Title
Binding and degradation of tissue-type plasminogen activator by the human hepatoma cell line Hep G2
Author
Otter, M.
van Berkel, T.J.C.
Rijken, D.C.
Gaubius Instituut TNO
Publication year
1989
Abstract
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. Chemicals/CAS: tissue plasminogen activator, 105913-11-9; Calcium, 7440-70-2; Tissue Plasminogen Activator, EC 3.4.21.68
Subject
Biology
catabolism
cell culture
cell line
liver cell carcinoma
priority journal
Binding, Competitive
Calcium
Human
Liver
Protein Binding
Support, Non-U.S. Gov't
Tissue Plasminogen Activator
Tumor Cells, Cultured
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TNO identifier
230795
ISSN
0340-6245
Source
Thrombosis and Haemostasis, 62 (2), 667-672
Document type
article