Biology subjects

Ellis, C. C.

Publications and source records attributed to Ellis, C. C..

5 recordsLinked to original sources

bioRxiv2025

Molecular Mechanisms of Priming Innate Immunity by Small Extracellular Vesicles Released during Infection with Gram-negative Bacteria

Much still remains to understand about the underlying molecular mechanisms by which the trafficking of small extracellular vesicles (sEVs) modulates innate immune responses during infection with pathogenic Gram-negative bacteria. To address this significant gap in knowledge, we used two infection models to investigate innate immune regulation by the sEVs released from cells infected with either Yersinia pestis (Yp) or Burkholderia thailandensis (Bt), designated as EXi-Yp and EXi-Bt respectively. The EXi induced differentiation of naive human monocytes to macrophages and triggered robust pro-inflammatory cytokine release, including release of IL-6, mirroring direct bacterial infection effects. Comprehensive cell signaling analyses revealed that the EXi modulate a small set of host signaling proteins, with p38 activation being primarily responsible for the observed protective effects. EXi-induced p38 activation leads to increased IL-6 release, which in turn is responsible for decreased bacterial survival within recipient immune cells that are subsequently infected. Consistent with the in vitro results, mice administered with EXi-Yp exhibited elevated serum IL-6 levels and were protected from Yp infection. Furthermore, using our microfluidic chip platform that allows functional interrogation of EV effects under physiologically relevant conditions, we have demonstrated that EXi exchange between Yp-infected cells and naive recipient monocytes leads to differentiation of the recipient cells to macrophages. Together, our findings reveal a largely unexplored aspect of innate immunity and provide a mechanistic model in which EXi prime local and distant naive monocytes via p38-induced differentiation and IL-6 production to protect against infection with Gram-negative bacteria.

immunology↗

bioRxiv2023

Mutation of gabra1 is associated with hypermotility and abnormal expression of proteins critical for ion homeostasis and synaptic vesicle transport.

Mutation of the GABRA1 gene is associated with neurodevelopmental defects and epilepsy. GABRA1 encodes for the 1 subunit of the gamma-aminobutyric acid type A receptor (GABAAR), which regulates the fast inhibitory impulses of the nervous system. Multiple model systems have previously been developed to understand the function of GABRA1 during development, but these models have produced complex and at times incongruent data. Thus, additional model systems are required to validate and substantiate previously published results. We investigated the behavioral swim patterns associated with a nonsense mutation of the zebrafish gabra1 (sa43718 allele) gene. The sa43718 allele causes a decrease in gabra1 mRNA expression, which is associated with light induced hypermotility, one phenotype associated with seizure like behavior in zebrafish. Mutation of gabra1 was accompanied by decreased mRNA expression of gabra2, gabra3, and gabra5, indicating a reduction in the expression of additional alpha sub-units of the GABAAR. Although multiple sub-units were decreased in total expression, larvae continued to respond to pentylenetetrazole (PTZ) indicating that a residual GABAAR exists in the sa43718 allele. Proteomics analysis demonstrated that nonsense mutation of gabra1 is associated with abnormal expression of proteins that regulate proton transport, ion homeostasis, vesicle transport, and mitochondrial protein complexes. These data support previous studies performed in a zebrafish nonsense allele created by CRISPR/Cas9 and validate that loss of function mutations in the gabra1 gene result in seizure like phenotypes with abnormal function of inhibitory synapses.

developmental biology↗

bioRxiv2022

Fatty acid elongases 1-3 have distinct roles in mitochondrial function, growth and lipid homeostasis in Trypanosoma cruzi.

Trypanosomatids are a diverse group of uniflagellate protozoa that include globally important pathogens such as Trypanosoma cruzi, the causative agent of Chagas disease. Trypanosomes lack the fatty acid synthase (FAS)-I system typically used for de novo synthesis of long chain fatty acids (LCFA) in other eukaryotes. Instead, these microbes have evolved a modular fatty acid elongase (ELO) system comprised of individual ELO enzymes that operate processively. The role of the ELO system in maintaining lipid homeostasis in trypanosomes has not been determined. Here we demonstrate that ELO2 and ELO3 are required for global lipidome maintenance in the insect stage of T. cruzi whereas ELO1 is dispensable for this function. Instead, ELO1 activity is needed to sustain mitochondrial activity and normal growth. The cross-talk between microsomal ELO1 and the mitochondrion is a novel finding that merits examination of the trypanosomatid ELO pathway as critical for central metabolism.

microbiology↗

bioRxiv2022

Differential Regulation of mTor signaling defines subtypes of cblX syndrome

Mutations in the HCFC1 transcriptional co-factor protein are the cause of cblX syndrome and X-linked intellectual disability (XLID). cblX is the more severe disorder associated with intractable epilepsy, abnormal cobalamin metabolism, facial dysmorphia, cortical gyral malformations, and intellectual disability. In vitro, Hcfc1 regulates neural precursor (NPCs) proliferation and number, which has been validated in zebrafish. However, conditional deletion of Hcfc1 in Nkx2.1+ NPCs increased cell death, reduced Gfap expression, and reduced numbers of GABAergic neurons. Thus, the role of HCFC1 in brain development is not completely understood. Recently, knock-in of both a cblX (HCFC1) and cblX-like (THAP11) allele were created in mice. Knock-in of the cblX-like allele was associated with increased expression of proteins required for ribosome biogenesis. However, the brain phenotypes were not comprehensively studied due to sub-viability and therefore, a mechanism underlying increased ribosome biogenesis was not described. We used a missense, a nonsense, and two conditional zebrafish alleles to further elucidate this mechanism during brain development. We observed contrasting phenotypes at the level of Akt/mTor activation, the number of radial glial cells, and the expression of two downstream target genes of HCFC1, asxl1 and ywhab. Despite these divergent phenotypes, each allele studied demonstrates with a high degree of face validity when compared to the phenotypes reported in the literature. Collectively, these data suggest that individual mutations in the HCFC1 protein result in differential mTor activity which is associated with contrasting cellular phenotypes.

developmental biology↗

bioRxiv2021

Extracellular vesicles regulate yeast growth, biofilm formation, and yeast-to-hypha differentiation in Candida albicans

The ability to undergo morphological changes during adaptation to distinct environments is exploited by Candida albicans and has a direct impact on virulence. In this study, we investigated the influence of fungal extracellular vesicles (EVs) during yeast growth, biofilm formation, and morphogenesis in C. albicans. Addition of C. albicans EVs (Ca EVs) to the culture medium positively affected yeast growth. Using crystal violet staining and scanning electron microscopy (SEM), we demonstrated that Ca EVs inhibited biofilm formation by C. albicans in vitro. By time-lapse microscopy and SEM, we showed that Ca EV-treatment stops filamentation promoting pseudohyphae formation with multiple sites for yeast budding. The ability of Ca EVs to regulate dimorphism was further compared to EVs isolated from different C. albicans strains, Saccharomyces cerevisiae, and Histoplasma capsulatum. Ca EVs from distinct strains robustly inhibited yeast-to-hyphae differentiation with morphological changes occurring in less than 4 hours. A minor inhibitory effect was promoted by EVs from S. cerevisiae and H. capsulatum only after 24 hours of incubation. The inhibitory effect of Ca EVs was promoted by a combination of lipid compounds identified by gas chromatography-tandem mass spectrometry analysis as sesquiterpenes, diterpenes, and fatty acids. Remarkably, Ca EVs were also able to reverse filamentation, transforming hyphal growth to yeast forms. Transcriptomic analysis demonstrated that treatment with Ca EVs modified the expression of more than 300 genes. The most effectively upregulated pathways were related to DNA metabolism. The downregulated genes were mostly associated with extracellular and adhesion proteins. Finally, yeast cells treated with Ca EVs for 24 hours lost their agar invasive ability and were avirulent when inoculated in Galleria mellonella larvae. In summary, our results indicate that fungal EVs can profoundly modify C. albicans growth and regulate yeast-to-hypha differentiation inhibiting biofilm formation and virulence.

microbiology↗