multi-modal-spatial-metabolomics-with-mid-infrared-microscope-guided

Multi-Modal Spatial Metabolomics with Mid-Infrared Microscope Guided Mass Spectrometry Imaging

Spatial metabolomics is a rapidly evolving field to map the distribution of metabolites within tissues, organs, and even single cells. This approach ...

Fudan University

Additional sex combs-like 1 (ASXL1) interacts with BRCA1-associated protein 1 (BAP1) deubiquitinase to oppose the polycomb repressive complex 1 (PRC1)-mediated histone H2A ubiquitylation. Germline BAP1 mutations are found in a spectrum of human malignancies, while ASXL1 mutations recurrently occur in myeloid neoplasm and are associated with poor prognosis. Nearly all ASXL1 mutations are heterozygous frameshift or nonsense mutations in the middle or to a less extent the C-terminal region, resulting in the production of C-terminally truncated mutant ASXL1 proteins. How ASXL1 regulates specific target genes and how the C-terminal truncation of ASXL1 promotes leukemogenesis are unclear. Here, we report that ASXL1 interacts with forkhead transcription factors FOXK1 and FOXK2 to regulate a subset of FOXK1/K2 target genes. We show that the C-terminally truncated mutant ASXL1 proteins are expressed at much higher levels than the wild-type protein in ASXL1 heterozygous leukemia cells, and lose the ability to interact with FOXK1/K2. Specific deletion of the mutant allele eliminates the expression of C-terminally truncated ASXL1 and increases the association of wild-type ASXL1 with BAP1, thereby restoring the expression of BAP1-ASXL1-FOXK1/K2 target genes, particularly those involved in glucose metabolism, oxygen sensing, and JAK-STAT3 signaling pathways. In addition to FOXK1/K2, we also identify other DNA-binding transcription regulators including transcription factors (TFs) which interact with wild-type ASXL1, but not C-terminally truncated mutant. Our results suggest that ASXL1 mutations result in neomorphic alleles that contribute to leukemogenesis at least in part through dominantly inhibiting the wild-type ASXL1 from interacting with BAP1 and thereby impairing the function of ASXL1-BAP1-TF in regulating target genes and leukemia cell growth.

Tumor-derived neomorphic mutations in ASXL1 impairs the BAP1-ASXL1-FOXK1/K2 transcription network.

Pathogens and inflammatory conditions rapidly induce the expression of immune-responsive gene 1 (IRG1) in cells of myeloid lineage. IRG1 encodes an aconitate decarboxylase (ACOD1) that produces the immunomodulatory metabolite itaconate (ITA). In addition to rapid intracellular accumulation, ITA is also secreted from the cell, but whether secreted ITA functions as a signaling molecule is unclear. Here, we identified ITA as an orthosteric agonist of the GPCR OXGR1, with an EC50 of approximately 0.3 mM, which was in the same range as the physiological concentration of extracellular ITA upon macrophage activation. ITA activated OXGR1 to induce Ca2+ mobilization, ERK phosphorylation, and endocytosis of the receptor. In a mouse model of pulmonary infection with bacterial Pseudomonas aeruginosa, ITA stimulated Oxgr1-dependent mucus secretion and transport in respiratory epithelium, the primary innate defense mechanism of the airway. Our study thus identifies ITA as a bona fide ligand for OXGR1 and the ITA/OXGR1 paracrine signaling pathway during the pulmonary innate immune response.

The immunometabolite itaconate stimulates OXGR1 to promote mucociliary clearance during the pulmonary innate immune response.

Itaconate is one of the most studied immunometabolites produced by myeloid cells during inflammatory response. It mediates a wide range of anti-inflammatory and immunoregulatory effects and plays a role in a number of pathological states, including autoimmunity and cancer. Itaconate and its derivatives are considered potential therapeutic agents for the treatment of inflammatory diseases. While immunoregulatory effects of itaconate have been extensively studied in vitro and using knockout mouse models, less is known about how therapeutic administration of this metabolite regulates inflammatory response in vivo. Here, we investigate the immunoregulatory properties of exogenous administration of itaconate and its derivative dimethyl itaconate in a mouse model of lipopolysaccharide-induced inflammation. The data show that administration of itaconate or dimethyl itaconate controls systemic production of multiple cytokines, including increased IL-10 production. However, only dimethyl itaconate was able to suppress systemic production of IFNγ and IL-1β. In contrast to in vitro data, administration of itaconate or dimethyl itaconate in vivo resulted in systemic upregulation of IL-6 in the blood. Electrophilic stress due to itaconate or dimethyl itaconate was not responsible for IL-6 upregulation. However, inhibition of succinate dehydrogenase with dimethyl malonate also resulted in elevated systemic levels of IL-6 and IL-10. Taken together, our study reports a novel effect of exogenous itaconate and its derivative dimethyl itaconate on the production of IL-6 in vivo, with important implications for the development of itaconate-based anti-inflammatory therapies.

Article	Year
Tumor-derived neomorphic mutations in ASXL1 impairs the BAP1-ASXL1-FOXK1/K2 transcription network. Protein & cell\| PubMed ID: 32683582	2021
The immunometabolite itaconate stimulates OXGR1 to promote mucociliary clearance during the pulmonary innate immune response. The Journal of clinical investigation\| PubMed ID: 36919698	2023
Itaconate and dimethyl itaconate upregulate IL-6 production in the LPS-induced inflammation in mice. Journal of leukocyte biology\| PubMed ID: 38941443	2024

Yirong Zeng

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