Mutant cell line demonstrating a block in insulin and insulin-like growth factor type 1 (IGF-1) induced mitogenesis.
Recently, we have isolated a Chinese hamster cell variant (IV-A1-j) resistant to an insulin-diphtheria-A chain toxic conjugate (Leckett and Germinario: Cytotechnology [in press]. This cell line exhibited a decreased level of insulin binding, but normal growth in serum-containing medium when compared to the parental cell line (V-79). In this paper we further demonstrate that while IV-A1-j cells are capable of growing in serum-containing medium, they are insensitive to the mitogenic actions of either insulin or IGF-1. In contrast, epidermal growth factor (EGF) and/or alpha-thrombin (THR) generate a mitogenic effect in IV-A1-j cells comparable to that observed in the parental V-79 cells. The combination of EGF and/or THR with either insulin or IGF-1 results in an increase in V-79 cell growth above EGF and/or THR alone. On the other hand, insulin or IGF-1 in the presence of other mitogens did not stimulate further growth in IV-A1-j cells. While insulin binding was lower in IV-A1-j cells, internalization of 125I-insulin was not different in the two cell types. Additionally, insulin-stimulated glycogen synthesis and protein synthesis were not different in the two cell types. These observations are consistent with insulin and IGF-1 sharing a mitogenic signalling pathway in Chinese hamster fibroblasts and that this pathway is distinct from other growth factor signalling pathways. The fact that this pathway is defective in the IV-A1-j cell line indicates the potential usefulness of these cells in identifying a key step(s) in the insulin (IGF-1) mitogenic pathway.
Leckett
B
B
Department of Medicine, McGill University, Quebec, Canada.
Spurmanis
A
A
Allen
C
C
Germinario
R J
RJ
D000818:Animals; D016466:CHO Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D006224:Cricetinae; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006003:Glycogen / Q000096:biosynthesis; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008938:Mitosis / Q000187:drug effects*; D009154:Mutation; D013917:Thrombin / Q000494:pharmacology
D007328:Insulin; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D006003:Glycogen; D013917:Thrombin