Single-cell metabolic profiling of human cytotoxic T cells

Cellular metabolism regulates immune cell activation, differentiation and effector functions but current metabolic approaches lack single-cell resolution and simultaneous characterization of cellular phenotype. Here, we developed an approach to characterize the metabolic regulome of single cells together with their phenotypic identity. The method, single-cell metabolic regulome profiling (scMEP), quantifies proteins that regulate metabolic pathway activity using a high-dimensional antibody-based approach. We employed mass cytometry (CyTOF) to benchmark scMEP against bulk metabolic assays by reconstructing the metabolic remodeling of in vitro-activated naïve and memory CD8(+) T cells. We applied the approach to clinical samples and identified tissue-restricted, metabolically repressed cytotoxic T cells in human colorectal carcinoma. Combining our method with imaging mass spectrometry (MIBI-TOF), we uncovered the spatial organization of metabolic programs, which indicated exclusion of metabolically repressed immune cells from the tumor-immune boundary. Overall, our approach enables robust approximation of metabolic and functional states in individual cells.