Biology subjects

Munier-Lehmann, H.

Publications and source records attributed to Munier-Lehmann, H..

4 recordsLinked to original sources

bioRxiv2026

Deciphering the nucleotide driven kinetic and oligomeric dynamics in IMPDH regulation

Inosine monophosphate dehydrogenase (IMPDH) controls guanine nucleotide biosynthesis. Here, using biochemical and integrative structural biology approaches, we characterize the class II bacterial IMPDH from Burkholderia thailandensis. We demonstrate that MgGTP acts as a direct allosteric inhibitor independently of MgATP, promoting tetramer-to-octamer assembly via the Bateman domain. When both nucleotides are present, the enzyme exhibits a biphasic response: low MgGTP concentrations enhance activity, whereas higher concentrations restore inhibition. Structural analyses reveal distinct octameric conformations and capture a pre-catalytic Michaelis complex with substrates and effectors bound. These findings uncover a regulatory mechanism where the Bateman domain integrates opposing nucleotide signals to dynamically control guanine nucleotide biosynthesis, highlighting IMPDH as a potential antimicrobial target in pathogenic Burkholderia species.

biochemistry↗

bioRxiv2025

Exploring the multi-protein assembly of the enzymes of the de novo purine nucleotide biosynthetic pathway from Pseudomonas aeruginosa

Purine nucleotide biosynthesis is a crucial metabolic pathway responsible that produces building blocks essential for a plethora of cellular processes. In bacteria, the de novo purine nucleotide biosynthetic pathway (DNPNB) involves fifteen chemical steps catalysed by fourteen different enzymes. While the mammalian orthologues have been extensively shown to interact and form a metabolon named "purinosome", the possible existence of a prokaryotic equivalent was only recently revealed for the case of Escherichia coli. In this study, we explored the potential conservation of a bacterial purinosome-like complex in Pseudomonas aeruginosa, an opportunistic pathogen known for its high antibiotic resistance. Using a bacterial two-hybrid system, we mapped protein-protein interactions among all tested DNPNB enzymes in P. aeruginosa and revealed a dense interaction network. An in-silico protein-protein docking approach on three core enzymes allowed the structural reconstitution of a complex composed of PurK, PurE and PurC with a 4:8:8 stoichiometry, respectively. Interestingly, a tunnel connecting the different active sites has been revealed, showing a metabolon-like property for possible efficient substrate channelling. These findings support a conserved regulatory organization of purine biosynthesis in bacteria, providing deeper insights into bacterial metabolism and paving the way for potential antibiotic targets.

biochemistry↗

bioRxiv2021

Steroid hormone catabolites activate the pyrin inflammasome through a non-canonical mechanism

The pyrin inflammasome acts as a guard of RhoA GTPases and is central to immune defences against RhoA-manipulating pathogens. Pyrin activation proceeds in two steps. Yet, the second step is still poorly understood. Using cells constitutively activated for the pyrin step 1, a chemical screen identified etiocholanolone and pregnanolone, two catabolites of testosterone and progesterone, acting at low concentrations as specific step-2 activators. High concentrations of these metabolites fully and rapidly activated pyrin, in a human-specific, B30.2 domain-dependent manner and without inhibiting RhoA. Mutations in MEFV, encoding pyrin, cause two distinct autoinflammatory diseases (PAAND and FMF). Monocytes from PAAND patients, and to a lower extent from FMF patients, displayed increased responses to these metabolites. This study provides a new perspective on pyrin activation, indicates that endogenous steroid catabolites can drive autoinflammation, through the pyrin inflammasome, and explains the "steroid fever" described in the late 1950s, upon steroid injection in humans.

immunology↗

bioRxiv2020

Replication of Equine arteritis virus is efficiently suppressed by purine and pyrimidine biosynthesis inhibitors

RNA viruses are responsible for a large variety of animal infections. Equine Arteritis Virus (EAV) is a positive single-stranded RNA virus member of the family Arteriviridae from the order Nidovirales like the Coronaviridae. EAV causes respiratory and reproductive diseases in equids. Although two vaccines are available, the vaccination coverage of the equine population is largely insufficient to prevent new EAV outbreaks around the world. In this study, we present a high-throughput in vitro assay suitable for testing candidate antiviral molecules on equine dermal cells infected by EAV. Using this assay, we identified three molecules that impair EAV infection in equine cells: the broad-spectrum antiviral and nucleoside analog ribavirin, and two compounds previously described as inhibitors of dihydroorotate dehydrogenase (DHODH), the fourth enzyme of the pyrimidine biosynthesis pathway. These molecules effectively suppressed cytopathic effects associated to EAV infection, and strongly inhibited viral replication and production of infectious particles. Since ribavirin is already approved in human and small animal, and that several DHODH inhibitors are in advanced clinical trials, our results open new perspectives for the management of EAV outbreaks.

microbiology↗