A family of human phosphodiesterases homologous to the dunce learning and memory gene product of Drosophila melanogaster are potential targets for antidepressant drugs.

Abstract

We have isolated cDNAs for four human genes (DPDE1 through DPDE4) closely related to the dnc learning and memory locus ofDrosophila melanogaster. The deduced amino acid sequences of the Drosophila and human proteins have considerable homology, extending beyond the putative catalytic region to include two novel, highly conserved, upstream conserved regions (UCR1 and UCR2). The upstream conserved regions are located in the amino-terminal regions of the proteins and appear to be unique to these genes. Polymerase chain reaction analysis suggested that these genes encoded the only homologs of dnc in the human genome. Three of the four genes were expressed in Saccharomyces cerevisiae and shown to encode cyclic AMP-specific phosphodiesterases. The products of the expressed genes displayed the pattern of sensitivity to inhibitors expected for members of the type IV, cyclic AMP-specific class of phosphodiesterases. Each of the four genes demonstrated a distinctive pattern of expression in RNA from human cell lines.Regulation of cyclic AMP (cAMP) is important in central nervous system (CNS) function in both invertebrates and mammals. Studies of two different invertebrates in particular have demonstrated a role for cAMP in learning and memory. InAplysia snails, long-term facilitation of neurons in the gill retraction reflex occurs with learning. These neuronal changes are associated with alterations in activity of several components of the cAMP signalling pathway, particularly adenylyl cyclase and a cAMP-dependent protein kinase (32). In Drosophila melanogaster, numerous mutations in genes affecting learning have been isolated, including dunce (dnc), which encodes a cAMP-specific phosphodiesterase (PDE), and rutabaga (rut), which encodes a calcium-calmodulinstimulated adenylyl cyclase (10,16,28). Electrophysiologic studies of neurons from dnc-and rut-flies have shown alterations in synaptic plasticity, suggesting that the functional changes occurring in learning in wild-type flies are similar to those seen in Aplysia snails (40). These observations suggest that modulation of the cAMP pathway can influence learning and memory in organisms widely separated in evolution.Evidence for a functional role of dunce-like PDEs in the mammalian CNS initially came from the development of specific inhibitors. Inhibitors of cAMP-specific PDEs, including the drug rolipram, have clinical activity as antidepressants (11). The initial biochemical analysis of mammalian CNS PDEs, and of these inhibitors, was limited to testing in partially purified preparations, which can contain multiple PDE isoforms (1). More recently, cDNAs for homologs of dnc have been cloned from rats (5,7,9,(36)(37)(38) and shown to be rolipram sensitive (14,37,38

Identification of cyclic AMP‐phosphodiesterase variants from the PDE4D gene expressed in human peripheral mononuclear cells

“…The human counterpart of this latter form has been described by Bolger et al [22]. A fourth variant (PDE4D4) was also detected in human [22] and rat (Vicini, E. and Conti, M., unpublished results), suggesting the presence of a third, distinct promoter. Hormones control the activation and expression of the PDE4D variants through an increase in intracellular cAMP levels.…”

“…Another variant, rat PDE4D3, detected in the brain and FRTL-5 cells, is derived from the activity of a different promoter and the transcription of upstream exons [27]. The human counterpart of this latter form has been described by Bolger et al [22]. A fourth variant (PDE4D4) was also detected in human [22] and rat (Vicini, E. and Conti, M., unpublished results), suggesting the presence of a third, distinct promoter.…”

“…A cDNA containing the entire predicted ORF of human PDE4D2 was obtained by a single RT-PCR amplification using oligonucleotide A and oligonucleotide E, 5'-GCACTGTTACGTGTCAGGAGAAC-GATC-3', corresponding to the 3'-end antisense sequence of human PDE4D3 ( [22], GenBank accession number: L20970). Amplification conditions were the same as above.…”

“…Four PDE4 genes (PDE4A, PDE4B, PDE4C, PDE4D) are expressed in rat [16][17][18][19], mouse [20], and human [21][22][23][24][25], and their characterization has shown a close relationship between genes from two different species [14]. Furthermore, for three out of four rat and human genes, multiple mRNA variants and corresponding protein products have been detected [13,14].…”

Anxiogenic-Like Behavioral Phenotype of Mice Deficient in Phosphodiesterase 4B (PDE4B)

“…PDE4B has five splice variants (PDE4B1, 4B2, 4B3, 4B4, and 4B5; Bolger et al, 1993Bolger et al, , 1994Cheung et al, 2007;Huston et al, 1997;Shepherd et al, 2003). While the roles of these variants are still not known, recent studies using mice deficient in PDE4B have shown that this subfamily plays a complementary role in the control of neutrophil function (Ariga et al, 2004) and is required for antipsychotic effects of rolipram (Siuciak et al, 2007).…”