Defective N-glycosylation in tumor-infiltrating CD8+ T cells impairs IFN-γ-mediated effector function.

T cell-mediated antitumor immunity is modulated, in part, by N-glycosylation. However, the interplay between N-glycosylation and the loss of effector function in exhausted T cells has not yet been fully investigated. Here, we delineated the impact of N-glycosylation on the exhaustion of tumor-infiltrating lymphocytes in a murine colon adenocarcinoma model, focusing on the IFN-γ-mediated immune response. We found that exhausted CD8+ T cells downregulated the oligosaccharyltransferase complex, which is indispensable for N-glycan transfer. Concordant N-glycosylation deficiency in tumor-infiltrating lymphocytes leads to loss of antitumor immunity. Complementing the oligosaccharyltransferase complex restored IFN-γ production and alleviated CD8+ T cell exhaustion, resulting in reduced tumor growth. Thus, aberrant glycosylation induced in the tumor microenvironment incapacitates effector CD8+ T cells. Our findings provide insights into CD8+ T cell exhaustion by incorporating N-glycosylation to understand the characteristic loss of IFN-γ, opening new opportunities to amend the glycosylation status in cancer immunotherapies.

Differentiation and homeostasis of effector Treg cells are regulated by inositol polyphosphates modulating Ca2+ influx.

Activated Foxp3+ regulatory T (Treg) cells differentiate into effector Treg (eTreg) cells to maintain peripheral immune homeostasis and tolerance. T cell receptor (TCR)-mediated induction and regulation of store-operated Ca2+ entry (SOCE) is essential for eTreg cell differentiation and function. However, SOCE regulation in Treg cells remains unclear. Here, we show that inositol polyphosphate multikinase (IPMK), which generates inositol tetrakisphosphate and inositol pentakisphosphate, is a pivotal regulator of Treg cell differentiation downstream of TCR signaling. IPMK is highly expressed in TCR-stimulated Treg cells and promotes a TCR-induced Treg cell program. IPMK-deficient Treg cells display aberrant T cell activation and impaired differentiation into RORγt+ Treg cells and tissue-resident Treg cells. Mechanistically, IPMK controls the generation of higher-order inositol phosphates, thereby promoting Ca2+ mobilization and Treg cell effector functions. Our findings identify IPMK as a critical regulator of TCR-mediated Ca2+ influx and highlight the importance of IPMK in Treg cell-mediated immune homeostasis.

Bap1/SMN axis in Dpp4+ skeletal muscle mesenchymal cells regulates the neuromuscular system.

The survival of motor neuron (SMN) protein is a major component of the pre-mRNA splicing machinery and is required for RNA metabolism. Although SMN has been considered a fundamental gene for the central nervous system, due to its relationship with neuromuscular diseases, such as spinal muscular atrophy, recent studies have also revealed the requirement of SMN in non-neuronal cells in the peripheral regions. Here, we report that the fibro-adipogenic progenitor subpopulation expressing Dpp4 (Dpp4+ FAPs) is required for the neuromuscular system. Furthermore, we also reveal that BRCA1-associated protein-1 (Bap1) is crucial for the stabilization of SMN in FAPs by preventing its ubiquitination-dependent degradation. Inactivation of Bap1 in FAPs decreased SMN levels and accompanied degeneration of the neuromuscular junction, leading to loss of motor neurons and muscle atrophy. Overexpression of the ubiquitination-resistant SMN variant, SMNK186R, in Bap1-null FAPs completely prevented neuromuscular degeneration. In addition, transplantation of Dpp4+ FAPs, but not Dpp4- FAPs, completely rescued neuromuscular defects. Our data reveal the crucial role of Bap1-mediated SMN stabilization in Dpp4+ FAPs for the neuromuscular system and provide the possibility of cell-based therapeutics to treat neuromuscular diseases.

BAP1 shapes the bone marrow niche for lymphopoiesis by fine-tuning epigenetic profiles in endosteal mesenchymal stromal cells.

Hematopoiesis occurs within a unique bone marrow (BM) microenvironment, which consists of various niche cells, cytokines, growth factors, and extracellular matrix components. These multiple components directly or indirectly regulate the maintenance and differentiation of hematopoietic stem cells (HSCs). Here we report that BAP1 in BM mesenchymal stromal cells (MSCs) is critical for the maintenance of HSCs and B lymphopoiesis. Mice lacking BAP1 in MSCs show aberrant differentiation of hematopoietic stem and progenitor cells, impaired B lymphoid differentiation, and expansion of myeloid lineages. Mechanistically, BAP1 loss in distinct endosteal MSCs, expressing PRX1 but not LEPR, leads to aberrant expression of genes affiliated with BM niche functions. BAP1 deficiency leads to a reduced expression of pro-hematopoietic factors such as Scf caused by increased H2AK119-ub1 and H3K27-me3 levels on the promoter region of these genes. On the other hand, the expression of myelopoiesis stimulating factors including Csf3 was increased by enriched H3K4-me3 and H3K27-ac levels on their promoter, causing myeloid skewing. Notably, loss of BAP1 substantially blocks B lymphopoiesis and skews the differentiation of hematopoietic precursors toward myeloid lineages in vitro, which is reversed by G-CSF neutralization. Thus, our study uncovers a key role for BAP1 expressed in endosteal MSCs in controlling normal hematopoiesis in mice by modulating expression of various niche factors governing lymphopoiesis and myelopoiesis via histone modifications.