Phosphorylation of the postsynaptic density-95 (PSD-95)/discs large/zona occludens-1 binding site of stargazin regulates binding to PSD-95 and synaptic targeting of AMPA receptors.
Dynamic regulation of AMPA-type receptors at the synapse is proposed to play a critical role in alterations of the synaptic strength seen in cellular models of learning and memory such as long-term potentiation in the hippocampus. Stargazin, previously identified as an AMPA receptor (AMPAR)-interacting protein, is critical for surface expression and synaptic targeting of AMPARs. Stargazin interacts with postsynaptic density-95/discs large/zona occludens-1 (PDZ) proteins via a C-terminal PDZ binding motif. Interestingly, the C terminal of stargazin also predicts phosphorylation at a threonine residue critical for PDZ protein binding. Because protein phosphorylation regulates synaptic plasticity, we characterized this site and the effects of stargazin phosphorylation on AMPAR function. In vitro peptide phosphorylation assays and Western blot analysis with phospho-stargazin-specific antibodies indicate that the critical threonine within the stargazin PDZ binding site is phosphorylated by protein kinase A. This phosphorylation disrupts stargazin interaction and clustering with postsynaptic density-95 (PSD-95) in transfected COS-7 cells. Furthermore, a stargazin construct with a Thr-to-Glu mutation that mimics phosphorylation fails to cluster at synaptic spines and downregulates synaptic AMPAR function in cultured hippocampal neurons. These data suggest that phosphorylation of the stargazin PDZ ligand can disrupt stargazin interaction with PSD-95 and thereby regulate synaptic AMPAR function.
Department of Neurology, University of California at San Francisco, San Francisco, California 94143-0444, USA.
Dane M
DM
Chetkovich
Lu
L
Chen
Timothy J
TJ
Stocker
Roger A
RA
Nicoll
David S
DS
Bredt
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D019556:COS Cells; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D029721:Drosophila Proteins; D019476:Insect Proteins / Q000378:metabolism; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D018091:Receptors, AMPA / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D062826:Zonula Occludens-1 Protein
D015220:Calcium Channels; D029721:Drosophila Proteins; D019476:Insect Proteins; D008024:Ligands; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D018091:Receptors, AMPA; D025521:Tumor Suppressor Proteins; D062826:Zonula Occludens-1 Protein; C033652:postsynaptic density proteins; C070350:dlg1 protein, Drosophila; D017868:Cyclic AMP-Dependent Protein Kinases