Activity-dependent translocation of neurogranin to neuronal nuclei.
Long-term changes of synaptic plasticity depend on protein synthesis and transcription. Ng (neurogranin) is a small protein concentrated at dendrites and spines of forebrain neurons, involved in synaptic plasticity through the regulation of CaM (calmodulin)-mediated signalling. Ng presents a central IQ motif that mediates its binding to CaM and PA (phosphatidic acid) and that can be phosphorylated by PKC (protein kinase C). In the present manuscript, we report that Ng displays a strong nuclear localization when expressed in cell lines and hippocampal neurons, either alone or fused to GFP (green fluorescent protein; GFP-Ng). Furthermore, using subcellular fractionation and immunocytochemical techniques, we were able to localize endogenous Ng in the nuclei of rat forebrain neurons. Nuclear localization of Ng depends on its IQ motif and is reduced by binding to cytoplasmic CaM. Also, PKC stimulation induces a transient nuclear translocation of Ng in acute hippocampal slices. A similar translocation is observed in the neurons of the cerebral cortex and hippocampus after the induction of generalized seizures in adult rats. In summary, the results of the present study show that a fraction of rat brain Ng is localized in the neuronal nuclei and that synaptic activity regulates its translocation from the cytoplasm. The possible involvement of Ng in the regulation of intranuclear Ca2+/CaM-dependent signalling and gene expression is discussed.
Garrido-García
Alberto
A
Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas - Universidad Autónoma de Madrid), Universidad Autónoma de Madrid, E-28049 Madrid, Spain.
Andrés-Pans
Beatriz
B
Durán-Trío
Lara
L
Díez-Guerra
F Javier
FJ
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D051579:Neurogranin / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology*
D002147:Calmodulin; D051579:Neurogranin; D049452:Green Fluorescent Proteins; D002118:Calcium