Assembly of high-affinity insulin receptor agonists and antagonists from peptide building blocks

Abstract

Insulin is thought to elicit its effects by crosslinking the two extracellular alpha-subunits of its receptor, thereby inducing a conformational change in the receptor, which activates the intracellular tyrosine kinase signaling cascade. Previously we identified a series of peptides binding to two discrete hotspots on the insulin receptor. Here we show that covalent linkage of such peptides into homodimers or heterodimers results in insulin agonists or antagonists, depending on how the peptides are linked. An optimized agonist has been shown, both in vitro and in vivo, to have a potency close to that of insulin itself. The ability to construct such peptide derivatives may offer a path for developing agonists or antagonists for treatment of a wide variety of diseases.

Figure 1

Model for activation of the IR by binding of insulin. P denotes tyrosine phosphorylation.

Figure 2

Synthesis of chemically linked peptide dimers.

Figure 3

In vitro properties of peptides. (A) Stimulation of glucose incorporation into lipids in mouse adipocytes by peptides, human insulin (*), S371 (■), S446 (○), S374 (▾), and S378 (▵). (B) Stimulation of glucose incorporation into lipids in mouse adipocytes by peptides, human insulin (*), RB539 (□), S454 (■), S455 (▵), S456 (▴), and S519 (●). (C) Inhibition of insulin-stimulated glucose incorporation by RB537 (○). (D) Activation of the IR kinase by peptides, human insulin (*), S371 (■), S374 (▾), RB537 (○), RB539 (□), S455 (▵), S456 (▴), and S519 (●).

Figure 4

Blood glucose after i.v. administration of vehicle (n = 8), human insulin (n = 5), or S519 (n = 8) to anesthetized Wistar rats.