A novel cell-permeable peptide prevents protein SUMOylation and supports the mislocalization and aggregation of TDP-43.

SUMOylation is a post-translational modification (PTM) that exerts a regulatory role in different cellular processes, including protein localization, aggregation, and biological activities. It consists of the dynamic formation of covalent isopeptide bonds between a family member of the Small Ubiquitin Like Modifiers (SUMOs) and the target proteins. Interestingly, it is a cellular mechanism implicated in several neurodegenerative pathologies and potentially it could become a new therapeutic target; however, there are very few pharmacological tools to modulate the SUMOylation process. In this study, we have designed and tested the activity of a novel small cell-permeable peptide, COV-1, in a neuroblastoma cell line that specifically prevents protein SUMOylation. COV-1 inhibits UBC9-protein target interaction and efficiently decreases global SUMO-1ylation. Moreover, it can perturb RanGAP-1 perinuclear localization by inducing the downregulation of UBC9. In parallel, we found that COV-1 causes an increase in the ubiquitin degradation system up to its engulfment while enhancing the autophagic flux. Surprisingly, COV-1 modifies protein aggregation, and specifically it mislocalizes TDP-43 within cells, inducing its aggregation and co-localization with SUMO-1. These data suggest that COV-1 could be taken into future consideration as an interesting pharmacological tool to study the cellular cascade effects of SUMOylation prevention.

Environmental training is beneficial to clinical symptoms and cortical presynaptic defects in mice suffering from experimental autoimmune encephalomyelitis.

The effect of "prophylactic" environmental stimulation on clinical symptoms and presynaptic defects in mice suffering from the experimental autoimmune encephalomyelitis (EAE) at the acute stage of disease (21 ±â€¯1 days post immunization, d.p.i.) was investigated. In EAE mice raised in an enriched environment (EE), the clinical score was reduced when compared to EAE mice raised in standard environment (SE).Concomitantly, gain of weight and increased spontaneous motor activity and curiosity were observed, suggesting increased well-being in mice. Impaired glutamate exocytosis and cyclic adenosine monophosphate (cAMP) production in cortical terminals of SE-EAE mice were evident at 21 ±â€¯1 d.p.i.. Differently, the 12 mM KCl-evoked glutamate exocytosis from cortical synaptosomes of EE-EAE mice was comparable to that observed in SE and EE-control mice, but significantly higher than that in SE-EAE mice. Similarly, the 12 mM KCl-evoked cAMP production in EE-EAE mice cortical synaptosomes recovered to the level observed in SE and EE-control mice. MUNC-18 and SNAP25 contents, but not Syntaxin-1a and Synaptotagmin 1 levels, were increased in cortical synaptosomes from EE-EAE mice when compared to SE-EAE mice. Circulating IL-1ß was increased in the spinal cord, but not in the cortex, of SE-EAE mice, and it did not recover in EE-EAE mice. Inflammatory infiltrates were reduced in the cortex but not in the spinal cord of EE-EAE mice. Demyelination was observed in the spinal cord; EE significantly diminished it. We conclude that "prophylactic" EE is beneficial to synaptic derangements and preserves glutamate transmission in the cortex of EAE mice. This article is part of the Special Issue entitled "Neurobiology of Environmental Enrichment".

Aging-related SUMOylation pattern in the cortex and blood plasma of wild type mice.

Protein activities and mechanisms related to aging has become a growing interest nowadays. Since SUMOylation is implicated in several cellular processes, its investigation related to senescence, aging and frailty is of high interest. In our study, wild type mice cortical lysates, synaptosomes and plasma have been processed to evaluate SUMOylation and SUMO machinery expression (Ubc9 and SENP1 enzymes) profile at different ages. In cortical lysates, SUMO-1ylation reached a peak at 6 months followed by a decrease; while in synaptosomes, it progressively increased till 18 months. Regarding SUMO-2/3ylation, it was observed a similar trend in both lysate and synaptosomes where the protein conjugation was the highest at 6 months but interestingly decreased afterwards. In addition, Ubc9 and SENP1 enzymes showed a linear increased expression level in both brain preparations. Since SUMOylation process is ubiquitously expressed, we were interested to identify SUMO conjugation at peripheral level too. Thus, SUMO-1ylation and SUMO-2/3ylation expression level has been detected in mouse plasma that revealed an inverted U-shaped curve trend during mice lifespan. Surprisingly, SENP1 enzyme was not present in the plasma while Ubc9 enzyme reached a plateau at 6 months and was highly expressed till 18 months. In conclusion, our data indicates that SUMOylation is highly correlated with age-related processes which indisputably need to be considered for further investigation.

Acid-sensing ion channel 1a is required for mGlu receptor dependent long-term depression in the hippocampus.

Acid-sensing ion channels (ASICs), members of the degenerin/epithelial Na+ channel superfamily, are widely distributed in the mammalian nervous system. ASIC1a is highly permeable to Ca2+ and are thought to be important in a variety of physiological processes, including synaptic plasticity, learning and memory. To further understand the role of ASIC1a in synaptic transmission and plasticity, we investigated metabotropic glutamate (mGlu) receptor-dependent long-term depression (LTD) in the hippocampus. We found that ASIC1a channels mediate a component of LTD in P30-40 animals, since the ASIC1a selective blocker psalmotoxin-1 (PcTx1) reduced the magnitude of LTD induced by application of the group I mGlu receptor agonist (S)-3,5-Dihydroxyphenylglycine (DHPG) or induced by paired-pulse low frequency stimulation (PP-LFS). Conversely, PcTx1 did not affect LTD in P13-18 animals. We also provide evidence that ASIC1a is involved in group I mGlu receptor-induced increase in action potential firing. However, blockade of ASIC1a did not affect DHPG-induced polyphosphoinositide hydrolysis, suggesting the involvement of some other molecular partners in the functional crosstalk between ASIC1a and group I mGlu receptors. Notably, PcTx1 was able to prevent the increase in GluA1 S845 phosphorylation at the post-synaptic membrane induced by group I mGlu receptor activation. These findings suggest a novel function of ASIC1a channels in the regulation of group I mGlu receptor synaptic plasticity and intrinsic excitability.

Potentiation of NMDA receptor function through somatostatin release: a possible mechanism for the cognition-enhancing activity of GABA(B) receptor antagonists.

CGP 36742 is a weak GABA(B) receptor antagonist. However, it improves cognitive performances at low doses; it blocks GABA(B) receptors potently and selectively on somatostatinergic terminals; it prevents kynurenate from antagonising NMDA-induced release of noradrenaline from rat brain slices potently. We here investigated whether and how somatostatin plays a role in the CGP 36742 activity. CGP 36742 increased the somatostatin-like immunoreactivity (SRIF-LI) release from hippocampal slices exposed to NMDA. In the kynurenate test with rat hippocampal slices SRIF-14 mimicked the effect of CGP 36742. CGP 36742 lost its activity in rats whose somatostatin content had been depleted with cysteamine. Exogenous SRIF-14 reverted kynurenate antagonism in somatostatin-depleted slices. L362855, an sst(5) receptor agonist, but not the selective sst(1)-sst(4) agonists, L797591, L779976, L796778 and L803087, displayed activity in the kynurenate test. The effects of CGP 36742, SRIF-14 and L362855 were antagonised by the sst(5)-preferring antagonist BIM-23056. The protein kinase C inhibitor GF 109203X prevented the reversal of the kynurenate antagonism by CGP 36742 or SRIF-14. In conclusion, by selectively blocking GABA(B) receptors on somatostatinergic terminals, CGP 36742 may disinhibit somatostatin release; the consequent activation of sst(5) receptors would potentiate the function of NMDA receptors coexisting with sst(5) receptors on noradrenergic neurons.