Inactivation of the phosphoinositide phosphatases Sac1p and Inp54p leads to accumulation of phosphatidylinositol 4,5-bisphosphate on vacuole membranes and vacuolar fusion defects

Wiradjaja, Fenny, Ooms, Lisa M., Tahirovic, Sabina, Kuhne, Ellie, Devenish, Rodney J., Munn, Alan L., Piper, Robert C., Mayinger, Peter Mayinger and Mitchell, Christina A. (2007) Inactivation of the phosphoinositide phosphatases Sac1p and Inp54p leads to accumulation of phosphatidylinositol 4,5-bisphosphate on vacuole membranes and vacuolar fusion defects. Journal of Biological Chemistry, 282 22: 16295-16307. doi:10.1074/jbc.M701038200

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Author Wiradjaja, Fenny
Ooms, Lisa M.
Tahirovic, Sabina
Kuhne, Ellie
Devenish, Rodney J.
Munn, Alan L.
Piper, Robert C.
Mayinger, Peter Mayinger
Mitchell, Christina A.
Title Inactivation of the phosphoinositide phosphatases Sac1p and Inp54p leads to accumulation of phosphatidylinositol 4,5-bisphosphate on vacuole membranes and vacuolar fusion defects
Journal name Journal of Biological Chemistry   Check publisher's open access policy
ISSN 0021-9258
Publication date 2007
Sub-type Article (original research)
DOI 10.1074/jbc.M701038200
Open Access Status File (Publisher version)
Volume 282
Issue 22
Start page 16295
End page 16307
Total pages 13
Place of publication Bethesda, USA
Publisher American Society for Biochemistry and Molecular Biology
Collection year 2008
Language eng
Subject C1
270199 Biochemistry and Cell Biology not elsewhere classified
730108 Cancer and related disorders
Abstract Phosphoinositides direct membrane trafficking, facilitating the recruitment of effectors to specific membranes. In yeast phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P-2) is proposed to regulate vacuolar fusion; however, in intact cells this phosphoinositide can only be detected at the plasma membrane. In Saccharomyces cerevisiae the 5-phosphatase, Inp54p, dephosphorylates PtdIns(4,5)P-2 forming PtdIns(4)P, a substrate for the phosphatase Sac1p, which hydrolyzes (PtdIns(4) P). We investigated the role these phosphatases in regulating PtdIns(4,5) P-2 subcellular distribution. PtdIns(4,5)P-2 bioprobes exhibited loss of plasma membrane localization and instead labeled a subset of fragmented vacuoles in Delta sac1 Delta inp54 and sac1(ts) Delta inp54 mutants. Furthermore, sac1(ts) Delta inp54 mutants exhibited vacuolar fusion defects, which were rescued by latrunculin A treatment, or by inactivation of Mss4p, a PtdIns(4)P 5-kinase that synthesizes plasma membrane PtdIns(4,5)P-2. Under these conditions PtdIns(4,5)P-2 was not detected on vacuole membranes, and vacuole morphology was normal, indicating vacuolar PtdIns(4,5)P-2 derives from Mss4p-generated plasma membrane PtdIns(4,5)P-2. Delta sac1 Delta inp54 mutants exhibited delayed carboxypeptidase Y sorting, cargo-selective secretion defects, and defects in vacuole function. These studies reveal PtdIns(4,5)P-2 hydrolysis by lipid phosphatases governs its spatial distribution, and loss of phosphatase activity may result in PtdIns(4,5)P-2 accumulation on vacuole membranes leading to vacuolar fragmentation/fusion defects.
Keyword Biochemistry & Molecular Biology
Pleckstrin Homology Domains
Inositol Polyphosphate 5-phosphatase
Yeast Saccharomyces-cerevisiae
Phospholipid Transfer Protein
Plasma-membrane
Cell-growth
Gene
Golgi
Mutations
Mutants
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Mon, 18 Feb 2008, 17:19:48 EST