How inflammatory macrophages instruct innate effector responses in the tumour microenvironment?

Macrophages instruct the functions of other innate cells to coordinate the type and timing of inflammatory responses. We recently identified CALHM6 as a TLR- and interferon-inducible membrane protein on macrophages, important for macrophage-mediated instruction of early innate responses to infections. Proteins of the CALHM family have only been characterised in the neuronal system, where they act as ATP-permeable ion channels. They promote cell-cell crosstalk at neuronal synapses by releasing a small molecule ATP, which acts as a neurotransmitter. CALHM6 is the only CALHM family member highly expressed in immune cells. It has been linked to the induction of natural killer (NK) cell anti-tumour activity. The mechanism of action and broader functions of CALHM6 in the immune system were unclear. We generated CALHM6-deficient mice and found that CALHM6 controlled infection-induced innate cell cross-talk at the immunological synapse, and was required for the early control of Listeria monocytogenes infection in vivo. CALHM6 expression was highest on activated macrophages in the presence of pathogen-derived signals or interferons. CALHM6 expression was transient and transcriptionally terminated by anti-inflammatory cytokines. Mechanistically, our patch clamp studies in Xenopus oocytes revealed that CALHM6 can form a membrane ion channel, in which a conserved acidic residue E119 controlled channel opening. When overexpressed in Xenopus oocytes, CALHM6 was constitutively open and toxic to cells. In mammalian cells, however, CALHM6 localized to the inside of the cell and, hence, no channel activity or toxicity was detected or reported. We found that only upon macrophage activation did CALHM6 rapidly re-localise from the intracellular compartment to the immune synapse, where it controlled the early kinetics of natural killer cell activation and innate defences from infection. Following this early work, the lab of the co-supervisor (Gerard) used scRNASeq and imaging to analyse the microenvironment of solid tumours and found an enriched signature of CALHM6-positive pro-inflammatory macrophage subset in tumours that also showed a strong pro-inflammatory and NK cell activation signature. What functional programmes CALHM6 regulate in tumour-associated NK cells and, and how mechanistically it may facilitate macrophage-mediated control of solid tumours will be explored in this project. 

KEYWORDS

Macrophages, Natural killer cells, Cell-cell communications, Tumours, CALHM6

TRAINING OPPORTUNITIES

Imaging, biochemistry, scRNASeq, spatial analysis of cell-cell interactions, tumour models 

KEY PUBLICATIONS

The ion channel CALHM6 controls bacterial infection‐induced cellular cross‐talk at the immunological synapse

Authors: Sara Danielli, Zhongming Ma, Eirini Pantazi, Amrendra Kumar, Benjamin Demarco, Fabian A Fischer, Usha Paudel, Jillian Weissenrieder, Robert J Lee, Sebastian Joyce, J Kevin Foskett, Jelena S Bezbradica, 2023, EMBO

IFNgamma-dependent remodelling of the myeloid landscape underlies control of IFNgamma-insensitive tumours

Vivian WC Lau, Gracie Mead, Julie M Mazet, Anagha Krishnan, Edward W Roberts, Gennaro Prota, Uzi Gileadi, Vincenzo Cerundolo, Audrey Gerard, 2024, bioRxiv

Integration of cytokine and heterologous receptor signaling pathways

Jelena S Bezbradica, R Medzhitov, 2009, Nature Immunology

THEMES

Inflammation, innate immunity, cell dynamics

CONTACT INFORMATION OF ALL SUPERVISORS

Jelena Bezbradica Mirkovic jelena.bezbradica@kennedy.ox.ac.uk

Audrey Gerard audrey.gerard@kennedy.ox.ac.uk

The Kennedy Institute is a proud supporter of the Academic Futures scholarship programme, designed to address under-representation and help improve equality, diversity and inclusion in our graduate student body.  The Kennedy and the wider University rely on bringing the very best minds from across the world together, whatever their race, gender, religion or background to create new ideas, insights and innovations to change the world for the better. Up to 50 full awards are available across the three programme streams, and you can find further information on each stream on their individual tabs (Academic futures | Graduate access | University of Oxford).

How to Apply

Please contact the relevant supervisor(s), to register your interest in the project, and the departmental Education Team (graduate.studies@ndorms.ox.ac.uk), who will be able to advise you of the essential requirements for the programme and provide further information on how to make an official application.

Interested applicants should have, or expect to obtain, a first or upper second-class BSc degree or equivalent in a relevant subject and will also need to provide evidence of English language competence (where applicable). The application guide and form is found online and the DPhil or MSc by research will commence in October 2025.

Applications should be made to the following programme using the specified course code.

D.Phil in Molecular and Cellular Medicine (course code: RD_MP1)

For further information, please visit http://www.ox.ac.uk/admissions/graduate/applying-to-oxford.

Interviews to be held week commencing 13th January 2025.