LRRTM2 controls presynapse nano-organization and AMPA receptor sub-positioning through Neurexin-binding interface.

Synapses are organized into nanocolumns that control synaptic transmission efficacy through precise alignment of postsynaptic neurotransmitter receptors and presynaptic release sites. Recent evidence show that Leucine-Rich Repeat Transmembrane protein LRRTM2, highly enriched and confined at synapses, interacts with Neurexins through its C-terminal cap, but the role of this binding interface has not been explored in synapse formation and function. Here, we develop a conditional knock-out mouse model (cKO) to address the molecular mechanisms of LRRTM2 regulation, and its role in synapse organization and function.

Peptide nucleic acids (PNAs) control function of SARS-CoV-2 frameshifting stimulatory element trough PNA-RNA-PNA triplex formation.

The highly structured nature of the SARS-CoV-2 genome provides many promising antiviral drug targets. One particularly promising target is a -acting RNA pseudoknot found within a critical region called the frameshifting stimulatory element (FSE). In this study, peptide nucleic acids (PNAs) binding to stem 2 of FSE RNA inhibited protein translation and frameshifting, as measured by a cell-free dual luciferase assay, more effectively than PNAs binding to stem 1, stem 3, or the slippery site.

Poly(malic acid)-budesonide nanoconjugates embedded in microparticles for lung administration.

To improve the therapeutic activity of inhaled glucocorticoids and reduce potential side effects, we designed a formulation combining the advantages of nanoparticles, which have an enhanced uptake by alveolar cells, allow targeted delivery and sustained drug release, as well as limited drug systemic passage, with those of microparticles, which display good alveolar deposition. Herein, a polymer-drug conjugate, poly(malic acid)-budesonide (PMAB), was first synthesized with either 11, 20, 33, or 43 mol% budesonide (drug:polymer from 1:8 to 3:4), the drug creating hydrophobic domains. The obtained conjugates self-assemble into nanoconjugates in water, yielding excellent drug loading of up to 73 wt%, with 80-100 nm diameters.

Improved Triplex-Forming Isoorotamide PNA Nucleobases for A-U Recognition of RNA Duplexes.

Four new isoorotamide (Io)-containing PNA nucleobases have been designed for A-U recognition of double helical RNA. New PNA monomers were prepared efficiently and incorporated into PNA nonamers for binding A-U in a PNA:RNA triplex. Isothermal titration calorimetry and UV thermal melting experiments revealed slightly improved binding affinity for singly modified PNA compared to known A-binding nucleobases.

Emerging nanoparticle platforms to improve the administration of glucocorticoids.

Glucocorticoids (GC) are common drugs used to treat acute and chronic inflammatory diseases, whose prolonged use can result in severe side effects hampering their efficacy. In addition, the pharmacokinetics, and biodistribution of GC are inadequate to support high efficacy with reduced toxicity. Following the marketing of GC prodrugs, new GC prodrug entities, and conjugates, have been developed.

Feasibility of a repositioning schedule on pressure ulcer prevention in a French Intensive Care Unit: A pre and post-intervention pilot study.

Aims: As a prerequisite of a multicentre study, we conducted a pilot study to assess the feasibility of a daily repositioning schedule in critically ill patients. The schedule was adapted to the patient's clinical condition, and the estimated risk for developing a pressure ulcer using the Braden scale.

Design: A single-center pre and post-intervention pilot study in a French Intensive Care Unit of a university teaching hospital.

Comparative study of open, laparoscopic and endoscopic treatments of intermediate grade vesicoureteral reflux in children.

Background: Low-grade vesicoureteral-reflux (VUR) are rather treated by endoscopic injection, whereas open or laparoscopic procedures are mainly performed for high-grade VURs. Management of intermediate grades is controversial and no study focused on grade III to date. This study aims to compare the results of open, laparoscopic, and endoscopic approaches in children with grade III VUR.

miR-124-dependent tagging of synapses by synaptopodin enables input-specific homeostatic plasticity.

Homeostatic synaptic plasticity is a process by which neurons adjust their synaptic strength to compensate for perturbations in neuronal activity. Whether the highly diverse synapses on a neuron respond uniformly to the same perturbation remains unclear. Moreover, the molecular determinants that underlie synapse-specific homeostatic synaptic plasticity are unknown.

Role of regulatory C-terminal motifs in synaptic confinement of LRRTM2.

Leucine Rich Repeat Transmembrane proteins (LRRTMs) are neuronal cell adhesion molecules involved in synapse development and plasticity. LRRTM2 is the most synaptogenic isoform of the family, and its expression is strongly restricted to excitatory synapses in mature neurons. However, the mechanisms by which LRRTM2 is trafficked and stabilized at synapses remain unknown.

Conservation genetics of the threatened plant species Physaria filiformis (Missouri bladderpod) reveals strong genetic structure and a possible cryptic species.

Understanding genetic diversity and structure in a rare species is critical for prioritizing both in situ and ex situ conservation efforts. One such rare species is Physaria filiformis (Brassicaceae), a threatened, winter annual plant species. The species has a naturally fragmented distribution, occupying three different soil types spread across four disjunct geographical locations in Missouri and Arkansas.

A cover flap reduces the rate of fistula after urethroplasty whatever the severity of hypospadias.

Objective: To determine which patients should benefit from the interposition of a well-vascularized flap between the neourethra and the penile skin and if it should be performed even in mild hypospadias.

Patients And Methods: A retrospective study on patients with a primary hypospadias repair was performed (2003-2017). Only patients undergoing urethroplasty based on the principle of a tubularization were selected to ensure comparable groups.

Optogenetic control of excitatory post-synaptic differentiation through neuroligin-1 tyrosine phosphorylation.

Neuroligins (Nlgns) are adhesion proteins mediating trans-synaptic contacts in neurons. However, conflicting results around their role in synaptic differentiation arise from the various techniques used to manipulate Nlgn expression level. Orthogonally to these approaches, we triggered here the phosphorylation of endogenous Nlgn1 in CA1 mouse hippocampal neurons using a photoactivatable tyrosine kinase receptor (optoFGFR1).

A unique intracellular tyrosine in neuroligin-1 regulates AMPA receptor recruitment during synapse differentiation and potentiation.

To better understand the molecular mechanisms by which early neuronal connections mature into synapses, we examined the impact of neuroligin-1 (Nlg1) phosphorylation on synapse differentiation, focusing on a unique intracellular tyrosine (Y782), which differentially regulates Nlg1 binding to PSD-95 and gephyrin. By expressing Nlg1 point mutants (Y782A/F) in hippocampal neurons, we show using imaging and electrophysiology that Y782 modulates the recruitment of functional AMPA receptors (AMPARs). Nlg1-Y782F impaired both dendritic spine formation and AMPAR diffusional trapping, but not NMDA receptor recruitment, revealing the assembly of silent synapses.

Mapping the dynamics and nanoscale organization of synaptic adhesion proteins using monomeric streptavidin.

The advent of super-resolution imaging (SRI) has created a need for optimized labelling strategies. We present a new method relying on fluorophore-conjugated monomeric streptavidin (mSA) to label membrane proteins carrying a short, enzymatically biotinylated tag, compatible with SRI techniques including uPAINT, STED and dSTORM. We demonstrate efficient and specific labelling of target proteins in confined intercellular and organotypic tissues, with reduced steric hindrance and no crosslinking compared with multivalent probes.

Mechanical coupling between transsynaptic N-cadherin adhesions and actin flow stabilizes dendritic spines.

The morphology of neuronal dendritic spines is a critical indicator of synaptic function. It is regulated by several factors, including the intracellular actin/myosin cytoskeleton and transcellular N-cadherin adhesions. To examine the mechanical relationship between these molecular components, we performed quantitative live-imaging experiments in primary hippocampal neurons.

Micropatterned substrates coated with neuronal adhesion molecules for high-content study of synapse formation.

Studying the roles of different proteins and the mechanisms involved in synaptogenesis is hindered by the complexity and heterogeneity of synapse types, and by the spatial and temporal unpredictability of spontaneous synapse formation. Here we demonstrate a robust and high-content method to induce selectively presynaptic or postsynaptic structures at controlled locations. Neurons are cultured on micropatterned substrates comprising arrays of micron-scale dots coated with various synaptogenic adhesion molecules.

Assembly of synapses: biomimetic assays to control neurexin/neuroligin interactions at the neuronal surface.

The role of adhesion molecules in the assembly of synapses in the nervous system is an important issue. To characterize the role of neurexin/neuroligin adhesion complexes in synapse differentiation, various imaging assays can be performed in primary hippocampal cultures. First, to temporally control contact formation, biomimetic assays can be performed using microspheres coated with purified neurexin or with antibody clusters that aggregate neurexin.

Neurexin-1β binding to neuroligin-1 triggers the preferential recruitment of PSD-95 versus gephyrin through tyrosine phosphorylation of neuroligin-1.

Adhesion between neurexin-1β (Nrx1β) and neuroligin-1 (Nlg1) induces early recruitment of the postsynaptic density protein 95 (PSD-95) scaffold; however, the associated signaling mechanisms are unknown. To dissociate the effects of ligand binding and receptor multimerization, we compared conditions in which Nlg1 in neurons was bound to Nrx1β or nonactivating HA antibodies. Time-lapse imaging, fluorescence recovery after photobleaching, and single-particle tracking demonstrated that in addition to aggregating Nlg1, Nrx1β binding stimulates the interaction between Nlg1 and PSD-95.

Integrins β1 and β3 exhibit distinct dynamic nanoscale organizations inside focal adhesions.

Integrins in focal adhesions (FAs) mediate adhesion and force transmission to extracellular matrices essential for cell motility, proliferation and differentiation. Different fibronectin-binding integrins, simultaneously present in FAs, perform distinct functions. Yet, how integrin dynamics control biochemical and biomechanical processes in FAs is still elusive.

Neurexin-neuroligin adhesions capture surface-diffusing AMPA receptors through PSD-95 scaffolds.

The mechanisms governing the recruitment of functional glutamate receptors at nascent excitatory postsynapses following initial axon-dendrite contact remain unclear. We examined here the ability of neurexin/neuroligin adhesions to mobilize AMPA-type glutamate receptors (AMPARs) at postsynapses through a diffusion/trap process involving the scaffold molecule PSD-95. Using single nanoparticle tracking in primary rat and mouse hippocampal neurons overexpressing or lacking neuroligin-1 (Nlg1), a striking inverse correlation was found between AMPAR diffusion and Nlg1 expression level.

Annexin-A6 presents two modes of association with phospholipid membranes. A combined QCM-D, AFM and cryo-TEM study.

Annexins are soluble proteins that bind to biological membranes in a Ca(2+)-dependent manner. Annexin-A6 (AnxA6) is unique in the annexin family as it consists of the repeat of two annexin core modules, while all other annexins consist of a single module. AnxA6 has been proposed to participate in various membrane-related processes, including endocytosis and exocytosis, yet the molecular mechanism of association of AnxA6 with biological membranes, especially its ability to aggregate membranes, is still unclear.