Expression of type I, but not type II insulin-like growth factor receptor on both undifferentiated and differentiated HT29 human colon carcinoma cell line.
The HT29 human colonic carcinoma cell line secretes insulin-like growth factor (IGF)-II. We have examined these cells for expression of IGF receptors. Competitive binding assays as affinity cross-linking experiments using 125I-IGF-II fail to reveal type II IGF receptors at the cell surface. In contrast, cross-linking studies with either 125I-IGF-I or 125I-IGF-II reveal an M(r) 135,000 protein that follows a peptide binding specificity characteristic of the alpha-subunit of the type I IGF receptor. However, 125I-IGF-II binding to this receptor is not inhibited at 4 C by alpha IR-3, a monoclonal antibody to the type I IGF receptor. Analysis of the competitive binding curves with each one of these radioligands suggests that HT29 cells express both a classical type I IGF receptor (about 6,000/cell; KdIGF-I = 0.48 nmol) and a variant one whose 125I-IGF-II binding is not blocked by alpha IR-3 (about 15,000/cell; KdIGF-II = 4.0 nmol). Endocytosis studies of specific cell-bound 125I-IGF-I or 125I-IGF-II suggest that ligand interaction with the classical, but not the variant, binding site is only able to induce receptor internalization. An identical IGF receptors pattern is observed with HT29-D4 clonal cells induced to differentiate by culture in a glucose-free medium.
Remacle-Bonnet
M M
MM
Laboratoire d'Immunopathologie, Faculté de Médecine, Marseille, 3, France.
Culouscou
J M
JM
Garrouste
F L
FL
Rabenandrasana
C
C
Marvaldi
J L
JL
Pommier
G J
GJ
D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology; D002454:Cell Differentiation; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D011956:Receptors, Cell Surface / Q000145:classification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism; D013696:Temperature; D014407:Tumor Cells, Cultured
D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins