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Molecular and Cellular Biology, April 2005, p. 2910-2923, Vol. 25, No. 8
0270-7306/05/$08.00+0     doi:10.1128/MCB.25.8.2910-2923.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

The Phosphoinositide Phosphatase Sjl2 Is Recruited to Cortical Actin Patches in the Control of Vesicle Formation and Fission during Endocytosis

Christopher J. Stefan, Steven M. Padilla, Anjon Audhya, and Scott D. Emr^*

Department of Cellular and Molecular Medicine, The Howard Hughes Medical Institute, University of California, San Diego, School of Medicine, La Jolla, California

Received 12 June 2004/ Returned for modification 26 July 2004/ Accepted 18 January 2005

The Saccharomyces cerevisiae synaptojanin-like proteins (Sjl1, Sjl2, and Sjl3) are phosphoinositide (PI) phosphatases that regulate PI metabolism in the control of actin organization and membrane trafficking. However, the primary sites of action for each of the yeast synaptojanin-like proteins remain unclear. In this study, we show that Sjl2 is localized to cortical actin patches, sites of endocytosis. Cortical recruitment of Sjl2 requires the actin patch component Abp1. Consistent with this, the SH3 domain-containing protein Abp1 physically associates with Sjl2 through its proline-rich domain. Furthermore, abp1 mutations confer defects resembling loss of SJL2; sjl1 abp1 double-mutant cells exhibit invaginated plasma membranes and impaired endocytosis, findings similar to those for sjl1 sjl2 mutant cells. Thus, Abp1 acts as an adaptor protein in the localization or concentration of Sjl2 during late stages of endocytic vesicle formation. Overexpression of the Hip1-related protein Sla2 delayed the formation of extended plasma membrane invaginations in sjl2^ts cells, indicating that Sla2 may become limiting or misregulated in cells with impaired PI phosphatase activity. Consistent with this, the cortical actin patch protein Sla2 is mislocalized in sjl1 sjl2 mutant cells. Together, our studies suggest that PI metabolism by the synaptojanin-like proteins coordinately directs actin dynamics and membrane invagination, in part by regulation of Sla2.

Supplemental material for this article may be found at http://mcb.asm.org/.

Present address: Veterans Medical Research Foundation, San Diego, CA 92161.

Present address: Ludwig Institute for Cancer Research, La Jolla, CA 92093.

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