Evidence that type II insulin-like growth factor receptor is coupled to calcium gating system.
In competent Balb/c 3T3 cells primed with epidermal growth factor (primed competent cells), insulin-like growth factor-II (IGF-II) stimulated calcium influx in a concentration dependent manner with the ED50 of 450 pM. When receptor-bound [125I]IGF-II was cross-linked by use of disuccinimidyl suberate, a 240 K-Da protein was radiolabeled. Excess amount of unlabeled IGF-II inhibited the affinity-labeling of the 240 K-Da protein. To further examine whether IGF-II stimulates calcium influx by acting on the type II IGF receptor, we employed polyclonal antibody raised against rat type II IGF receptor, R-II-PABl. This antibody immunoprecipitated the type II IGF receptor and inhibited IGF-II binding in Balb/c 3T3 cell membrane without affecting IGF-I binding. In primed competent cells, R-II-PABl elicited an agonistic action in stimulating [3H]thymidine incorporation. Under the same condition, R-II-PABl elicited a marked stimulation of calcium influx. These results suggest that, in Balb/c 3T3 cells, 1) relatively low concentrations of IGF-II act mainly on the type II IGF receptor; 2) the type II IGF receptor is coupled to a calcium gating system; and 3) binding of a ligand to the type II IGF receptor leads to the stimulation of DNA synthesis.
Kojima
I
I
Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan.
Nishimoto
I
I
Iiri
T
T
Ogata
E
E
Rosenfeld
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D011972:Receptor, Insulin / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*; D013388:Succinimides / Q000494:pharmacology
D003432:Cross-Linking Reagents; D007473:Ion Channels; D017451:Receptors, Somatomedin; D013002:Somatomedins; D013388:Succinimides; D007335:Insulin-Like Growth Factor II; D011972:Receptor, Insulin; D002118:Calcium; C019358:disuccinimidyl suberate