Selective requirement of glycosphingolipid synthesis for natural killer and cytotoxic T cells.

Cell identity genes that exhibit complex regulation are marked by super-enhancer (SE) architecture. Assessment of SEs in natural killer (NK) cells identified Ugcg, encoding the enzyme responsible for glycosphingolipid (GSL) synthesis. Conditional deletion of Ugcg in early hematopoiesis abrogated NK cell generation while sparing other lineages. Pharmacological inhibition of UGCG disrupted cytotoxic granules and cytotoxicity, reduced expansion after viral infection, and promoted apoptosis. B4galt5 transcribes an enzyme downstream of UGCG and possesses SE structure. Addition of its product, lactosylceramide (LacCer), reversed apoptosis due to UGCG inhibition. By contrast, complex GSLs, such as asialo-GM1, were not required for NK cell viability and granule integrity. Ugcg and B4galt5 were upregulated in CD8+ T cells during viral infection, correlating with the acquisition of cytotoxic machinery. Antigen-specific CD8+ T cells lacking Ugcg failed to expand during infection. Our study reveals a selective and essential role of GSL metabolism in NK and CD8+ T cell biology.