The down-regulation of the mitogenic fibrinogen receptor (MFR) in serum-containing medium does not occur in defined medium.
Normal human hemopoietic cells such as early bone marrow progenitors, or lymphoma-derived cell lines such as Raji or JM cells, possess a low-affinity receptor specific for fibrinogen. This receptor triggers a mitogenic effect. It differs from the glycoprotein IIb-IIIa which is involved in fibrinogen-induced platelet aggregation. We demonstrate here that this mitogenic fibrinogen receptor (MFR) can be internalized or reexpressed, depending on culture conditions. Internalization was temperature-dependent. At 37 degrees C in the presence of cycloheximide or actinomycin D, the half-life of cell surface MFRs was 2 h, independent of receptor occupancy. Binding of fibrinogen to the MFR resulted in a down-regulation which was fibrinogen dose-dependent. This occurred in serum-supplemented medium but not in defined medium supplemented with fatty acids. Reexpression of MFRs could be induced in 28 to 42 h by serum removal. The down-regulation of mitogenic receptors in plasma or serum could explain why normal cells do not proliferate in the peripheral blood.
Laboratoire de Biologie Cellulaire et Moléculaire des Facteurs de Croissance, C.N.R.S., Hôpital Paul Brousse, Villejuif, France.
J P
JP
Levesque
A
A
Hatzfeld
I
I
Domart
J
J
Hatzfeld
D001769:Blood; D002455:Cell Division; D002478:Cells, Cultured; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015536:Down-Regulation; D005340:Fibrinogen / Q000378:metabolism / Q000494:pharmacology*; D006207:Half-Life; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D007163:Immunosorbent Techniques; D007700:Kinetics; D008223:Lymphoma / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D003470:Culture Media; D010980:Platelet Membrane Glycoproteins; D003609:Dactinomycin; D005340:Fibrinogen; D003513:Cycloheximide