Regulation of Id2 Gene Expression by the Type 1 IGF Receptor and the Insulin Receptor Substrate-1

Abstract

The Id family of helix-loop-helix proteins is known to be involved in the proliferation and differentiation of several types of cells. The type 1 IGF receptor (IGF-IR) induces either proliferation or differentiation in 32D cells, a murine hemopoietic cell line, depending on the availability of the appropriate substrates for the receptor. We have previously reported that the IGF-IR regulates the expression of the Id2 gene in 32D cells. We now show that the IGF-IR controls the increase in Id2 gene expression through at least three pathways. These three pathways originate from the tyrosine residue at 950, a domain in the C-terminus, and the activation of the insulin receptor substrate-1 (IRS-1) by the receptor. IRS-1 is the preponderant signal, and its effect on Id2 gene expression requires a functional phosphotyrosine binding domain. With wild-type IRS-1, Id2 gene expression is increased, even in those cells that express IGF-I receptors defective in Id2 signaling. Rapamycin, an inhibitor of p70(S6K), a downstream effector of IRS-1 signaling, partially inhibits (but does not completely abrogate) the increase in Id2 gene expression. A mutant IRS-1 with a deletion of the Pleckstrin domain is as effective as wild-type IRS-1 in up-regulating Id2 gene expression. In addition, it seems to increase the stability of p70(S6K). Our results indicate that the IGF-IR regulates Id2 gene expression through different pathways. At least in 32D cells, increased Id2 gene expression seems to correlate more with inhibition of differentiation than with proliferation.

Role of Pescadillo and Upstream Binding Factor in the Proliferation and Differentiation of Murine Myeloid Cells

“…In 32D IGF-IR cells, ID2 gene expression is very low, almost undetectable. Ectopic expression of IRS-1 in these cells causes a dramatic increase in ID2 gene expression (2,40,47; this study). Neither UBF1 nor PES1 is capable of inducing ID2 expression in 32D IGF-IR cells.…”

Nuclear Translocation of Insulin Receptor Substrate-1 by the Simian Virus 40 T Antigen and the Activated Type 1 Insulin-like Growth Factor Receptor

“…The fact that the ␦PTB mutant does not translocate in response to IGF-I stimulation is not surprising because this mutant is not completely inactive but is strongly impaired in its function (23,27). It indirectly confirms, however, that the wild type IRS-1 found in the nucleus is really IRS-1, because the same antibody was used as for the wild type IRS-1.…”

“…32D IRS-1/IGF-IR cells express both the human wild type IGF-IR and mouse IRS-1 (7), are IL-3 independent, and form tumors in nude mice (11). 32D IGF-IR cells expressing the mutant IRS-1 proteins have been described previously (22,23). They are 32D IGF-IR cells stably transfected with plasmids expressing mutant IRS-1 proteins.…”

“…In addition, such an experiment can give clues on the mechanism of IRS-1 translocation. The IRS-1 mutants used have been described in previous papers from our laboratory (22,23,31) and are the same used by Yenush et al (27) to study the insulin receptor. These IRS-1 mutants were expressed in 32D IGF-IR cells (23), so that they can be compared directly with the 32D IGF-IR/IRS-1 cells described above in Fig.…”

PD98059 enhances C2 myoblast differentiation through p38 MAPK activation: a novel role for PD98059

“…Indeed, studies by Navarro et al (2001) have suggested that IGF causes upregulation of Id2; therefore in our model, Id3 may be increased as a consequence of increased IGF-II expression as a mechanism of controlling the rate of differentiation in a feed-forward loop. In addition, utilising the non-differentiating myoblast cell line NFB4, Sarbassov et al has shown that myogenin and IGF-II are capable of activating each other's expression.…”