Abstract
Despite their low abundance, phosphoinositides are critical regulators of intracellular signaling and membrane compartmentalization. However, little is known of phosphoinositide function at the postsynaptic membrane. Here we show that continuous synthesis and availability of phosphatidylinositol-(3,4,5)-trisphosphate (PIP(3)) at the postsynaptic terminal is necessary for sustaining synaptic function in rat hippocampal neurons. This requirement was specific for synaptic, but not extrasynaptic, AMPA receptors, nor for NMDA receptors. PIP(3) downregulation impaired PSD-95 accumulation in spines. Concomitantly, AMPA receptors became more mobile and migrated from the postsynaptic density toward the perisynaptic membrane within the spine, leading to synaptic depression. Notably, these effects were only revealed after prolonged inhibition of PIP(3) synthesis or by direct quenching of this phosphoinositide at the postsynaptic cell. Therefore, we conclude that a slow, but constant, turnover of PIP(3) at synapses is required for maintaining AMPA receptor clustering and synaptic strength under basal conditions.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / genetics
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
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Carrier Proteins / genetics
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Dendrites / metabolism
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Dendrites / ultrastructure
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Dendritic Spines / metabolism
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Dendritic Spines / ultrastructure
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Disks Large Homolog 4 Protein
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Enzyme Inhibitors / pharmacology
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Excitatory Postsynaptic Potentials / drug effects
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Excitatory Postsynaptic Potentials / physiology
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Green Fluorescent Proteins / genetics
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Hippocampus / cytology
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Immunoprecipitation
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Intracellular Signaling Peptides and Proteins / metabolism
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Long-Term Potentiation / drug effects
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Long-Term Potentiation / physiology
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Membrane Proteins / metabolism
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Microscopy, Immunoelectron / methods
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Mutagenesis, Site-Directed / methods
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Nerve Tissue Proteins / genetics
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Organ Culture Techniques
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Patch-Clamp Techniques / methods
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Phosphatidylinositol 3-Kinases / physiology
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Phosphatidylinositol Phosphates / metabolism*
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Phosphatidylinositols / metabolism
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Phosphoinositide-3 Kinase Inhibitors
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Presynaptic Terminals / physiology
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Presynaptic Terminals / ultrastructure
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Protein Binding
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Protein Transport / drug effects
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Protein Transport / physiology
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Pyramidal Cells / cytology*
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Pyramidal Cells / ultrastructure
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Rats
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Receptors, AMPA / genetics
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Receptors, AMPA / metabolism*
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Synapses / drug effects
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Synapses / physiology*
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Synapses / ultrastructure
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology*
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Time Factors
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Transfection / methods
Substances
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Carrier Proteins
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Disks Large Homolog 4 Protein
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Dlg4 protein, rat
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Enzyme Inhibitors
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Grip1 protein, rat
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Intracellular Signaling Peptides and Proteins
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Membrane Proteins
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Nerve Tissue Proteins
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Phosphatidylinositol Phosphates
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Phosphatidylinositols
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Phosphoinositide-3 Kinase Inhibitors
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Receptors, AMPA
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enhanced green fluorescent protein
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phosphatidylinositol 3,4,5-triphosphate
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Green Fluorescent Proteins
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Calcium-Calmodulin-Dependent Protein Kinase Type 2