Binding and degradation of tissue-type plasminogen activator by the human hepatoma cell line Hep G2
article
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
Topics
TNO Identifier
230795
ISSN
03406245
Source
Thrombosis and Haemostasis, 62(2), pp. 667-672.
Pages
667-672
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