Biology subjects

Mathews, I.

Publications and source records attributed to Mathews, I..

3 recordsLinked to original sources

bioRxiv2025

LPC 18:2-Driven Apoptosis In Neutrophils Is Non-Inflammatory and Lipid Raft Dependent

Lysophosphatidylcholines (LPCs) are potent bioactive lipids whose fatty acid compositions dictate their immunomodulatory effects. Here, we delineate how unsaturated LPC 18:2 and saturated LPC 16:0 differentially regulate neutrophil survival and inflammatory programs. LPC 18:2 markedly increased reactive oxygen species (ROS) generation and caspase-3/7 activation, mitochondrial membrane depolarization, and cytochrome c release, features consistent with intrinsic apoptosis. In contrast, LPC 16:0 induced robust LDH and HMGB-1 release, indicating membrane rupture and pyroptosis-like death. Bulk RNA sequencing revealed that LPC 16:0 strongly upregulated inflammatory and cytokine gene expression. Disruption of lipid-raft integrity abolished LPC 18:2-induced ROS and apoptosis, underscoring the dependence of these effects on membrane organization. Collectively, these results identify LPC 18:2 as a non-inflammatory, mitochondria-dependent inducer of neutrophil apoptosis, whereas LPC 16:0 promotes inflammatory, lytic death programs. These findings highlight how lipid saturation determines neutrophil fate and immune tone, providing mechanistic insight into how distinct LPC species shape inflammation and tissue injury.

immunology↗

bioRxiv2025

A Novel Unorthodox Dimeric Primary Enoyl-CoA Reductase Structure

Enoyl-CoA carboxylases/reductases (ECRs) are enzymes with the fastest carbon dioxide (CO2) fixation capabilities, yet the precise mechanisms behind their assembly and catalytic activity are structurally not yet fully understood. Here, we employed cryo X-ray crystallography to reveal the dimeric structural organization of a novel ECR, isolated from mesophilic Mesorhizobium metallidurans (M. metallidurans). We examined the interactions in silico and compared oligomerization of our dimeric ECR from M. metallidurans (ECRMm_Dim) with tetrameric ECR from Burkholderia ambifaria (ECRBa_Tet)by using size exclusion chromatography in solution. Our in silico analysis revealed that specific residues in the M. metallidurans ECR that preclude tetramer formation, which could affect the enzymes catalytic activity. Additionally, we compared primary ECR sequences and structural variations between K. setae and M. metallidurans to explore their evolutionary relationships, along with their functional diversity. Our study presents the first example of a dimeric ECR structure which may provide new insights into how dimerization versus tetramerization may have an impact on catalytic function. By detailing how different oligomeric states influence enzyme activity and exploring active site conformational changes, we may offer a further understanding of ECR assembly. This work paves the way for future research into the precise molecular mechanisms that drive ECRs exceptional overall catalytic activity, efficiency and efficacy.

biochemistry↗

bioRxiv2021

Structural and functional characterization of NEMO cleavage by SARS-CoV-2 3CLpro

In addition to its essential role in viral polyprotein processing, the SARS-CoV-2 3C-like (3CLpro) protease can cleave human immune signaling proteins, like NF-{kappa}B Essential Modulator (NEMO) and deregulate the host immune response. Here, in vitro assays show that SARS-CoV-2 3CLpro cleaves NEMO with fine-tuned efficiency. Analysis of the 2.14 [A] resolution crystal structure of 3CLpro C145S bound to NEMO226-235 reveals subsites that tolerate a range of viral and host substrates through main chain hydrogen bonds while also enforcing specificity using side chain hydrogen bonds and hydrophobic contacts. Machine learning- and physics-based computational methods predict that variation in key binding residues of 3CLpro- NEMO helps explain the high fitness of SARS-CoV-2 in humans. We posit that cleavage of NEMO is an important piece of information to be accounted for in the pathology of COVID-19.

molecular biology↗