Biology subjects

Maglio, L. E.

Publications and source records attributed to Maglio, L. E..

6 recordsLinked to original sources

bioRxiv2023

Bidirectional Modulation Of Synaptic Transmission By Insulin-Like Growth Factor I

Insulin-like growth factor-I (IGF-I) plays a key role in the modulation of synaptic plasticity, and is an essential factor in learning and memory processes. Indeed, we have demonstrated that IGF-IR activation induces long-term potentiation (LTP) of synaptic transmission (LTPIGF-I) both in the barrel cortex, improving object recognition (Noriega-Prieto et al., 2021), and in the prefrontal cortex, facilitating the extinction of conditioned fear (Maglio et al., 2021). However, during aging, IGF-I levels are decreased, and the effect of this decrease in the induction of synaptic plasticity remains unknown. Here we show that the induction of NMDAR-dependent LTP at layer 2/3 PNs of the mouse barrel cortex is favored or prevented by IGF-I (10nM) or IGF-I (7nM), respectively, when IGF-I is applied 1 hour before the induction of Hebbian LTP. Analyzing the cellular basis of this bidirectional control of synaptic plasticity, we observed that while 10nM IGF-I generates LTP (LTPIGF-I) of the post-synaptic potentials (PSPs) by inducing LTD of the inhibitory post-synaptic currents (IPSCs), 7nM IGF-I generates LTD of the PSPs (LTDIGF-I) by inducing LTD of the excitatory post-synaptic currents (EPSCs). This bidirectional effect of IGF-I is supported by the observation of IGF-IR immunoreactivity at both excitatory and inhibitory synapses. Therefore, IGF-I controls the induction of Hebbian NMDAR-dependent plasticity depending on its concentration, revealing novel cellular mechanisms of IGF-I on synaptic plasticity and in the learning and memory machinery of the brain. SIGNIFICANCE STATEMENTInsulin-like growth factor-I (IGF-I) signalling plays key regulatory roles in multiple processes of brain physiology, such as learning and memory, and brain pathology, such as Alzheimer disease. Yet, the underlying mechanisms remain largely undefined. Here we demonstrate that IGF-I signalling triggers long-term potentiation (LTP) or long-term depression (LTD) of synaptic transmission at cortical synapses in a concentration dependent manner, thus regulating the induction of Hebbian synaptic plasticity. The present work represents an important conceptual advance in our knowledge of the cellular basis of IGF-I signalling in brain function.

neuroscience↗

bioRxiv2020

Synaptic plasticity of somatosensory neurons is determined by functional coupling between NMDA receptors and BK channels

Postsynaptic N-methyl-D-aspartate receptors (NMDARs) are crucial mediators of synaptic plasticity due to their ability to act as coincidence detectors of presynaptic and postsynaptic neuronal activity. However, NMDARs exist within the molecular context of a variety of postsynaptic signaling proteins, which can fine-tune their function. Here we describe a novel form of NMDAR suppression by large-conductance Ca2+- and voltage-gated K+ (BK) channels in the basal dendrites of a subset of barrel cortex layer 5 pyramidal neurons. We show that NMDAR activation increases intracellular Ca2+ in the vicinity of BK channels, thus activating K+ efflux and strong negative feedback inhibition. We further show that neurons exhibiting such NMDAR-BK coupling serve as high-pass filters for incoming synaptic inputs, precluding the induction of spike-timing-dependent plasticity. Together, these data suggest that NMDAR-localized BK channels regulate synaptic integration and provide input-specific synaptic diversity to a thalamocortical circuit.

neuroscience↗

bioRxiv2020

IGF-1 facilitates extinction of conditioned fear

Insulin-like growth factor-1 (IGF-1) plays a key role in synaptic plasticity, degenerative diseases, spatial learning, and anxiety-like behavioral processes. While IGF-1 regulates neuronal activity in many areas of the brain, its effect on synaptic plasticity and animal behavior dependent on the prefrontal cortex remain unexplored. Here, we show that IGF-1 induces a long-lasting depression of the medium and slow post-spike afterhyperpolarization (mAHP and sAHP), increasing the excitability of layer 5 pyramidal neurons of the infralimbic cortex. Besides, IGF-1 mediates a long-term depression of both inhibitory and excitatory synaptic transmission that results in a longterm potentiation of the postsynaptic potentials. We demonstrate that these synaptic and intrinsic regulatory processes mediated by IGF-1 favor the fear extinction memory. These results show novel functional consequences of IGF-1 signaling on animal behavior tasks dependent on the prefrontal cortex, revealing IGF-1 as a key element in the control of the fear extinction memory. Impact StatementIGF-1 modulates the neuronal firing and synaptic plasticity in infralimbic cortex, favoring the extinction memory

neuroscience↗

bioRxiv2020

Neuronal kinase SGK1.1 protects against brain damage after status epilepticus

Epilepsy is a neurological condition associated to significant brain damage produced by status epilepticus (SE) including neurodegeneration, gliosis and ectopic neurogenesis. Reduction of these processes constitutes a useful strategy to improve recovery and ameliorate negative outcomes after an initial insult. SGK1.1, the neuronal isoform of the serum and glucocorticoids-regulated kinase 1 (SGK1), has been shown to increase M-current density in neurons, leading to reduced excitability and protection against seizures. We now show that SGK1.1 activation potently reduces levels of neuronal death and gliosis after SE induced by kainate, even in the context of high seizure activity. This neuroprotective effect is not exclusively a secondary effect of M-current activation but is also directly linked to decreased apoptosis levels through regulation of Bim and Bcl-xL cellular levels. Our results demonstrate that this newly described antiapoptotic role of SGK1.1 activation acts synergistically with the regulation of cellular excitability, resulting in a significant reduction of SE-induced brain damage. The protective role of SGK1.1 occurs without altering basal neurogenesis in brain areas relevant to epileptogenesis. SIGNIFICANCE STATEMENTApproaches to control neuronal death and inflammation are of increasing interest in managing epilepsy, one of the most important idiopathic brain diseases. We have previously shown that activation of SGK1.1 reduces neuronal excitability by increasing M-current levels, significantly reducing seizure severity. We now describe a potent neuroprotective role of SGK1.1, which dramatically reduces neuronal death and gliosis after status epilepticus. This effect is partially dependent on M-current activation and includes an additional anti-apoptotic role of SGK1.1. Our data strongly support the relevance of this kinase as a potential target for epilepsy treatment.

neuroscience↗

bioRxiv2020

IGF-I Governs Cortical Inhibitory Synaptic Plasticity By Astrocyte Activation

Insulin-like growth factor-I (IGF-I) signaling plays key regulatory roles in multiple processes of brain physiology and pathology. While the direct effects of IGF-I in neurons have been extensively studied, the astrocyte involvement in IGF-I signaling and the consequences on synaptic plasticity and animal behavior remain unknown. Here we show that IGF-I induces the long-term depression (LTD) of inhibitory synaptic transmission in the mouse barrel cortex. This LTD requires the activation of the IGF-I receptor (IGF-IR) in astrocytes, which stimulates astrocyte Ca2+ signaling and the release of ATP/adenosine that in turn activates A2A adenosine receptors at presynaptic inhibitory terminals. Specific deletion of IGF-IR in cortical astrocytes (IGF-IR-/-) impaired the behavioral performance in a whisker discrimination task. These results show novel mechanisms and functional consequences of IGF-I signaling on cortical inhibitory synaptic plasticity and animal behavior, revealing astrocytes as key elements in these processes.

neuroscience↗

bioRxiv2019

SGK1.1 activation causes early seizure termination via effects on M-current

Early termination of status epilepticus affords protection against brain damage and associated pathologies. Regulation of Kv7.2/7.3 potassium channels, underlying the neuronal M-current, is key for seizure control. This conductance is maintained during initiation of action potentials, affecting neuronal excitability and thus inhibiting epileptic discharges. The M-current is upregulated by the neuronal isoform of the serum and glucocorticoid-regulated kinase SGK1 (SGK1.1). We tested whether SGK1.1 is an anticonvulsant factor using the kainic acid (KA) model of acute seizures in a transgenic mouse model with expression of a constitutively active form of the kinase. Our results demonstrate that SGK1.1 confers robust protection against seizures associated to lower mortality levels, independently of sex or genetic background. SGK1.1-dependent protection results in reduced number, shorter duration, and early termination of EEG seizures. At the cellular level, it is associated to increased M-current amplitude mediated by Nedd4-2 phosphorylation, leading to decreased excitability of hippocampal CA1 neurons without alteration of basal synaptic transmission. Altogether, our results reveal that SGK1.1-mediated M-current upregulation in the hippocampus is a key component of seizure resistance in the KA epileptic paradigm, suggesting that regulation of this anticonvulsant pathway may improve adverse outcomes to status epilepticus, constituting a potential target for antiepileptic drugs.

neuroscience↗