Structural pathway of regulated substrate transfer and threading through an Hsp100 disaggregase

Refolding aggregated proteins is essential in combating cellular proteotoxic stress. Together with Hsp70, Hsp100 chaperones, including Escherichia coli ClpB, form a powerful disaggregation machine that threads aggregated polypeptides through the central pore of tandem adenosine triphosphatase (ATPase) rings. To visualize protein disaggregation, we determined cryo–electron microscopy structures of inactive and substrate-bound ClpB in the presence of adenosine 5′-O-(3-thiotriphosphate), revealing closed AAA+ rings with a pronounced seam. In the substrate-free state, a marked gradient of resolution, likely corresponding to mobility, spans across the AAA+ rings with a dynamic hotspot at the seam. On the seam side, the coiled-coil regulatory domains are locked in a horizontal, inactive orientation. On the opposite side, the regulatory domains are accessible for Hsp70 binding, substrate targeting, and activation. In the presence of the model substrate casein, the polypeptide threads through the entire pore channel and increased nucleotide occupancy correlates with higher ATPase activity. Substrate-induced domain displacements indicate a pathway of regulated substrate transfer from Hsp70 to the ClpB pore, inside which a spiral of loops contacts the substrate. The seam pore loops undergo marked displacements, along with ordering of the regulatory domains. These asymmetric movements suggest a mechanism for ATPase activation and substrate threading during disaggregation

Structural Characterization of N-WASP Domain V Using MD Simulations with NMR and SAXS Data

International audienceBecause of their large conformational heterogeneity, structural characterization of intrinsically disordered proteins (IDPs) is very challenging using classical experimental methods alone. In this study, we use NMR and small-angle x-ray scattering (SAXS) data with multiple molecular dynamics (MD) simulations to describe the conformational ensemble of the fully disordered verprolin homology domain of the neural Aldrich syndrome protein involved in the regulation of actin polymerization. First, we studied several back-calculation software of SAXS scattering intensity and optimized the adjustable parameters to accurately calculate the SAXS intensity from an atomic structure. We also identified the most appropriate force fields for MD simulations of this IDP. Then, we analyzed four conformational ensembles of neural Aldrich syndrome protein verprolin homology domain, two generated with the program flexible-meccano with or without NMR-derived information as input and two others generated by MD simulations with two different force fields. These four conformational ensembles were compared to available NMR and SAXS data for validation. We found that MD simulations with the AMBER-03w force field and the TIP4P/2005s water model are able to correctly describe the conformational ensemble of this 67-residue IDP at both local and global level

Medication Reconciliation Associated with Comprehensive Geriatric Assessment in Older Patients with Cancer: ChimioAge Study

International audienceBackground: Polymorbidity induces polypharmacy in older patients may lead to potential drug–drug interactions (DDI) which can modify the tolerance and safety of oncological treatments and alter the intended therapeutic effect. The objective of our study was to describe the decision-making process for oncological treatment and related outcomes, in a population of older adults undergoing a comprehensive geriatric assessment (CGA) associated to a comprehensive medication reconciliation (CMR) prior to initiating oncological treatment.Methods: ChimioAge is a prospective observational study conducted between 01/2017 and 07/2018 at Marseille University Hospital and approved by the French National Ethics Committee. It comprised all consecutive patients aged 70 years and over who were referred for a CGA as part of CMR, before initiating systemic treatment.Results: One hundred and seventy-one cancer patients were included. Mean age was 79.2 years, over half had metastatic cancers, 75% had an ECOG performance status zero or one, and two-thirds were independent in daily activities. Two-thirds of the patients had polypharmacy and the CMR identified potential DDI with systemic treatment in 43.3% of patients. Following the CGA, the CMR and the hospital oncologists decision, 30% of the patients received adapted systemic treatment with reduced doses at initiation. They presented fewer toxicities – irrespective of grade and type – than patients who received standard treatment (p< 0.001) and had comparable overall survival (Log rank p=0.21).Conclusion: This is one of the first studies to highlight the value in conducting CMR and a CGA simultaneously before initiating systemic treatment in older patients with cancer. These two evaluations could give oncologists decisive information to personalize cancer treatment of older patients and optimize treatment dose to offer the best efficacy and minimize toxicity

Differential regulation of actin-activated nucleotidyl cyclase virulence factors by filamentous and globular actin

<div><p>Several bacterial pathogens produce nucleotidyl cyclase toxins to manipulate eukaryotic host cells. Inside host cells they are activated by endogenous cofactors to produce high levels of cyclic nucleotides (cNMPs). The ExoY toxin from <i>Pseudomonas aeruginosa</i> (PaExoY) and the ExoY-like module (VnExoY) found in the MARTX (Multifunctional-Autoprocessing Repeats-in-ToXin) toxin of <i>Vibrio nigripulchritudo</i> share modest sequence similarity (~38%) but were both recently shown to be activated by actin after their delivery to the eukaryotic host cell. Here, we further characterized the ExoY-like cyclase of <i>V</i>. <i>nigripulchritudo</i>. We show that, in contrast to PaExoY that requires polymerized actin (F-actin) for maximum activation, VnExoY is selectively activated by monomeric actin (G-actin). These two enzymes also display different nucleotide substrate and divalent cation specificities. <i>In vitro</i> in presence of the cation Mg²⁺, the F-actin activated PaExoY exhibits a promiscuous nucleotidyl cyclase activity with the substrate preference GTP>ATP≥UTP>CTP, while the G-actin activated VnExoY shows a strong preference for ATP as substrate, as it is the case for the well-known calmodulin-activated adenylate cyclase toxins from <i>Bordetella pertussis</i> or <i>Bacillus anthracis</i>. These results suggest that the actin-activated nucleotidyl cyclase virulence factors despite sharing a common activator may actually display a greater variability of biological effects in infected cells than initially anticipated.</p></div

A chemical probe for BAG1 targets androgen receptor-positive prostate cancer through oxidative stress signaling pathway

International audienceBAG1 is a family of polypeptides with a conserved C-terminal BAG domain that functions as a nucleotide exchange factor for the molecular chaperone HSP70. BAG1 proteins also control several signaling processes including proteostasis, apoptosis, and transcription. The largest isoform, BAG1L, controls the activity of the androgen receptor (AR) and is upregulated in prostate cancer. Here, we show that BAG1L regulates AR dynamics in the nucleus and its ablation attenuates AR target gene expression especially those involved in oxidative stress and metabolism. We show that a small molecule, A4B17, that targets the BAG domain downregulates AR target genes similar to a complete BAG1L knockout and upregulates the expression of oxidative stress-induced genes involved in cell death. Furthermore, A4B17 outperformed the clinically approved antagonist enzalutamide in inhibiting cell proliferation and prostate tumor development in a mouse xenograft model. BAG1 inhibitors therefore offer unique opportunities for antagonizing AR action and prostate cancer growth