Abstract
Sec14, the major yeast phosphatidylinositol (PtdIns)/phosphatidylcholine (PtdCho) transfer protein, regulates essential interfaces between lipid metabolism and membrane trafficking from the trans-Golgi network (TGN). How Sec14 does so remains unclear. We report that Sec14 binds PtdIns and PtdCho at distinct (but overlapping) sites, and both PtdIns- and PtdCho-binding activities are essential Sec14 activities. We further show both activities must reside within the same molecule to reconstitute a functional Sec14 and for effective Sec14-mediated regulation of phosphoinositide homeostasis in vivo. This regulation is uncoupled from PtdIns-transfer activity and argues for an interfacial presentation mode for Sec14-mediated potentiation of PtdIns kinases. Such a regulatory role for Sec14 is a primary counter to action of the Kes1 sterol-binding protein that antagonizes PtdIns 4-OH kinase activity in vivo. Collectively, these findings outline functional mechanisms for the Sec14 superfamily and reveal additional layers of complexity for regulating phosphoinositide homeostasis in eukaryotes.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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1-Phosphatidylinositol 4-Kinase / chemistry
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1-Phosphatidylinositol 4-Kinase / genetics
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1-Phosphatidylinositol 4-Kinase / metabolism
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Biological Transport / physiology
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Cell Membrane / chemistry
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Cell Membrane / genetics
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Cell Membrane / metabolism*
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Golgi Apparatus / chemistry
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Golgi Apparatus / genetics
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Golgi Apparatus / metabolism
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Homeostasis / physiology*
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Lipid Metabolism / physiology*
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Membrane Proteins / chemistry
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Membrane Proteins / metabolism
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Phosphatidylcholines / chemistry
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Phosphatidylcholines / genetics
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Phosphatidylcholines / metabolism
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Phosphatidylinositols / chemistry
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Phosphatidylinositols / genetics
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Phosphatidylinositols / metabolism*
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Phospholipid Transfer Proteins / chemistry
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Phospholipid Transfer Proteins / genetics
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Phospholipid Transfer Proteins / metabolism*
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Protein Structure, Tertiary
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Receptors, Steroid
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Saccharomyces cerevisiae / chemistry
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
Substances
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KES1 protein, S cerevisiae
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Membrane Proteins
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Phosphatidylcholines
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Phosphatidylinositols
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Phospholipid Transfer Proteins
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Receptors, Steroid
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SEC14 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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1-Phosphatidylinositol 4-Kinase
Associated data
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PDB/3B74
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PDB/3B7N
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PDB/3B7Q
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PDB/3B7Z