Phosphatidylglucoside Forms Specific Lipid Domains on the Outer Leaflet of the Plasma Membrane

摘要

Phosphatidylglucoside (PtdGlc) is a recently discovered unique glycophospholipid involved inngranulocytic differentiation of human promyelocytic leukemia cell line HL60 and in astrocytic differentiationnin developing rodent brains. Using a PtdGlc-specific monoclonal antibody in immunofluorescence andnimmunoelectron microscopy, we showed that PtdGlc forms distinct lipid domains on the outer leaflet of thenplasma membrane of HL60 cells and the human alveolar epithelial cell line, A549. Similar to glyco-nsphingolipid, glucosylceramide (GlcCer), the natural form of PtdGlc exhibited a high main phase transitionntemperature in differential scanning calorimetry (DSC). However, unlike GlcCer, PtdGlc did not exhibit anlarge difference in the main phase transition temperature between the heating and cooling scans. DSC furthernindicated that GlcCer, but not PtdGlc, was miscible with sphingomyelin. In addition, DSC and small-anglenX-ray scattering (SAXS) experiments revealed that PtdGlc was poorly miscible with phosphatidylcholine.nOur results suggest that the lack of tight intermolecular interaction excludes PtdGlc from other lipid domainsnon the plasma membrane.