title: Insight into binding of phosphodiesterase-9A selective inhibitors by crystal structures and mutagenesis.
abstract: PDE9 inhibitors have been studied as therapeutics for treatment of cardiovascular diseases, diabetes, and neurodegenerative disorders. To illustrate the inhibitor selectivity, the crystal structures of the PDE9A catalytic domain in complex with the enantiomers of PDE9 inhibitor 1-(2-chlorophenyl)-6-(3,3,3-trifluoro-2-methylpropyl)-1H-pyrazolo[3,4-d]pyrimidine-4(5H)-one ((R)-BAY73-6691 or (S)-BAY73-6691, 1r or 1s) were determined and mutagenesis was performed. The structures showed that the fluoromethyl groups of 1r and 1s had different orientations while the other parts of the inhibitors commonly interacted with PDE9A. These differences may explain the slightly different affinity of 1r (IC(50) = 22 nM) and 1s (IC(50) = 88 nM). The mutagenesis experiments revealed that contribution of the binding residues to the inhibitor sensitivity varies dramatically, from few-fold to 3 orders of magnitude. On the basis of the crystal structures, a hypothesized compound that simulates the recently published PDE9 inhibitors was modeled to provide insight into the inhibitor selectivity.
authors.affiliation: Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, The University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA.
authors.forename: Huanchen
authors.initials: H
authors.lastname: Wang
authors.forename: Xuan
authors.initials: X
authors.lastname: Luo
authors.forename: Mengchun
authors.initials: M
authors.lastname: Ye
authors.forename: Jing
authors.initials: J
authors.lastname: Hou
authors.forename: Howard
authors.initials: H
authors.lastname: Robinson
authors.forename: Hengming
authors.initials: H
authors.lastname: Ke
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D011720:Pyrazoles / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: C507056:BAY 73-6691; D011720:Pyrazoles; D011743:Pyrimidines; D015105:3',5'-Cyclic-AMP Phosphodiesterases; C116137:PDE9A protein, human