Structural and functional characterization of HQL-79, an orally selective inhibitor of human hematopoietic prostaglandin D synthase.

Abstract

We determined the crystal structure of human hematopoietic prostaglandin (PG) D synthase (H-PGDS) as the quaternary complex with glutathione (GSH), Mg2+, and an inhibitor, HQL-79, having anti-inflammatory activities in vivo, at a 1.45-A resolution. In the quaternary complex, HQL-79 was found to reside within the catalytic cleft between Trp104 and GSH. HQL-79 was stabilized by interaction of a phenyl ring of its diphenyl group with Trp104 and by its piperidine group with GSH and Arg14 through water molecules, which form a network with hydrogen bonding and salt bridges linked to Mg2+. HQL-79 inhibited human H-PGDS competitively against the substrate PGH2 and non-competitively against GSH with Ki of 5 and 3 microm, respectively. Surface plasmon resonance analysis revealed that HQL-79 bound to H-PGDS with an affinity that was 12-fold higher in the presence of GSH and Mg2+ (Kd, 0.8 microm) than in their absence. Mutational studies revealed that Arg14 was important for the Mg2+-mediated increase in the binding affinity of H-PGDS for HQL-79, and that Trp104, Lys112, and Lys198 were important for maintaining the HQL-binding pocket. HQL-79 selectively inhibited PGD2 production by H-PGDS-expressing human megakaryocytes and rat mastocytoma cells with an IC50 value of about 100 microm but only marginally affected the production of other prostanoids, suggesting the tight functional engagement between H-PGDS and cyclooxygenase. Orally administered HQL-79 (30 mg/kg body weight) inhibited antigen-induced production of PGD2, without affecting the production of PGE2 and PGF2alpha, and ameliorated airway inflammation in wild-type and human H-PGDS-overexpressing mice. Knowledge about this structure of quaternary complex is useful for understanding the inhibitory mechanism of HQL-79 and should accelerate the structure-based development of novel anti-inflammatory drugs that inhibit PGD2 production specifically.

• Authors: Kosuke Aritake, Yuji Kado, Tsuyoshi Inoue, Masashi Miyano, Yoshihiro Urade
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 281 Issue 22 Pg. 15277-86 (Jun 02 2006) ISSN: 0021-9258 [Print] United States
• PMID: 16547010 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 4-benzhydryloxy-1-(3-(1H-tetrazol-5-yl-)-propyl)piperidine
• Enzyme Inhibitors
• Lipocalins
• Piperidines
• Intramolecular Oxidoreductases
• prostaglandin R2 D-isomerase

Topics

• Administration, Oral
• Animals
• Binding Sites
• Binding, Competitive
• Cell Line
• Crystallography, X-Ray
• Enzyme Inhibitors (administration & dosage, chemistry, pharmacology)
• Hematopoietic System (drug effects, enzymology)
• Humans
• Hydrogen Bonding
• In Vitro Techniques
• Intramolecular Oxidoreductases (antagonists & inhibitors, chemistry)
• Lipocalins
• Mice
• Models, Molecular
• Molecular Structure
• Piperidines (administration & dosage, chemistry, pharmacology)
• Protein Conformation
• Rats