Activation and selective inhibition of a cyclic AMP-specific phosphodiesterase, PDE-4D3

R. Alvarez, C. Sette, D. Yang, R. M. Eglen, R. Wilhelm, E. R. Shelton, M. Conti

Research output: Contribution to journalArticlepeer-review

Abstract

Prostaglandin E2 produces a transient increase in the intracellular concentration of cAMP in a human promonocytic cell line (U937). The temporal pattern consists of a rapid increase followed by a gradual decline to a new steady state. The decline phase coincides with an increase in the activity of a high affinity form of cAMP phosphodiesterase (PDE). Immunoprecipitation with specific antibodies revealed that the activated enzyme is a variant of PDE-4D. To confirm this observation, three isoforms of human PDE-4 (A, B, and D) were cloned and expressed in Sf9 cells with recombinant baculovirus infection. The activity of only one of the isoforms (PDE-4D3) increased after incubation with the catalytic subunit of protein kinase A and Mg-ATP. Hydrolytic activity of human PDE-4D3 was dependent on Mg2+. Before phosphorylation, the concentration-response curve for Mg2+ was biphasic and ranged from 0.1 to 100 mM. Phosphorylation of PDE-4D3 by protein kinase A produced a monophasic Mg2+ response curve (0.5 V(max) = 0.2 mM). Phosphorylation of PDE-4D3 increased the sensitivity of the enzyme to inhibition by RS-25344 (~100-fold) and RS-33793 (~330-fold). Thus, phosphorylation of PDE-4D3 induces an apparent conformation change that increases maximum velocity and sensitivity to inhibition by some analogues of nitraquazone. These observations provide the basis for a novel pharmacological strategy that targets an activated form of PDE in human leukocytes. Selective PDE-4D3 inhibitors may have useful ante inflammatory properties with fewer adverse side effects than other PDE-4 inhibitors.

Original languageEnglish
Pages (from-to)616-622
Number of pages7
JournalMolecular Pharmacology
Volume48
Issue number4
Publication statusPublished - 1995

ASJC Scopus subject areas

  • Pharmacology

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