title: Evidence for the involvement of GD3 ganglioside in autophagosome formation and maturation.
abstract: Sphingolipids are structural lipid components of cell membranes, including membrane of organelles, such as mitochondria or endoplasmic reticulum, playing a role in signal transduction as well as in the transport and intermixing of cell membranes. Sphingolipid microdomains, also called lipid rafts, participate in several metabolic and catabolic cell processes, including apoptosis. However, the defined role of lipid rafts in the autophagic flux is still unknown. In the present study we analyzed the role of gangliosides, a class of sphingolipids, in autolysosome morphogenesis in human and murine primary fibroblasts by means of biochemical and analytical cytology methods. Upon induction of autophagy, by using amino acid deprivation as well as tunicamycin, we found that GD3 ganglioside, considered as a paradigmatic raft constituent, actively contributed to the biogenesis and maturation of autophagic vacuoles. In particular, fluorescence resonance energy transfer (FRET) and coimmunoprecipitation analyses revealed that this ganglioside interacts with phosphatidylinositol 3-phosphate and can be detected in immature autophagosomes in association with LC3-II as well as in autolysosomes associated with LAMP1. Hence, it appears as a structural component of autophagic flux. Accordingly, we found that autophagy was significantly impaired by knocking down ST8SIA1/GD3 synthase (ST8 α-N-acetyl-neuraminide α-2,8-sialyltransferase 1) or by altering sphingolipid metabolism with fumonisin B1. Interestingly, exogenous administration of GD3 ganglioside was capable of reactivating the autophagic process inhibited by fumonisin B1. Altogether, these results suggest that gangliosides, via their molecular interaction with autophagy-associated molecules, could be recruited to autophagosome and contribute to morphogenic remodeling, e.g., to changes of membrane curvature and fluidity, finally leading to mature autolysosome formation.
authors.affiliation: Section of Cell Aging and Degeneration; Department of Drug Research and Evaluation; Istituto Superiore di Sanita; Rome, Italy; Center of Metabolomics; Rome, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Matarrese
authors.affiliation: Department of Experimental Medicine; Sapienza University; Rome, Italy.
authors.forename: Tina
authors.initials: T
authors.lastname: Garofalo
authors.affiliation: Department of Experimental Medicine; Sapienza University; Rome, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Manganelli
authors.affiliation: Section of Cell Aging and Degeneration; Department of Drug Research and Evaluation; Istituto Superiore di Sanita; Rome, Italy.
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Gambardella
authors.affiliation: Section of Cell Aging and Degeneration; Department of Drug Research and Evaluation; Istituto Superiore di Sanita; Rome, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Marconi
authors.affiliation: Department of Experimental Medicine; Sapienza University; Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Grasso
authors.affiliation: Department of Technology and Health; Istituto Superiore di Sanita, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Tinari
authors.affiliation: Department of Experimental Medicine; Sapienza University; Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Misasi
authors.affiliation: Section of Cell Aging and Degeneration; Department of Drug Research and Evaluation; Istituto Superiore di Sanita; Rome, Italy; Istituto San Raffaele Sulmona; L'Aquila, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Malorni
authors.affiliation: Department of Experimental Medicine; Sapienza University; Rome, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Sorice
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005732:Gangliosides / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007790:Lactosylceramides / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1 / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D034741:RNA, Small Interfering / Q000494:pharmacology; D012799:Sialyltransferases / Q000235:genetics / Q000378:metabolism
chemical_list: D005732:Gangliosides; D007790:Lactosylceramides; D052118:Lysosomal-Associated Membrane Protein 1; D034741:RNA, Small Interfering; C026226:ganglioside, GD3; C025575:lactotriaosylceramide; D012799:Sialyltransferases; C043662:alpha-N-acetylneuraminate alpha-2,8-sialyltransferase
keywords: autophagosome; autophagy; gangliosides; mitochondria; rafts