title: Helix-1 of the cAMP-specific phosphodiesterase PDE4A1 regulates its phospholipase-D-dependent redistribution in response to release of Ca2+.
abstract: The unique N-terminal regions of PDE4 cAMP-specific phosphodiesterases confer interaction with distinct signalling and scaffolding proteins. The PDE4A1 isoform is unique in being entirely membrane associated. Its N-terminal region is formed from two helices separated by a mobile hinge, where helix-2 contains a TAPAS1 domain that inserts into the lipid bilayer in a Ca2+-triggered fashion. Here we show that helix-1 is important for intracellular targeting of PDE4A1 in living cells, facilitating membrane association, targeting to the trans-Golgi stack and conferring Ca2+-stimulated intracellular redistribution in a manner that is dependent on the phospholipase-D-mediated generation of phosphatidic acid. The LxDFF motif within helix-1 is pivotal to this, where Leu4-Phe6-Phe7 forms a compact hydrophobic pocket on one side of helix-1 whereas Asp5, located on the opposite face of helix-1, provides the Ca2+-regulation site. Mutation of Asp5 to Ala or the release of Ca2+ from intracellular stores de-restricts trans-Golgi localisation of PDE4A1 allowing it to redistribute in cells in a phosphatidic-acid-dependent manner. This study provides the first evidence for Ca2+-triggered relocalisation of a cAMP phosphodiesterase and indicates a potential means for allowing cross-talk between the cAMP, phospholipase D and Ca2+-signalling pathways.
authors.affiliation: Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, UK.
authors.forename: Elaine
authors.initials: E
authors.lastname: Huston
authors.forename: Irene
authors.initials: I
authors.lastname: Gall
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Houslay
authors.forename: Miles D
authors.initials: MD
authors.lastname: Houslay
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010712:Phosphatidic Acids / Q000096:biosynthesis; D010739:Phospholipase D / Q000378:metabolism*; D017433:Protein Structure, Secondary; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D019284:Thapsigargin / Q000494:pharmacology; D021601:trans-Golgi Network / Q000187:drug effects
chemical_list: D010712:Phosphatidic Acids; D011993:Recombinant Fusion Proteins; D019284:Thapsigargin; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D010739:Phospholipase D; D002118:Calcium