Activation of mGluR5 Induces Rapid and Long-Lasting Protein Kinase D Phosphorylation in Hippocampal Neurons

Metabotropic glutamate receptors (mGluRs), including mGluR5, play a central role in regulating the strength and plasticity of synaptic connections in the brain. However, the signaling pathways that connect mGluRs to their downstream effectors are not yet fully understood. Here, we report that stimulation of mGluR5 in hippocampal cultures and slices results in phosphorylation of protein kinase D (PKD) at the autophosphorylation site Ser-916. This phosphorylation event occurs within 30 s of stimulation, persists for at least 24 h, and is dependent on activation of phospholipase C and protein kinase C. Our data suggest that activation of PKD may represent a novel signaling pathway linking mGluR5 to its downstream targets. These findings have important implications for the study of the molecular mechanisms underlying mGluR-dependent synaptic plasticity.Howard Hughes Medical InstituteFRAXA Research FoundationNational Institute of Mental Health (U.S.)Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.

Protein kinase D interacts with neuronal nitric oxide synthase and phosphorylates the activatory residue serine1412

Neuronal Nitric Oxide Synthase (nNOS) is the biosynthetic enzyme responsible for nitric oxide (·NO) production in muscles and in the nervous system. This constitutive enzyme, unlike its endothelial and inducible counterparts, presents an N-terminal PDZ domain known to display a preference for PDZ-binding motifs bearing acidic residues at -2 position. In a previous work, we discovered that the C-terminal end of two members of protein kinase D family (PKD1 and PKD2) constitutes a PDZ-ligand. PKD1 has been shown to regulate multiple cellular processes and, when activated, becomes autophosphorylated at Ser 916, a residue located at -2 position of its PDZ-binding motif. Since nNOS and PKD are spatially enriched in postsynaptic densities and dendrites, the main objective of our study was to determine whether PKD1 activation could result in a direct interaction with nNOS through their respective PDZ-ligand and PDZ domain, and to analyze the functional consequences of this interaction. Herein we demonstrate that PKD1 associates with nNOS in neurons and in transfected cells, and that kinase activation enhances PKD1-nNOS co-immunoprecipitation and subcellular colocalization. However, transfection of mammalian cells with PKD1 mutants and yeast two hybrid assays showed that the association of these two enzymes does not depend on PKD1 PDZ-ligand but its pleckstrin homology domain. Furthermore, this domain was able to pull-down nNOS from brain extracts and bind to purified nNOS, indicating that it mediates a direct PKD1-nNOS interaction. In addition, using mass spectrometry we demonstrate that PKD1 specifically phosphorylates nNOS in the activatory residue Ser 1412, and that this phosphorylation increases nNOS activity and ·NO production in living cells. In conclusion, these novel findings reveal a crucial role of PKD1 in the regulation of nNOS activation and synthesis of ·NO, a mediator involved in physiological neuronal signaling or neurotoxicity under pathological conditions such as ischemic stroke or neurodegeneration.This work was supported by the Ministerio de Economía y Competitividad [SAF2011-26233 to T.I., BFU2009-10442 and BFU2012-37934 to I.R-C.]; Comunidad de Madrid [S2010/BMD-2331-Neurodegmodels-CM to T.I.]; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas – CIBERNED, Instituto de Salud Carlos III, to T.I. Postdoctoral fellows L.S-R. and L.G-G. have been funded by research contracts from CIBERNED; Clara Aicart-Ramos is a recipient of a FPU predoctoral fellowship from Ministerio de Economía y Competitividad.Peer Reviewe

14q12 and severe Rett-like phenotypes: new clinical insights and physical mapping of FOXG1-regulatory elements

Advance online publication 27 June 2012The Forkhead box G1 (FOXG1) gene has been implicated in severe Rett-like phenotypes. It encodes the Forkhead box protein G1, a winged-helix transcriptional repressor critical for forebrain development. Recently, the core FOXG1 syndrome was defined as postnatal microcephaly, severe mental retardation, absent language, dyskinesia, and dysgenesis of the corpus callosum. We present seven additional patients with a severe Rett-like neurodevelopment disorder associated with de novo FOXG1 point mutations (two cases) or 14q12 deletions (five cases). We expand the mutational spectrum in patients with FOXG1-related encephalopathies and precise the core FOXG1 syndrome phenotype. Dysgenesis of the corpus callosum and dyskinesia are not always present in FOXG1-mutated patients. We believe that the FOXG1 gene should be considered in severely mentally retarded patients (no speech-language) with severe acquired microcephaly (−4 to−6 SD) and few clinical features suggestive of Rett syndrome. Interestingly enough, three 14q12 deletions that do not include the FOXG1 gene are associated with phenotypes very reminiscent to that of FOXG1-mutation-positive patients. We physically mapped a putative long-range FOXG1-regulatory element in a 0.43 Mb DNA segment encompassing the PRKD1 locus. In fibroblast cells, a cis-acting regulatory sequence located more than 0.6 Mb away from FOXG1 acts as a silencer at the transcriptional level. These data are important for clinicians and for molecular biologists involved in the management of patients with severe encephalopathies compatible with a FOXG1-related phenotype.Lila Allou, Laetitia Lambert, Daniel Amsallem, Eric Bieth, Patrick Edery, Anne Destrée, François Rivier, David Amor, Elizabeth Thompson, Julian Nicholl, Michael Harbord, Christophe Nemos, Aline Saunier, Aissa Moustaïne, Adeline Vigouroux, Philippe Jonveaux and Christophe Philipp