Characterization of the insulin-like growth factor (IGF) receptor in K562 erythroleukemia cells; evidence for a biological function for the type II IGF receptor.
Erythroleukemia cells (K562) were found to bind insulin-like growth factor-II (IGF-II) about 10 times as much as IGF-I, insulin and human growth hormone. The specific binding of IGF-II increased as a function of cell number in a range of 0.5-6 X 10(6) cell/ml. Kinetic studies revealed that binding was time and temperature dependent and showed a broad pH optimum. Specificity studies showed no inhibition of 125I-IGF-II binding by insulin or unrelated peptide hormones. The half-maximal inhibition of 125I-IGF-II binding to K562 cells was achieved at 87 and 28 ng/ml of IGF-I and IGF-II respectively. However, the addition of 7.5 and 1.7 ng/ml of unlabeled IGF-I and IGF-II respectively increased the binding of 125I-IGF-II by 55%. This 'hook' effect was greatly reduced when K562 cell membranes were used. Scatchard analysis of IGF-II binding showed a comparable equilibrium constant with either intact cells (Ka = 8.9 X 10(8) M-1) or microsomal membranes (Ka = 5.4 X 10(8) M-1). Cross-linking studies indicated that both 125I-IGF-II and 125I-IGF-I bound to an entity of 215 kDa which increased to 260 kDa under reducing conditions. Both IGF-I and II stimulated 3H-thymidine incorporation into K562 cells whereas insulin was without effect. These data show that both IGF-I and II bind predominantly to a type II-IGF receptor in K562 cells. Since both peptides stimulate 3H-thymidine incorporation in these cells it is possible that the type II-IGF receptor is mediating an anabolic biological response in these cells.
Blanchard
M M
MM
Department of Medicine, McGill University, Montreal, Canada.
Barenton
B
B
Sullivan
A
A
Foster
B
B
Guyda
H J
HJ
Posner
B I
BI
D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute; D011972:Receptor, Insulin / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA; D011972:Receptor, Insulin; D013936:Thymidine