Biology subjects

Chaconas, G.

Publications and source records attributed to Chaconas, G..

3 recordsLinked to original sources

bioRxiv2026

Making the best of a sticky situation: Infection-mediated endothelial activation promotes new interactions with adhesins of the host-adapted Lyme disease spirochete

Lyme disease, caused by the spirochete Borrelia burgdorferi and closely related Lyme Borrelia, is the most prevalent tick-borne illness in the northern hemisphere. An important pathway for B. burgdorferi dissemination is its interaction with, and traversal of the vascular endothelium, a process that is not well understood and is mediated by spirochete surface adhesins. We show here that infection-induced activation of the endothelium in BALB/c mice results in new B. burgdorferi-endothelial interactions, indicating the presence of spirochete factors that interact specifically with activated endothelial cells. We show that these interactions are mediated by spirochetal surface proteins whose synthesis is dependent upon B. burgdorferi host adaptation. We used intravital microscopy and a functional gain approach to assess the binding of spirochetes that withstand the shear force of blood flow in post-capillary venules of living mice. We identified five previously undescribed, shear force-resistant adhesins that selectively mediate binding to activated endothelium (BBA66, P66, BBA36, BBA07 and DbpA) and interact with activation-induced endothelial surface changes. Two of these adhesins (P66 and DbpA) have been implicated in the spirochete extravasation process. We also identified seven previously undescribed shear force-resistant adhesins that target pre-activated endothelium (BBA04, BBK53, BBK07, BBA65, BB0844, ErpK and OspC). Three of these (BBK53, ErpK and OspC), display reduced binding to activated endothelium, a property that may facilitate the multi-step pathway of vascular transmigration. In particular, OspC has been previously implicated in spirochete extravasation. In summary, our results reveal a dynamic interaction network between the spirochete and the endothelium where the spirochete capitalizes on activation of the endothelium to establish new interactions and at the same time disrupt others. We propose that this scenario is part of a sequential interaction network leading to transendothelial migration of the spirochetes and subsequent tissue invasion. This work opens a new area of study focusing on eleven new adhesins described here and their vascular interactions and role in spirochete extravasation.

microbiology↗

bioRxiv2024

Transendothelial migration of the Lyme disease spirochete involves spirochete internalization as an intermediate step through a transcellular pathway that involves Cdc42 and Rac1

Despite its importance in pathogenesis, the hematogenous dissemination pathway of B. burgdorferi is still largely uncharacterized. To probe the molecular details of transendothelial migration more easily, we studied this process using cultured primary or telomerase-immortalized human microvascular endothelial cells in a medium that maintains both the human cells and the spirochetes. In B. burgdorferi infected monolayers we observed [~]55% of wild-type spirochetes crossing the monolayer. Microscopic characterization revealed entrance points across the cellular surface rather than at cellular junctions, supporting a transcellular route. In support of this pathway, locking the endothelial junctions using a VE-PTP inhibitor did not reduce transendothelial migration. We also used inhibitors to block the most common endocytic pathways to elucidate effectors that might be involved in B. burgdorferi uptake and/or transmigration. Directly inhibiting Cdc42 reduced spirochete transmigration by impeding internalization. However, blocking Rac1 alone dramatically reduced transmigration and resulted in a concomitant increase in spirochete accumulation in the cell. Our combined results support that B. burgdorferi internalization is an intermediate step in the transendothelial migration process which requires both Cdc42 and Rac1; Cdc42 is needed for spirochete internalization while Rac1 is required for cellular egress. These are the first two host proteins implicated in B. burgdorferi transmigration across endothelial cells. IMPORTANCELyme borreliosis is caused by Borrelia burgdorferi and related bacteria. It is the most common tick-transmitted illness in the Northern Hemisphere. The ability of this pathogen to spread to a wide variety of locations results in a diverse set of clinical manisfestations, yet little is known regarding vascular escape of the spirochete, an important pathway for dissemination. Our current work has studied the traversal of B. burgdorferi across a monolayer of microvascular endothelial cells grown in culture. We show that this occurs by passage of the spirochetes directly through these cells rather than at cellular junctions and that internalization of B. burgdorferi is an intermediate step in the transmigration process. We also identify the first two host proteins, Cdc42 and Rac1, that are used by the spirochetes to promote traversal of the cellular monolayer. Our new experimental system also provides a new avenue for further studies of this important process.

microbiology↗

bioRxiv2023

Metabolic Interactive Nodular Network for Omics (MINNO): Refining and investigating metabolic networks based on empirical metabolomics data

Metabolomics is a powerful tool for uncovering biochemical diversity in a wide range of organisms, and metabolic network modeling is commonly used to frame results in the context of a broader homeostatic system. However, network modeling of poorly characterized, non-model organisms remains challenging due to gene homology mismatches. To address this challenge, we developed Metabolic Interactive Nodular Network for Omics (MINNO), a web-based mapping tool that takes in empirical metabolomics data to refine metabolic networks for both model and unusual organisms. MINNO allows users to create and modify interactive metabolic pathway visualizations for thousands of organisms, in both individual and multi-species contexts. Herein, we demonstrate an important application of MINNO in elucidating the metabolic networks of understudied species, such as those of the Borrelia genus, which cause Lyme disease and relapsing fever. Using a hybrid genomics-metabolomics modeling approach, we constructed species-specific metabolic networks for three Borrelia species. Using these empirically refined networks, we were able to metabolically differentiate these genetically similar species via their nucleotide and nicotinate metabolic pathways that cannot be predicted from genomic networks. These examples illustrate the use of metabolomics for the empirical refining of genetically constructed networks and show how MINNO can be used to study non-model organisms. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/548964v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@8cdee6org.highwire.dtl.DTLVardef@7de3ddorg.highwire.dtl.DTLVardef@fac57forg.highwire.dtl.DTLVardef@1bc2efe_HPS_FORMAT_FIGEXP M_FIG MINNO tool facilitates refining of metabolic networks, multi omics integration and investigation of cross-species interactions. C_FIG

bioinformatics↗