In-plane nanoelectromechanical resonators based on silicon nanowire piezoresistive detection

We report an actuation/detection scheme with a top-down nano-electromechanical system for frequency shift-based sensing applications with outstanding performance. It relies on electrostatic actuation and piezoresistive nanowire gauges for in-plane motion transduction. The process fabrication is fully CMOS compatible. The results show a very large dynamic range (DR) of more than 100dB and an unprecedented signal to background ratio (SBR) of 69dB providing an improvement of two orders of magnitude in the detection efficiency presented in the state of the art in NEMS field. Such a dynamic range results from both negligible 1/f-noise and very low Johnson noise compared to the thermomechanical noise. This simple low-power detection scheme paves the way for new class of robust mass resonant sensor

LptM promotes oxidative maturation of the lipopolysaccharide translocon by substrate binding mimicry

Insertion of lipopolysaccharide (LPS) into the bacterial outer membrane (OM) is mediated by a druggable OM translocon consisting of a β-barrel membrane protein, LptD, and a lipoprotein, LptE. The β-barrel assembly machinery (BAM) assembles LptD together with LptE at the OM. In the enterobacterium Escherichia coli, formation of two native disulfide bonds in LptD controls translocon activation. Here we report the discovery of LptM (formerly YifL), a lipoprotein conserved in Enterobacteriaceae, that assembles together with LptD and LptE at the BAM complex. LptM stabilizes a conformation of LptD that can efficiently acquire native disulfide bonds, whereas its inactivation makes disulfide bond isomerization by DsbC become essential for viability. Our structural prediction and biochemical analyses indicate that LptM binds to sites in both LptD and LptE that are proposed to coordinate LPS insertion into the OM. These results suggest that, by mimicking LPS binding, LptM facilitates oxidative maturation of LptD, thereby activating the LPS translocon

Death of an alcohol-dependent patient following intentional drug intoxication: implication of baclofen?

International audienceUsed in the treatment of spasticity at low doses, baclofen is also prescribed off-label at high doses for the treatment of alcohol dependence. Several cases of baclofen intoxication have been reported, but only 1 case deals with the treatment of alcohol dependence. Thus, we report the first death in the context of baclofen off-label use of an alcohol-dependent patient with a high blood baclofen concentration after intentional drug intoxication. The safety profile of baclofen in the treatment of alcohol dependence is reviewed and discussed, underlining the obligatory caution that may support any prescription of high doses of baclofen in this off-label indication and especially in patients with concomitant psychiatric disorders

Death in an alcohol-dependent patient treated with baclofen: be careful !

International audienc

The final step of 40S ribosomal subunit maturation is controlled by a dual key lock

Preventing premature interaction of pre-ribosomes with the translation apparatus is essential for translational accuracy. Hence, the final maturation step releasing functional 40S ribosomal subunits, namely processing of the 18S ribosomal RNA 3′ end, is safeguarded by the protein DIM2, which both interacts with the endoribonuclease NOB1 and masks the rRNA cleavage site. To elucidate the control mechanism that unlocks NOB1 activity, we performed cryo-electron microscopy analysis of late human pre-40S particles purified using a catalytically inactive form of the ATPase RIO1. These structures, together with in vivo and in vitro functional analyses, support a model in which ATP-loaded RIO1 cooperates with ribosomal protein RPS26/eS26 to displace DIM2 from the 18S rRNA 3′ end, thereby triggering final cleavage by NOB1; release of ADP then leads to RIO1 dissociation from the 40S subunit. This dual key lock mechanism requiring RIO1 and RPS26 guarantees the precise timing of pre-40S particle conversion into translation-competent ribosomal subunits

Lipoprotein DolP supports proper folding of BamA in the bacterial outer membrane promoting fitness upon envelope stress

International audienceIn Proteobacteria, integral outer membrane proteins (OMPs) are crucial for the maintenance of the envelope permeability barrier to some antibiotics and detergents. In Enterobacteria, envelope stress caused by unfolded OMPs activates the sigmaE (σ E ) transcriptional response. σ E upregulates OMP biogenesis factors, including the β-barrel assembly machinery (BAM) that catalyses OMP folding. Here we report that DolP (formerly YraP), a σ E -upregulated and poorly understood outer membrane lipoprotein, is crucial for fitness in cells that undergo envelope stress. We demonstrate that DolP interacts with the BAM complex by associating with outer membrane-assembled BamA. We provide evidence that DolP is important for proper folding of BamA that overaccumulates in the outer membrane, thus supporting OMP biogenesis and envelope integrity. Notably, mid-cell recruitment of DolP had been linked to regulation of septal peptidoglycan remodelling by an unknown mechanism. We now reveal that, during envelope stress, DolP loses its association with the mid-cell, thereby suggesting a mechanistic link between envelope stress caused by impaired OMP biogenesis and the regulation of a late step of cell division

Establishing 20S Proteasome Genetic, Translational and Post-Translational Status from Precious Biological and Patient Samples with Top-Down MS

International audienceThe mammalian 20S catalytic core of the proteasome is made of 14 different subunits (α1-7 and β1-7) but exists as different subtypes depending on the cell type. In immune cells, for instance, constitutive catalytic proteasome subunits can be replaced by the so-called immuno-catalytic subunits, giving rise to the immunoproteasome. Proteasome activity is also altered by post-translational modifications (PTMs) and by genetic variants. Immunochemical methods are commonly used to investigate these PTMs whereby protein-tagging is necessary to monitor their effect on 20S assembly. Here, we present a new miniaturized workflow combining top-down and bottom-up mass spectrometry of immunopurified 20S proteasomes that analyze the proteasome assembly status as well as the full proteoform footprint, revealing PTMs, mutations, single nucleotide polymorphisms (SNPs) and induction of immune-subunits in different biological samples, including organoids, biopsies and B-lymphoblastoid cell lines derived from patients with proteasome-associated autoinflammatory syndromes (PRAAS). We emphasize the benefits of using top-down mass spectrometry in preserving the endogenous conformation of protein modifications, while enabling a rapid turnaround (1 h run) and ensuring high sensitivity (1–2 pmol) and demonstrate its capacity to semi-quantify constitutive and immune proteasome subunits