Characterization of induction of protooncogene c-myc and cellular growth in human vascular smooth muscle cells by insulin and IGF-I.
Insulin and insulin-like growth factor I (IGF-I) are structurally related polypeptides that stimulate DNA synthesis and cellular proliferation, probably through a common pathway. Human arterial smooth muscle cells in culture demonstrated the presence of high-affinity receptors for both these hormones. Insulin and IGF-I both exhibited cross-reactivity to each other's receptors but with an affinity that is 100-fold less than for the homologous receptor. To examine more closely the receptor responsible for producing the growth effects, we used the polyclonal antibody against the insulin receptor, B2, and a monoclonal antibody to the IGF-I receptor, alpha IR3. We studied the growth effects of insulin and IGF-I as measured by stimulation of c-myc, DNA synthesis, and cellular proliferation in the presence and absence of these antibodies. F(ab') fragments of the anti-insulin-receptor antibody at a concentration of 10 micrograms/ml were capable of displacing greater than 90% of the bound insulin, thus establishing an effective insulin-receptor blockade. Under such blockade, insulin and IGF-I were both capable of doubling the amount of DNA synthesis and cell number in cultured human arterial smooth muscle cells. However, in the presence of a 1:2500 dilution of the monoclonal antibody alpha IR3, which caused a 90% displacement of IGF-I bound to its receptor, both the insulin and IGF-I effects on stimulating DNA synthesis or cellular proliferation were inhibited by greater than 90%. These findings demonstrate that the IGF-I receptor is the common pathway for the growth effects of both insulin and IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)
Banskota
N K
NK
Research Division, Joslin Diabetes Center, Boston, Massachusetts 02215.
Taub
R
R
Zellner
K
K
Olsen
P
P
King
G L
GL
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011519:Proto-Oncogenes; D012333:RNA, Messenger / Q000032:analysis; D011972:Receptor, Insulin / Q000032:analysis; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000494:pharmacology*
D007328:Insulin; D012333:RNA, Messenger; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D004247:DNA; D011972:Receptor, Insulin