title: PSD-95 promotes synaptogenesis and multiinnervated spine formation through nitric oxide signaling.
abstract: Postsynaptic density 95 (PSD-95) is an important regulator of synaptic structure and plasticity. However, its contribution to synapse formation and organization remains unclear. Using a combined electron microscopic, genetic, and pharmacological approach, we uncover a new mechanism through which PSD-95 regulates synaptogenesis. We find that PSD-95 overexpression affected spine morphology but also promoted the formation of multiinnervated spines (MISs) contacted by up to seven presynaptic terminals. The formation of multiple contacts was specifically prevented by deletion of the PDZ(2) domain of PSD-95, which interacts with nitric oxide (NO) synthase (NOS). Similarly, PSD-95 overexpression combined with small interfering RNA-mediated down-regulation or the pharmacological blockade of NOS prevented axon differentiation into varicosities and multisynapse formation. Conversely, treatment of hippocampal slices with an NO donor or cyclic guanosine monophosphate analogue induced MISs. NOS blockade also reduced spine and synapse density in developing hippocampal cultures. These results indicate that the postsynaptic site, through an NOS-PSD-95 interaction and NO signaling, promotes synapse formation with nearby axons.
authors.affiliation: Department of Fundamental Neuroscience, Geneva Neuroscience Center, University of Geneva School of Medicine, CH-1211 Geneva, Switzerland.
authors.forename: Irina
authors.initials: I
authors.lastname: Nikonenko
authors.forename: Bernadett
authors.initials: B
authors.lastname: Boda
authors.forename: Sylvain
authors.initials: S
authors.lastname: Steen
authors.forename: Graham
authors.initials: G
authors.lastname: Knott
authors.forename: Egbert
authors.initials: E
authors.lastname: Welker
authors.forename: Dominique
authors.initials: D
authors.lastname: Muller
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D049229:Dendritic Spines / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D000076122:Disks Large Homolog 4 Protein; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D041681:NIH 3T3 Cells; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D009603:Nitroso Compounds / Q000494:pharmacology; D038081:Organogenesis / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017966:Pyramidal Cells / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013569:Synapses / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D014162:Transfection
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009603:Nitroso Compounds; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D006152:Cyclic GMP