title: PDE4B5, a novel, super-short, brain-specific cAMP phosphodiesterase-4 variant whose isoform-specifying N-terminal region is identical to that of cAMP phosphodiesterase-4D6 (PDE4D6).
abstract: The cAMP-specific phosphodiesterase-4 (PDE4) gene family is the target of several potential selective therapeutic inhibitors. The four PDE4 genes generate several distinct protein-coding isoforms through the use of alternative promoters and 5'-coding exons. Using mouse transcripts, we identified a novel, super-short isoform of human PDE4B encoding a novel 5' terminus, which we label PDE4B5. The protein-coding region of the novel 5' exon is conserved across vertebrates, chicken, zebrafish, and fugu. Reverse-transcription-polymerase chain reaction (PCR) and quantitative (PCR) measurements show that this isoform is brain-specific. The novel protein is 58 +/- 2 kDa; it has cAMP hydrolyzing enzymatic activity and is inhibited by PDE4-selective inhibitors rolipram and cilomilast (Ariflo). Confocal and subcellular fractionation analyses show that it is distributed predominantly and unevenly within the cytosol. The 16 novel N-terminal residues of PDE4B5 are identical to the 16 N-terminal residues of the super-short isoform of PDE4D (PDE4D6), which is also brain-specific. PDE4B5 is able to bind the scaffold protein DISC1, whose gene has been linked to schizophrenia. Microarray expression profiling of the PDE4 gene family shows that specific PDE4 genes are enriched in muscle and blood fractions; however, only by monitoring the individual isoforms is the brain specificity of the super-short PDE4D and PDE4B isoforms revealed. Understanding the distinct tissue specificity of PDE4 isoforms will be important for understanding phosphodiesterase biology and opportunities for therapeutic intervention.
authors.affiliation: Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom.
authors.forename: York-Fong
authors.initials: YF
authors.lastname: Cheung
authors.forename: Zhengyan
authors.initials: Z
authors.lastname: Kan
authors.forename: Philip
authors.initials: P
authors.lastname: Garrett-Engele
authors.forename: Irene
authors.initials: I
authors.lastname: Gall
authors.forename: Hannah
authors.initials: H
authors.lastname: Murdoch
authors.forename: George S
authors.initials: GS
authors.lastname: Baillie
authors.forename: Luiz Miguel
authors.initials: LM
authors.lastname: Camargo
authors.forename: Jason M
authors.initials: JM
authors.lastname: Johnson
authors.forename: Miles D
authors.initials: MD
authors.lastname: Houslay
authors.forename: John C
authors.initials: JC
authors.lastname: Castle
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001921:Brain / Q000378:metabolism; D019556:COS Cells; D002264:Carboxylic Acids / Q000494:pharmacology; D002384:Catalysis / Q000187:drug effects; D002522:Chlorocebus aethiops; D019295:Computational Biology; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D003509:Cyclohexanecarboxylic Acids; D015870:Gene Expression; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D020411:Oligonucleotide Array Sequence Analysis; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D020889:Rolipram / Q000494:pharmacology; D016415:Sequence Alignment; D014162:Transfection
chemical_list: D002264:Carboxylic Acids; D003509:Cyclohexanecarboxylic Acids; C412476:DISC1 protein, human; D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D009570:Nitriles; D010726:Phosphodiesterase Inhibitors; C433247:Cilomilast; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517360:PDE4B protein, human; C517376:PDE4D protein, human; D020889:Rolipram