Abstract
AbstractSomatic mutations can lead to the transformation of healthy cells into malignant cells and allow their evasion from immune surveillance. To uncover genes that play a role in the detection and lysis of tumor cells by natural killer (NK) cells, a B lymphoblastoid cell line was subjected to a genome-wide CRISPR screen. Among the top hits that facilitated NK evasion wasSPPL3, which encodes an intramembrane protease that cleaves transmembrane glycosyltransferases in the Golgi apparatus.SPPL3-deficient cells accumulated glycosyltransferases, such as acetylglucosaminyltransferase 5 (MGAT5), and displayed increased N-glycosylation. Binding of NK receptors NKG2D and CD2 to their corresponding ligands MICB and CD58, and binding of rituximab to CD20, was disrupted bySPPL3-deletion. Inhibition of N-glycan maturation restored receptor binding and sensitivity to NK cells. To elucidate the mechanism of this resistant phenotype, a secondary CRISPR screen was performed inSPPL3-deficient cells. This screen identified glycosyltransferases that catalyze the formation of highly branched N-glycans and N-acetyl-lactosamine (LacNAc) extensions as key regulators that prevent killing. A significant enrichment of poly-LacNAc-containing tetra-antennary species was confirmed by glycoproteomic analysis. These findings provide mechanistic insight into howSPPL3deletions have been linked to cancer.
Publisher
Cold Spring Harbor Laboratory