In a comparison study of 2 related cell lines you find that one responds normally to insulin while the other has an impaired response. You discover that both cell lines bind insulin with equal affinity but that the impaired response is manifest in an inability to recruit the insulin receptor substrate 1 (IRS1) protein to the receptor. This would most likely be due to which of the following?
A) decreased activation of the tyrosine phosphatase activity of the receptor preventing removal of phosphate from the IRS1 docking site
B) inability of the receptor to phosphorylate the G-protein, RAS
C) loss of activation of PLCb in response to insulin-binding receptor
D) serine phosphorylation of the insulin receptor preventing IRS1 from binding
E) tyrosine phosphorylation of the insulin receptor leading to the loss of the IRS1 binding site

Question

Quizplus · Accepted Answer

Serine phosphorylation of the insulin receptor can inhibit its ability to recruit IRS1 by altering the receptor's conformation, preventing IRS1 from binding effectively.  All of the postreceptor responses initiated by insulin binding to its receptor are mediated as a consequence of the activation of several signal transduction pathways that require autophosphorylation of tyrosine residues in the intracellular portion of the insulin receptor. These tyrosine phosphates are docking sites for proteins, such as IRS1, involved in insulin signaling. Serine phosphorylation of the insulin receptor, as well as IRS1, interferes with the ability of IRS1 to bind to the receptor resulting in reduced signaling in response to insulin receptor interaction.

In a Comparison Study of 2 Related Cell Lines You