Nuclear calcium sensors reveal that repetition of trains of synaptic stimuli boosts nuclear calcium signaling in CA1 pyramidal neurons.

Nuclear calcium is a key signal in the dialogue between synapse and nucleus that controls the genomic responses required for persistent adaptations, including memory and acquired neuroprotection. The amplitude and duration of nuclear calcium transients specify activity-induced transcriptional changes. However, the precise relationship between synaptic input and nuclear calcium output is unknown. Here, we used stereotaxic delivery to the rat brain of recombinant adeno-associated viruses encoding nuclear-targeted calcium sensors to assess nuclear calcium transients in CA1 pyramidal neurons after stimulation of the Schaffer collaterals. We show that in acute hippocampal slices, a burst of synaptic activity elicits a nuclear calcium signal with a regenerative component at above-threshold stimulation intensities. Using classical stimulation paradigms (i.e., high-frequency stimulation (HFS) and θ burst stimulation (TBS)) to induce early LTP (E-LTP) and transcription-dependent late LTP (L-LTP), we found that the magnitude of nuclear calcium signals and the number of action potentials activated by synaptic stimulation trains are greatly amplified by their repetition. Nuclear calcium signals and action potential generation were reduced by blockade of either NMDA receptors or L-type voltage-gated calcium channels, but not by procedures that lead to internal calcium store depletion or by blockade of metabotropic glutamate receptors. These findings identify a repetition-induced switch in nuclear calcium signaling that correlates with the transition from E-LTP to L-LTP, and may explain why the transcription-dependent phase of L-LTP is not induced by a single HFS or TBS but requires repeated trains of activity. Recombinant, nuclear-targeted indicators may prove useful for further analysis of nuclear calcium signaling in vivo.

[1]  W. Regehr,et al.  Short-term synaptic plasticity. , 2002, Annual review of physiology.

[2]  M. Ohkura,et al.  A high signal-to-noise Ca2+ probe composed of a single green fluorescent protein , 2001, Nature Biotechnology.

[3]  K. Becker,et al.  Gene Expression in the Conversion of Early‐Phase to Late‐Phase Long‐Term Potentiation , 2005, Annals of the New York Academy of Sciences.

[4]  M. Berridge.  Neuronal Calcium Signaling , 1998, Neuron.

[5]  H. Bading,et al.  Coupling of extrasynaptic NMDA receptors to a CREB shut-off pathway is developmentally regulated. , 2002, Biochimica et biophysica acta.

[6]  N. Hardingham,et al.  Nuclear Ca2+ and the cAMP Response Element-Binding Protein Family Mediate a Late Phase of Activity-Dependent Neuroprotection , 2005, The Journal of Neuroscience.

[7]  Shigeo Watanabe,et al.  Synaptically Activated Ca2+ Waves in Layer 2/3 and Layer 5 Rat Neocortical Pyramidal Neurons , 2003, The Journal of physiology.

[8]  T. Curran,et al.  Mapping patterns of c-fos expression in the central nervous system after seizure. , 1987, Science.

[9]  J. Lambert,et al.  Role of presynaptic L-type Ca2+ channels in GABAergic synaptic transmission in cultured hippocampal neurons. , 1999, Journal of neurophysiology.

[10]  E. Kandel,et al.  Recruitment of long-lasting and protein kinase A-dependent long-term potentiation in the CA1 region of hippocampus requires repeated tetanization. , 1994, Learning & memory.

[11]  O. Garaschuk,et al.  Optical monitoring of brain function in vivo: from neurons to networks , 2006, Pflügers Archiv.

[12]  Hilmar Bading,et al.  Microelectrode array recordings of cultured hippocampal networks reveal a simple model for transcription and protein synthesis‐dependent plasticity , 2005, The Journal of physiology.

[13]  Hilmar Bading,et al.  Nuclear Calcium Signaling Controls Expression of a Large Gene Pool: Identification of a Gene Program for Acquired Neuroprotection Induced by Synaptic Activity , 2009, PLoS genetics.

[14]  K. Deisseroth,et al.  Signaling from Synapse to Nucleus: Postsynaptic CREB Phosphorylation during Multiple Forms of Hippocampal Synaptic Plasticity , 1996, Neuron.

[15]  W. N. Ross,et al.  Priming of intracellular calcium stores in rat CA1 pyramidal neurons , 2007, The Journal of physiology.

[16]  Karel Svoboda,et al.  Monitoring Neural Activity and [Ca2+] with Genetically Encoded Ca2+ Indicators , 2004, The Journal of Neuroscience.

[17]  Hilmar Bading,et al.  Decoding NMDA Receptor Signaling: Identification of Genomic Programs Specifying Neuronal Survival and Death , 2007, Neuron.

[18]  Javier Díez-García,et al.  Optical probing of neuronal circuit dynamics: genetically encoded versus classical fluorescent sensors , 2006, Trends in Neurosciences.

[19]  E. Kandel,et al.  Long-lasting forms of synaptic potentiation in the mammalian hippocampus. , 1996, Learning & memory.

[20]  R. Yuste,et al.  Detecting action potentials in neuronal populations with calcium imaging. , 1999, Methods.

[21]  Mark Mayford,et al.  Nuclear Calcium/Calmodulin Regulates Memory Consolidation , 2004, The Journal of Neuroscience.

[22]  Shigeo Watanabe,et al.  Modulation of calcium wave propagation in the dendrites and to the soma of rat hippocampal pyramidal neurons , 2006, The Journal of physiology.

[23]  J. Connor,et al.  Ca2+ release from intracellular stores induced by afferent stimulation of CA3 pyramidal neurons in hippocampal slices. , 1996, Journal of neurophysiology.

[24]  Andrew J. Cole,et al.  Rapid increase of an immediate early gene messenger RNA in hippocampal neurons by synaptic NMDA receptor activation , 1989, Nature.

[25]  K. Holthoff,et al.  Nuclear calcium signals during L-LTP induction do not predict the degree of synaptic potentiation. , 2007, Cell calcium.

[26]  M. Yeckel,et al.  Hippocampal mossy fiber activity evokes Ca2+ release in CA3 pyramidal neurons via a metabotropic glutamate receptor pathway , 2001, Neuroscience.

[27]  Hilmar Bading,et al.  Nuclear calcium signaling controls CREB-mediated gene expression triggered by synaptic activity , 2001, Nature Neuroscience.

[28]  M E Greenberg,et al.  Regulation of gene expression in hippocampal neurons by distinct calcium signaling pathways. , 1993, Science.

[29]  W. Catterall.  Structure and regulation of voltage-gated Ca2+ channels. , 2000, Annual review of cell and developmental biology.

[30]  Guy Salama,et al.  Imaging cellular signals in the heart in vivo: Cardiac expression of the high-signal Ca2+ indicator GCaMP2. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[31]  W. N. Ross,et al.  Inositol 1,4,5-Trisphosphate (IP3)-Mediated Ca2+ Release Evoked by Metabotropic Agonists and Backpropagating Action Potentials in Hippocampal CA1 Pyramidal Neurons , 2000, The Journal of Neuroscience.

[32]  Pankaj Sah,et al.  Nuclear Calcium Signaling Evoked by Cholinergic Stimulation in Hippocampal CA1 Pyramidal Neurons , 2002, The Journal of Neuroscience.

[33]  William A. Catterall,et al.  Clustering of L-type Ca2+ channels at the base of major dendrites in hippocampal pyramidal neurons , 1990, Nature.

[34]  W. N. Ross,et al.  Synergistic Release of Ca2+ from IP3-Sensitive Stores Evoked by Synaptic Activation of mGluRs Paired with Backpropagating Action Potentials , 1999, Neuron.

[35]  R. Leapman,et al.  Activity-Dependent Calcium Sequestration in Dendrites of Hippocampal Neurons in Brain Slices , 1997, The Journal of Neuroscience.

[36]  T. Pozzan,et al.  Nuclear Ca2+ concentration measured with specifically targeted recombinant aequorin. , 1993, The EMBO journal.

[37]  T. Teyler,et al.  Electrical stimuli patterned after the theta-rhythm induce multiple forms of LTP. , 2001, Journal of neurophysiology.

[38]  M. Yeckel,et al.  MGluR-mediated calcium waves that invade the soma regulate firing in layer V medial prefrontal cortical pyramidal neurons. , 2008, Cerebral cortex.

[39]  T. Murphy,et al.  Activation of Nuclear Calcium Dynamics by Synaptic Stimulation in Cultured Cortical Neurons , 1999, Journal of neurochemistry.

[40]  Stephen J Redman,et al.  Spatial segregation of neuronal calcium signals encodes different forms of LTP in rat hippocampus , 2006, The Journal of physiology.

[41]  Alexander Borst,et al.  Fluorescence Changes of Genetic Calcium Indicators and OGB-1 Correlated with Neural Activity and Calcium In Vivo and In Vitro , 2008, The Journal of Neuroscience.

[42]  Junichi Nakai,et al.  Characterization and Subcellular Targeting of GCaMP-Type Genetically-Encoded Calcium Indicators , 2008, PloS one.

[43]  S. Lowen.  The Biophysical Journal , 1960, Nature.

[44]  S. Dudek,et al.  Pattern-Dependent Role of NMDA Receptors in Action Potential Generation: Consequences on Extracellular Signal-Regulated Kinase Activation , 2005, The Journal of Neuroscience.

[45]  M.,et al.  L-type VoltageSensitive Calcium Channels Mediate Synaptic Activation of Immediate Early , 2003 .

[46]  M. Ohkura,et al.  Genetically encoded bright Ca2+ probe applicable for dynamic Ca2+ imaging of dendritic spines. , 2005, Analytical chemistry.

[47]  B L McNaughton,et al.  Persistent increase of hippocampal presynaptic axon excitability after repetitive electrical stimulation: dependence on N-methyl-D-aspartate receptor activity, nitric-oxide synthase, and temperature. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[48]  E. Kandel,et al.  Requirement of a critical period of transcription for induction of a late phase of LTP. , 1994, Science.

[49]  Hilmar Bading,et al.  Distinct functions of nuclear and cytoplasmic calcium in the control of gene expression , 1997, Nature.

[50]  D. Wilkin,et al.  Neuron , 2001, Brain Research.

[51]  W. N. Ross,et al.  Spatial Segregation and Interaction of Calcium Signalling Mechanisms in Rat Hippocampal CA1 Pyramidal Neurons , 2002, The Journal of physiology.

[52]  W. N. Ross,et al.  Synaptically activated increases in Ca2+ concentration in hippocampal CA1 pyramidal cells are primarily due to voltage-gated Ca2+ channels , 1992, Neuron.

[53]  H. Bading,et al.  Synaptic versus extrasynaptic NMDA receptor signalling: implications for neurodegenerative disorders , 2010, Nature Reviews Neuroscience.

[54]  Lawrence M. Grover,et al.  Two components of long-term potentiation induced by different patterns of afferent activation , 1990, Nature.

[55]  R. Tsien,et al.  Fluorescent indicators for Ca2+based on green fluorescent proteins and calmodulin , 1997, Nature.

[56]  T J Teyler,et al.  VDCCs and NMDARs underlie two forms of LTP in CA1 hippocampus in vivo. , 1999, Journal of neurophysiology.

[57]  P. Sah,et al.  Distribution of IP3‐mediated calcium responses and their role in nuclear signalling in rat basolateral amygdala neurons , 2007, The Journal of physiology.