title: Discovery and characterization of a substrate selective p38alpha inhibitor.
abstract: A novel inhibitor of p38 mitogen-activated protein kinase (p38), CMPD1, identified by high-throughput screening, is characterized herein. Unlike the p38 inhibitors described previously, this inhibitor is substrate selective and noncompetitive with ATP. In steady-state kinetics experiments, CMPD1 was observed to prevent the p38alpha-dependent phosphorylation (K(i)(app) = 330 nM) of the splice variant of mitogen-activated protein kinase-activated protein kinase 2 (MK2a) that contains a docking domain for p38alpha and p38beta, but it did not prevent the phosphorylation of ATF-2 (K(i)(app) > 20 microM). In addition to kinetic studies, isothermal titration calorimetry and surface plasmon resonance experiments were performed to elucidate the mechanism of inhibition. While isothermal titration calorimetry analysis indicated that CMPD1 binds to p38alpha, CMPD1 was not observed to compete with ATP for p38alpha, nor was it able to interrupt the binding of p38alpha to MK2a observed by surface plasmon resonance. Therefore, deuterium exchange mass spectrometry (DXMS) was employed to study the p38alpha.CMPD1 inhibitory complex, to provide new insight into the mechanism of substrate selective inhibition. The DXMS data obtained for the p38alpha.CMPD1 complex were compared to the data obtained for the p38alpha.MK2a complex and a p38alpha.active site binding inhibitor complex. Alterations in the DXMS behavior of both p38alpha and MK2a were observed upon complex formation, including but not limited to the interaction between the carboxy-terminal docking domain of MK2a and its binding groove on p38alpha. Alterations in the D(2)O exchange of p38alpha produced by CMPD1 suggest that the substrate selective inhibitor binds in the vicinity of the active site of p38alpha, resulting in perturbations to regions containing nucleotide binding pocket residues, docking groove residues (E160 and D161), and a Mg(2+) ion cofactor binding residue (D168). Although the exact mechanism of substrate selective inhibition by this novel inhibitor has not yet been disclosed, the results suggest that CMPD1 binding in the active site region of p38alpha induces perturbations that may result in the suboptimal positioning of substrates and cofactors in the transition state, resulting in selective inhibition of p38alpha activity.
authors.affiliation: Department of Immunology and Inflammation, Boehringer Ingelheim Pharmaceuticals, Research and Development Center, 900 Ridgebury Road, Ridgefield, Connecticut 06877, USA.
authors.forename: Walter
authors.initials: W
authors.lastname: Davidson
authors.forename: Lee
authors.initials: L
authors.lastname: Frego
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Peet
authors.forename: Rachel R
authors.initials: RR
authors.lastname: Kroe
authors.forename: Mark E
authors.initials: ME
authors.lastname: Labadia
authors.forename: Susan M
authors.initials: SM
authors.lastname: Lukas
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Snow
authors.forename: Scott
authors.initials: S
authors.lastname: Jakes
authors.forename: Christine A
authors.initials: CA
authors.lastname: Grygon
authors.forename: Christopher
authors.initials: C
authors.lastname: Pargellis
authors.forename: Brian G
authors.initials: BG
authors.lastname: Werneburg
mesh_terms: D051698:Activating Transcription Factor 2; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001713:Biphenyl Compounds / Q000737:chemistry / Q000378:metabolism*; D002151:Calorimetry; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D048308:Mitogen-Activated Protein Kinase 14; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D020349:Surface Plasmon Resonance; D014157:Transcription Factors / Q000378:metabolism; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D051698:Activating Transcription Factor 2; D000255:Adenosine Triphosphate; D001713:Biphenyl Compounds; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D048308:Mitogen-Activated Protein Kinase 14; D020928:Mitogen-Activated Protein Kinases; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; D014157:Transcription Factors; D000099190:MAP-Kinase-Activated Kinase 2; C497106:Atf2 protein, mouse; C492719:p38alpha inhibitor CMPD1