Transport and sorting of lipids must occur with specific mechanisms because the membranes of intracellular organelles differ in lipid composition even though most lipid biosynthesis begins in the ER. In yeast, ceramide is synthesized in the ER and transferred to the Golgi apparatus where inositolphosphorylceramide (IPC) is formed. These two facts imply that ceramide can be transported to the Golgi independent of vesicular traffic because IPC synthesis still continues when vesicular transport is blocked in sec mutants. Nonvesicular IPC synthesis in intact cells is not affected by ATP depletion. Using an in vitro assay that reconstitutes the nonvesicular pathway for transport of ceramide, we found that transport is temperature and cytosol dependent but energy independent. Preincubation of ER and Golgi fractions together at 4°C, where ceramide transport does not occur, rendered the transport reaction membrane concentration independent, providing biochemical evidence that ER-Golgi membrane contacts stimulate ceramide transport. A cytosolic protease-sensitive factor is required after establishment of ER-Golgi contacts.
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10 December 2001
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December 03 2001
Vesicular and nonvesicular transport of ceramide from ER to the Golgi apparatus in yeast
Kouichi Funato,
Kouichi Funato
Biozentrum of the University of Basel, CH-4056 Basel, Switzerland
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Howard Riezman
Howard Riezman
Biozentrum of the University of Basel, CH-4056 Basel, Switzerland
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Kouichi Funato
Biozentrum of the University of Basel, CH-4056 Basel, Switzerland
Howard Riezman
Biozentrum of the University of Basel, CH-4056 Basel, Switzerland
Address correspondence to Howard Riezman, Biozentrum, University of Basel, Klingelbergstr. 70, Basel CH-4056, Switzerland. Tel.: 41-61-267-2160. Fax: 41-61-267-2149. E-mail: [email protected]
*
Abbreviations used in this paper: AbA, aureobasidin A; Chx, cycloheximide; DHS, dihydrosphingosine; DHS-Cer, dihydroceramide; DHS-1-P, [3H]DHS-1-phosphate; FuB, fumonisin B1; HA, hemagglutinin; IPC, inositolphosphorylceramide; NEM, N-ethylmaleimide; PC, phosphatidylcholine; PHS, phytosphingosine; PI, phosphatidylinositol.
Received:
May 07 2001
Revision Received:
October 24 2001
Accepted:
October 24 2001
Online ISSN: 1540-8140
Print ISSN: 0021-9525
The Rockefeller University Press
2001
J Cell Biol (2001) 155 (6): 949–960.
Article history
Received:
May 07 2001
Revision Received:
October 24 2001
Accepted:
October 24 2001
Citation
Kouichi Funato, Howard Riezman; Vesicular and nonvesicular transport of ceramide from ER to the Golgi apparatus in yeast . J Cell Biol 10 December 2001; 155 (6): 949–960. doi: https://doi.org/10.1083/jcb.200105033
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