Biology subjects

Lapointe, R.

Publications and source records attributed to Lapointe, R..

4 recordsLinked to original sources

bioRxiv2026

Peptidoglycan remodeling prevents antibiotic resistance during oxidative stress

ABSTRACT: The bacterial small RNA (sRNA) OxyS is expressed in Escherichia coli during oxidative stress. The sRNA OxyS enhances cell survival by controlling genes involved in the regulation of hydrogen peroxide (H2O2) and iron-sulfur (Fe-S) cluster formation. Here, we used the MS2 affinity purification coupled with RNA sequencing (MAPS) technique to identify new target mRNAs of the sRNA OxyS. Our analysis revealed a significant enrichment of mepS mRNA, which encodes a peptidoglycan endopeptidase that promotes cell growth. Our results confirm a previous report on the sRNA OxyS repressing the translation of mepS. We also found that an {Delta}oxyS background facilitates the emergence of mutations, conferring increased resistance to the last-resort antibiotics polymyxin B and E (colistin), but only in the presence of the target mepS gene. This suggests that the translation repression of mepS by OxyS could prevent mutations in bacterial DNA during H2O2-induced oxidative stress. Moreover, we show that adding the antioxidant thiourea or sequestering iron in the {Delta}oxyS background effectively reduces the emergence of resistance against both polymyxin B and colistin. These results suggest that reactive oxygen species (ROS), in conjunction with intracellular iron, play a key role in driving the emergence of antibiotic resistance. Overall, our work underlines a mechanism of antimicrobial emergence implicating oxidative stress, intracellular Fe, and cell wall remodeling in E. coli. IMPORTANCE: This study uncovers an underexplored link between peptidoglycan remodeling and oxidative stress responses during exposure to antibiotics. By elucidating how MepS and the sRNA OxyS interact in the presence of polymyxins and oxidative stress, our study suggests that MepS may exert an anti-mutator function. The repression of mepS translation by OxyS seems to limit the emergence of antibiotic resistance driven by DNA mutations. Together, these findings suggest cell wall remodeling and oxidative stress response pathways as promising targets to enhance antibiotic efficacy and limit the emergence of resistance.

microbiology↗

bioRxiv2024

Optically Mapped Black Genomes: Distinct Structures and 22q11.2 Deletion Syndrome Mechanisms

The genomic architecture of 22q11.2 Deletion Syndrome (22q11.2DS) has focused on analysis of white genomes. However, Black individuals appear to have a lower prevalence of 22q11.2DS compared to whites. To improve the understanding of different populations in relation to 22q11.2DS, optical mapping data from 106 genomes across various Black and white genomes were used to determine the organization of 22q11.2 genomic structures. This revealed extensive variability between the groups regarding copy number and orientation changes of the elements comprising the 22q11.2 low copy repeats (LCR22s). Several novel CNVs and whole haplotype configurations, private and of different prevalence to each group were detected. The diversity of CNVs within Black genomes compared to white genomes was especially striking. To determine the impact of this variability, Black families with de novo 22q11.2DS probands were compared to white families. The highly variable configurations of Black and white haplotypes led to several unique non-allelic homologous recombination (NAHR) scenarios with recombinations at different loci. In particular, Black families had unique recombinations yet to be observed. Thus, the unique and highly variable haplotype configurations of LCR22s in Black individuals may play a role in their decreased incidence of 22q11.2DS.

genomics↗

bioRxiv2023

Predicting developmental relationships of tumor resident and circulating T cells in ovarian cancer

Characterizing T cell populations and understanding their developmental relationships may help design more effective cancer immunotherapies. We coupled single-cell transcriptomics and T cell receptor (TCR) {beta} profiling of intratumoral and peripheral T cells in ovarian cancer patients to identify transcriptional programs and infer their relationship by trajectory and TCR overlap analyses. We proposed a model of differentiation pathway from an intermediate GZMH-expressing CD8 T cell subset found in the blood and tumor that progressively reinforces the exhaustion and tissue residency programs from a CCL4-expressing cluster towards XCL1- and CXCL13-expressing terminally exhausted cells. Inferred cell communication analysis suggests that interaction with CXCL13-expressing CD4 T cells, which we refer to as Tfh-like cells, sustains the effector function of this intermediate GZMH-expressing CD8 T cell subset. Moreover, our results suggest that Tfh-like cells attract cells expressing GPR183 through the production of its ligand 7,25 dihydroxycholesterol (7,25-HC). Finally, we demonstrated that GPR183 is highly expressed in a subset of pre-effector GZMK-expressing CD8 T cells and plasmacytoid dendritic cells. Collectively, our results suggest that Tfh-like cells expressing IL-21 help promote antitumor immunity against ovarian tumors by coordinating the action of immune cells responsive to 7,25-HC.

immunology↗

bioRxiv2020

The pleiotropic effects of the MNK1/2-eIF4E axis support immune suppression and metastasis in a model of postpartum breast cancer.

PurposeBreast cancer diagnosed within 10 years following childbirth is defined as postpartum breast cancer (PPBC) and is highly metastatic. Interactions between immune cells and other stromal cells within the involuting mammary gland are fundamental in facilitating an aggressive tumor phenotype. The MNK1/2-eIF4E axis promotes the translation of pro-metastatic mRNAs in tumor cells, but its role in modulating the function of non-tumor cells in the PPBC microenvironment, and in particular its activity in human PPBC, has not been explored. Experimental designWe used a combination of in vivo PPBC models and in vitro assays to study the effects of phospho-eIF4E deficiency on the pro-tumor function of select cells of the TME. Furthermore, we employed Imaging Mass Cytometry on PPBC and non-PPBC patient samples, to chart the expression of the MNK1/2-eIF4E axis components in the TME. ResultsHere, we show that phospho-eIF4E deficient (eIF4ES209A) PPBC mice are protected against lung metastasis and reveal differences in the lung immune microenvironment of the WT and eIF4ES209A mice. Moreover, we show that the expression of fibroblast-derived IL-33, an alarmin known to induce invasion, was repressed upon MNK1/2-eIF4E axis inhibition. Imaging Mass Cytometry results indicated that human PPBC contain phospho-eIF4E high-expressing tumor cells and CD8+ T cells displaying an activated dysfunctional phenotype. Finally, we block lung metastasis in PPBC mice, using combined MNK1/2 inhibition and anti-PD-1 therapy. ConclusionsThese findings implicate the involvement of the MNK1/2-eIF4E axis during PPBC metastasis and suggest a promising immunomodulatory route to enhance the efficacy of immunotherapy by blocking phospho-eIF4E. Translational relevancePostpartum breast cancer (PPBC) is highly aggressive. It is hypothesized that involution-induced changes in the postpartum breast microenvironment, which include an influx of inflammatory immune cells and activation of resident fibroblasts, facilitate the invasiveness of an existing neoplasm. We used imaging mass cytometry to do an in-depth profiling of the MNK1-eIF4E axis in the TME of a unique cohort of PPBC and non-PPBC patients. We observed patterns of phospho-eIF4E in non-tumor cells that were specific to the TME of PPBC. We also noted that the CD8+ T cells present in PPBC express an activated dysfunctional phenotype characterized by the co-expression of HLA-DR and PD-1. This study represents a first look at the expression of the MNK1-eIF4E axis in the stromal cells of metastatic breast cancer and has therapeutic implications as we show, in an animal model of PPBC, that MNK1/2 inhibition can be used to sensitize tumors to anti-PD1 immunotherapy.

cancer biology↗