Biology subjects

Cerny, O.

Publications and source records attributed to Cerny, O..

4 recordsLinked to original sources

bioRxiv2026

Flagellar system translocates T3SS effectors critical for Salmonella infection

Type 3 secretion system (T3SS) injectisomes, the essential virulence factors of many bacterial pathogens, are thought to have evolved from the flagellar T3SS. Despite their high degree of structural similarity, whether flagella can translocate effector proteins typically associated with T3SS injectisomes remains poorly understood. Here, we demonstrate that the flagellar T3SS of Salmonella translocates T3SS effectors directly into the host cell cytosol and that this process is critical for productive infection. We show that upon host cell adhesion, flagella were required for efficient Salmonella invasion. Fully assembled flagella enabled effector translocation in a process dependent on the flagellar motor. Notably, flagella continued to translocate effectors within the Salmonella-containing vacuole until expression of the Salmonella pathogenicity island 2-encoded T3SS injectisome was induced. Together, these findings reveal a previously overlooked function of bacterial flagella in host-pathogen interactions and redefine their contribution to Salmonella virulence.

microbiology↗

bioRxiv2025

Limited response of primary nasal epithelial cells to Bordetella pertussis infection and the effector protein BteA

Bordetella pertussis is a Gram-negative coccobacillus that causes whooping cough or pertussis, a respiratory disease that has recently experienced a resurgence. Upon entering the respiratory tract, B. pertussis colonizes the airway epithelium and attaches to ciliated cells. Here, we used primary human nasal epithelial cells (hNECs) cultured at the air-liquid interface, and investigated their interaction with the B. pertussis B1917, focusing on the role of the type III secretion system effector protein BteA. In this model, which resembles the epithelial cells of nasal epithelium in vivo, B. pertussis B1917 initially replicated in the overlying mucus and scarcely colonized the cell cilia. The colonization led to a gradual decline in epithelial barrier function, as shown by measurements of trans-epithelial electrical resistance (TEER) and staining of the tight junction protein zonula occludens 1 (ZO-1). The decrease in TEER occurred independently of the cytotoxic effector protein BteA. Transcriptomic and proteomic analyses of hNECs showed only moderate changes following infection, primarily characterized by increased mucus production, including upregulation of mucin MUC5AC. No profound response to BteA was detected. Furthermore, the infection did not induce production of inflammatory cytokines, suggesting that B. pertussis B1917 evades recognition by hNECs in this model system. These findings suggest that the bacterium may utilize the mucus layer in the airways as a protective niche to minimize epithelial recognition and damage. ImportanceThe nasal epithelium is the initial site where B. pertussis comes into contact with the host during respiratory infection. This work established human nasal epithelial cells (hNECs) cultured at the air-liquid interface (ALI) as an in vitro model to investigate B. pertussis infection. Using this system, we were able to show that in the early stages of colonization the clinical isolate B. pertussis B1917 replicates in the mucus without disrupting epithelial barrier function. Infection results in moderate transcriptomic and proteomic changes and is characterized by increased mucus production and minimal inflammatory signaling.

microbiology↗

bioRxiv2024

The Bordetella effector protein BteA induces host cell death by disruption of calcium homeostasis

Bordetella pertussis is the causative agent of whooping cough in humans, a disease that has recently experienced a resurgence. In contrast, Bordetella bronchiseptica infects the respiratory tract of various mammalian species, causing a range of symptoms from asymptomatic chronic carriage to acute illness. Both pathogens utilize type III secretion system (T3SS) to deliver the effector protein BteA into host cells. Once injected, BteA triggers a cascade of events leading to caspase 1-independent necrosis through a mechanism that remains incompletely understood. We demonstrate that BteA-induced cell death is characterized by the fragmentation of the cellular endoplasmic reticulum and mitochondria, the formation of necrotic balloon-like protrusions, and plasma membrane permeabilization. Importantly, genome-wide CRISPR-Cas9 screen targeting 19,050 genes failed to identify any host factors required for BteA cytotoxicity, suggesting that BteA does not require a single nonessential host factor for its cytotoxicity. We further reveal that BteA triggers rapid and sustained influx of calcium ions, which is associated with organelle fragmentation and plasma membrane permeabilization. The sustained elevation of cytosolic Ca2+ levels results in mitochondrial calcium overload, mitochondrial swelling, cristolysis, and loss of mitochondrial membrane potential. Inhibition of calcium channels with 2-APB delays both the Ca2+ influx and BteA-induced cell death. Our findings indicate that BteA exploits essential host processes and/or redundant pathways to disrupt calcium homeostasis and mitochondrial function, ultimately leading to host cell death. ImportanceThe respiratory pathogens, Bordetella pertussis and Bordetella bronchiseptica, exhibit cytotoxicity towards a variety of mammalian cells, which depends on the type III secretion effector BteA. Moreover, the increased virulence of B. bronchiseptica is associated with enhanced expression of T3SS and BteA effector. However, the molecular mechanism underlying BteA cytotoxicity is elusive. In this study, we performed a CRISPR-Cas9 screen, revealing that BteA-induced cell death depends on essential or redundant host processes. Additionally, we demonstrate that BteA disrupts calcium homeostasis, which leads to mitochondrial dysfunction and cell death. These findings contribute to closing the gap in our understanding of the signaling cascades targeted by BteA.

microbiology↗

bioRxiv2022

The Salmonella transmembrane effector SteD hijacks AP1-mediated vesicular trafficking for delivery to antigen-loading MHCII compartments

SteD is a transmembrane effector of the Salmonella SPI-2 type III secretion system that inhibits T cell activation by reducing the amounts of at least three proteins - major histocompatibility complex II (MHCII), CD86 and CD97 - from the surface of antigen-presenting cells. SteD specifically localises at the trans-Golgi network (TGN) and MHCII compartments; however, the targeting, membrane integration and trafficking of SteD are not understood. Using systematic mutagenesis, we identify distinct regions of SteD that are required for these processes. We show that SteD integrates into membranes of the ER/Golgi through a two-step mechanism of membrane recruitment from the cytoplasm followed by integration. SteD then migrates to and accumulates within the TGN. From here it hijacks the host adaptor protein (AP)1-mediated trafficking pathway from the TGN to MHCII compartments. AP1 binding and post-TGN trafficking require a short sequence in the N-terminal cytoplasmic tail of SteD that resembles the AP1-interacting dileucine sorting signal, but in inverted orientation, suggesting convergent evolution.

microbiology↗