Atypical mannolipids characterize Thy-1-negative lymphoma mutants.

Essentially all eukaryotic cells, including murine lymphomas, express surface proteins, such as Thy-1, which are anchored by a phosphoinositol mannolipid. Putative mannolipid anchor precursors can be detected in these cells. Six distinct Thy-1-negative lymphoma mutants lack complete mannolipids, and three mutants synthesize atypical mannolipids. The absence of complete mannolipids can account for the lack of expression of multiple mannolipid-anchored proteins and may also account for the lack of lipid anchoring in the human disease paroxysmal nocturnal hemoglobinuria. Structural information on the mannolipids of wild-type and mutant cells indicates that anchor biosynthesis in these cells may involve both transmembrane flip-flop of intermediates and a deacylation step.