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PSD-95 promotes synaptogenesis and multiinnervated spine formation through nitric oxide signaling.

Nikonenko I, Boda B, Steen S, Knott G, Welker E, Muller D - J. Cell Biol. (2008)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental Neuroscience, Geneva Neuroscience Center, University of Geneva School of Medicine, CH-1211 Geneva, Switzerland.

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.

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NO regulates spine and synapse formation under control conditions. (A) 3D reconstruction of a dendritic segment from a control pyramidal neuron treated for 2 d with 200 μM L-NAME. Note the decrease in spine density. (B) Quantitative analysis of the spine density measured in control (ctrl; n = 8 cells; total length = 134 μm; 145 spines) and L-NAME–treated slice cultures (n = 8 cells; total length = 99 μm; 59 spines; *, P < 0.05). (C) Same as in B but for the synapse density measured by analyzing all PSDs per micrometer of length on dendritic segments of control and L-NAME–treated slice cultures (n = 8 cells; *, P < 0.05). Data are mean ± SEM (error bars). Bar, 1 μm.
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fig9: NO regulates spine and synapse formation under control conditions. (A) 3D reconstruction of a dendritic segment from a control pyramidal neuron treated for 2 d with 200 μM L-NAME. Note the decrease in spine density. (B) Quantitative analysis of the spine density measured in control (ctrl; n = 8 cells; total length = 134 μm; 145 spines) and L-NAME–treated slice cultures (n = 8 cells; total length = 99 μm; 59 spines; *, P < 0.05). (C) Same as in B but for the synapse density measured by analyzing all PSDs per micrometer of length on dendritic segments of control and L-NAME–treated slice cultures (n = 8 cells; *, P < 0.05). Data are mean ± SEM (error bars). Bar, 1 μm.

Mentions: We then asked whether NO also contributed to synapse formation under control conditions. For this, we examined the morphology and density of spines in slice cultures treated for 2 d with the NOS inhibitor L-NAME. This condition clearly affected the mechanisms of spine and synapse formation as both the density of spines and of synapses considerably decreased upon L-NAME treatment (0.65 ± 0.11 spines/μm vs. 1.08 ± 0.12 spines/μm and 0.72 ± 0.12 synapses/μm vs. 1.2 ± 0.12 synapses/μm; n = 8 cells; P < 0.05; Fig. 9, A and B; and Table S1). However, the morphology of remaining spines was not affected, as both the spine volume and PSD area were only slightly different from the values obtained in control tissue (0.078 ± 0.016 μm3 and 0.042 ± 0.008 μm2), and the number of MISs was also very low (1.7 ± 1.7%). Thus, synapse formation under control conditions also appears to require NO signaling to be effective.


PSD-95 promotes synaptogenesis and multiinnervated spine formation through nitric oxide signaling.

Nikonenko I, Boda B, Steen S, Knott G, Welker E, Muller D - J. Cell Biol. (2008)

NO regulates spine and synapse formation under control conditions. (A) 3D reconstruction of a dendritic segment from a control pyramidal neuron treated for 2 d with 200 μM L-NAME. Note the decrease in spine density. (B) Quantitative analysis of the spine density measured in control (ctrl; n = 8 cells; total length = 134 μm; 145 spines) and L-NAME–treated slice cultures (n = 8 cells; total length = 99 μm; 59 spines; *, P < 0.05). (C) Same as in B but for the synapse density measured by analyzing all PSDs per micrometer of length on dendritic segments of control and L-NAME–treated slice cultures (n = 8 cells; *, P < 0.05). Data are mean ± SEM (error bars). Bar, 1 μm.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2600742&req=5

fig9: NO regulates spine and synapse formation under control conditions. (A) 3D reconstruction of a dendritic segment from a control pyramidal neuron treated for 2 d with 200 μM L-NAME. Note the decrease in spine density. (B) Quantitative analysis of the spine density measured in control (ctrl; n = 8 cells; total length = 134 μm; 145 spines) and L-NAME–treated slice cultures (n = 8 cells; total length = 99 μm; 59 spines; *, P < 0.05). (C) Same as in B but for the synapse density measured by analyzing all PSDs per micrometer of length on dendritic segments of control and L-NAME–treated slice cultures (n = 8 cells; *, P < 0.05). Data are mean ± SEM (error bars). Bar, 1 μm.
Mentions: We then asked whether NO also contributed to synapse formation under control conditions. For this, we examined the morphology and density of spines in slice cultures treated for 2 d with the NOS inhibitor L-NAME. This condition clearly affected the mechanisms of spine and synapse formation as both the density of spines and of synapses considerably decreased upon L-NAME treatment (0.65 ± 0.11 spines/μm vs. 1.08 ± 0.12 spines/μm and 0.72 ± 0.12 synapses/μm vs. 1.2 ± 0.12 synapses/μm; n = 8 cells; P < 0.05; Fig. 9, A and B; and Table S1). However, the morphology of remaining spines was not affected, as both the spine volume and PSD area were only slightly different from the values obtained in control tissue (0.078 ± 0.016 μm3 and 0.042 ± 0.008 μm2), and the number of MISs was also very low (1.7 ± 1.7%). Thus, synapse formation under control conditions also appears to require NO signaling to be effective.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Fundamental Neuroscience, Geneva Neuroscience Center, University of Geneva School of Medicine, CH-1211 Geneva, Switzerland.

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.

Show MeSH
Related in: MedlinePlus