Publications by authors named "Flavia Valtorta"

79 Publications

An interaction between PRRT2 and Na/K ATPase contributes to the control of neuronal excitability.

Cell Death Dis 2021 Mar 17;12(4):292. Epub 2021 Mar 17.

Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132, Genoa, Italy.

Mutations in PRoline Rich Transmembrane protein 2 (PRRT2) cause pleiotropic syndromes including benign infantile epilepsy, paroxysmal kinesigenic dyskinesia, episodic ataxia, that share the paroxysmal character of the clinical manifestations. PRRT2 is a neuronal protein that plays multiple roles in the regulation of neuronal development, excitability, and neurotransmitter release. To better understand the physiopathology of these clinical phenotypes, we investigated PRRT2 interactome in mouse brain by a pulldown-based proteomic approach and identified α1 and α3 Na/K ATPase (NKA) pumps as major PRRT2-binding proteins. We confirmed PRRT2 and NKA interaction by biochemical approaches and showed their colocalization at neuronal plasma membrane. The acute or constitutive inactivation of PRRT2 had a functional impact on NKA. While PRRT2-deficiency did not modify NKA expression and surface exposure, it caused an increased clustering of α3-NKA on the plasma membrane. Electrophysiological recordings showed that PRRT2-deficiency in primary neurons impaired NKA function during neuronal stimulation without affecting pump activity under resting conditions. Both phenotypes were fully normalized by re-expression of PRRT2 in PRRT2-deficient neurons. In addition, the NKA-dependent afterhyperpolarization that follows high-frequency firing was also reduced in PRRT2-silenced neurons. Taken together, these results demonstrate that PRRT2 is a physiological modulator of NKA function and suggest that an impaired NKA activity contributes to the hyperexcitability phenotype caused by PRRT2 deficiency.
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http://dx.doi.org/10.1038/s41419-021-03569-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7969623PMC
March 2021

Giving names to the actors of synaptic transmission: The long journey from synaptic vesicles to neural plasticity.

Adv Pharmacol 2021 26;90:19-37. Epub 2021 Feb 26.

IRCCS San Raffaele Scientific Institute, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.

More than a scientific paper or a review article, this is a remembrance of a unique time of science and life that the authors spent in Paul Greengard's laboratory at the Rockefeller University in New York in the 1980s and 1990s, forming the so-called synaptic vesicle group. It was a time in which the molecular mechanisms of synaptic transmission and the nature of the organelles in charge of storing and releasing neurotransmitter were just beginning to be understood. It was an exciting time in which the protein composition of synaptic vesicles started to be identified. It turned out that the interactions of synaptic vesicle proteins with the cytoskeleton and the presynaptic membrane and their modulation by protein phosphorylation represented an essential network regulating the efficiency of neurotransmitter release and thereby synaptic strength and plasticity. This is also a description of the distinct scientific journeys that the three authors took on going back to Europe and how they were strongly influenced by the generous and outstanding mentorship of Paul Greengard, his genuine interest in their lives and careers and the life-long friendship with him.
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http://dx.doi.org/10.1016/bs.apha.2020.09.007DOI Listing
April 2021

Pharmacological antagonism of kainate receptor rescues dysfunction and loss of dopamine neurons in a mouse model of human parkin-induced toxicity.

Cell Death Dis 2020 11 10;11(11):963. Epub 2020 Nov 10.

Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Via Olgettina 58, 20132, Milan, Italy.

Mutations in the PARK2 gene encoding the protein parkin cause autosomal recessive juvenile Parkinsonism (ARJP), a neurodegenerative disease characterized by dysfunction and death of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). Since a neuroprotective therapy for ARJP does not exist, research efforts aimed at discovering targets for neuroprotection are critically needed. A previous study demonstrated that loss of parkin function or expression of parkin mutants associated with ARJP causes an accumulation of glutamate kainate receptors (KARs) in human brain tissues and an increase of KAR-mediated currents in neurons in vitro. Based on the hypothesis that such KAR hyperactivation may contribute to the death of nigral DA neurons, we investigated the effect of KAR antagonism on the DA neuron dysfunction and death that occur in the parkinQ311X mouse, a model of human parkin-induced toxicity. We found that early accumulation of KARs occurs in the DA neurons of the parkinQ311X mouse, and that chronic administration of the KAR antagonist UBP310 prevents DA neuron loss. This neuroprotective effect is associated with the rescue of the abnormal firing rate of nigral DA neurons and downregulation of GluK2, the key KAR subunit. This study provides novel evidence of a causal role of glutamate KARs in the DA neuron dysfunction and loss occurring in a mouse model of human parkin-induced toxicity. Our results support KAR as a potential target in the development of neuroprotective therapy for ARJP.
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http://dx.doi.org/10.1038/s41419-020-03172-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7656261PMC
November 2020

Dysfunction of the serotonergic system in the brain of synapsin triple knockout mice is associated with behavioral abnormalities resembling synapsin-related human pathologies.

Prog Neuropsychopharmacol Biol Psychiatry 2021 Mar 12;105:110135. Epub 2020 Oct 12.

IRCCS San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Via Olgettina 58, 20132 Milano, Italy; Department of Psychiatry, McGill University, Montreal, QC, Canada. Electronic address:

Synapsins (Syns) are a family of phosphoproteins associated with synaptic vesicles (SVs). Their main function is to regulate neurotransmitter release by maintaining a reserve pool of SVs at the presynaptic terminal. Previous studies reported that the deletion of one or more Syn genes in mice results in an epileptic phenotype and autism-related behavioral abnormalities. Here we aimed at characterizing the behavioral phenotype and neurobiological correlates of the deletion of Syns in a Syn triple knockout (TKO) mouse model. Wild type (WT) and TKO mice were tested in the open field, novelty suppressed feeding, light-dark box, forced swim, tail suspension and three-chamber sociability tests. Using in vivo electrophysiology, we recorded the spontaneous activity of dorsal raphe nucleus (DRN) serotonin (5-HT) and ventral tegmental area (VTA) dopamine (DA) neurons. Levels of 5-HT and DA in the frontal cortex and hippocampus of WT and TKO mice were also assessed using a High-Performance Liquid Chromatography. TKO mice displayed hyperactivity and impaired social and anxiety-like behavior. Behavioral dysfunctions were accompanied by reduced firing activity of DRN 5-HT, but not VTA DA, neurons. TKO mice also showed increased responsiveness of DRN 5-HT-1A autoreceptors, measured as a reduced dose of the 5-HT-1A agonist 8-OH-DPAT necessary to inhibit DRN 5-HT firing activity by 50%. Finally, hippocampal 5-HT levels were lower in TKO than in WT mice. Overall, Syns deletion in mice leads to a reduction in DRN 5-HT firing activity and hippocampal 5-HT levels along with behavioral alterations reminiscent of human neuropsychiatric conditions associated with Syn dysfunction.
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http://dx.doi.org/10.1016/j.pnpbp.2020.110135DOI Listing
March 2021

Proline-rich transmembrane protein 2 (PRRT2) regulates the actin cytoskeleton during synaptogenesis.

Cell Death Dis 2020 10 14;11(10):856. Epub 2020 Oct 14.

IRCCS San Raffaele Scientific Institute, Via Olgettina 60, 20132, Milan, Italy.

Mutations in proline-rich transmembrane protein 2 (PRRT2) have been recently identified as the leading cause of a clinically heterogeneous group of neurological disorders sharing a paroxysmal nature, including paroxysmal kinesigenic dyskinesia and benign familial infantile seizures. To date, studies aimed at understanding its physiological functions in neurons have mainly focused on its ability to regulate neurotransmitter release and neuronal excitability. Here, we show that PRRT2 expression in non-neuronal cell lines inhibits cell motility and focal adhesion turnover, increases cell aggregation propensity, and promotes the protrusion of filopodia, all processes impinging on the actin cytoskeleton. In primary hippocampal neurons, PRRT2 silencing affects the synaptic content of filamentous actin and perturbs actin dynamics. This is accompanied by defects in the density and maturation of dendritic spines. We identified cofilin, an actin-binding protein abundantly expressed at the synaptic level, as the ultimate effector of PRRT2. Indeed, PRRT2 silencing unbalances cofilin activity leading to the formation of cofilin-actin rods along neurites. The expression of a cofilin phospho-mimetic mutant (cof-S3E) is able to rescue PRRT2-dependent defects in synapse density, spine number and morphology, but not the alterations observed in neurotransmitter release. Our data support a novel function of PRRT2 in the regulation of the synaptic actin cytoskeleton and in the formation of synaptic contacts.
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http://dx.doi.org/10.1038/s41419-020-03073-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560900PMC
October 2020

Prenatal IL-6 levels and activation of the tryptophan to kynurenine pathway are associated with depressive but not anxiety symptoms across the perinatal and the post-partum period in a low-risk sample.

Brain Behav Immun 2020 10 9;89:175-183. Epub 2020 Jun 9.

IRCCS E. Medea Scientific Institute, Child Psychopathology Unit, Bosisio Parini, Lecco, Italy.

Depression and anxiety symptoms are highly prevalent among women during pregnancy and post-partum. Previous studies suggest that one of the pathophysiological underpinnings could be an enhanced metabolism of tryptophan (Trp) into kynurenine (Kyn) due to increased inflammation. However, the longitudinal changes in the Kyn pathway and the complex interplay with inflammation and stress in women with perinatal depressive or anxiety symptoms are incompletely understood. We examined a cohort of healthy women at 34-36 gestational weeks. One hundred and ten women were assessed for salivary cortisol and 97 participants were also assessed for serum levels of Trp, Kyn and Interleukin 6 (IL-6). Women filled in two screening questionnaires for depressive (Edinburgh Postnatal Depression Scale (EPDS)) and anxiety (State Trait Anxiety Inventory subscale (STAI-S)) symptoms at 34-36 gestational weeks, delivery, 3 and 12 months postpartum. Unexpectedly, lower prenatal Kyn levels were associated with higher depressive symptoms in late pregnancy. Furthermore, prenatal Trp levels and the Kyn/Trp ratio moderate the association between IL-6 levels and depressive symptoms during the perinatal and the post-partum period. We found no interactions between Trp and Kyn biomarkers and cortisol on depressive symptoms. The observed associations were more robustly found for depressive symptoms, whereas weak and non-significant effects were found for the trajectory of anxiety symptoms. Overall, our data support the involvement of the Trp to Kyn pathway and inflammation in the course of depressive but not anxiety symptoms in women from late pregnancy until one-year post-partum, providing new evidence on the mechanisms regulating emotions during pregnancy and after delivery in a low-risk sample.
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http://dx.doi.org/10.1016/j.bbi.2020.06.015DOI Listing
October 2020

Transcranial direct current stimulation of the mouse prefrontal cortex modulates serotonergic neural activity of the dorsal raphe nucleus.

Brain Stimul 2020 May - Jun;13(3):548-550. Epub 2020 Jan 17.

San Raffaele Scientific Institute and Vita Salute University, Department of Neuroscience, Milan, Italy; Department of Psychiatry, McGill University, Montreal, Quebec, Canada. Electronic address:

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http://dx.doi.org/10.1016/j.brs.2020.01.012DOI Listing
January 2020

Investigating the relationship between melatonin levels, melatonin system, microbiota composition and bipolar disorder psychopathology across the different phases of the disease.

Int J Bipolar Disord 2019 Dec 9;7(1):27. Epub 2019 Dec 9.

San Raffaele Scientific Institute and Vita Salute University, Via Olgettina 58, 20132, Milan, Italy.

Background: Bipolar disorder (BD) is characterized by recurrent episodes of depression and mania/hypomania alternating with intervals of well-being. The neurobiological underpinnings of BD are still veiled although there is evidence pointing to a malfunction of the circadian clock system that is regulated by the neuromodulator melatonin (MLT). Small sample size studies in BD patients have shown that changes in the levels of MLT are associated with shifts in illness status. Moreover, mood stabilizers (including lithium and valproic acid) influence the MLT system. Of interest, MLT also modulates intestinal microbiota, and recent work suggests an important role of microbiota alterations in neuropsychiatric disorders, including BD. This study is designed to explore whether the possible patterns of associations between changes in the levels of MLT and its precursors and BD mood phases are modulated by variants within the genes encoding for the elements of the MLT system and/or by the microbiota composition.

Methods: We will conduct a 2-year follow-up study in 50 BD patients during the three different mood phases of the disease. For each phase, we will perform a blood withdrawal for the analysis of MLT levels and of variants of the genes related to the MLT pathway between 8 and 10 a.m. after an overnight fasting, a stool specimen collection for the analysis of microbiota composition, and a detailed psychometric assessment for depression, mania, impulsivity and cognitive abilities. We will also recruit 50 healthy age-matched controls in whom we will perform a blood withdrawal between 8 and 10 a.m. after an overnight fasting, a stool specimen collection, and a psychometric assessment to exclude the presence of psychiatric disorders.

Discussion: In this cross sectional (case-control vs. BD comparisons) and longitudinal (24 months) study, we expect to clarify the link between the MLT system, microbiota and BD psychopathology. We expect to identify some typical BD symptomatic clusters that will be more strictly associated with variations in the MLT system. In a personalized medicine perspective, this subgroup of BD patients may benefit from a pharmacological therapy targeting the MLT system. Trial registration This study protocol was approved by the Ethics Committee of the University Hospital Agency of Cagliari (PG/2019/6277).
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http://dx.doi.org/10.1186/s40345-019-0163-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6900376PMC
December 2019

Grey and white matter structure associates with the activation of the tryptophan to kynurenine pathway in bipolar disorder.

J Affect Disord 2019 12 19;259:404-412. Epub 2019 Aug 19.

Division of Neuroscience, San Raffaele Scientific Institute, Vita-Salute University, San Raffaele Turro, Via Stamira d'Ancona 20, Milan, Italy.

Background: Bipolar disorder (BD) is a severe mental illness characterised by reduced grey matter (GM) volumes and cortical thickness, and disrupted white matter (WM) microstructure. Activation of indoleamine 2,3-dioxygenase following a pro-inflammatory state could increase the amount of tryptophan (Trp) converted to kynurenine (Kyn) possibly leading to the production of detrimental catabolites of the Kyn pathway with neurotoxic effects. We investigated if peripheral levels of Trp-and Kyn and the breakdown of Trp-into Kyn (Kyn/Trp-ratio) are related to WM and GM integrity in BD.

Methods: Peripheral levels of Trp-and Kyn were analysed in 72 patients with BD and 33 controls. Patients also underwent MRI in a Philips 3T scanner.

Results: Patients showed higher Kyn levels and Kyn/Trp-ratio compared to controls. MRI analyses performed in patients with BD showed a negative association between the Kyn/Trp-ratio and the integrity of corpus callosum microstructure, the volume of the amygdala and cortical thickness in fronto-parietal regions.

Limitation: The lack of information on the levels of downstream metabolites of Kyn prevent us to confirm the possible unbalance between quinolinic and kynurenic acids as well as their possible relationship with changes in GM and WM markers. The activation of the Kyn pathway as suggested by the increased Kyn/Trp-ratio may lead to an imbalance of the neurotoxic vs the neuroprotective arm of the biochemical pathway, resulting in significant changes in GM and WM regions of brain areas strongly implicated in the pathophysiology of BD, such as amygdala and corpus callosum.
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http://dx.doi.org/10.1016/j.jad.2019.08.034DOI Listing
December 2019

Early Dyskinesias in Parkinson's Disease Patients With Parkin Mutation: A Primary Corticostriatal Synaptopathy?

Front Neurosci 2019 26;13:273. Epub 2019 Mar 26.

Department of Neurology, IRCCS Istituto Auxologico Italiano, Milan, Italy.

Mutations in the gene cause early-onset Parkinson's disease (PD). Despite the high proportion of still missing phenotyping data in the literature devoted to early-onset PD, studies suggest that, as compared with late-onset PD, patients show dystonia at onset and extremely dose-sensitive levodopa-induced dyskinesia (LID). What pathophysiological mechanisms underpin such early and atypical dyskinesia in patients with mutations? Though the precise mechanisms underlying dystonia and LID are still unclear, evidence suggests that hyperkinetic disorders in PD are a behavioral expression of maladaptive functional and morphological changes at corticostriatal synapses induced by long-term dopamine (DA) depletion. However, since the dyskinesia in patients can also be present at onset, other mechanisms beside the well-established DA depletion may play a role in the development of dyskinesia in these patients. Because cortical and striatal neurons express parkin protein, and parkin modulates the function of ionotropic glutamatergic receptors (iGluRs), an intriguing explanation may rest on the potential role of parkin in directly controlling the glutamatergic corticostriatal synapse transmission. We discuss the novel theory that loss of parkin function can dysregulate transmission at the corticostriatal synapses where they cause early maladaptive changes that co-occur with the changes stemming from DA loss. This hypothesis suggests an early striatal synaptopathy; it could lay the groundwork for pharmacological treatment of dyskinesias and LID in patients with mutations.
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http://dx.doi.org/10.3389/fnins.2019.00273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443894PMC
March 2019

Role of palmitoylethanolamide (PEA) in depression: Translational evidence: Special Section on "Translational and Neuroscience Studies in Affective Disorders". Section Editor, Maria Nobile MD, PhD. This Section of JAD focuses on the relevance of translational and neuroscience studies in providing a better understanding of the neural basis of affective disorders. The main aim is to briefly summaries relevant research findings in clinical neuroscience with particular regards to specific innovative topics in mood and anxiety disorders.

J Affect Disord 2019 08 25;255. Epub 2018 Oct 25.

Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada; San Raffaele Scientific Institute and Vita Salute University, Via Olgettina 58, Milano 20132, Italy. Electronic address:

Background: Antidepressants have a low rate of response paired with a delayed onset of action. Translational studies are thus seeking for novel targets for antidepressant drug development. Preclinical evidence has demonstrated that the endocannabinoid system plays an important role in mood and stress response, even if drugs targeting this system have not yet become available for clinical use. The dietary supplement N-Palmitoylethanolamide (PEA) is a fatty acid amide belonging to the endocannabinoid system with potential antidepressant properties.

Methods: We performed a bibliographic search to review current knowledge on the potential antidepressant effects of PEA and its underlying mechanism of action.

Results: PEA targets not only the peroxisome proliferator-activated receptor-alpha (PPAR-α), but also the endocannabinoid system, binding the G-protein-coupled receptor 55, a non-CB/CB cannabinoid receptor, and also the CB/CB receptors, although with a weak affinity. Preclinical studies have shown antidepressant activity of PEA in animal paradigms of depression and of depression associated with neuropathic pain and traumatic brain injury. In a translational perspective, PEA is increased in stress conditions, and a randomized, double-blind study in depressed patients indicated a fast-antidepressant action of PEA when associated with citalopram.

Limitations: There are still limited preclinical and clinical studies investigating the effect of PEA upon the endocannabinoid system and its potential as antidepressant.

Conclusions: PEA has potential antidepressant effects alone or in combinations with other classes of antidepressants. Future studies in depressed patients are needed to confirm the mood-modulating properties of PEA and its role as a biomarker of depression.
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http://dx.doi.org/10.1016/j.jad.2018.10.117DOI Listing
August 2019

Constitutive Inactivation of the PRRT2 Gene Alters Short-Term Synaptic Plasticity and Promotes Network Hyperexcitability in Hippocampal Neurons.

Cereb Cortex 2019 05;29(5):2010-2033

Department of Experimental Medicine, University of Genova, Viale Benedetto XV 3, Genova, Italy.

Mutations in PRoline-Rich Transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders including epilepsy, kinesigenic dyskinesia and migraine. Most of the mutations lead to impaired PRRT2 expression and/or function, emphasizing the pathogenic role of the PRRT2 deficiency. In this work, we investigated the phenotype of primary hippocampal neurons obtained from mouse embryos in which the PRRT2 gene was constitutively inactivated. Although PRRT2 is expressed by both excitatory and inhibitory neurons, its deletion decreases the number of excitatory synapses without significantly affecting the number of inhibitory synapses or the nerve terminal ultrastructure. Analysis of synaptic function in primary PRRT2 knockout excitatory neurons by live imaging and electrophysiology showed slowdown of the kinetics of exocytosis, weakened spontaneous and evoked synaptic transmission and markedly increased facilitation. Inhibitory neurons showed strengthening of basal synaptic transmission, accompanied by faster depression. At the network level these complex synaptic effects resulted in a state of heightened spontaneous and evoked activity that was associated with increased excitability of excitatory neurons in both PRRT2 knockout primary cultures and acute hippocampal slices. The data indicate the existence of network instability/hyperexcitability as the possible basis of the paroxysmal phenotypes associated with PRRT2 mutations.
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http://dx.doi.org/10.1093/cercor/bhy079DOI Listing
May 2019

Constitutive Inactivation of the PRRT2 Gene Alters Short-Term Synaptic Plasticity and Promotes Network Hyperexcitability in Hippocampal Neurons.

Cereb Cortex 2019 05;29(5):2010-2033

Department of Experimental Medicine, University of Genova, Viale Benedetto XV 3, Genova, Italy.

Mutations in PRoline-Rich Transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders including epilepsy, kinesigenic dyskinesia and migraine. Most of the mutations lead to impaired PRRT2 expression and/or function, emphasizing the pathogenic role of the PRRT2 deficiency. In this work, we investigated the phenotype of primary hippocampal neurons obtained from mouse embryos in which the PRRT2 gene was constitutively inactivated. Although PRRT2 is expressed by both excitatory and inhibitory neurons, its deletion decreases the number of excitatory synapses without significantly affecting the number of inhibitory synapses or the nerve terminal ultrastructure. Analysis of synaptic function in primary PRRT2 knockout excitatory neurons by live imaging and electrophysiology showed slowdown of the kinetics of exocytosis, weakened spontaneous and evoked synaptic transmission and markedly increased facilitation. Inhibitory neurons showed strengthening of basal synaptic transmission, accompanied by faster depression. At the network level these complex synaptic effects resulted in a state of heightened spontaneous and evoked activity that was associated with increased excitability of excitatory neurons in both PRRT2 knockout primary cultures and acute hippocampal slices. The data indicate the existence of network instability/hyperexcitability as the possible basis of the paroxysmal phenotypes associated with PRRT2 mutations.
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http://dx.doi.org/10.1093/cercor/bhy079DOI Listing
May 2019

A Method to Culture GABAergic Interneurons Derived from the Medial Ganglionic Eminence.

Front Cell Neurosci 2017 8;11:423. Epub 2018 Jan 8.

Cell Adhesion Unit San Raffaele Scientific Institute and San Raffaele University, Milan, Italy.

Understanding the mechanisms guiding interneuron development is a central aspect of the current research on cortical/hippocampal interneurons, which is highly relevant to brain function and pathology. In this methodological study we have addressed the setup of protocols for the reproducible culture of dissociated cells from murine medial ganglionic eminences (MGEs), to provide a culture system for the analysis of interneurons . This study includes the detailed protocols for the preparation of the dissociated cells, and for their culture on optimal substrates for cell migration or differentiation. These cultures enriched in interneurons may allow the investigation of the migratory behavior of interneuron precursors and their differentiation , up to the formation of morphologically identifiable GABAergic synapses. Live imaging of MGE-derived cells plated on proper substrates shows that they are useful to study the migratory behavior of the precursors, as well as the behavior of growth cones during the development of neurites. Most MGE-derived precursors develop into polarized GABAergic interneurons as determined by axonal, dendritic, and GABAergic markers. We present also a comparison of cells from WT and mutant mice as a proof of principle for the use of these cultures for the analysis of the migration and differentiation of GABAergic cells with different genetic backgrounds. The culture enriched in interneurons described here represents a useful experimental system to examine in a relatively easy and fast way the morpho-functional properties of these cells under physiological or pathological conditions, providing a powerful tool to complement the studies .
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http://dx.doi.org/10.3389/fncel.2017.00423DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766683PMC
January 2018

APache Is an AP2-Interacting Protein Involved in Synaptic Vesicle Trafficking and Neuronal Development.

Cell Rep 2017 Dec;21(12):3596-3611

Department of Experimental Medicine, University of Genova, 16132 Genova, Italy. Electronic address:

Synaptic transmission is critically dependent on synaptic vesicle (SV) recycling. Although the precise mechanisms of SV retrieval are still debated, it is widely accepted that a fundamental role is played by clathrin-mediated endocytosis, a form of endocytosis that capitalizes on the clathrin/adaptor protein complex 2 (AP2) coat and several accessory factors. Here, we show that the previously uncharacterized protein KIAA1107, predicted by bioinformatics analysis to be involved in the SV cycle, is an AP2-interacting clathrin-endocytosis protein (APache). We found that APache is highly enriched in the CNS and is associated with clathrin-coated vesicles via interaction with AP2. APache-silenced neurons exhibit a severe impairment of maturation at early developmental stages, reduced SV density, enlarged endosome-like structures, and defects in synaptic transmission, consistent with an impaired clathrin/AP2-mediated SV recycling. Our data implicate APache as an actor in the complex regulation of SV trafficking, neuronal development, and synaptic plasticity.
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http://dx.doi.org/10.1016/j.celrep.2017.11.073DOI Listing
December 2017

Impaired GABA-mediated presynaptic inhibition increases excitatory strength and alters short-term plasticity in synapsin knockout mice.

Oncotarget 2017 Oct 30;8(52):90061-90076. Epub 2017 Sep 30.

Department of Experimental Medicine, Section of Physiology, University of Genoa, 16132 Genova, Italy.

Synapsins are a family of synaptic vesicle phosphoproteins regulating synaptic transmission and plasticity. genes are major epilepsy susceptibility genes in humans. Consistently, synapsin I/II/III triple knockout (TKO) mice are epileptic and exhibit severe impairments in phasic and tonic GABAergic inhibition that precede the appearance of the epileptic phenotype. These changes are associated with an increased strength of excitatory transmission that has never been mechanistically investigated. Here, we observed that an identical effect in excitatory transmission could be induced in wild-type (WT) Schaffer collateral-CA1 pyramidal cell synapses by blockade of GABA receptors (GABARs). The same treatment was virtually ineffective in TKO slices, suggesting that the increased strength of the excitatory transmission results from an impairment of GABA presynaptic inhibition. Exogenous stimulation of GABARs in excitatory autaptic neurons, where GABA spillover is negligible, demonstrated that GABARs were effective in inhibiting excitatory transmission in both WT and TKO neurons. These results demonstrate that the decreased GABA release and spillover, previously observed in TKO hippocampal slices, removes the tonic brake of presynaptic GABARs on glutamate transmission, making the excitation/inhibition imbalance stronger.
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http://dx.doi.org/10.18632/oncotarget.21405DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5685732PMC
October 2017

Synapsin I deletion reduces neuronal damage and ameliorates clinical progression of experimental autoimmune encephalomyelitis.

Brain Behav Immun 2018 02 21;68:197-210. Epub 2017 Oct 21.

Division of Neuroscience, San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy; Vita-Salute San Raffaele University, Via Olgettina 58, 20132 Milan, Italy. Electronic address:

The classical view of multiple sclerosis (MS) pathogenesis states that inflammation-mediated demyelination is responsible for neuronal damage and loss. However, recent findings show that impairment of neuronal functions and demyelination can be independent events, suggesting the coexistence of other pathogenic mechanisms. Due to the inflammatory milieu, subtle alterations in synaptic function occur, which are probably at the basis of the early cognitive decline that often precedes the neurodegenerative phases in MS patients. In particular, it has been reported that inflammation enhances excitatory synaptic transmission while it decreases GABAergic transmission in vitro and ex vivo. This evidence points to the idea that an excitation/inhibition imbalance occurs in the inflamed MS brain, even though the exact molecular mechanisms leading to this synaptic dysfunction are as yet not completely clear. Along this line, we observed that acute treatment of primary hippocampal neurons in culture with pro-inflammatory cytokines leads to an increased phosphorylation of synapsin I (SynI) by ERK1/2 kinase and to an increase in the frequency of spontaneous synaptic vesicle release events, which is prevented by SynI deletion. In vivo, the ablation of SynI expression is protective in terms of disease progression and neuronal damage in the experimental autoimmune encephalomyelitis mouse model of MS. Our results point to a possible key role in MS pathogenesis of the neuronal protein SynI, a regulator of excitation/inhibition balance in neuronal networks.
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http://dx.doi.org/10.1016/j.bbi.2017.10.018DOI Listing
February 2018

A novel SYN1 missense mutation in non-syndromic X-linked intellectual disability affects synaptic vesicle life cycle, clustering and mobility.

Hum Mol Genet 2017 12;26(23):4699-4714

Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milan, Italy.

Intellectual Disability is a common and heterogeneous disorder characterized by limitations in intellectual functioning and adaptive behaviour, whose molecular mechanisms remain largely unknown. Among the numerous genes found to be involved in the pathogenesis of intellectual disability, 10% are located on the X-chromosome. We identified a missense mutation (c.236 C > G; p.S79W) in the SYN1 gene coding for synapsin I in the MRX50 family, affected by non-syndromic X-linked intellectual disability. Synapsin I is a neuronal phosphoprotein involved in the regulation of neurotransmitter release and neuronal development. Several mutations in SYN1 have been identified in patients affected by epilepsy and/or autism. The S79W mutation segregates with the disease in the MRX50 family and all affected members display intellectual disability as sole clinical manifestation. At the protein level, the S79W Synapsin I mutation is located in the region of the B-domain involved in recognition of highly curved membranes. Expression of human S79W Synapsin I in Syn1 knockout hippocampal neurons causes aberrant accumulation of small clear vesicles in the soma, increased clustering of synaptic vesicles at presynaptic terminals and increased frequency of excitatory spontaneous release events. In addition, the presence of S79W Synapsin I strongly reduces the mobility of synaptic vesicles, with possible implications for the regulation of neurotransmitter release and synaptic plasticity. These results implicate SYN1 in the pathogenesis of non-syndromic intellectual disability, showing that alterations of synaptic vesicle trafficking are one possible cause of this disease, and suggest that distinct mutations in SYN1 may lead to distinct brain pathologies.
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http://dx.doi.org/10.1093/hmg/ddx352DOI Listing
December 2017

eIF4B phosphorylation at Ser504 links synaptic activity with protein translation in physiology and pathology.

Sci Rep 2017 09 5;7(1):10563. Epub 2017 Sep 5.

Unit of Cellular Neurophysiology and Unit of Neuropsychopharmacology, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, via Olgettina 60, I-20132, Milano, Italy.

Neuronal physiology requires activity-driven protein translation, a process in which translation initiation factors are key players. We focus on eukaryotic initiation factor 4B (eIF4B), a regulator of protein translation, whose function in neurons is undetermined. We show that neuronal activity affects eIF4B phosphorylation and identify Ser504 as a phosphorylation site regulated by casein kinases and sensitive to the activation of metabotropic glutamate receptors. Ser504 phosphorylation increases eIF4B recruitment to the pre-initiation complex and influences eIF4B localization at synapses. Moreover, Ser504 phosphorylation modulates the translation of protein kinase Mζ. Therefore, by sensing synaptic activity, eIF4B could adjust translation to neuronal needs, promoting adaptive changes in synaptic plasticity. We also show that Ser504 phosphorylation is increased in vivo in a rat model of epilepsy during epileptogenesis i.e. when translation drives maladaptive synaptic changes. We propose eIF4B as a mediator between neuronal activity and translation, with relevance in the control of synaptic plasticity.
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http://dx.doi.org/10.1038/s41598-017-11096-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585320PMC
September 2017

Serotonin Dysfunction, Aggressive Behavior, and Mental Illness: Exploring the Link Using a Dimensional Approach.

ACS Chem Neurosci 2017 05 10;8(5):961-972. Epub 2017 Apr 10.

San Raffaele Scientific Institute and Vita Salute University , Via Olgettina 58, 20132 Milano, Italy.

Aggressive individuals have higher rates of mental illness compared to non-aggressive individuals. Multiple factors, including psychosocial, genetic, and neurobiological determinants modulate the liability to both aggressive behavior and mental illness. Concerning the latter factors, multiple lines of evidence have shown a dysfunction in the serotonin (5-HT) system occurring in aggressive and in mentally ill individuals. In particular, reduced 5-HT activity has been associated with depression as well as with aggressive behavior, especially with impulsive aggression. Consistently, psychopharmacological interventions aimed at boosting the 5-HT system (e.g., with selective serotonin reuptake inhibitors) have demonstrated therapeutic efficacy in a high percentage of patients with either or both pathological conditions. Current knowledge does not yet allow to clearly disentangle whether 5-HT dysfunction, most often a 5-HT deficiency, is the cause or the consequence of the aggressive/violent behavior, of the underlying mental disease/s, or the expression of the comorbidity. Future studies are thus needed to clarify the association between changes in 5-HT levels, altered activity of 5-HT receptors and their intracellular signaling cascades, and modifications of 5-HT genes, and in particular the neurobiological link between the altered 5-HT machinery and aggressive behavior in the context or in the absence of mental illness. In this Review, we employ a dimensional approach to discuss the trivariate relationship among the 5-HT system, aggressive behavior, and mental illness, focusing our attention on 5-HT levels, 5-HT receptors, metabolic enzymes, and their genes. Emphasis is given to controversial findings, still unanswered questions, and future perspectives.
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http://dx.doi.org/10.1021/acschemneuro.6b00427DOI Listing
May 2017

The synaptic function of parkin.

Brain 2017 Sep;140(9):2265-2272

IRCCS Istituto Auxologico Italiano, Department of Neurology and Laboratory of Neuroscience, Milan, Italy.

Loss of function mutations in the gene PARK2, which encodes the protein parkin, cause autosomal recessive juvenile parkinsonism, a neurodegenerative disease characterized by degeneration of the dopaminergic neurons localized in the substantia nigra pars compacta. No therapy is effective in slowing disease progression mostly because the pathogenesis of the disease is yet to be understood. From accruing evidence suggesting that the protein parkin directly regulates synapses it can be hypothesized that PARK2 gene mutations lead to early synaptic damage that results in dopaminergic neuron loss over time. We review evidence that supports the role of parkin in modulating excitatory and dopaminergic synapse functions. We also discuss how these findings underpin the concept that autosomal recessive juvenile parkinsonism can be primarily a synaptopathy. Investigation into the molecular interactions between parkin and synaptic proteins may yield novel targets for pharmacologic interventions.
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http://dx.doi.org/10.1093/brain/awx006DOI Listing
September 2017

The PRRT2 knockout mouse recapitulates the neurological diseases associated with PRRT2 mutations.

Neurobiol Dis 2017 Mar 20;99:66-83. Epub 2016 Dec 20.

Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy; Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy. Electronic address:

Heterozygous and rare homozygous mutations in PRoline-Rich Transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders including epilepsy, kinesigenic dyskinesia episodic ataxia and migraine. Most of the mutations lead to impaired PRRT2 expression and/or function. Recently, an important role for PRTT2 in the neurotransmitter release machinery, brain development and synapse formation has been uncovered. In this work, we have characterized the phenotype of a mouse in which the PRRT2 gene has been constitutively inactivated (PRRT2 KO). β-galactosidase staining allowed to map the regional expression of PRRT2 that was more intense in the cerebellum, hindbrain and spinal cord, while it was localized to restricted areas in the forebrain. PRRT2 KO mice are normal at birth, but display paroxysmal movements at the onset of locomotion that persist in the adulthood. In addition, adult PRRT2 KO mice present abnormal motor behaviors characterized by wild running and jumping in response to audiogenic stimuli that are ineffective in wild type mice and an increased sensitivity to the convulsive effects of pentylentetrazol. Patch-clamp electrophysiology in hippocampal and cerebellar slices revealed specific effects in the cerebellum, where PRRT2 is highly expressed, consisting in a higher excitatory strength at parallel fiber-Purkinje cell synapses during high frequency stimulation. The results show that the PRRT2 KO mouse reproduces the motor paroxysms present in the human PRRT2-linked pathology and can be proposed as an experimental model for the study of the pathogenesis of the disease as well as for testing personalized therapeutic approaches.
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http://dx.doi.org/10.1016/j.nbd.2016.12.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321265PMC
March 2017

PRRT2: from Paroxysmal Disorders to Regulation of Synaptic Function.

Trends Neurosci 2016 10 10;39(10):668-679. Epub 2016 Sep 10.

San Raffaele Scientific Institute and Vita Salute University, Via Olgettina 58, 20132 Milano, Italy.

In the past few years, proline-rich transmembrane protein (PRRT)2 has been identified as the causative gene for several paroxysmal neurological disorders. Recently, an important role of PRRT2 in synapse development and function has emerged. Knock down of the protein strongly impairs the formation of synaptic contacts and neurotransmitter release. At the nerve terminal, PRRT2 endows synaptic vesicle exocytosis with Ca sensitivity by interacting with proteins of the fusion complex and with the Ca sensors synaptotagmins (Syts). In the postsynaptic compartment, PRRT2 interacts with glutamate receptors. The study of PRRT2 and of its mutations may help in refining our knowledge of the process of synaptic transmission and elucidating the pathogenetic mechanisms leading to derangement of network function in paroxysmal disorders.
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http://dx.doi.org/10.1016/j.tins.2016.08.005DOI Listing
October 2016

Sphingosine-1-Phosphate (S1P) Impacts Presynaptic Functions by Regulating Synapsin I Localization in the Presynaptic Compartment.

J Neurosci 2016 Apr;36(16):4624-34

Consiglio Nazionale delle Ricerche Institute of Neuroscience, Milano 20129, Italy, Istituto Di Ricovero e Cura a Carattere Scientifico Humanitas, Rozzano 20089, Italy

Unlabelled: Growing evidence indicates that sphingosine-1-P (S1P) upregulates glutamate secretion in hippocampal neurons. However, the molecular mechanisms through which S1P enhances excitatory activity remain largely undefined. The aim of this study was to identify presynaptic targets of S1P action controlling exocytosis. Confocal analysis of rat hippocampal neurons showed that S1P applied at nanomolar concentration alters the distribution of Synapsin I (SynI), a presynaptic phosphoprotein that controls the availability of synaptic vesicles for exocytosis. S1P induced SynI relocation to extrasynaptic regions of mature neurons, as well as SynI dispersion from synaptic vesicle clusters present at axonal growth cones of developing neurons. S1P-induced SynI relocation occurred in a Ca(2+)-independent but ERK-dependent manner, likely through the activation of S1P3 receptors, as it was prevented by the S1P3 receptor selective antagonist CAY1044 and in neurons in which S1P3 receptor was silenced. Our recent evidence indicates that microvesicles (MVs) released by microglia enhance the metabolism of endogenous sphingolipids in neurons and stimulate excitatory transmission. We therefore investigated whether MVs affect SynI distribution and whether endogenous S1P could be involved in the process. Analysis of SynI immunoreactivity showed that exposure to microglial MVs induces SynI mobilization at presynaptic sites and growth cones, whereas the use of inhibitors of sphingolipid cascade identified S1P as the sphingolipid mediating SynI redistribution. Our data represent the first demonstration that S1P induces SynI mobilization from synapses, thereby indicating the phosphoprotein as a novel target through which S1P controls exocytosis.

Significance Statement: Growing evidence indicates that the bioactive lipid sphingosine and its metabolite sphingosine-1-P (S1P) stimulate excitatory transmission. While it has been recently clarified that sphingosine influences directly the exocytotic machinery by activating the synaptic vesicle protein VAMP2 to form SNARE fusion complexes, the molecular mechanism by which S1P promotes neurotransmission remained largely undefined. In this study, we identify Synapsin I, a presynaptic phosphoprotein involved in the control of availability of synaptic vesicles for exocytosis, as the key target of S1P action. In addition, we provide evidence that S1P can be produced at mature axon terminals as well as at immature growth cones in response to microglia-derived signals, which may be important to stabilize nascent synapses and to restore or potentiate transmission.
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http://dx.doi.org/10.1523/JNEUROSCI.3588-15.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6601834PMC
April 2016

PRRT2 Is a Key Component of the Ca(2+)-Dependent Neurotransmitter Release Machinery.

Cell Rep 2016 Apr 24;15(1):117-131. Epub 2016 Mar 24.

Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy; Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy. Electronic address:

Heterozygous mutations in proline-rich transmembrane protein 2 (PRRT2) underlie a group of paroxysmal disorders, including epilepsy, kinesigenic dyskinesia, and migraine. Most of the mutations lead to impaired PRRT2 expression, suggesting that loss of PRRT2 function may contribute to pathogenesis. We show that PRRT2 is enriched in presynaptic terminals and that its silencing decreases the number of synapses and increases the number of docked synaptic vesicles at rest. PRRT2-silenced neurons exhibit a severe impairment of synchronous release, attributable to a sharp decrease in release probability and Ca(2+) sensitivity and associated with a marked increase of the asynchronous/synchronous release ratio. PRRT2 interacts with the synaptic proteins SNAP-25 and synaptotagmin 1/2. The results indicate that PRRT2 is intimately connected with the Ca(2+)-sensing machinery and that it plays an important role in the final steps of neurotransmitter release.
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http://dx.doi.org/10.1016/j.celrep.2016.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826441PMC
April 2016

eEF2K/eEF2 Pathway Controls the Excitation/Inhibition Balance and Susceptibility to Epileptic Seizures.

Cereb Cortex 2017 03;27(3):2226-2248

CNR Neuroscience Institute, Milan, Italy, Università degli Studi di Milano, Milan, Italy.

Alterations in the balance of inhibitory and excitatory synaptic transmission have been implicated in the pathogenesis of neurological disorders such as epilepsy. Eukaryotic elongation factor 2 kinase (eEF2K) is a highly regulated, ubiquitous kinase involved in the control of protein translation. Here, we show that eEF2K activity negatively regulates GABAergic synaptic transmission. Indeed, loss of eEF2K increases GABAergic synaptic transmission by upregulating the presynaptic protein Synapsin 2b and α5-containing GABAA receptors and thus interferes with the excitation/inhibition balance. This cellular phenotype is accompanied by an increased resistance to epilepsy and an impairment of only a specific hippocampal-dependent fear conditioning. From a clinical perspective, our results identify eEF2K as a potential novel target for antiepileptic drugs, since pharmacological and genetic inhibition of eEF2K can revert the epileptic phenotype in a mouse model of human epilepsy.
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http://dx.doi.org/10.1093/cercor/bhw075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5963824PMC
March 2017

A Novel Topology of Proline-rich Transmembrane Protein 2 (PRRT2): HINTS FOR AN INTRACELLULAR FUNCTION AT THE SYNAPSE.

J Biol Chem 2016 Mar 21;291(12):6111-23. Epub 2016 Jan 21.

From the Department of Experimental Medicine, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy, the Center for Synaptic Neuroscience and Technology, Fondazione Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genoa, Italy, and

Proline-rich transmembrane protein 2 (PRRT2) has been identified as the single causative gene for a group of paroxysmal syndromes of infancy, including epilepsy, paroxysmal movement disorders, and migraine. On the basis of topology predictions, PRRT2 has been assigned to the recently characterized family of Dispanins, whose members share the two-transmembrane domain topology with a large N terminus and short C terminus oriented toward the outside of the cell. Because PRRT2 plays a role at the synapse, it is important to confirm the exact orientation of its N and C termini with respect to the plasma membrane to get clues regarding its possible function. Using a combination of different experimental approaches, including live immunolabeling, immunogold electron microscopy, surface biotinylation and computational modeling, we demonstrate a novel topology for this protein. PRRT2 is a type II transmembrane protein in which only the second hydrophobic segment spans the plasma membrane, whereas the first one is associated with the internal surface of the membrane and forms a helix-loop-helix structure without crossing it. Most importantly, the large proline-rich N-terminal domain is not exposed to the extracellular space but is localized intracellularly, and only the short C terminus is extracellular (N cyt/C exo topology). Accordingly, we show that PRRT2 interacts with the Src homology 3 domain-bearing protein Intersectin 1, an intracellular protein involved in synaptic vesicle cycling. These findings will contribute to the clarification of the role of PRRT2 at the synapse and the understanding of pathogenic mechanisms on the basis of PRRT2-related neurological disorders.
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http://dx.doi.org/10.1074/jbc.M115.683888DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4813553PMC
March 2016

Distinct temporal hierarchies in membrane and cytoskeleton dynamics precede the morphological polarization of developing neurons.

J Cell Sci 2014 Oct 15;127(Pt 20):4409-19. Epub 2014 Aug 15.

VIB Center for the Biology of Disease, KULeuven Center for Human Genetics, Leuven, Belgium and KULeuven, Department of Development and Regeneration, 3000 Leuven, Belgium Centro de Biología Molecular Severo Ochoa, CSIC/UAM, 28049 Madrid, Spain

Final morphological polarization of neurons, with the development of a distinct axon and several dendrites, is preceded by phases where they have a non-polarized architecture. The earliest of these phases is that of the round neuron arising from the last mitosis. A second non-polarized stage corresponds to the bipolar neuron, with two morphologically identical neurites. Both phases have their distinctive relevance in the establishment of neuronal polarity. During the round cell stage, a decision is made as to where from the cell periphery a first neurite will form, thus creating the first sign of asymmetry. At the bipolar stage a decision is made as to which of the two neurites becomes the axon in neurons polarizing in vitro, and the leading edge in neurons in situ. In this study, we analysed cytoskeletal and membrane dynamics in cells at these two 'pre-polarity' stages. By means of time lapse imaging in dissociated hippocampal neurons and ex vivo cortical slices, we show that both stages are characterized by polarized intracellular arrangements. However, the stages have distinct temporal hierarchies: polarized actin dynamics marks the site of first polarization in round cells, whereas polarized membrane dynamics precedes asymmetric growth in the bipolar stage.
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http://dx.doi.org/10.1242/jcs.149815DOI Listing
October 2014

Phosphorylation of synapsin I by cyclin-dependent kinase-5 sets the ratio between the resting and recycling pools of synaptic vesicles at hippocampal synapses.

J Neurosci 2014 May;34(21):7266-80

Department of Neuroscience and Brain Technologies, Instituto Italiano di Tecnologia, 16163 Genoa, Italy, Department of Experimental Medicine, University of Genoa, I-16132 Genova, Italy.

Cyclin-dependent kinase-5 (Cdk5) was reported to downscale neurotransmission by sequestering synaptic vesicles (SVs) in the release-reluctant resting pool, but the molecular targets mediating this activity remain unknown. Synapsin I (SynI), a major SV phosphoprotein involved in the regulation of SV trafficking and neurotransmitter release, is one of the presynaptic substrates of Cdk5, which phosphorylates it in its C-terminal region at Ser(549) (site 6) and Ser(551) (site 7). Here we demonstrate that Cdk5 phosphorylation of SynI fine tunes the recruitment of SVs to the active recycling pool and contributes to the Cdk5-mediated homeostatic responses. Phosphorylation of SynI by Cdk5 is physiologically regulated and enhances its binding to F-actin. The effects of Cdk5 inhibition on the size and depletion kinetics of the recycling pool, as well as on SV distribution within the nerve terminal, are virtually abolished in mouse SynI knock-out (KO) neurons or in KO neurons expressing the dephosphomimetic SynI mutants at sites 6,7 or site 7 only. The observation that the single site-7 mutant phenocopies the effects of the deletion of SynI identifies this site as the central switch in mediating the synaptic effects of Cdk5 and demonstrates that SynI is necessary and sufficient for achieving the effects of the kinase on SV trafficking. The phosphorylation state of SynI by Cdk5 at site 7 is regulated during chronic modification of neuronal activity and is an essential downstream effector for the Cdk5-mediated homeostatic scaling.
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http://dx.doi.org/10.1523/JNEUROSCI.3973-13.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6608192PMC
May 2014