title: Isoform-selective susceptibility of DISC1/phosphodiesterase-4 complexes to dissociation by elevated intracellular cAMP levels.
abstract: Disrupted-in-schizophrenia 1 (DISC1) is a genetic susceptibility factor for schizophrenia and related severe psychiatric conditions. DISC1 is a multifunctional scaffold protein that is able to interact with several proteins, including the independently identified schizophrenia risk factor phosphodiesterase-4B (PDE4B). Here we report that the 100 kDa full-length DISC1 isoform (fl-DISC1) can bind members of each of the four gene, cAMP-specific PDE4 family. Elevation of intracellular cAMP levels, so as to activate protein kinase A, caused the release of PDE4D3 and PDE4C2 isoforms from fl-DISC1 while not affecting binding of PDE4B1 and PDE4A5 isoforms. Using a peptide array strategy, we show that PDE4D3 binds fl-DISC1 through two regions found in common with PDE4B isoforms, the interaction of which is supplemented because of the presence of additional PDE4B-specific binding sites. We propose that the additional binding sites found in PDE4B1 underpin its resistance to release during cAMP elevation. We identify, for the first time, a functional distinction between the 100 kDa long DISC1 isoform and the short 71 kDa isoform. Thus, changes in the expression pattern of DISC1 and PDE4 isoforms offers a means to reprogram their interaction and to determine whether the PDE4 sequestered by DISC1 is released after cAMP elevation. The PDE4B-specific binding sites encompass point mutations in mouse Disc1 that confer phenotypes related to schizophrenia and depression and that affect binding to PDE4B. Thus, genetic variation in DISC1 and PDE4 that influence either isoform expression or docking site functioning may directly affect psychopathology.
authors.affiliation: Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Hannah
authors.initials: H
authors.lastname: Murdoch
authors.forename: Shaun
authors.initials: S
authors.lastname: Mackie
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Collins
authors.forename: Elaine V
authors.initials: EV
authors.lastname: Hill
authors.forename: Graeme B
authors.initials: GB
authors.lastname: Bolger
authors.forename: Enno
authors.initials: E
authors.lastname: Klussmann
authors.forename: David J
authors.initials: DJ
authors.lastname: Porteous
authors.forename: J Kirsty
authors.initials: JK
authors.lastname: Millar
authors.forename: Miles D
authors.initials: MD
authors.lastname: Houslay
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D047468:Immunoprecipitation / Q000379:methods; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D020033:Protein Isoforms / Q000378:metabolism; D014162:Transfection / Q000379:methods
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; C412476:DISC1 protein, human; D009419:Nerve Tissue Proteins; D010726:Phosphodiesterase Inhibitors; D020033:Protein Isoforms; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517360:PDE4B protein, human; D015056:1-Methyl-3-isobutylxanthine