Interaction of Janus Kinases JAK-1 and JAK-2 with the Insulin Receptor and the Insulin-Like Growth Factor-1 Receptor

P. Gual
1998 Endocrinology  
Insulin and insulin-like growth factor-1 (IGF-1) treatment of cells overexpressing the insulin receptor or the IGF-1 receptor promotes phosphorylation and activation of Janus kinases JAK-1 and JAK-2 but not of TYK-2. With insulin, we observed maximal phosphorylation of JAK-1 within 2 min (5.2 Ϯ 0.6-fold) and maximal phosphorylation of JAK-2 within 10 min (2.4 Ϯ 0.6-fold). In cells incubated with IGF-1, we found maximal phosphorylation of JAK-2 within 2 min (1.9 Ϯ 0.2-fold) and of JAK-1 within 5
more » ... d of JAK-1 within 5 min (4.5 Ϯ 0.4-fold). The JAKs from insulin-or IGF-1-stimulated cells were activated, as shown by their autophosphorylation in vitro. Moreover, they were able to phosphorylate in vitro native insulin receptor substrate (IRS)-1 and a fragment of IRS-2 (GST-IRS-2591-786). Comparison of 32 P-peptide maps of IRS-1 phosphorylated in vitro by the insulin receptor vs. JAK-1 showed the occurrence of different phosphopeptides, suggesting that different sites are likely to be phosphorylated by the two kinases. Finally, coprecipitation of receptors and JAK-1 was seen, and phosphorylation of both receptors was found to be necessary for receptor binding to JAK-1. Two domains of JAK-1 are involved in the formation of the complex between receptor and JAK-1, i.e. the N-terminal portion containing JH7 and JH6 domains, and the C-terminal kinase domain (JH1 domain). Taking our data together, we conclude that: 1) insulin and IGF-1 lead to phosphorylation and activation of JAK-1 and JAK-2 in intact cells; 2) phosphorylation of IRS-I by JAK-1 seems to occur on sites different from those phosphorylated by the insulin receptor; 3) JAK-1 interacts directly with phosphorylated insulin and IGF-1 receptors; and 4) the JH7-JH6 and JH1 domains of JAK-1 are responsible for the interaction with insulin and IGF-1 receptors. (Endocrinology 139: 884 -893, 1998)
doi:10.1210/en.139.3.884 pmid:9492017 fatcat:tawzlvy3d5fhrnskp6ktge5xdm