Eukaryotic Cell doi:10.1128/EC.00087-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Regulation of Phosphoinositide Levels by the Phospholipid Transfer Protein Sec14p Controls Cdc42p/PAK Mediated Cell Cycle Progression at Cytokinesis
Alicia G. Howe,
Gregory D. Fairn,
Kendra MacDonald,
Vytas A. Bankaitis,
and
Christopher R. McMaster*
Atlantic Research Centre, Departments of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4H7 Canada, and Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 USA
* To whom correspondence should be addressed. Email:
christopher.mcmaster{at}dal.ca.
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Abstract |
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Sec14p is an essential phosphatidylcholine/phosphatidylinositol transfer protein with a well described role in the regulation of Golgi derived vesicular transport in yeast. Inactivation of the CDP-choline pathway for phosphatidylcholine synthesis allows cells to survive in the absence of Sec14p function through restoration of Golgi vesicular transport capability. In this study, yeast cells containing a SEC14 temperature sensitive allele along with an inactivated CDP-choline pathway were transformed with a high copy number yeast genomic library. Genes whose increased expression inhibited cell growth in the absence of Sec14p function were identified. Increasing levels of the Rho GTPase Cdc42p and its direct effector kinases Cla4p and Ste20p prevented growth of cells lacking Sec14p and CDP-choline pathway function. Growth suppression was accompanied by an increase in large and multiply budded cells. This effect on polarized cell growth did not appear to be due to an inability to establish cell polarity as both the actin cytoskeleton and localization of the septin Cdc12p were unaffected by increased expression of Cdc42p, Cla4p, or Ste20p. Nuclei were present in both the mother cell and the emerging bud consistent with Sec14p regulating the cell cycle subsequent to anaphase but prior to cytokinesis/septum breakdown. Increased expression of phosphatidylinositol 4-kinases and phosphatidylinositol 4-phosphate 5-kinase prevented growth arrest by CDC42, CLA4, or STE20 upon inactivation of Sec14p function. Sec14p regulation of phosphoinositide levels affects cytokinesis at the level of the Cdc42p/Cla4p/Ste20p signaling cascade.
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