Phosphodiesterase 8A

Details Phosphodiesterase 8A Phosphodiesterase 8A

2000-10-11

2003-05-20

Prouty, Rebecca E. (Department: 1652)

Chemistry: molecular biology and microbiology

Measuring or testing process involving enzymes or...

Involving hydrolase

C435S007100, C435S007710, C435S004000, C435S183000, C435S196000

Reexamination Certificate

active

06566087

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a family of phosphodiesterases designated PDE8A and uses thereof.
BACKGROUND OF THE INVENTION
Phosphodiesterases (PDEs) hydrolyze 3′,5′ cyclic nucleotides to their respective nucleoside 5′ monophosphates. The cyclic nucleotides cAMP and cGMP are synthesized by adenylyl and guanylyl cyclases, respectively, and serve as second messengers in a number of cellular signaling pathways. The duration and strength of the second messenger signal is a function of the rate of synthesis and the rate of hydrolysis of the cyclic nucleotide.
Multiple families of PDEs have been identified. The nomenclature system includes first a number that indicates the PDE family. To date, seven families (PDE1-7) are known which are classified by: (i) primary structure; (ii) substrate preference; (iii) response to different modulators; (iv) sensitivity to specific inhibitors; and (v) modes of regulation [Loughney and Ferguson, in
Phosphodiesterase Inhibitors
, Schudt, et al. (Eds.), Academic Press: New York, New York (1996) pp. 1-19]. The number indicating the family is followed by a capital letter, indicating a distinct gene, and the capital letter followed by a second number, indicating a specific splice variant or a specific transcript which utilizes a unique transcription initiation site.
The amino acid sequences of all mammalian PDEs identified to date include a highly conserved region of approximately 270 amino acids located in the carboxy terminal half of the protein [Charbonneau, et al.,
Proc. Natl. Acad Sci
. (
USA
) 83:9308-9312 (1986)]. The conserved domain includes the catalytic site for cAMP and/or cGMP hydrolysis and two putative zinc binding sites as well as family specific determinants [Beavo,
Physiol. Rev
. 75:725-748 (1995); Francis, el al.,
J. Biol. Chem
. 269:22477-22480 (1994)]. The amino terminal regions of the various PDEs are highly variable and include other family specific determinants such as: (i) calmodulin binding sites (PDE1); (ii) noncatalytic cyclic GMP binding sites (PDE2, PDE5, PDE6); (iii) membrane targeting sites (PDE4); (iv) hydrophobic membrane association sites (PDE3); and (v) phosphorylation sites for either the calmodulin-dependent kinase II (PDE1), the cAMP-dependent kinase (PDE1, PDE3, PDE4), or the cGMP dependent kinase (PDE5) [Beavo,
Physiol. Rev
. 75:725-748 (1995); Manganiello, et al.,
Arch. Biochem. Acta
322:1-13 (1995); Conti, et al.,
Physiol. Rev
. 75:723-748 (1995)].
Members of the PDE1 family are activated by calcium-calmodulin. Three genes have been identified; PDE1A and PDE1B preferentially hydrolyze cGMP while PDE1C has been shown to exhibit a high affinity for both cAMP and cGMP. The PDE2 family is characterized as being specifically stimulated by cGMP [Loughney and Ferguson, supra]. Only one gene has been identified, PDE2A, the enzyme product of which is specifically inhibited by erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). Enzymes in the PDE3 family are specifically inhibited by cGMP. Two genes are known, PDE3A and PDE3B, both having high affinity for both cAMP and cGMP, although the V
max
for cGMP hydrolysis is low enough that cGMP functions as a competitive inhibitor for cAMP hydrolysis. PDE3 enzymes are specifically inhibited by milinone and enoximone [Loughney and Ferguson, supra]. The PDE4 family effects cAMP hydrolysis and includes four genes, PDE4A, PDE4B, PDE4C, and PDE4D, each having multiple splice variants. Members of this family are specifically inhibited by the anti-depressant drug rolipram. Members of PDE5 family bind cGMP at non-catalytic sites and preferentially hydrolyze cGMP. Only one gene, PDE5A, has been identified. The photoreceptor PDE6 enzymes specifically hydrolyze cGMP [oughney and Ferguson, supra]. Genes include PDE6A and PDE6B (the protein products of which dimerize and bind two copies of a smaller &ggr; inhibitory subunit to form rod PDE), in addition to PDE6C which associates with three smaller proteins to form cone PDE. The PDE7 family effects cAMP hydrolysis but, in contrast to the PDE4 family, is not inhibited by rolipram [Loughney and Ferguson, supra]. Only one gene, PDE7A, has been identified.
1. Given the importance of cAMP and cGMP in intracellular second messenger signaling, there thus exists an ongoing need in the art to identify addition PDE species. Identification of heretofore unknown families of PDEs, and genes and splice variants thereof, will provide additional pharmacological approaches to treating conditions in which cyclic nucleotide pathways are aberrant as well as conditions in which modulation of intracellular cAMP and/or cGMP levels in certain cell types is desirable.
SUMMARY OF THE INVENTION
In brief, the present invention provides polypeptides and underlying polynucleotides for a novel PDE family designated PDE8. The invention includes both naturally occurring and non-naturally occurring PDE8 polynucleotides and polypeptide products thereof Naturally occurring PDE8 products include distinct gene and polypeptide species within the PDE8 family (i.e., PDE8A); these species include those which are expressed within cells of the same animal and well as corresponding species homologs expressed in cells of other animals. Within each PDE8 species, the invention further provides splice variants encoded by the same polynucleotide but which arise from distinct mRNA transcripts (i.e., PDE8A1 and PDE8A2). Non-naturally occurring PDE8 products include variants of the naturally occurring products such as analogs (i.e., wherein one or more amino acids are added, substituted, or deleted) and those PDE8 products which include covalent modifications (i.e., fusion proteins, glycosylation variants, Met
−1
PDE8s, Met
−2
-Lys
−1
-PDE8s, Gly
−1
PDE8s and the like). The PDE8 family is distinguished from previously known PDE families in exhibiting high affinity for hydrolysis of both cAMP and cGMP but relatively low sensitivity to enzyme inhibitors specific for other PDE families. In a preferred embodiment, the invention provides a polynucleotide comprising the sequence set forth in SEQ ID NO: 1. The invention also embraces polynucleotides encoding the amino acid sequence set out in SEQ ID NO: 2. A presently preferred polypeptide of the invention comprises the amino acid sequence set out in SEQ ID NO: 2. The invention provides two splice variant cDNAs which give rise to two polypeptides designated PDE8A1 and PDE8A2. PDE8A1 and PDE8A2 polypeptides, and the polynucleotides encoding the polypeptides, are discussed herein as representative of the PDE8 enzyme family embraced by the invention.
The present invention provides novel purified and isolated polynucleotides (e.g., DNA sequences and RNA transcripts, both sense and complementary antisense strands, including splice variants thereof) encoding the human PDE8s. DNA sequences of the invention include genomic and cDNA sequences as well as wholly or partially chemically synthesized DNA sequences. “Synthesized,” as used herein and is understood in the art, refers to purely chemical, as opposed to enzymatic, methods for producing polynucleotides. “Wholly” synthesized DNA sequences are therefore produced entirely by chemical means, and “partially” synthesized DNAs embrace those wherein only portions of the resulting DNA were produced by chemical means. A preferred DNA sequence encoding a human PDE8 polypeptide is set out in SEQ ID NO: 1. Also preferred are polynucleotides encoding the PBE8 polypeptide of SEQ ID NO: 2 and the PDE8A1 and PDE8A2 splice variant polypeptides set out in SEQ ID NOs: 6 and 4, respectively. Preferred polynucleotides encoding PDE8A1 and PDE8A2 are set out in SEQ ID NOs: 5 and 3, respectively. The invention further embraces species, preferably mammalian, homologs of the human PDE8 DNA.
The invention also embraces DNA sequences encoding PDE8 species which hybridize under moderately stringent conditions to the non-coding strands, or complements, of the polynucleotides

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