Identification and Characterization of a Novel Family of Cyclic Nucleotide Phosphodiesterases

Scott H Soderling,Sharon J Bayuga,Joseph A Beavo

doi:10.1074/jbc.273.25.15553

Scott H Soderling, Sharon J Bayuga + Show 1 more

Open Access

https://doi.org/10.1074/jbc.273.25.15553

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Abstract

We report the cloning, expression, and characterization of a new family of cyclic nucleotide phosphodiesterase (PDE) that has unique kinetic and inhibitor specificities. A clone corresponding to the C terminus of this PDE was initially identified by a bioinformatic approach and used to isolate a cDNA that is likely full-length. This novel PDE, designated as MMPDE9A1, shows highest mRNA expression in kidney with lower levels in liver, lung, and brain. The mRNA size by Northern blot analysis is approximately 2.0 kilobases, and the cDNA encoding PDE9A1 is 1929 base pairs in length. The largest open reading frame predicts a protein of 534 amino acids with a molecular mass of 62,000 Da. When expressed in COS-7 cells, PDE9A1 activity was not inhibited well by either the nonselective inhibitor 3-isobutyl-1-methyl-xanthine or the new selective PDE5 inhibitor, sildenafil, but it is inhibited by the PDE1/5 inhibitor (+)-cis-5,6a, 7,8,9 hyl] phenylmethyl]-5-methyl-cylopent[4,5]imidao[2, 1-b]purin-49(3H)one (SCH51866) with an IC50 of 1.55 microM. This new phosphodiesterase is highly specific for cGMP. Its Km of approximately 0.07 microM for cGMP is the lowest yet reported for a PDE, being at least 40-170 times lower than that of PDE5 and PDE6, respectively.

Highlights

The cyclic nucleotides cAMP and cGMP serve as second messengers for a wide variety of extracellular signals such as neurotransmitters, hormones, light, and odorants
1 is activated by Ca2ϩ/ calmodulin and hydrolyzes both cAMP and cGMP; family 2 is stimulated by cGMP, and both cAMP and cGMP serve as substrate; family 3 is distinguished by cAMP hydrolysis that is inhibited by cGMP; family 4 is cAMP-specific; family 5 binds cGMP at a noncatalytic site and hydrolyzes cGMP; family 6 is the retinal PDE that is inhibited by a ␥ subunit in the absence of activated transducin and hydrolyzes cGMP; and family 7 is a very low Km cAMP-specific PDE
Physiologic Roles for PDE9A1— at this time it is unknown what physiologic roles PDE9 may regulate, the identification and initial description of this new family will aid in defining these roles in future studies

Summary

Introduction

The cyclic nucleotides cAMP and cGMP serve as second messengers for a wide variety of extracellular signals such as neurotransmitters, hormones, light, and odorants. The diverse cellular and behavioral responses to these second messengers are mediated by the action of cAMP and cGMP on their intracelluar targets, which include kinases, ion channels, transcriptional activators, and several isoforms of phosphodiesterases (PDEs).. The diverse cellular and behavioral responses to these second messengers are mediated by the action of cAMP and cGMP on their intracelluar targets, which include kinases, ion channels, transcriptional activators, and several isoforms of phosphodiesterases (PDEs).1 These responses are regulated by the rates of synthesis of cyclic nucleotides by cyclases and their degradation by PDEs to biologically inactive 5Ј monophosphate nucleosides. The precise cellular and subcellular profile of PDE expression will determine the cyclic nucleotide phenotype of a cell and how it responds to first messengers Identifying and characterizing these functionally distinct PDEs is crucial for our understanding of the mechanisms by which cyclic nucleotides moderate their biologic effects.

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