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Determination of theintracellular sitesand topology ofglucosylceramidesynthesis in ratliver Anthony H. FutermanRichard E. Pagano1991 год

Determination of the intracellular sites and topology of glucosylceramide synthesis in rat liver
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Аннотация: We examined the intracellular site(s) and topology of glucosylceramide (GlcCer) synthesis in subcellular fractions from rat liver, using radioactive and fluorescent ceramide analogues as precursors, and compared these results with those obtained in our recent study of sphingomyelin (SM) synthesis in rat liver [Futerman, Stieger, Hubbard & Pagano (1990) J. Biol. Chem. 265, 8650-8657]. In contrast with SM synthesis, which occurs principally at the cis/medial Golgi apparatus, GlcCer synthesis was more widely distributed, with substantial amounts of synthesis detected in a heavy (cis/medial) Golgi-apparatus subfraction, a light smooth-vesicle fraction that is almost devoid of an endoplasmic-reticulum marker enzyme (glucose-6-phosphatase), and a heavy vesicle fraction. Furthermore, no GlcCer synthesis was detected in an enriched plasma-membrane fraction after accounting for contamination by Golgi-apparatus membranes. These results suggest that a significant amount of GlcCer may be synthesized in a pre- or early Golgi-apparatus compartment. Unlike SM synthesis, which occurs at the luminal surface of the Golgi apparatus, GlcCer synthesis appeared to occur at the cytosolic surface of intracellular membranes, since (i) limited proteolytic digestion of intact Golgi-apparatus vesicles almost completely inhibited GlcCer synthesis, and (ii) the extent of UDP-glucose translocation into the Golgi apparatus was insufficient to account for the amount of GlcCer synthesis measured. These findings imply that, after its synthesis, GlcCer must undergo transbilayer movement to the luminal surface to account for the known topology of higher-order glycosphingolipids within the Golgi apparatus and plasma membrane.
Год издания: 1991
Авторы: Anthony H. Futerman, Richard E. Pagano
Издательство: Portland Press
Источник: Biochemical Journal
Ключевые слова: Sphingolipid Metabolism and Signaling, Cellular transport and secretion, Lipid Membrane Structure and Behavior
Другие ссылки: Biochemical Journal (HTML)
Europe PMC (PubMed Central) (PDF)
Europe PMC (PubMed Central) (HTML)
PubMed Central (HTML)
PubMed (HTML)