Abstract
α-Series gangliosides define a particular sub-class of glycosphingolipids containing sialic acid α2,6-linked to GalNAc residue that was isolated as a minor compound from the brain. The sialyltransferase ST6GalNAc V was cloned from mouse brain and showed α2,6-sialyltransferase activity almost exclusively for GM1b, to form GD1α and is considered as the main enzyme involved in the biosynthesis of α-series gangliosides. Recently, ST6GALNAC5 was identified as one of the genes over-expressed in breast cancer cell populations selected for their ability to produce brain metastasis. However, the capacity of human breast cancer cells to produce α-series gangliosides has never been clearly demonstrated. Here, we show by stable transfection and MS-MS analysis of total glycosphingolipids that ST6GALNAC5 expressing MDA-MB-231 breast cancer cells accumulate GD1α ganglioside (IV3Neu5Ac1, III6Neu5Ac1Gg4-Cer).
Highlights
Gangliosides, the glycosphingolipids (GSL) carrying one or several sialic acid residues, are essentially located on the outer leaflet of the plasma membrane where they form lipid rafts with cholesterol and other sphingolipids
MDA-MB-231 cells were transfected with the pIRES2-AcGFP1 expression vector containing the full-length cDNA of human ST6GalNAc V or the empty vector as control. pIRES2-AcGFP1 is a bicistronic expression vector designed for the simultaneous expression of green fluorescent protein (GFP) and a protein of interest in mammalian cells
The α-series gangliosides define a rare subclass of GSL essentially restricted to some area of mammalian brain. α-gangliosides biological function, remains mostly unknown
Summary
Gangliosides, the glycosphingolipids (GSL) carrying one or several sialic acid residues, are essentially located on the outer leaflet of the plasma membrane where they form lipid rafts with cholesterol and other sphingolipids. The recombinant mouse ST6GalNAc VI was shown to convert in vitro GM1b, GD1a, and GT1b into α-series gangliosides GD1α, GT1aα, and GQ1bα, respectively [13]. This enzyme was lately demonstrated to be responsible for the synthesis of disialyl-Lea but not for α-series gangliosides in human colon tissues [14]. ST6GALNAC5 gene was shown playing a role in HeLa. cell adhesion [17,18] and recently, ST6GALNAC5 was identified as one of the genes over-expressed in breast cancer cell populations selected for their ability to produce brain metastasis [19]. The capacity of Human breast cancer cells that express ST6GALNAC5 to produce α-series gangliosides has never been clearly demonstrated. We show by MS analysis of total GSL that ST6GALNAC5 expressing MDA-MB-231 breast cancer cells accumulate GD1α ganglioside
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