Plasmin

Robbins, Kenneth C.

doi:10.1007/978-3-642-66863-0_11

Cited by 3 publications

(2 citation statements)

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“…4). 12,1-Pg used in these studies did not contain Pm (i.e., no radioactivity migrated at a M, of 58 kDa which represents the heavy chain (HC) portion of Pm (Robbins, 1978). In the present study, aprotinin apparent1 inhibits the appearance of an apparent HC radioactive band at -68 kDa reflects the activation of 1251-G1~-Pg to 1251-GluPm, presumably by cell surface active uPA.…”

Section: -Pg Binding Experimentsmentioning

confidence: 53%

“…When bound to MG-63 cells, 1251-Pg was activated to Pm as evidenced by the appearance of the 58 kDa band of radioactivity. Using densimetric scans of autoradiographs to quantitate Pm formation, Pm HC formation in the presence of uPA antibodies was (Robbins, 1978). In the present study, aprotinin apparent1 inhibits the appearance of an apparent HC radioactive band at -68 kDa reflects the activation of 1251-G1~-Pg to 1251-Glu-Pm, presumably by cell surface active uPA.…”

Section: -Pg Binding Experimentsmentioning

confidence: 57%

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Binding and activation of plasminogen on the surface of osteosarcoma cells

Campbell

Yanosick

et al. 1994

Journal Cellular Physiology

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Plasmin (Pm) is a broad action serine protease implicated in numerous physiological functions. In bone, Pm may play a role in growth, resorption, metastasis, and the activation of growth factors. The various components of the Pm system are known to bind and function on the cell surface of various cell types, but no pertinent data are available describing membrane-bound Pm or its zymogen, plasminogen (Pg), in either normal or neoplastic bone cells. We report here that Pg binds to the surface of the human osteosarcoma cell line MG-63 and is activated to Pm by endogenous urokinase plasminogen activator (uPA). These conclusions are based on experiments utilizing radiolabeled compounds and a cell surface proteolytic assay measuring amidolytic activity of Pm. 125I-Pg binding to cells was time dependent, saturable, reversible, and specific. Binding was characterized by a relatively low affinity (Kd approximately 0.9 microM) and a high capacity (approximately 7.5 x 10(6) sites/cell). The binding of 125I-Pg was associated with lysine binding sites of the plasminogen molecule. Activation of 125I-Pg to 125I-Pm occurred on the cell surface and was dependent upon cell bound uPA, as determined by inhibitory antibodies. Binding of Pg to MG-63 monolayers represented approximately 80% bound specifically to the cell surface and the remainder to the surrounding extra-cellular matrix. Either co-incubation with uPA or pre-incubation with Pm resulted in increased 125I-Pg binding to osteosarcoma cells. Cell surface Pm proteolytic activity was confirmed by an amidolytic chromogenic assay. Both Pm and Pg bound to cells with Pg being activated by endogenous uPA. Plasmin activated on the cell surface was partially protected from inhibition by alpha 2-antiPm (requiring Pm lysine binding site interaction) but inhibited by aprotinin, (interacting directly with the Pm catalytic site). Resistance of cell bound Pm to alpha 2-antiPm inhibition suggests that cell surface proteolysis can occur in the presence of a soluble Pm inhibitor known to exist in the extracellular space. Based on these results, we speculate that the various bone physiological processes implicating Pm may occur at or near the bone cell surface.

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Section: -Pg Binding Experimentsmentioning

confidence: 53%

Section: -Pg Binding Experimentsmentioning

confidence: 57%