Temperature-Dependent Olive Pomace Extraction for Obtaining Bioactive Compounds Preventing the Death of Murine Cortical Neurons.

High-pressure and temperature extraction (HPTE) can effectively recover bioactive compounds from olive pomace (OP). HPTE extract obtained by extracting OP with ethanol and water (50:50 /) at 180 °C for 90 min demonstrated a pronounced ability to preserve intracellular calcium homeostasis, shielding neurons from the harmful effects induced by N-methyl-d-aspartate (NMDA) receptor (NMDAR) overactivation, such as aberrant calpain activation. In this study, the extraction temperature was changed from 37 to 180 °C, and the extracts were evaluated for their antioxidant potency and ability to preserve crucial intracellular Ca-homeostasis necessary for neuronal survival.

Synapsin III Regulates Dopaminergic Neuron Development in Vertebrates.

Attention deficit and hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by alterations in the mesocorticolimbic and nigrostriatal dopaminergic pathways. Polymorphisms in the Synapsin III (Syn III) gene can associate with ADHD onset and even affect the therapeutic response to the gold standard ADHD medication, methylphenidate (MPH), a monoamine transporter inhibitor whose efficacy appears related with the stimulation of brain-derived neurotrophic factor (BDNF). Interestingly, we previously showed that MPH can bind Syn III, which can regulate neuronal development.

REST/NRSF drives homeostatic plasticity of inhibitory synapses in a target-dependent fashion.

The repressor-element 1-silencing transcription/neuron-restrictive silencer factor (REST/NRSF) controls hundreds of neuron-specific genes. We showed that REST/NRSF downregulates glutamatergic transmission in response to hyperactivity, thus contributing to neuronal homeostasis. However, whether GABAergic transmission is also implicated in the homeostatic action of REST/NRSF is unknown.

PRRT2 modulates presynaptic Ca influx by interacting with P/Q-type channels.

Loss-of-function mutations in proline-rich transmembrane protein-2 (PRRT2) cause paroxysmal disorders associated with defective Ca dependence of glutamatergic transmission. We find that either acute or constitutive PRRT2 deletion induces a significant decrease in the amplitude of evoked excitatory postsynaptic currents (eEPSCs) that is insensitive to extracellular Ca and associated with a reduced contribution of P/Q-type Ca channels to the EPSC amplitude. This synaptic phenotype parallels a decrease in somatic P/Q-type Ca currents due to a decreased membrane targeting of the channel with unchanged total expression levels.

A Bioactive Olive Pomace Extract Prevents the Death of Murine Cortical Neurons Triggered by NMDAR Over-Activation.

We have recently demonstrated that bioactive molecules, extracted by high pressure and temperature from olive pomace, counteract calcium-induced cell damage to different cell lines. Here, our aim was to study the effect of the same extract on murine cortical neurons, since the preservation of the intracellular Ca-homeostasis is essential for neuronal function and survival. Accordingly, we treated neurons with different stimuli in order to evoke cytotoxic glutamatergic activation.

Presynaptic L-Type Ca Channels Increase Glutamate Release Probability and Excitatory Strength in the Hippocampus during Chronic Neuroinflammation.

Neuroinflammation is involved in the pathogenesis of several neurologic disorders, including epilepsy. Both changes in the input/output functions of synaptic circuits and cell Ca dysregulation participate in neuroinflammation, but their impact on neuron function in epilepsy is still poorly understood. Lipopolysaccharide (LPS), a toxic byproduct of bacterial lysis, has been extensively used to stimulate inflammatory responses both and LPS stimulates Toll-like receptor 4, an important mediator of the brain innate immune response that contributes to neuroinflammation processes.

Leucine-rich repeat kinase 2 phosphorylation on synapsin I regulates glutamate release at pre-synaptic sites.

Leucine-rich repeat kinase 2 (LRRK2) is a large multidomain scaffolding protein with kinase and GTPase activities involved in synaptic vesicle (SV) dynamics. While its role in Parkinson's disease has been largely investigated, little is known about LRRK2 physiological role and until now few proteins have been described as substrates. We have previously demonstrated that LRRK2 through its WD40 domain interacts with synapsin I, an important SV-associated phosphoprotein involved in neuronal development and in the regulation of neurotransmitter release.

Synapsin I and Synapsin II regulate neurogenesis in the dentate gyrus of adult mice.

Adult neurogenesis is emerging as an important player in brain functions and homeostasis, while impaired or altered adult neurogenesis has been associated with a number of neuropsychiatric diseases, such as depression and epilepsy. Here we investigated the possibility that synapsins (Syns) I and II, beyond their known functions in developing and mature neurons, also play a role in adult neurogenesis. We performed a systematic evaluation of the distinct stages of neurogenesis in the hippocampal dentate gyrus of Syn I and Syn II knockout (KO) mice, before (2-months-old) and after (6-months-old) the appearance of the epileptic phenotype.

Altered mechanisms underlying the abnormal glutamate release in amyotrophic lateral sclerosis at a pre-symptomatic stage of the disease.

Abnormal Glu release occurs in the spinal cord of SOD1(G93A) mice, a transgenic animal model for human ALS. Here we studied the mechanisms underlying Glu release in spinal cord nerve terminals of SOD1(G93A) mice at a pre-symptomatic disease stage (30days) and found that the basal release of Glu was more elevated in SOD1(G93A) with respect to SOD1 mice, and that the surplus of release relies on synaptic vesicle exocytosis. Exposure to high KCl or ionomycin provoked Ca(2+)-dependent Glu release that was likewise augmented in SOD1(G93A) mice.

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

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.

LRRK2 phosphorylates pre-synaptic N-ethylmaleimide sensitive fusion (NSF) protein enhancing its ATPase activity and SNARE complex disassembling rate.

Background: Lrrk2, a gene linked to Parkinson's disease, encodes a large scaffolding protein with kinase and GTPase activities implicated in vesicle and cytoskeletal-related processes. At the presynaptic site, LRRK2 associates with synaptic vesicles through interaction with a panel of presynaptic proteins.

Results: Here, we show that LRRK2 kinase activity influences the dynamics of synaptic vesicle fusion.

Synapsins Are Downstream Players of the BDNF-Mediated Axonal Growth.

Synapsins (Syns) are synaptic vesicle-associated phosphoproteins involved in neuronal development and neurotransmitter release. While Syns are implicated in the regulation of brain-derived neurotrophic factor (BDNF)-induced neurotransmitter release, their role in the BDNF developmental effects has not been fully elucidated. By using primary cortical neurons from Syn I knockout (KO) and Syn I/II/III KO mice, we studied the effects of BDNF and nerve growth factor (NGF) on axonal growth.

Functional role of ATP binding to synapsin I in synaptic vesicle trafficking and release dynamics.

Synapsins (Syns) are synaptic vesicle (SV)-associated proteins involved in the regulation of synaptic transmission and plasticity, which display a highly conserved ATP binding site in the central C-domain, whose functional role is unknown. Using molecular dynamics simulations, we demonstrated that ATP binding to SynI is mediated by a conformational transition of a flexible loop that opens to make the binding site accessible; such transition, prevented in the K269Q mutant, is not significantly affected in the absence of Ca(2+) or by the E373K mutation that abolishes Ca(2+)-binding. Indeed, the ATP binding to SynI also occurred under Ca(2+)-free conditions and increased its association with purified rat SVs regardless of the presence of Ca(2+) and promoted SynI oligomerization.

LRRK2 kinase activity regulates synaptic vesicle trafficking and neurotransmitter release through modulation of LRRK2 macro-molecular complex.

Mutations in Leucine-rich repeat kinase 2 gene (LRRK2) are associated with familial and sporadic Parkinson's disease (PD). LRRK2 is a complex protein that consists of multiple domains executing several functions, including GTP hydrolysis, kinase activity, and protein binding. Robust evidence suggests that LRRK2 acts at the synaptic site as a molecular hub connecting synaptic vesicles to cytoskeletal elements via a complex panel of protein-protein interactions.

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

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.

Leucine-rich repeat kinase 2 binds to neuronal vesicles through protein interactions mediated by its C-terminal WD40 domain.

Mutations in the leucine-rich repeat kinase 2 gene (LRRK2) are associated with familial and sporadic Parkinson's disease (PD). LRRK2 is a complex protein that consists of multiple domains, including predicted C-terminal WD40 repeats. In this study, we analyzed functional and molecular features conferred by the WD40 domain.

Synapsin I senses membrane curvature by an amphipathic lipid packing sensor motif.

Sustained neurotransmitter release at synapses during high-frequency synaptic activity involves the mobilization of synaptic vesicles (SVs) from the tightly clustered reserve pool (RP). Synapsin I (Syn I), a brain-specific peripheral membrane protein that undergoes activity-dependent cycles of SV association and dissociation, is implicated in RP organization via its ability to cluster SVs. Although Syn I has affinity for phospholipids, the mechanism for the reversible association of synapsin with SV membranes remains enigmatic.

SYN1 loss-of-function mutations in autism and partial epilepsy cause impaired synaptic function.

Several genes predisposing to autism spectrum disorders (ASDs) with or without epilepsy have been identified, many of which are implicated in synaptic function. Here we report a Q555X mutation in synapsin 1 (SYN1), an X-linked gene encoding for a neuron-specific phosphoprotein implicated in the regulation of neurotransmitter release and synaptogenesis. This nonsense mutation was found in all affected individuals from a large French-Canadian family segregating epilepsy and ASDs.

Abnormal exocytotic release of glutamate in a mouse model of amyotrophic lateral sclerosis.

Glutamate-mediated excitotoxicity plays a major role in the degeneration of motor neurons in amyotrophic lateral sclerosis and reduced astrocytary glutamate transport, which in turn increases the synaptic availability of the amino acid neurotransmitter, was suggested as a cause. Alternatively, here we report our studies on the exocytotic release of glutamate as a possible source of excessive glutamate transmission. The basal glutamate efflux from spinal cord nerve terminals of mice-expressing human soluble superoxide dismutase (SOD1) with the G93A mutation [SOD1/G93A(+)], a transgenic model of amyotrophic lateral sclerosis, was elevated when compared with transgenic mice expressing the wild-type human SOD1 or to non-transgenic controls.

Binding of protein kinase inhibitors to synapsin I inferred from pair-wise binding site similarity measurements.

Predicting off-targets by computational methods is getting increasing importance in early drug discovery stages. We herewith present a computational method based on binding site three-dimensional comparisons, which prompted us to investigate the cross-reaction of protein kinase inhibitors with synapsin I, an ATP-binding protein regulating neurotransmitter release in the synapse. Systematic pair-wise comparison of the staurosporine-binding site of the proto-oncogene Pim-1 kinase with 6,412 druggable protein-ligand binding sites suggested that the ATP-binding site of synapsin I may recognize the pan-kinase inhibitor staurosporine.