The oxysterol binding protein Kes1p regulates Golgi apparatus phosphatidylinositol-4-phosphate function.

The Saccharomyces cerevisiae phosphatidylcholine/phosphatidylinositol transfer protein Sec14p is required for Golgi apparatus-derived vesicular transport through coordinate regulation of phospholipid metabolism. Sec14p is normally essential. The essential requirement for SEC14 can be bypassed by inactivation of (i) the CDP-choline pathway for phosphatidylcholine synthesis or (ii) KES1, which encodes an oxysterol binding ...
protein. A unique screen was used to determine genome-wide genetic interactions for the essential gene SEC14 and to assess whether the two modes of "sec14 bypass" were similar or distinct. The results indicate that inactivation of the CDP-choline pathway allows cells with inactivated SEC14 to live through a mechanism distinct from that of inactivation of KES1. We go on to demonstrate an important biological function of Kes1p. Kes1p regulates Golgi apparatus-derived vesicular transport by inhibiting the function of Pik1p-generated Golgi apparatus phosphatidylinositol-4-phosphate (PI-4P). Kes1p affects both the availability and level of Golgi apparatus PI-4P. A set of potential PI-4P-responsive proteins that include the Rab GTPase Ypt31p and its GTP exchange factor are described.
Mesh Terms:
1-Phosphatidylinositol 4-Kinase, Genome, Fungal, Golgi Apparatus, Membrane Proteins, Models, Biological, Phosphatidylcholines, Phosphatidylinositol Phosphates, Phosphatidylinositols, Phospholipid Transfer Proteins, Receptors, Steroid, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sterols, beta-Fructofuranosidase, rab GTP-Binding Proteins
Proc. Natl. Acad. Sci. U.S.A.
Date: Sep. 25, 2007
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