Krawczyk, P. A. | bioRxiv Science

bioRxiv2023

Perforin-2 is a pore-forming effector of endocytic escape in cross- presenting dendritic cells

During initiation of antiviral and antitumour T cell-mediated immune responses, dendritic cells (DCs) cross-present exogenous antigens on MHC class I. Cross-presentation relies on the unique leakiness of endocytic compartments in DCs, whereby internalised proteins escape into the cytosol for proteasome-mediated generation of MHC I-binding peptides. Given that type 1 conventional DCs excel at cross-presentation, we searched for cell-type specific effectors of endocytic escape. We devised an escape assay suitable for genetic screening and identified a pore-forming protein, perforin-2, as a dedicated effector exclusive to cross-presenting cells. Perforin-2 is recruited to antigen-containing compartments, where it undergoes maturation, releasing its pore-forming domain. Mpeg1-/- mice fail to efficiently prime CD8+ T cells to cell-associated antigens, revealing an important role of perforin-2 in cytosolic entry of antigens during cross-presentation. One-Sentence SummaryPore-forming protein perforin-2 is a dedicated effector of endocytic escape specific to cross-presenting cells

cell biology↗

bioRxiv2020

Dihydroxyacetone phosphate signals glucose availability to mTORC1

In response to nutrients, the mTOR complex 1 (mTORC1) kinase regulates cell growth by setting the balance between anabolic and catabolic processes. To be active, mTORC1 requires the environmental presence of amino acids and glucose, which provide the building blocks for the biosynthesis of most macromolecules. While a mechanistic understanding of amino acid sensing by mTORC1 is emerging, how glucose activates mTORC1 remains mysterious. Here, we used metabolically engineered human cells to identify glucose-derived metabolites required to activate mTORC1. We find that mTORC1 senses a metabolite downstream of the aldolase and upstream of the glyceraldehyde 3-phosphate dehydrogenase steps of glycolysis and pinpoint dihydroxyacetone phosphate (DHAP) as the key molecule. In cells expressing a triose kinase, the synthesis of DHAP from dihydroxyacetone is sufficient to activate mTORC1 even in the absence of glucose. Genetic perturbations in the GATOR-Rag signaling axis abrogate glucose sensing by mTORC1. DHAP is the glycolytic metabolite along with glyceraldehyde 3-phosphate (GAP) that has the greatest fold-change between cells in high and low glucose. DHAP is a precursor for lipid synthesis, a process under the control of mTORC1, which provides a potential rationale for the sensing of DHAP by mTORC1.

cell biology↗