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Interaction of the human insulin receptor with the ras oncogene product p21
Abstract:
Autophosphorylation of the purified human insulin receptor tyrosyl kinase was found to be inhibited by the ras oncogene product p21 in a concentration- and GDP-dependent manner. GDP-beta-S but not Gpp(NH)p could substitute for GDP in eliciting the ras-dependent inhibition. The inhibition was seen with both normal or mutant (Lys-61) p21N-ras and normal or mutant (Val-12) p21Ha-ras. Inhibition occurred at 23 degrees C but not 4 degrees C and was unaffected by the presence or absence of insulin although insulin stimulated the autophosphorylation rate of the receptor beta-subunit some 2-fold. The insulin receptor did not phosphorylate native p21Ha-ras in the presence or absence of added guanine nucleotide. After denaturation of p21Ha-ras with urea it became a substrate, but then failed to inhibit receptor autophosphorylation even in the presence of added GDP.
Insights
The ras oncogene product p21 inhibits insulin receptor autophosphorylation in a GDP-dependent manner. This interaction is specific and requires the native form of p21, impacting cell signaling pathways.
Area of Science:
- Molecular Biology
- Cell Signaling
- Oncology
Background:
- The insulin receptor (IR) is a key regulator of glucose metabolism and cellular growth.
- The ras oncogene product p21 is a small GTPase involved in cell proliferation and differentiation.
- Dysregulation of ras signaling is implicated in various cancers.
Purpose of the Study:
- To investigate the interaction between the human insulin receptor tyrosyl kinase and the ras oncogene product p21.
- To determine the conditions and factors influencing this interaction and its effect on receptor activity.
Main Methods:
- Purified human insulin receptor tyrosyl kinase was used.
- Autophosphorylation assays were performed in the presence of varying concentrations of ras p21 and guanine nucleotides (GDP, GDP-beta-S, Gpp(NH)p).
- Experiments were conducted at different temperatures and in the presence or absence of insulin.
Main Results:
- Ras p21 inhibited insulin receptor autophosphorylation in a concentration- and GDP-dependent manner.
- GDP-beta-S mimicked GDP, while Gpp(NH)p did not substitute for GDP.
- Inhibition was observed with both normal and mutant forms of N-ras and Ha-ras p21.
- The effect was temperature-dependent (observed at 23°C, not 4°C) and independent of insulin.
- Insulin stimulated receptor autophosphorylation.
- The insulin receptor did not phosphorylate native ras p21, but phosphorylated denatured ras p21, which then failed to inhibit receptor autophosphorylation.
Conclusions:
- Ras p21 directly inhibits the autophosphorylation of the human insulin receptor tyrosyl kinase.
- The inhibitory mechanism is dependent on the guanine nucleotide-bound state of ras p21, specifically GDP-bound.
- The interaction requires the native conformation of ras p21, suggesting a specific protein-protein interaction rather than a substrate relationship.