Very low density lipoprotein receptor binds and mediates endocytosis of urokinase-type plasminogen activator-type-1 plasminogen activator inhibitor complex.
Very low density lipoprotein receptor (VLDL-R) was found to be expressed in bovine mammary gland and the human breast carcinoma cell line MCF-7 as an M(r) 105,000 variant, and in Chinese hamster ovary (CHO) cells transfected with human VLDL-R cDNA as an M(r) 130,000 variant. The receptor was purified by ligand affinity chromatography with immobilized M(r) 40,000 receptor-associated protein (RAP). The purified receptor was found to bind urokinase-type plasminogen activator-type-1 plasminogen activator inhibitor complex (u-PA.PAI-1), while there was no or very weak binding of active site blocked u-PA (DFP-u-PA), PAI-1 or u-PA-type-2 plasminogen activator inhibitor complex. The binding of u-PA.PAI-1 was blocked by RAP. The transfected CHO cells had an efficient, RAP-sensitive endocytosis of u-PA.PAI-1, severalfold higher than non-transfected parental CHO cells. u-PA.PAI-1 endocytosis was partially inhibited by DFP-u-PA, which blocks binding of the complex to the u-PA receptor. RAP and DFP-u-PA sensitive u-PA.PAI-1 endocytosis was also observed in MCF-7 cells, which were without detectable levels of other RAP-binding endocytosis receptors. These results show that VLDL-R represents a novel endocytosis mechanism for u-PA receptor-bound u-PA.PAI-1.
Heegaard
C W
CW
Department of Molecular Biology, University of Aarhus, Denmark.
Simonsen
A C
AC
Oka
K
K
Kjøller
L
L
Christensen
A
A
Madsen
B
B
Ellgaard
L
L
Chan
L
L
Andreasen
P A
PA
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001943:Breast Neoplasms; D016466:CHO Cells; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004705:Endocytosis; D014644:Genetic Variation; D006801:Humans; D007700:Kinetics; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D011973:Receptors, LDL / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D008079:Lipoproteins, VLDL; D010455:Peptides; D017395:Plasminogen Activator Inhibitor 1; D011973:Receptors, LDL; D011994:Recombinant Proteins; C036053:VLDL receptor; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate