Retention of the Yeast Sac1p Phosphatase in the Endoplasmic Reticulum Causes Distinct Changes in Cellular Phosphoinositide Levels and Stimulates Microsomal ATP Transport

The yeast phosphoinositide phosphatase Sac1p localizes to endoplasmic reticulum (ER) and Golgi membranes and has compartment-specific functions in these organelles. In this study we analyzed in detail the topology of Sac1p. Our data show that Sac1p is a type II transmembrane protein with a large N-t...

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Bibliographic Details
Published in:The Journal of biological chemistry 2002-03, Vol.277 (12), p.10547-10554
Main Authors: Konrad, Gerlinde, Schlecker, Tanja, Faulhammer, Frank, Mayinger, Peter
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Amino Acid Motifs
Bacterial Proteins - metabolism
Biological Transport
Cell Membrane - metabolism
Cell Wall - metabolism
Cytosol - metabolism
DNA - metabolism
Endoplasmic Reticulum - metabolism
Gene Deletion
Genetic Complementation Test
Golgi Apparatus - metabolism
Lipid Metabolism
Membrane Proteins
Membrane Transport Proteins
Microscopy, Fluorescence
Microsomes - metabolism
Mutation
Phosphatidylinositol Phosphates - metabolism
Phosphatidylinositols - metabolism
phosphoinositide phosphatase
Plasmids - metabolism
Protein Structure, Tertiary
Sac1 protein
Saccharomyces cerevisiae
Time Factors
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Summary:The yeast phosphoinositide phosphatase Sac1p localizes to endoplasmic reticulum (ER) and Golgi membranes and has compartment-specific functions in these organelles. In this study we analyzed in detail the topology of Sac1p. Our data show that Sac1p is a type II transmembrane protein with a large N-terminal cytosolic domain, which is anchored in the membrane by the two potential transmembrane helices near the C terminus. Based on this topology, we created a mutation that caused retention of Sac1p in the ER and as a consequence showed specific alterations in cellular phosphoinositide levels. Our results suggest that Sac1p controls a pool of phosphatidylinositol 3-phosphate and phosphatidylinositol 4-phosphate in the ER. Retention of Sac1p in the ER also stimulates ATP transport into the ER lumen but causes the same Golgi-specific defects that are seen in asac1 null mutant. Taken together this study provides evidence that Sac1p is an important 4-phosphatase in the ER controlling different aspects of ER-based protein processing and secretion.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M200090200