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Thromb Haemost 1989; 62(02): 667-672
DOI: 10.1055/s-0038-1646880
Original Article
Schattauer GmbH Stuttgart

Binding and Degradation of Tissue-Type Plasminogen Activator by the Human Hepatoma Cell Line Hep G2

M Otter
1   The Gaubius Institute TNO, Leiden, The Netherlands
,
Th J C Van Berkel
2   The Division of Biopharmaceutics, Center for Bio-Pharmaceutical Sciences, Sylvius Laboratories, University of Leiden, The Netherlands
,
D C Rijken
1   The Gaubius Institute TNO, Leiden, The Netherlands
› Author Affiliations
Further Information

Publication History

Received 06 October 1988

Accepted after revision 03 April 1989

Publication Date:
30 June 2018 (online)

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Summary

In this study, binding and degradation of tissue-type plasminogen activator (t-PA) by the human hepatoma cell line Hep G2 was investigated. Binding at 4° C was time-dependent and reached a maximum after ca. 2 hours. Scatchard analysis of saturation experiments showed about 170,000 high affinity binding sites for t-PA per cell with an apparent Kd of 90 nM. These binding sites were calcium-dependent. Part of the binding to the hepatoma cells was non-saturable, owing to a large amount of low affinity binding sites which are at least partially located on the extracellular matrix of the cells. Competition with mannose- and galactose-terminated glycoproteins had no effect on total binding of 125I-t-PA. Degradation products of 125I-t-PA were found in the supernatant after a short lag phase and then increased linearly for at least 5 hours at 37° C. Degradation could be inhibited by chloroquine, NH4Cl and NaN3. We conclude that the human hepatoma cell line Hep G2 has a specific binding mechanism for t-PA which is not mediated by known carbohydrate receptor systems. Binding is followed by cellular uptake and degradation in the lysosomes.

Keywords

Plasminogen activator - Tissue-type plasminogen activator - Catabolism - Receptor binding - Hep G2
 

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