ATP from synaptic terminals and astrocytes regulates NMDA receptors and synaptic plasticity through PSD-95 multi-protein complex

Recent studies highlighted the importance of astrocyte-secreted molecules, such as ATP, for the slow modulation of synaptic transmission in central neurones. Biophysical mechanisms underlying the impact of gliotransmitters on the strength of individual synapse remain, however, unclear. Here we show that purinergic P2X receptors can bring significant contribution to the signalling in the individual synaptic boutons. ATP released from astrocytes facilitates a recruitment of P2X receptors into excitatory synapses by Ca2+-dependent mechanism. P2X receptors, co-localized with NMDA receptors in the excitatory synapses, can be activated by ATP co-released with glutamate from pre-synaptic terminals and by glia-derived ATP. An activation of P2X receptors in turn leads to down-regulation of postsynaptic NMDA receptors via Ca2+-dependent de-phosphorylation and interaction with PSD-95 multi-protein complex. Genetic deletion of the PSD-95 or P2X4 receptors obliterated ATP-mediated down-regulation of NMDA receptors. Impairment of purinergic modulation of NMDA receptors in the PSD-95 mutants dramatically decreased the threshold of LTP induction and increased the net magnitude of LTP. Our findings show that synergistic action of glia- and neurone-derived ATP can pre-modulate efficacy of excitatory synapses and thereby can have an important role in the glia-neuron communications and brain meta-plasticity

A Neuron-Glial Perspective for Computational Neuroscience

International audienceThere is growing excitement around glial cells, as compelling evidence point to new, previously unimaginable roles for these cells in information processing of the brain, with the potential to affect behavior and higher cognitive functions. Among their many possible functions, glial cells could be involved in practically every aspect of the brain physiology in health and disease. As a result, many investigators in the field welcome the notion of a Neuron-Glial paradigm of brain function, as opposed to Ramon y Cayal's more classical neuronal doctrine which identifies neurons as the prominent, if not the only, cells capable of a signaling role in the brain. The demonstration of a brain-wide Neuron-Glial paradigm however remains elusive and so does the notion of what neuron-glial interactions could be functionally relevant for the brain computational tasks. In this perspective, we present a selection of arguments inspired by available experimental and modeling studies with the aim to provide a biophysical and conceptual platform to computational neuroscience no longer as a mere prerogative of neuronal signaling but rather as the outcome of a complex interaction between neurons and glial cells

Purinergic receptors profile in the ARPKD cystic epithelia

Polycystic kidney diseases (PKD) are a group of inherited nephropathies marked with the formation of fluid-filled cysts along the nephron. Growing evidence suggests that autocrine and paracrine effects of purinergic signaling via P2 receptors could detrimentally contribute to cyst expansion. However, little is known about purinergic signaling in renal cyst epithelium, which is characterized by loss of polarity, dedifferentiation and other abnormalities which can lead to purinergic signaling remodeling. We have proposed that ATP via associated intracellular signaling can contribute to cystogenesis by modulation of calcium influx. PCK/CrljCrl-Pkhd1pck/CRL (PCK) rat, an established model of ARPKD, was used here to test this hypothesis. The cystic fluid of PCK rats and their cortical tissues exhibited significantly higher levels of ATP compared to Sprague Dawley (SD) rat kidney cortical interstitium as assessed by highly sensitive for ATP enzymatic biosensors (211±55 vs 1082±147 nM for SD and PCK cortex correspondingly, and 2,078±391 nM for cystic fluid). Confocal calcium imaging of the freshly isolated cystic monolayers revealed a stronger response to ATP in a higher range of concentrations (above 100 μM). The removal of extracellular calcium results in the absence of ATP evoked transient, which pointed towards the extracellular (ionotropic) calcium entry in cyst-lining cells rather than the metabotropic P2Y-mediated internal depot. Application of iso-PPADS (a non-selective P2X antagonist) resulted in partial blockade of ATP response (calcium release after ATP was 30.1 ± 0.9, 22.2 ± 1.8 and 19.5 ± 3.2 a.u. in control, after incubation with iso-PPADS, and after washout, respectively) indicating the contribution of P2X4 purinoreceptor in the cystic monolayer. Next, to specifically assess the role of P2X7 in the ATP-mediated calcium influx, we employed AZ10606120, a potent P2X7 receptor antagonist. Application of AZ10606120 (5 μM) resulted in a bunted calcium response to ATP (32.4 ± 2.2, 13.5 ± 6.4, and 11.1 ± 3.1 a.u. of total calcium release in control, after incubation with AZ10606120, and after washout, respectively), which corroborates the commonly hypothesized role of P2X7 in cyst development. Further use of pharmacological agents (α,β-methylene-ATP, 5-BDBD, and NF449) allowed to narrow down potential candidate receptors and suggested a significant involvement of the P2X4 and/or P2X7 signaling axis in the regulation of cytosolic calcium level in the cystic epithelia. In conclusion, our ex vivo study provides direct evidence that the profile of P2 receptors is altered in the ARPKD cystic epithelia towards the prevalence of P2X4 and/or P2X7 receptors, which opens new avenues for the treatment of this disease

Knockout of kcnj16 (kir5.1) in Dahl salt-sensitive rats produces seizure phenotype

Kir5.1 is a member of an inwardly rectifying potassium (Kir) channel family notably present in the kidney and brain. We previously established that a knockout rat model of Kcnj16 (gene encoding Kir5.1) on a Dahl salt-sensitive background (SSKcnj16-/-) exhibits a severe cardiovascular phenotype (Palygin et al., JCI Insight, 2017). Mutations in ion channel genes can alter neuronal excitability and mutations in Kir genes have been linked to seizure disorders in humans. Since Kir5.1 is known to be expressed in the brain and may contribute to neuronal membrane potential and spatial potassium buffering, we hypothesized that in addition to cardiovascular and renal dysfunction, neurological phenotypes, including seizures, would be prevalent in the SSKcnj16-/-rats. We found that SSKcnj16-/- rats (but not control SS rats) experience tonic-clonic seizures when exposed to a 10 kHz tone (86 dB for 2 min), whereas other frequencies (0.1 or 1 kHz) did not elicit seizures. When exposed to the seizure-inducing acoustic stimulus once/day for 10 days, we noted that SSKcnj16-/- rats experienced a seizure in response to 92% of stimuli. SSKcnj16-/- rats also showed spontaneous mortality within hours after a stimulus with a survival rate of 67% (N=21) for the duration of the 10 day protocol. Control rats (N=10) had no incidence of seizure or death during the 10 days of acoustic stimulation. We found no difference among male and female SSKcnj16-/- rats, where both sexes had a similar audiogenic seizure response and reduced survival. Behavioral tests including a modified Irwin screen and open field test revealed that before and after seizure stimulation SSKcnj16-/- rats tended to have altered activity levels, gait, piloerection, and respiration rates. Analysis of blood electrolytes revealed critically low serum potassium levels in SSKcnj16-/- compared to SS controls, a difference that appeared to be exacerbated by repeated seizures. We hypothesize that seizures may be intensifying potassium imbalance and disrupting the homeostasis that is particularly essential for excitable cells such as neurons. We conclude that knockout of Kir5.1 leads to distinct neurological phenotypes including a seizure disorder and subsequent spontaneous death, which may have relevance to channelopathies associated with seizure disorders in humans

Transcriptome-wide co-expression analysis identifies LRRC2 as a novel mediator of mitochondrial and cardiac function

10.1371/journal.pone.0170458PLoS ONE122e0170458