Biology subjects

Timms, P.

Publications and source records attributed to Timms, P..

3 recordsLinked to original sources

bioRxiv2025

Control of antigen presentation on MHC-I by a bacterial secretion system

Mycobacterium tuberculosis (Mtb) remains one of the worlds leading infectious killers. Although CD8{square} T cells contribute to immune control of tuberculosis, the pathways through which bacterial antigens access major histocompatibility complex class I (MHC-I) antigen presentation remain incompletely defined. Here, we show that the activity of an Mtb secretion system actively promotes antigen presentation on MHC-I. Using quantitative immunopeptidomics, host and bacterial genetic perturbations, and T cell activation assays, we demonstrate that presentation of Mtb-derived peptides on MHC-I requires the ESX-1 type VII secretion system. Presentation of these peptides proceeds in a manner dependent on the transporter associated with antigen processing (TAP) but independent of host cell mechanisms such as autophagy or MPEG1-mediated pore formation. Chemical induction of phagosomal membrane damage fails to restore antigen presentation in the absence of ESX-1 activity, suggesting that pathogen-encoded secretion, not nonspecific membrane rupture, governs access to MHC-I antigen processing pathways. These findings reveal a secretion system-driven mechanism of antigen presentation, redefining how mycobacteria interface with host MHC-I pathways, potentially informing tuberculosis vaccine design strategies, and highlighting a potential route for synthetic antigen delivery to the cytosol in therapeutics and vaccination. One-sentence summaryPresentation of Mycobacterium tuberculosis antigens on MHC class I through a cytosolic pathway depends on a bacterial secretion system rather than host response and cross-presentation pathways.

immunology↗

bioRxiv2022

Aspirin reprogrammes colorectal cancer cell metabolism and sensitises to glutaminase inhibition

To support proliferation and survival within a challenging microenvironment, cancer cells must reprogramme their metabolism. As such, targeting cancer cell metabolism is a promising therapeutic avenue. However, identifying tractable nodes of metabolic vulnerability in cancer cells is challenging due to their metabolic plasticity. Identification of effective treatment combinations to counter this is an active area of research. Aspirin has a well-established role in cancer prevention, particularly in colorectal cancer (CRC), although the mechanisms are not fully understood. Here, we comprehensively characterise the metabolic impact of long-term aspirin exposure (2-4mM for 52 weeks) on CRC cells. We show that aspirin regulates several enzymes and transporters of central carbon metabolism and results in a reduction in glutaminolysis and a concomitant increase in glucose metabolism, demonstrating reprogramming of nutrient utilisation. We show that aspirin causes likely compensatory changes that renders the cells sensitive to the glutaminase 1 (GLS1) inhibitor - CB-839. Of note given the clinical interest, treatment with CB-839 alone had little effect on CRC cell growth or survival. However, in combination with aspirin, CB-839 inhibited CRC cell proliferation and induced apoptosis in vitro, and importantly, reduced crypt proliferation in Apcfl/fl mice in vivo. Together, these results show that aspirin leads to significant metabolic reprogramming in colorectal cancer cells and raises the possibility that aspirin could significantly increase the efficacy of metabolic cancer therapies in CRC.

cancer biology↗

bioRxiv2021

Loss of BCL-3 sensitises colorectal cancer cells to DNA damage, revealing a role for BCL-3 in double strand break repair by homologous recombination

ObjectiveThe proto-oncogene BCL-3 is upregulated in a subset of colorectal cancers (CRC) and increased expression of the gene correlates with poor patient prognosis. The aim is to investigate whether inhibiting BCL-3 can increase the response to DNA damage in CRC. DesignThe function of BCL-3 in DNA damage response was studied in vitro using siRNA and CRISPR-Cas9 genome editing and in vivo using Bcl3-/- mice. DNA damage induced by {gamma}-irradiation and/or cisplatin was quantified using H2AX and RAD51 foci, repair pathways investigated using HR/NHEJ assays and treatment with the PARP inhibitor olaparib. ResultSuppression of BCL-3 increases double strand break number and decreases homologous recombination in CRC cells, supported by reduced RAD51 foci number and increased sensitivity to PARP inhibition. Importantly, a similar phenotype is seen in Bcl3-/- mice, where the intestinal crypts of these mice exhibit sensitivity to DNA damage and a greater number of double strand breaks compared to wild type mice. Furthermore Apc.Krasmutant x Bcl3-/- mice exhibit increased DNA damage and reduced RAD51+ cells compared to their wild type counterparts when treated with cisplatin. ConclusionThis work identifies BCL-3 as a regulator of the cellular response to DNA damage and suggests that elevated BCL-3 expression could increase resistance of tumour cells to DNA damaging agents including radiotherapy. These findings offer a rationale for targeting BCL-3 in CRC as an adjuvant to conventional therapies and suggest that BCL-3 expression in tumours could be a useful biomarker in stratification of rectal cancer patients for neo-adjuvant chemoradiotherapy.

cancer biology↗