Factor VIIa binding and internalization in hepatocytes
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Factor VIIa binding and internalization in hepatocytes. / Hjortoe, G; Sorensen, B B; Petersen, L C; Rao, L.V.M.
In: Journal of Thrombosis and Haemostasis, Vol. 3, No. 10, 10.2005, p. 2264-73.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Factor VIIa binding and internalization in hepatocytes
AU - Hjortoe, G
AU - Sorensen, B B
AU - Petersen, L C
AU - Rao, L.V.M.
PY - 2005/10
Y1 - 2005/10
N2 - The liver is believed to be the primary clearance organ for coagulation proteases, including factor VIIa (FVIIa). However, at present, clearance mechanisms for FVIIa in liver are unknown. To obtain information on the FVIIa clearance mechanism, we investigated the binding and internalization of FVIIa in liver cells using a human hepatoma cell line (HEPG2), and primary rat and human hepatocytes as cell models. 125I-FVIIa bound to HEPG2 cells in a time- and dose-dependent manner. Anti-tissue factor antibodies reduced the binding by about 25%, whereas 50-fold molar excess of unlabeled FVIIa had no effect. HEPG2 cells internalized FVIIa with a rate of 10 fmol 10(-5) cells h(-1). In contrast to HEPG2 cells, FVIIa binding to primary rat hepatocytes was completely independent of TF, and excess unlabeled FVIIa partly reduced the binding of 125I-FVIIa to rat hepatocytes. Further, compared with HEPG2 cells, three- to fourfold more FVIIa bound to rat primary hepatocytes, and the bound FVIIa was internalized at a faster rate. Similar FVIIa binding and internalization profiles were observed in primary human hepatocytes. Plasma inhibitors had no effect on FVIIa binding and internalization in hepatocytes. In contrast, annexin V, which binds to phosphatidylserine, blocked the binding and internalization. Consistent with this, binding of gla-domain-deleted FVIIa to hepatocytes was markedly diminished. In summary, the data presented herein reveal differences between HEPG2 cells and primary liver cells in FVIIa binding and internalization, and suggest that the rapid turnover of membrane and not a receptor-mediated endocytosis may be responsible for internalization of FVII/FVIIa in primary hepatocytes.
AB - The liver is believed to be the primary clearance organ for coagulation proteases, including factor VIIa (FVIIa). However, at present, clearance mechanisms for FVIIa in liver are unknown. To obtain information on the FVIIa clearance mechanism, we investigated the binding and internalization of FVIIa in liver cells using a human hepatoma cell line (HEPG2), and primary rat and human hepatocytes as cell models. 125I-FVIIa bound to HEPG2 cells in a time- and dose-dependent manner. Anti-tissue factor antibodies reduced the binding by about 25%, whereas 50-fold molar excess of unlabeled FVIIa had no effect. HEPG2 cells internalized FVIIa with a rate of 10 fmol 10(-5) cells h(-1). In contrast to HEPG2 cells, FVIIa binding to primary rat hepatocytes was completely independent of TF, and excess unlabeled FVIIa partly reduced the binding of 125I-FVIIa to rat hepatocytes. Further, compared with HEPG2 cells, three- to fourfold more FVIIa bound to rat primary hepatocytes, and the bound FVIIa was internalized at a faster rate. Similar FVIIa binding and internalization profiles were observed in primary human hepatocytes. Plasma inhibitors had no effect on FVIIa binding and internalization in hepatocytes. In contrast, annexin V, which binds to phosphatidylserine, blocked the binding and internalization. Consistent with this, binding of gla-domain-deleted FVIIa to hepatocytes was markedly diminished. In summary, the data presented herein reveal differences between HEPG2 cells and primary liver cells in FVIIa binding and internalization, and suggest that the rapid turnover of membrane and not a receptor-mediated endocytosis may be responsible for internalization of FVII/FVIIa in primary hepatocytes.
KW - Animals
KW - Annexin A5
KW - Cell Line
KW - Cell Membrane
KW - Cells, Cultured
KW - Factor VIIa
KW - Hepatocytes
KW - Humans
KW - Phosphatidylserines
KW - Protein Binding
KW - Protein Transport
KW - Rats
KW - Thromboplastin
KW - Journal Article
KW - Research Support, N.I.H., Extramural
KW - Research Support, U.S. Gov't, P.H.S.
U2 - 10.1111/j.1538-7836.2005.01542.x
DO - 10.1111/j.1538-7836.2005.01542.x
M3 - Journal article
C2 - 16194204
VL - 3
SP - 2264
EP - 2273
JO - Journal of Thrombosis and Haemostasis
JF - Journal of Thrombosis and Haemostasis
SN - 1538-7933
IS - 10
ER -
ID: 182199422