title: An Aplysia type 4 phosphodiesterase homolog localizes at the presynaptic terminals of Aplysia neuron and regulates synaptic facilitation.
abstract: The cAMP-dependent signaling pathway is critically involved in memory-related synaptic plasticity. cAMP-specific type 4 phosphodiesterases (PDE4) play a role in this process by regulating the cAMP concentration. However, it is unclear how PDE4 is involved in regulating synaptic plasticity. To address this issue in Aplysia sensory-to-motor synapses, we identified a long isoform of the PDE4 homolog in Aplysia kurodai (apPDE), with genetic and biochemical properties similar to those of mammalian PDE4s. Furthermore, apPDE is localized to the membrane and presynaptic region. Both apPDE overexpression and knock-down impaired short- and long-term facilitation, indicating that an appropriate expression level of apPDE in synaptic regions is required for normal synaptic facilitation. By using fluorescence resonance energy transfer-based measurement of in vivo protein kinase A (PKA) activation, we found that the PKA activation by 5-hydroxytryptamine (5-HT) was impaired in both apPDE-overexpressed and knock-down synapses. Analogous to the inhibition of apPDE by RNA interference, chronic rolipram treatment before 5-HT stimulation also impaired the PKA activation by 5-HT, suggesting that regulation of the synaptic cAMP level by PDE4 is critical for normal synaptic facilitation. Together, we suggest that PDE4s localized in the synapses play a critical role in regulating the optimum cAMP level required for normal synaptic plasticity.
authors.affiliation: National Research Laboratory of Neurobiology, Institute of Molecular Biology and Genetics, School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Hyungju
authors.initials: H
authors.lastname: Park
authors.forename: Jin-A
authors.initials: JA
authors.lastname: Lee
authors.forename: Changhoon
authors.initials: C
authors.lastname: Lee
authors.forename: Min-Jeong
authors.initials: MJ
authors.lastname: Kim
authors.forename: Deok-Jin
authors.initials: DJ
authors.lastname: Chang
authors.forename: Hyoung
authors.initials: H
authors.lastname: Kim
authors.forename: Seung-Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Yong-Seok
authors.initials: YS
authors.lastname: Lee
authors.forename: Bong-Kiun
authors.initials: BK
authors.lastname: Kaang
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D001048:Aplysia / Q000201:enzymology / Q000502:physiology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D004334:Drug Administration Schedule; D004789:Enzyme Activation / Q000502:physiology; D018390:Gene Targeting; D007700:Kinetics; D009046:Motor Neurons / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D020889:Rolipram / Q000008:administration & dosage / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D020889:Rolipram