Membrane microdomains are assembled by lipid partitioning (e.g., rafts) or by protein–protein interactions (e.g., coated vesicles). During docking, yeast vacuoles assemble “vertex” ring-shaped microdomains around the periphery of their apposed membranes. Vertices are selectively enriched in the Rab GTPase Ypt7p, the homotypic fusion and vacuole protein sorting complex (HOPS)–VpsC Rab effector complex, SNAREs, and actin. Membrane fusion initiates at vertex microdomains. We now find that the “regulatory lipids” ergosterol, diacylglycerol and 3- and 4-phosphoinositides accumulate at vertices in a mutually interdependent manner. Regulatory lipids are also required for the vertex enrichment of SNAREs, Ypt7p, and HOPS. Conversely, SNAREs and actin regulate phosphatidylinositol 3-phosphate vertex enrichment. Though the PX domain of the SNARE Vam7p has direct affinity for only 3-phosphoinositides, all the regulatory lipids which are needed for vertex assembly affect Vam7p association with vacuoles. Thus, the assembly of the vacuole vertex ring microdomain arises from interdependent lipid and protein partitioning and binding rather than either lipid partitioning or protein interactions alone.
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20 December 2004
Article|
December 20 2004
Interdependent assembly of specific regulatory lipids and membrane fusion proteins into the vertex ring domain of docked vacuoles
Rutilio A. Fratti,
Rutilio A. Fratti
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
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Youngsoo Jun,
Youngsoo Jun
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
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Alexey J. Merz,
Alexey J. Merz
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
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Nathan Margolis,
Nathan Margolis
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
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William Wickner
William Wickner
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
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Rutilio A. Fratti
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
Youngsoo Jun
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
Alexey J. Merz
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
Nathan Margolis
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
William Wickner
Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755
Correspondence to Bill Wickner: [email protected]
A.J. Merz's current address is Dept. of Biochemistry, University of Washington, Seattle, WA 98195
Abbreviations used in this paper: 3NC, 3-nitrocoumarin; ENTH, epsin NH2-terminal homology domain; HOPS, homotypic fusion and vacuole protein sorting complex; LatB, latrunculin B; MED, MARCKS effector domain; PI, phosphatidylinositol; PI(3)P, PI 3-phosphate; PX, Phox homology.
Received:
September 13 2004
Accepted:
November 08 2004
Online ISSN: 1540-8140
Print ISSN: 0021-9525
The Rockefeller University Press
2004
J Cell Biol (2004) 167 (6): 1087–1098.
Article history
Received:
September 13 2004
Accepted:
November 08 2004
Citation
Rutilio A. Fratti, Youngsoo Jun, Alexey J. Merz, Nathan Margolis, William Wickner; Interdependent assembly of specific regulatory lipids and membrane fusion proteins into the vertex ring domain of docked vacuoles . J Cell Biol 20 December 2004; 167 (6): 1087–1098. doi: https://doi.org/10.1083/jcb.200409068
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