Copine-6 is a Ca2+ sensor for activity-induced AMPA receptor exocytosis

The recruitment of synaptic AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors underlies the strengthening of neuronal connectivity during learning and memory. This process is triggered by NMDA (N-methyl-D-aspartate) receptor-dependent postsynaptic Ca2+ influx. Synaptotagmin (Syt)-1 and −7 have been proposed as Ca2+-sensors for AMPA receptor exocytosis, but are functionally redundant. Here we identify a cytosolic C2 domain-containing Ca2+-binding protein Copine-6 that forms a complex with AMPA receptors. Loss of Copine-6 expression impairs activity-induced exocytosis of AMPA receptors in primary hippocampal neurons, which is rescued by wild-type Copine-6, but not Ca2+-binding mutants. In contrast, Copine-6 loss-of-function has no effects on steady-state expression or tetrodotoxin-induced synaptic upscaling of surface AMPA receptors. Loss of Syt-1/-7 significantly reduces Copine-6 protein expression. Interestingly, overexpression of wild-type Copine-6, but not the Ca2+-binding mutant, restores activity-dependent exocytosis of AMPA receptors in Syt-1/-7 double-knockdown neurons. We conclude that Copine-6 is a postsynaptic Ca2+-sensor that mediates AMPA receptor exocytosis during synaptic potentiation.

[1]  Daniel B. McClatchy,et al.  Activity-Induced Cortical Glutamatergic Neuron Nascent Proteins , 2022, The Journal of Neuroscience.

[2]  M. Murayama,et al.  Stepwise synaptic plasticity events drive the early phase of memory consolidation , 2021, Science.

[3]  Y. Hayashi.  Molecular mechanism of hippocampal long-term potentiation – Towards multiscale understanding of learning and memory , 2021, Neuroscience Research.

[4]  Grant F Kusick,et al.  Synaptotagmin 7 is targeted to the axonal plasma membrane through γ-secretase processing to promote synaptic vesicle docking in mouse hippocampal neurons , 2021, eLife.

[5]  E. Kavalali,et al.  Copine-6 Binds to SNAREs and Selectively Suppresses Spontaneous Neurotransmission , 2018, The Journal of Neuroscience.

[6]  R. Nicoll,et al.  The CaMKII/NMDA receptor complex controls hippocampal synaptic transmission by kinase-dependent and independent mechanisms , 2018, Nature Communications.

[7]  A. Fischer,et al.  Regulation of Dendritic Spine Morphology in Hippocampal Neurons by Copine-6 , 2018, Cerebral cortex.

[8]  Y. Humeau,et al.  Hippocampal LTP and contextual learning require surface diffusion of AMPA receptors , 2017, Nature.

[9]  T. Südhof,et al.  Postsynaptic Synaptotagmins Mediate AMPA Receptor Exocytosis During LTP , 2017, Nature.

[10]  K. Vogt,et al.  The calcium sensor Copine-6 regulates spine structural plasticity and learning and memory , 2016, Nature Communications.

[11]  R. Huganir,et al.  Activity-Dependent Ubiquitination of GluA1 and GluA2 Regulates AMPA Receptor Intracellular Sorting and Degradation , 2015, Cell reports.

[12]  Sadegh Nabavi,et al.  Engineering a memory with LTD and LTP , 2014, Nature.

[13]  Tomonori Takeuchi,et al.  The synaptic plasticity and memory hypothesis: encoding, storage and persistence , 2014, Philosophical Transactions of the Royal Society B: Biological Sciences.

[14]  Thomas C. Südhof,et al.  Synaptotagmin-1 and Synaptotagmin-7 Trigger Synchronous and Asynchronous Phases of Neurotransmitter Release , 2013, Neuron.

[15]  Richard L. Huganir,et al.  AMPARs and Synaptic Plasticity: The Last 25 Years , 2013, Neuron.

[16]  T. Südhof,et al.  Neurotransmitter Release: The Last Millisecond in the Life of a Synaptic Vesicle , 2013, Neuron.

[17]  T. Südhof,et al.  LTP Requires a Unique Postsynaptic SNARE Fusion Machinery , 2013, Neuron.

[18]  R. Huganir,et al.  Regulation of AMPA receptor trafficking and synaptic plasticity , 2012, Current Opinion in Neurobiology.

[19]  R. Huganir,et al.  PICK1 Loss of Function Occludes Homeostatic Synaptic Scaling , 2011, The Journal of Neuroscience.

[20]  D. Choquet,et al.  A three-step model for the synaptic recruitment of AMPA receptors , 2011, Molecular and Cellular Neuroscience.

[21]  P. Perestenko,et al.  Copines‐1, ‐2, ‐3, ‐6 and ‐7 show different calcium‐dependent intracellular membrane translocation and targeting , 2010, The FEBS journal.

[22]  M. Ehlers,et al.  Syntaxin-4 Defines a Domain for Activity-Dependent Exocytosis in Dendritic Spines , 2010, Cell.

[23]  Roberto Malinow,et al.  AMPA Receptor Incorporation into Synapses during LTP: The Role of Lateral Movement and Exocytosis , 2009, Neuron.

[24]  R. Huganir,et al.  Regulation of AMPA receptor extrasynaptic insertion by 4.1N, phosphorylation and palmitoylation , 2009, Nature Neuroscience.

[25]  Roberto Malinow,et al.  Synaptic AMPA Receptor Plasticity and Behavior , 2009, Neuron.

[26]  Wei-Yang Lu,et al.  Activation of Synaptic NMDA Receptors Induces Membrane Insertion of New AMPA Receptors and LTP in Cultured Hippocampal Neurons , 2001, Neuron.

[27]  K. Svoboda,et al.  Rapid spine delivery and redistribution of AMPA receptors after synaptic NMDA receptor activation. , 1999, Science.

[28]  R. Zucker,et al.  Selective induction of LTP and LTD by postsynaptic [Ca2+]i elevation. , 1999, Journal of neurophysiology.

[29]  G. Kuwajima,et al.  Localization and Subcellular Distribution of N‐Copine in Mouse Brain , 1999, Journal of neurochemistry.

[30]  G. Kuwajima,et al.  N‐copine: a novel two C2‐domain‐containing protein with neuronal activity‐regulated expression , 1998, FEBS letters.

[31]  R. Nicoll,et al.  Postsynaptic membrane fusion and long-term potentiation. , 1998, Science.

[32]  S. Tonegawa,et al.  The Essential Role of Hippocampal CA1 NMDA Receptor–Dependent Synaptic Plasticity in Spatial Memory , 1996, Cell.