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Originally published as MBC in Press, 10.1091/mbc.E08-03-0280 on December 10, 2008

Vol. 20, Issue 3, 1081-1088, February 1, 2009

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Coordination of Cytokinesis and Cell Separation by Endosomal Targeting of a Cdc42-specific Guanine Nucleotide Exchange Factor in Ustilago maydis

Kay Oliver Schink, and Michael Bölker

Philipps-University Marburg, Department of Biology, D-35032 Marburg, Germany

Submitted March 14, 2008; Revised December 1, 2008; Accepted December 2, 2008
Monitoring Editor: Daniel J. Lew

The small GTPase Cdc42 is a key regulator of cell polarity and cytoskeletal organization in most eukaryotic cells. In Ustilago maydis, Cdc42 and the guanine nucleotide exchange factor (GEF) Don1 regulate cytokinesis and cell separation. Don1 belongs to the FGD1 family of Cdc42-specific GEFs that are characterized by a C-terminal lipid-binding FYVE domain. Although the FGD1/frabin family of Rho-GEFs is evolutionary conserved from fungi to mammals the role of the FYVE domain for its biological function is unknown. Here, we show that the FYVE domain is specific for phosphatidylinositol-3-phosphate (PtdIns(3)P) and targets Don1 to endosomal vesicles. During cytokinesis asymmetric accumulation of Don1-containing vesicles occurs at the site of septation. We could show that FYVE-dependent localization is critical for the function of Don1 at normal expression levels but can be compensated for by overexpression of Don1 lacking a functional FYVE domain. Our results demonstrate that endosomal compartmentalization of a Cdc42-specific exchange factor is involved in the coordination of cytokinesis and cell separation.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08-03-0280) on December 10, 2008.

Address correspondence to: Michael Bölker (boelker{at}staff.uni-marburg.de)

Abbreviations used: GEF, guanine nucleotide exchange factor.






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