘surface’ materials, but its physiological activator remained elusive. We found that FXII is activated by misfolded proteins with crossbeta structure and that this specifically leads to the formation of kallikrein in vitro and in patients with systemic amyloidosis. These results identified misfolded proteins as activators of FXII and have solved the paradoxical role of FXII in coagulation. Besides FXII we have demonstrated that tPA is activated by misfolded proteins with crossbeta structure in general. We also identified amyloid-binding cellular receptors. Our discoveries have uncovered new roles for the fibrinolytic system (tPA), the contact activation system (FXII) and cellular receptors, which open avenues for the development of novel disease modifying agents.

Role of plasminogen activation in neuronal organization and survival

We characterized the interactions between plasminogen and neurons and investigated the associated effects on extracellular matrix proteolysis, cell morphology, adhesion, signaling and survival. Upon binding of plasminogen to neurons, the plasmin formed by constitutively expressed tissue plasminogen activator (tPA) degrades extracellular matrix proteins, leading to retraction of the neuron monolayer that detaches from the matrix. This sequence of events required both interaction of plasminogen with carboxy-terminal lysine residues and the proteolytic activity of plasmin. Surprisingly, 24 h after plasminogen addition, plasmin-detached neurons survived and remained associated in clusters maintaining focal adhesion kinase phosphorylation contrasting with other adherent cell types fully dissociated by plasmin. However, long-term incubation (72 h) with plasminogen was associated with an increased rate of apoptosis, suggesting that prolonged exposure to plasmin may cause neurotoxicity. Regulation of neuronal organization and survival by plasminogen may be of pathophysiological relevance, as plasminogen is expressed in the brain and/or extravasate during vascular accidents or inflammatory processes.

Role of plasminogen activator in spinal cord remodeling after spinal cord injury

Plasminogen activators play an active role in synaptic plasticity associated with the crossed phrenic phenomenon (CPP) and recovery of respiratory function following spinal cord injury. A genetic approach has been used to identify molecular mechanisms underlying this synaptic plasticity. Knockout mice lacking different genes in the plasminogen activator/plasmin system demonstrate that expression of urokinase plasminogen activator (uPA) is required during the critical 1-2h delay period following C2-hemisection for the acquisition of a good CPP response. uPA knockout mice fail to show the structural remodeling of phrenic motorneuron synapses that underlie the CPP response. Potential mechanisms by which uPA may promote phrenic motorneuron synaptic plasticity have been explored. Expression of uPA receptors, uPAR and LRP-1, are both up-regulated in the ipsilateral phrenic motor nucleus (PMN) following C2-hemisection. A comparison of microarray data and real-time PCR analysis of mRNAs induced in the PMN after hemisection indicate potential cell signaling pathways downstream of uPA's interaction with these cell surface receptors in the PMN. Knowledge of these uPA-mediated signaling pathways may identify potential means for the pharmacological activation of the synaptic plasticity required for recovery of phrenic motorneuron activity.

New role of plasminogen activator inhibitor‐1 in alcohol‐induced liver injury

Plasminogen activator inhibitor-1 (PAI-1) is the main inhibitor of plasminogen activators, thereby playing a major role in fibrinolysis. Whereas hyperfibrinolysis is common in alcoholic cirrhosis, hypofibrinolysis (driven mostly by elevated levels of PAI-1) is common during the development of alcoholic liver disease (ALD). However, whether or not PAI-1 plays a causal role in the development of ALD has been unclear. The role of PAI-1 was therefore investigated in models of early (steatosis), intermediate (inflammation/necrosis) and late (fibrosis) stages of alcoholic liver disease. For example, hepatic steatosis caused by both acute and chronic ethanol was blunted by inhibiting PAI-1 activation. This effect of inhibiting PAI-1 appears to be mediated, at least in part, by an increase in very low-density lipoprotein (VLDL) synthesis in the absence of PAI-1. The results from that study also indicated that PAI-1 plays a critical role in both acute and chronic hepatic inflammation. Lastly, knocking out PAI-1 potently protected against experimental hepatic fibrosis; the mechanism of this protective effect appears to be mediated predominantly by extracellular matrix (ECM) resolution by matrix metalloproteases, which are indirectly inhibited by PAI-1. In summary, targeting PAI-1 protects against all three stages of ALD in model systems. The mechanisms by which PAI-1 contributes to these disease stages appear to not only involve the 'classical' function of PAI-1 (i.e. in mediating fibrinolysis), but also other functions of this protein. These data support a role of PAI-1 in the initiation and progression of ALD, and suggest that PAI-1 may be a useful target for clinical therapy to halt or blunt disease progression.

Conflicting Results from Clinical Observations and Murine Models: What Is the Role of Plasminogen Activators in Tumor Growth?

Tissue invasion and metastasis can compromise vital body functions and are the main causes of death from cancer. By invading locally and dislodging cells or fragments to distant sites, primary tumors can access a rich supply of oxygen and nutrients that is limited at the primary site. Invasion and metastasis are exceedingly complex and incompletely understood multistep processes. Often, they are accompanied by the activation of proteases, which degrade proteins that tether tumor cells to surrounding cells and extracellular matrix. By changing the physical coupling of tumor cells to their microenvironment, proteases are thought to promote local cancer spread and formation of metastases ( 1 – 3 ) . Proteases can also promote tumor angiogenesis ( 4 ) and stimulate tumor cell growth ( 5 , 6 ) . Invasive tumor cells and reactive stromal cells recruited to the tumor site secrete proteinases such as matrix metalloproteinases (MMPs) and their endogenous tissue inhibitors (TIMPs), urokinasetype plasminogen activator (uPA) and its inhibitors (PAIs), and cathepsins. Many studies have focused on the precise identifi cation of these enzymes, evaluation of their contribution to tumor pathogenesis, predictive prognostic value, and their potential as therapeutic targets. Considerable progress has been made. We now know, for example, that many MMPs and TIMPs secreted by cancer cells can facilitate tumor invasion and that elevated serum TIMP-1 levels are associated with poor cancer survival ( 7 , 8 ) . We also know that active enzymes of the cysteine cathepsin family localize to the invasive front of tumors and to the angiogenic tumor vasculature ( 9 ) . Importantly, we have learned from several large studies that high tumor levels of uPA and its inhibitor PAI-1 are poor prognostic factors for patients with breast cancer ( 10 – 12 ) and gastrointestinal, lung, brain, kidney, bladder, and soft tissue tumors ( 11 , 13 – 15 ) .

Direct interaction of the kringle domain of urokinase-type plasminogen activator (uPA) and integrin αvβ3 induces signal transduction and enhances plasminogen activation

It has been questioned whether there are receptors for urokinase-type plasminogen activator (uPA) that facilitate plasminogen activation other than the high affinity uPA receptor (uPAR/CD87) since studies of uPAR knockout mice did not support a major role of uPAR in plasminogen activation. uPA also promotes cell adhesion, chemotaxis, and proliferation besides plasminogen activation. These uPA-induced signaling events are not mediated by uPAR, but mediated by unidentified, lower-affinity receptors for the uPA kringle. We found that uPA binds specifically to integrin alpha v beta 3 on CHO cells depleted of uPAR. The binding of uPA to alpha v beta 3 required the uPA kringle domain. The isolated uPA kringle domain binds specifically to purified, recombinant soluble, and cell surface alpha v beta 3, and other integrins (alpha 4 beta 1 and alpha 9 beta 1), and induced migration of CHO cells in an alpha v beta 3-dependent manner. The binding of the uPA kringle to alpha v beta 3 and uPA kringle-induced alpha v beta 3-dependent cell migration were blocked by homologous plasminogen kringles 1-3 or 1-4 (angiostatin), a known integrin antagonist. We studied whether the binding of uPA to integrin alpha v beta 3 through the kringle domain plays a role in plasminogen activation. On CHO cell depleted of uPAR, uPA enhanced plasminogen activation in a kringle and alpha v beta 3-dependent manner. Endothelial cells bound to and migrated on uPA and uPA kringle in an alpha v beta 3-dependent manner. These results suggest that uPA binding to integrins through the kringle domain plays an important role in both plasminogen activation and uPA-induced intracellular signaling. The uPA kringle-integrin interaction may represent a novel therapeutic target for cancer, inflammation, and vascular remodeling.

Effects of Pseudomonas fluorescens M3/6 Bacterial Protease on Plasmin System and Plasminogen Activation

Heat-stable proteases produced by the psychrotroph Pseudomonas fluorescens M3/6 have been shown to affect the plasmin system in milk, which in turn will affect the quality of processed milk. The M3/6 proteases cause dissociation of plasmin from casein in minimally processed milk. The objective of this work was to study the effect of M3/6 protease on the plasmin system, as well as its role in plasminogen activation, under commonly applied cheese-making conditions. Isolated M3/6 protease was added to raw milk, which then was pasteurized, and subjected to pH adjustments and CaCl2 addition. Casein and whey fractions were separated by chymosin treatment then analyzed for plasmin activity. Individual and interaction effects of M3/6 protease addition, pH treatment, and CaCl2 addition on plasmin activity were studied. Enzyme activity assays were carried out to study individually the effect of M3/6 protease on plasmin system components. Kinetic parameters were calculated to characterize the effect of M3/6 protease on plasminogen activation. Plasmin activity increased in the curd fractions of the protease-treated milk that was subjected to conditions most resembling cheese-making conditions, indicating that M3/6 protease triggered plasminogen activation rather than dissociation of plasmin from casein micelles. Results from the studies on plasminogen activation confirmed that the observed activation of plasminogen in protease-treated samples subjected to cheese making conditions was attributed to the stimulatory effect M3/6 protease had on plasminogen activators (PA). The M3/6 protease stimulated human and bovine PA by increasing their activity 4.5- and 2.5-fold, respectively. Similarly, the catalytic efficiencies of human urokinase-type PA and bovine PA were increased in the presence of M3/6 protease by 12- and 4-fold, respectively. Our research presented a basic step toward fully understanding the effect of bacterial proteases under different processing conditions, where the gathered information can aid in better control of processing conditions based on the desired outcome.

Tissue plasminogen activator is a potent activator of PDGF-CC.

Tissue plasminogen activator (tPA) is a serine protease involved in the degradation of blood clots through the activation of plasminogen to plasmin. Here we report on the identification of tPA as a specific protease able to activate platelet-derived growth factor C (PDGF-C). The newly identified PDGF-C is secreted as a latent dimeric factor (PDGF-CC) that upon proteolytic removal of the N-terminal CUB domains becomes a PDGF receptor alpha agonist. The CUB domains in PDGF-CC directly interact with tPA, and fibroblasts from tPA-deficient mice fail to activate latent PDGF-CC. We further demonstrate that growth of primary fibroblasts in culture is dependent on a tPA-mediated cleavage of latent PDGF-CC, generating a growth stimulatory loop. Immunohistochemical analysis showed similar expression patterns of PDGF-C and tPA in developing mouse embryos and in tumors, indicating both autocrine and paracrine modes of activation of PDGF receptor-mediated signaling pathways. The identification of tPA as an activator of PDGF signaling establishes a novel role for the protease in normal and pathological tissue growth and maintenance, distinct from its well-known role in plasminogen activation and fibrinolysis.

Differences in the implantation rates of rat embryos developed in vivo and in vitro: possible role for plasminogen activators

Objective To assess the participation of urokinase-type (uPA) and tissue-type (tPA) plasminogen activators in embryo development and implantation. Design The study was set to compare the activities of PAs in embryos developed in vivo and in vitro and their implantation rates. Endometrial PA activity was studied as well. Setting University laboratories. Patient(s) None. Intervention(s) None. Main outcome measure(s) Plasminogen activator activity in embryos. Result(s) Whereas tPA activity in in vivo-developed embryos decreased from the zygote to the blastocyst stages, it did not change in embryos developed in vitro. The activity of uPA was lowest in two-cell-stage embryos, both in vivo and in vitro, and increased as embryos developed into blastocysts. The activity of uPA in the in vitro-developed embroys was lower in all developmental stages as compared with those developed in vivo. Whereas endometrial tPA activity did not change during the preimplantation period, uPA activity increased gradually toward the time of implantation. The implantation rate of the in vitro-developed embryos was much lower than that of those developed in vivo. Conclusion(s) Taken together, these data indicate that in vitro embryo development leads to lower PA activities as compared with in vivo development. The increased activity of uPA toward the blastocyst stage supports uPA's role in the implantation process. Moreover, the rise in endometrial uPA might also indicate its importance in this process.

Role of plasminogen activators during healing after uterine serosal lesioning in the rat

Objective Study the expression pattern of tissue-type (t-PA) and urokinase-type (u-PA) plasminogen activators during uterine serosal healing after lesioning in a rat model. Design Descriptive study with an adhesion model using reverse transcriptase-polymerase chain reaction (PCR) and immuncytochemical techniques. Setting Academic medical center. Patient(s) None. Intervention(s) None. Main outcome measure(s) Expression profiles of t-PA and u-PA were examined in the uteroperitoneal adhesion tissues of rat from the time of injury until day 7 after surgery using relative abundance reverse transcriptase-PCR and immunocytochemical techniques. Result(s) The t-PA transcript levels dropped in uteroperitoneal tissues by 6 hours after surgery and remained low until day 5. Thereafter, a rapid up-regulation of this transcript was observed at day 7. In contrast, the u-PA transcript levels demonstrated a biphasic profile during the progression of adhesion development with peaks at 2 and 5 days after surgery. Immunocytochemical staining demonstrated expression of these plasminogen activators in the newly formed blood vessels. Conclusion(s) Altered levels of t-PA and u-PA transcripts and its expression in newly formed blood vessels during healing and adhesion development indicate involvement of these plasminogen activators in serosal healing and adhesion development.

Extracellular proteolysis in brain injury and inflammation: role for plasminogen activators and matrix metalloproteinases.

The role of intracellular proteases (e.g., calpains and caspases) in the pathophysiology of neuronal cell death has been extensively investigated. More recently, accumulating data have suggested that extracellular proteolysis also plays a critical role. The two major systems that modify the extracellular matrix in brain are the plasminogen activator (PA) and matrix metalloproteinase (MMP) axes. This Mini-Review delineates major pathways of PA and MMP action after stroke, brain trauma, and chronic inflammation. Deleterious effects include the disruption of blood-brain barrier integrity, amplification of inflammatory infiltrates, demyelination, and possibly interruption of cell-cell and cell-matrix interactions that may trigger cell death. In contrast, PA-MMP actions may contribute to extracellular proteolysis that mediates parenchymal and angiogenic recovery after brain injury. As the mechanisms of deleterious vs. potentially beneficial PA and MMP actions become better defined, it is hoped that new therapeutic targets will emerge for ameliorating the sequelae of brain injury and inflammation.

Plasminogen activators in vascular remodeling and angiogenesis.

This review considers cellular and molecular mechanisms of the involvement of plasminogen activators in extracellular proteolysis and cell migration and proliferation. The role of plasminogen activators in vascular remodeling in atherosclerosis, restenosis, and angiogenesis is discussed.