Small molecule peptidomimetics containing a novel phosphotyrosine bioisostere inhibit protein tyrosine phosphatase 1B and augment insulin actions

Protein tyrosine phosphatase 1B (PTP1B) attenuates insulin signaling by cat alyzing dephosphorylation of insulin receptors (IR) and is an attractive ta rget of potential new drugs for treating the insulin resistance that is cen tral to type II diabetes. Several analogues of cholecystokinin(26-33) (CCK- 8) were found to be surprisingly potent inhibitors of PTP1B, and a common N -terminal tripeptide, N-acetyl-Asp-Tyr(SO3H)-Nle-, was shown to be necessar y and sufficient for inhibition. This tripeptide was modified to reduce siz e and peptide character, and to replace the metabolically unstable sulfotyr osyl group. This led to the discovery of a novel phosphotyrosine bioisoster e, 2-carboxymethoxybenzoic acid, and to analogues that were >100-fold more potent than the CCK-8 analogues and >10-fold selective for PTP1B over two o ther PTP enzymes (LAR and SHP-2), a dual specificity phosphatase (cdc25b), and a serine/threonine phosphatase (calcineurin). These inhibitors disrupte d the binding of PTP1B to activated IR in vitro and prevented the loss of t yrosine kinase (IRTK) activity that accompanied PTP1B-catalyzed dephosphory lation of IR. Introduction of these poorly cell permeant inhibitors into in sulin-treated cells by microinjection (oocytes) or by esterification to mor e lipophilic proinhibitors (3T3-L1 adipocytes and L6 myocytes) resulted in increased potency, but not efficacy, of insulin. In some instances, PTP1B i nhibitors were insulin-mimetic, suggesting that in unstimulated cells PTP1B may suppress basal IRTK activity. X-ray crystallography of PTP1B-inhibitor complexes revealed that binding of an inhibitor incorporating phenyl-O-mal onic acid as a phosphotyrosine bioisostere occurred with the mobile WPD loo p in the open conformation, while a closely related inhibitor with a 2-carb oxymethoxybenzoic acid bioisostere bound with the WPD loop closed, perhaps accounting for its superior potency. These CCK-derived peptidomimetic inhib itors of PTP1B represent a novel template for further development of potent , selective inhibitors, and their cell activity further justifies the selec tion of PTP1B as a therapeutic target.