The SPPL3-Defined Glycosphingolipid Repertoire Orchestrates HLA Class I-Mediated Immune Responses.

Jongsma, Marlieke L M; de Waard, Antonius A; Raaben, Matthijs; Zhang, Tao; Cabukusta, Birol; Platzer, René; Blomen, Vincent A; Xagara, Anastasia; Verkerk, Tamara; Bliss, Sophie; Kong, Xiangrui; Gerke, Carolin; Janssen, Lennert; Stickel, Elmer; Holst, Stephanie; Plomp, Rosina; Mulder, Arend; Ferrone, Soldano; Claas, Frans H J; Heemskerk, Mirjam H M; Griffioen, Marieke; Halenius, Anne; Overkleeft, Hermen; Huppa, Johannes B; Wuhrer, Manfred; Brummelkamp, Thijn R; Neefjes, Jacques; Spaapen, Robbert M

HLA class I (HLA-I) glycoproteins drive immune responses by presenting antigens to cognate CD8+ T cells. This process is often hijacked by tumors and pathogens for immune evasion. Because options for restoring HLA-I antigen presentation are limited, we aimed to identify druggable HLA-I pathway targets. Using iterative genome-wide screens, we uncovered that the cell surface glycosphingolipid (GSL) repertoire determines effective HLA-I antigen presentation. We show that absence of the protease SPPL3 augmented B3GNT5 enzyme activity, resulting in upregulation of surface neolacto-series GSLs. These GSLs sterically impeded antibody and receptor interactions with HLA-I and diminished CD8+ T cell activation. Furthermore, a disturbed SPPL3-B3GNT5 pathway in glioma correlated with decreased patient survival. We show that the immunomodulatory effect could be reversed through GSL synthesis inhibition using clinically approved drugs. Overall, our study identifies a GSL signature that inhibits immune recognition and represents a potential therapeutic target in cancer, infection, and autoimmunity.