Biology subjects

Trillo-Muyo, S.

Publications and source records attributed to Trillo-Muyo, S..

4 recordsLinked to original sources

bioRxiv2025

Cryo-EM structure of CLCA1 identifies CLCA1 as a founding member of a novel metzincin family.

Calcium-activated chloride channel regulator 1 (CLCA1) is implicated in several diseases, especially mucus-associated airway diseases, but its molecular function and regulation have remained unclear. By determining the structure of CLCA1 by negative stain electron microscopy and cryo-EM, we could confirm that CLCA1 forms large oligomeric complexes which adopts a compact domain organization comprising a metallohydrolase (MH), von Willebrand type A (VWA), {beta}-sheet-rich (BSR), inhibitory (ID), and fibronectin type III-like (FnIII-l) domains. The unusually large MH domain bears hallmarks of metzincins but is distinguished by several unique features including an atypical active site zinc-coordination environment and a second Zn2+ -coordination site. Unlike classical metzincins, CLCA1 lacks a pro-domain; instead, a C-terminal inhibitory loop occludes the MH active site, providing an alternative mechanism of autoinhibition. The adjacent VWA domain, resolved in its closed state, is poised for conformational change upon ligand binding, suggesting a route for allosteric regulation of protease activity. Structural and functional assays support a role for CLCA1 in cleaving glycosylated substrates, leading to alterations in mucin architecture consistent with a regulated function in mucus remodeling. Together, these data establish CLCA1 as the founding member of a new eukaryotic metzincin family, here termed CLCAsins, with unique regulatory mechanisms.

molecular biology↗

bioRxiv2025

Degradation of the intestinal mucus layer by the ETEC protease EatA is species specific determined by the structure of the MUC2 mucin

Enterotoxigenic Escherichia coli (ETEC) infections are a leading cause of diarrheal illness, responsible for an estimated 100,000 deaths annually. ETEC pathogenesis is driven by various virulence factors, including toxins, adhesins, and noncanonical factors such as the protease EatA. The first line of host defense against intestinal pathogenic bacterial infections is the protective intestinal mucus layer. Here, we demonstrate the mechanism by which EatA facilitates access to the epithelial cell surface by degrading the core mucus component MUC2, thereby aiding to the infection. We identify the specific cleavage site region localized at the C-terminal of MUC2. EatAs protease activity depends on the interaction between two distinct domains, which are uniquely spaced in human MUC2, contributing to species specificity. This was confirmed using a novel chimeric mouse model solely expressing human MUC2, which allowed us to study the role of the mucus layer in the infection of human intestinal pathogens. These findings highlight how ETEC has adapted to specifically degrade the mucus layer of its human host.

molecular biology↗

bioRxiv2024

Structural mechanism of MUC5AC mucin net-like polymer formation and its SNP variability that affect risk of the lung diseases COPD and IPF

Gel-forming mucins MUC5AC and MUC5B constitute the main structural component of the mucus in the respiratory system. Secreted mucins interact specifically with each other and other molecules giving mucus specific properties. We determined the cryoEM structures of the wild type MUC5AC-D3 assembly and the structural SNP variants R996Q and R1201W. Our structures explain the basis of MUC5AC N-terminal non-covalent oligomerization upon secretion. The MUC5AC-D3 assembly forms covalent dimers in two alternative conformations, open and closed. The closed conformation dimers interact through an arginine rich loop in the TIL3 domain forming tetramers. Moreover, we found a positive disease correlation between the SNP (R996Q, rs878913005), Chronic Obstructive Pulmonary Disease (COPD), and Idiopathic Pulmonary Fibrosis (IPF). The well-known MUC5B promotor SNP (rs35705950) association with IPF is much stronger when combined with the MUC5AC SNP. Our study provides a model to explain the formation of MUC5AC net-like structures and how both SNPs will affect mucus organization and increase risk of lung disease.

biochemistry↗

bioRxiv2024

BPP43_05035 is a Brachyspira pilosicoli cell surface adhesin that weakens the integrity of the epithelial barrier during infection

The anaerobic spirochete Brachyspira causes intestinal spirochetosis, characterized by the intimate attachment of bacterial cells to the colonic mucosa, potentially leading to symptoms such as diarrhea, abdominal pain, and weight loss. Despite the clinical significance of Brachyspira infections, the mechanism behind the interaction between Brachyspira and the colonic epithelium is not known. In this study, we characterized the molecular mechanism of B. pilosicoli-epithelium interaction and its impact on the epithelial barrier during infection. Through a proteomics approach, we identified BPP43_05035 as a candidate B. pilosicoli adhesion protein that mediates bacterial attachment to cultured human colonic epithelial cells. The crystal structure of BPP43_05035 revealed a globular lipoprotein with a six-bladed beta-propeller domain. Blocking the native BPP43_05035 on B. pilosicoli, either with a specific antibody or via competitive inhibition, abrogated its binding to epithelial cells. Furthermore, the binding of BPP43_05035 to epithelial cells required surface-exposed host N-glycans. Proximity labeling and interaction assays revealed that BPP43_05035 bound to tight junctions, thereby increasing the permeability of the epithelial monolayer. Extending our investigation to human patients, we identified a downregulation of tight junction and brush border genes in B. pilosicoli-infected patients carrying detectible levels of epithelium-bound BPP43_05035. Collectively, our findings identify BPP43_05035 as a B. pilosicoli adhesin that weakens the colonic epithelial barrier during infection.

microbiology↗