Isolation and characterization of two novel phosphodiesterase PDE11A variants showing unique structure and tissue-specific expression

cDNAs encoding a novel phosphodiesterase, phosphodiesterase 11A (PDE11A), were isolated by a combination of reverse transcriptase-polymerase chain reaction using degenerate oligonucleotide primers and rapid amplification of cDNA ends, Their catalytic domain was identical to that of PDE11A1 (490 amino acids) reported during the course of this study. However, the cDNAs we isolated had N termini distinct from PDE11A1, indicating two novel N-terminal variants of PDE11A, PDE11A3 cDNA encoded a 684-amino acid protein including one complete and one incomplete GAF domain in the N-terminal region. PDE11A4 was composed of 934 amino acids including two complete GAF domains and shared 630 C-terminal amino acids with PDE11A3 but had a distinct N terminus containing the putative phosphorylation sites for cAMP- and cGMP dependent protein kinases, PDE11A3 transcripts were specifically expressed in testis, whereas PDE11A4 transcripts were particularly abundant in prostate. Recombinant PDE11A4 expressed in COS-7 cells hydrolyzed cAMP and cGMP with K-m values of 3.0 and 1.4 mu M, respectively, and the V-max value with cAMP was almost twice that with cGMP. Although PDE11A3 showed the same Ii, values as PDE11A4, the relative V-max values of PDE11A3 were ap proximately one-sixth of those of PDE11A4. PDE11A4, but not PDE11A3, was phosphorylated by both cAMP- and cGMP-dependent protein kinases in vitro, Thus, the PDE11A gene undergoes tissue-specific alternative splicing that generates structurally and functionally distinct gene products.