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Abbreviations:
BORIS brother of the regulator of imprinted sites
CGT ceramide galactosyltransferase
CST cerebroside sulfotransferase
GalCer galactosylceramide
GalEAG galactosylalkylacylglycerol
Gal3ST βGal 3-O-sulfotransferase
MCT monocarboxylate transporter
MRI magnetic resonance imaging
PAPS 3'-phosphoadenosine 5'-phosphosulfate
PPAR peroxisome proliferator-activated receptor
UTR untranslated region
UUO unilateral ureteral obstruction
Introduction
Glycolipids are membrane lipids with a carbohydrate attached. They are located predominantly in the outer leaflet of the plasma membrane and contribute to cell recognition and membrane microdomain formation during various biological events such as differentiation, development and immune reactions. Sulfation, phosphorylation and sialylation confer negative charge on glycolipids and such structures form a part of determinants for the molecular interactions.
The first one of the mammalian sulfoglycolipids, sulfatide was isolated from the human brain by Thudichum in as early as 1884 (reviewed in Ref. 1). The correct structure of sulfatide was determined by Yamakawa in 1962.2 Thereafter, many kinds of sulfoglycolipids have been discovered from various organs.1 Among them is a unique testis-specific seminolipid.3,4 The carbohydrate moiety of sulfatide and seminolipid has the same structure, HSO3 -3Gal but their lipid moiety is different from each other (Fig. 1 ). Sulfatide is a sphingolipid, while seminolipid is a glycerolipid. The distribution of sulfoglycolipids is tissue-specific and they are abundant in myelin, spermatozoa, kidney, and alimentary canal.1 Especially, sulfatide is a major lipid component of the myelin sheath and synthesized in myelin-generating cells, oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system.1,5 On the other hand, seminolipid is synthesized in spermatocytes and maintained in the subsequent germ cell stages.1,5 The carbohydrate moiety of sulfatide and seminolipid is biosynthesized via sequential reactions catalyzed by common enzymes: ceramide galactosyltransferase (CGT, EC 2.4.1.45) and cerebroside sulfotransferase (CST, EC 2.8.2.11) (Fig. 2 ). Sulfoglycolipids have been implicated in a variety of physiological functions through their interactions with extracellular matrix proteins, cellular adhesive receptors, blood coagulation systems, and microorganisms.1,5
Figure 1.
Structure of sulfatide and seminolipid.
Figure 2.
Biosythetic pathway of sulfatide and seminolipid.
1. Purification and molecular cloning of human CST
Since glycolipid sulfotransferase was identified as an enzyme to catalyze the transfer of a sulfate group from the sulfate donor, PAPS to the C3...