Modifications of LDL-receptor-mediated endocytosis rates in CEM lymphoblastic cells grown in lipoprotein-depleted fetal calf serum.
The efficiency of supplying cholesterol by the LDL endocytic pathway of lymphoblastic T CEM cells was compared when incubated in the presence of either fetal calf serum (FCS) or lipoprotein-depleted fetal calf serum (LDFCS). In the presence of FCS, there were 8600 +/- 2000 LDL receptors/cell with a Kd of (2.2 +/- 0.8).10(-8) M and a receptor cycling time of about 7 min; about 90% of the internalized LDL was degraded. LDL degradation produced 98% of total cellular cholesterol and only 2% came from endogenous synthesis. The absence of LDL in the culture medium of lymphoblastic CEM cells deeply modified certain metabolic and structural characteristics of the cells. Their cholesterol content decreased; the total number of LDL receptors increased 6-fold, whereas their affinity for the ligand decreased by the same factor (Kd = (1.2 +/- 0.2).10(-7) M); the receptor cycling time increased 3-fold. Finally, LDL degraded by cholesterol-depleted CEM cells amounted to about 40% of that degraded by untreated CEM cells.
Sainte-Marie
J
J
U.A. 530, INSERM U.58, Montpellier, France.
Vidal
M
M
Sune
A
A
Ravel
S
S
Philippot
J R
JR
Bienvenüe
A
A
D002784:Cholesterol / Q000378:metabolism; D004705:Endocytosis; D005312:Fetal Blood / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D015458:Leukemia, T-Cell / Q000378:metabolism / Q000473:pathology; D008077:Lipoproteins, LDL / Q000502:physiology*; D011973:Receptors, LDL / Q000032:analysis / Q000502:physiology*; D014407:Tumor Cells, Cultured
D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D002784:Cholesterol