Evidence for membrane association of plasminogen activator activity in mouse macrophages

Solomon, James A.; Chou, Iih Nan; Schroder, Edward W.; Black, Paul H.

doi:10.1016/0006-291x(80)91256-5

Cited by 26 publications

(9 citation statements)

References 22 publications

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“…However, in a study of HT-1080 cells PA of non-determined type was found associated solely with a cellular fraction representing either the Golgi apparatus or secretory granules rather than plasma membrane (39). Interestingly, either u-PA or PA of nondetermined type from several cell lines includ- ing HT-1080, has been found resistant to various solubilization procedures that would be expected to solubilize nonmembrane integrated proteins (28,39,41,43,57,69). As for the light microscopic studies the subcellular distribution of u-PA differs greatly in different cell types (38,67).…”

Section: Discussionmentioning

confidence: 99%

Distinct localizations of urokinase-type plasminogen activator and its type 1 inhibitor under cultured human fibroblasts and sarcoma cells

Pöllänen¹,

Saksela²,

Salonen³

et al. 1987

The Journal of Cell Biology

296

127

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Abstract. We studied the immunocytochemical localization of urokinase-type plasminogen activator (u-PA) and the type 1 plasminogen activator inhibitor (PAI-1) in human fibroblasts and sarcoma cells, using both polyclonal and monoclonal antibodies. The u-PA was found to be located at discrete cell-substratum contact sites, and also at areas of cell-cell contacts, whereas PAI-1 was distributed as a homogenous carpet excluding strialike areas on the substrate under the cells. To confirm the extracellular localization of u-PA and PAIl, we stained the cells live at 0°C before fixation. A double-labeling experiment showed different distribution of u-PA and PAI-1 under the cells, and especially their peripheral parts. The staining pattern of u-PA and PAI-1 resisted treatment with 0.2% saponin followed by mechanical removal of cells, a method previously reported to isolate focal contact membranes of fibroblasts. We further demonstrated the deposition of u-PA to the contact areas of cells obtained by saponin treatment by zymography, and that of PAI-1 by metabolic labeling, reverse zymography, immunoblotting, and immunoprecipitation. Fibronectin was also present in the preparations. The deposition of both PAI-1 and fibronectin by the sarcoma cells was enhanced, after treating the cells with 10 -6 M dexamethasone. The confinement of u-PA to discrete contact sites and the more uniform distribution of PAI-1 on the cell substratum may explain how cells producing large amounts of enzyme inhibitors can produce PAmediated focal proteolysis.

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Section: Discussionmentioning

confidence: 99%

Distinct localizations of urokinase-type plasminogen activator and its type 1 inhibitor under cultured human fibroblasts and sarcoma cells

Pöllänen¹,

Saksela²,

Salonen³

et al. 1987

The Journal of Cell Biology

296

127

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“…An association of uPA activity with cell membranes was noted in early studies (Quigley, 1976;Dvorak et al, 1978;Jaken and Black, 1979;Solomon et al, 1980), although without characterizing the binding site. As a defined component, uPAR was recognized in 1985 as a specific and saturable binding site for uPA on human monocytes and monocyte-like U937 cells (Vassalli et al, 1985;Stoppelli et al, 1985) and on cultured fibroblasts (Bajpai and Baker, 1985), binding uPA with a K d of 0.1 to 1 nM and typically occurring with 10 4 to 10 6 copies per cell.…”

Section: Upar: the Specific Cellular Receptor For Upamentioning

confidence: 95%

The urokinase receptor (uPAR) and the uPAR-associated protein (uPARAP/ Endo180): membrane proteins engaged in matrix turnover during tissue remodeling

Behrendt

2004

Biological Chemistry

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The breakdown of the barriers formed by extracellular matrix proteins is a pre-requisite for all processes of tissue remodeling. Matrix degradation reactions take part in specific physiological events in the healthy organism but also represent a crucial step in cancer invasion. These degradation processes involve a highly organized interplay between proteases and their cellular binding sites as well as specific substrates and internalization receptors. This review article is focused on two components, the urokinase plasminogen activator receptor (uPAR) and the uPAR-associated protein (uPARAP, also designated Endo180), that are considered crucially engaged in matrix degradation. uPAR and uPARAP have highly diverse functions, but on certain cell types they interact with each other in a process that is still incompletely understood. uPAR is a glycosyl-phosphatidylinositol-anchored glycoprotein on the surface of various cell types that serves to bind the urokinase plasminogen activator and localize the activation reactions in the proteolytic cascade system of plasminogen activation. uPARAP is an integral membrane protein with a pronounced role in the internalization of collagen for intracellular degradation. Both receptors have additional functions that are currently being unraveled. The present discussion of uPAR and uPARAP is centered on their protein structure and molecular and cellular function.

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“…That PA may be involved enzymatically at the cell membrane is supported by the following. First, PA is associated with and is firmly bound to cell membranes, including the plasma membrane (20,21), and is also secreted into the extracellular environment. Also, PA retains activity-at the cell surface despite the approximation of proteinase inhibitors in the serum (22).…”

mentioning

confidence: 99%

Down-regulation of epidermal growth factor receptor correlates with plasminogen activator activity in human A431 epidermoid carcinoma cells.

Gross¹,

Krupp²,

Db³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

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Human A431 epidermoid carcinoma cells in culture exhibit epidermal growth factor (EGF)-induced "down-regulation" of cell-surface and total cellular (Triton X-100 extractable) EGF receptors caused entirely by an enhanced rate (4-fold) of receptor inactivation [Krupp, M. N., Connolly, D. T. & Lane, M. D. (1982) J. Biol. Chem. 257, 11489-11496]. The following observations show that this enhanced rate of EGF receptor inactivation is closely correlated with an increased cellular activity of plasminogen activator (PA), a serine protease. First, EGF-induced down-regulation of cell-surface and total cellular EGF receptors and the concomitant increase in cellular PA activity occur with identical kinetics, the tl/2 for both processes being 3-3.5 hr.Second, the EGF dose-response curves for down-regulation of total cellular EGF receptor and increased PA activity are similar. The EGF concentrations for half-maximal responses of both processes are 10-15 nM and 20 nM, respectively. Third, the removal of EGF from previously down-regulated cells results in the recovery of total cellular EGF binding activity with a concurrent loss of cellular PA activity. Fourth, blocking PA synthesis or activity with cycloheximide or dexamethasone prevents down-regulation of the EGF receptor. Fifth, the addition of leupeptin, an inhibitor of PA and plasmin action, blocks EGF-induced receptor downregulation as well as the increase of PA activity. That EGF receptor down-regulation is independent of plasminogen per se in the culture medium suggests that PA-mediated events may initiate the rapid inactivation of the EGF receptor that occurs during downregulation.The interaction of epidermal growth factor (EGF), a polypeptide hormone, with specific cell-surface receptors initiates numerous biochemical events (1) in target cells, most notably mitogenesis (2). Such factors as the period of exposure to EGF, the concentration of EGF, and the level of functional receptors at the plasma membrane affect the magnitude of ligand-receptor interactions and, thus, the cellular response to EGF (3-5). It has been established that cells can modulate their level of surface EGF receptors in response to EGF and thereby alter the biological response to this potent mitogen (3-5).Like other receptors for polypeptide hormones (6), the EGF receptor exhibits ligand-induced "down-regulation" of cell-surface EGF binding capacity (3-5). This negative modulation of EGF receptor level in vitro is rapid, EGF concentration dependent, and EGF specific and occurs in many cell types (1, 3, 5). Reduced EGF binding capacity is the result of a lowered EGF receptor level rather than an altered affinity of the EGF receptor for its ligand (3,5 Although the mechanism by which ligand-induced downregulation promotes EGF receptor inactivation is unknown, there is some evidence with another cell-surface receptor that proteolysis modulates receptor metabolism. When proteolysis in chicken myogenic cultures is induced by chemical or viral transformation, both the steady-state concentratio...

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Evidence for membrane association of plasminogen activator activity in mouse macrophages

Cited by 26 publications

References 22 publications

Distinct localizations of urokinase-type plasminogen activator and its type 1 inhibitor under cultured human fibroblasts and sarcoma cells

Distinct localizations of urokinase-type plasminogen activator and its type 1 inhibitor under cultured human fibroblasts and sarcoma cells

The urokinase receptor (uPAR) and the uPAR-associated protein (uPARAP/ Endo180): membrane proteins engaged in matrix turnover during tissue remodeling

Down-regulation of epidermal growth factor receptor correlates with plasminogen activator activity in human A431 epidermoid carcinoma cells.

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