Received for publication March 14, 2007.
Revised May 28, 2007.
Accepted for publication May 29, 2007.

Structurally Unique Inhibitors of Human Mitogen-activated Protein Kinase Phosphatase-1 Identified in a Pyrrole Carboxamide Library

Abstract

Mitogen-activated protein kinase phosphatase 1 (MKP-1) is a tyrosine phosphatase superfamily member that dephosphorylates and inactivates cardinal mitogen-activated protein kinase (MAPK) substrates, such as p38, JNK, and Erk. Although these MAPK substrates regulate many essential cellular processes associated with human diseases, few pharmacological inhibitors have been described. The lack of readily available selective MKP-1 inhibitors has severely limited interrogation of its biological role and was one rationale for employing a recently described tricyclic pyrrole-2-carboxamide library in our screening efforts. In this report we demonstrate the pharmacological richness of the pyrrole carboxamide library by finding 10 of 172 members inhibited human MKP-1. Two of the pyrrole carboxamides, PSI2106 and MDF2085, were especially notable in vitro inhibitors of recombinant human MKP-1 enzyme activity with IC₅₀ values of 8.0 ± 0.9 µM and 8.3 ± 0.8 µM, respectively. Both showed some selectivity for MKP-1 over the closely related phosphatases MKP-3, Cdc25B, VHR, and PTP1B. Computational examination of the surface properties near the catalytic site revealed that the studied phosphatases significantly differ in their electrostatic potential at the substrate binding site. The compounds inhibited MKP-1 reversibly but displayed mixed kinetics. Phosphatase inhibition was retained in the presence of physiologically relevant concentrations of glutathione. Molecular docking studies suggested PSI2106 may interact with His²²⁹ and Phe²⁹⁹ on MKP-1. These results reveal the power of using a small focused library for identifying pharmacological probes.

Key words: Protein tyrosine phosphatase, chemical probes, enzyme inhibition, mitogenic signaling, molecular docking, targeted chemical libraries

This article has been cited by other articles:

				K. Przyklenk, M. Maynard, C. E. Darling, and P. Whittaker Aging Mouse Hearts Are Refractory to Infarct Size Reduction With Post-Conditioning J. Am. Coll. Cardiol., April 8, 2008; 51(14): 1393 - 1398. [Abstract] [Full Text] [PDF]

				A. Vogt, P. R. McDonald, A. Tamewitz, R. P. Sikorski, P. Wipf, J. J. Skoko III, and J. S. Lazo A cell-active inhibitor of mitogen-activated protein kinase phosphatases restores paclitaxel-induced apoptosis in dexamethasone-protected cancer cells Mol. Cancer Ther., February 1, 2008; 7(2): 330 - 340. [Abstract] [Full Text] [PDF]