Published online April 23, 2007
doi:10.1083/jcb.200611011
The Journal of Cell Biology, Vol. 177, No. 2, 355-367
The Rockefeller University Press, 0021-9525 $30.00
© 2007 Sun et al.
PtdIns(4,5)P2 turnover is required for multiple stages during clathrin- and actin-dependent endocytic internalization
Yidi Sun,
Susheela Carroll,
Marko Kaksonen,
Junko Y. Toshima, and
David G. Drubin
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
Correspondence to David G. Drubin: drubin{at}berkeley.edu
The lipid phosphatidylinositol-4,5-bisphosphate (PtdIns[4,5]P2) appears to play an important role in endocytosis. However, the timing of its formation and turnover, and its specific functions at different stages during endocytic internalization, have not been established. In this study, Sla2 ANTH-GFP and Sjl2-3GFP were expressed as functional fusion proteins at endogenous levels to quantitatively explore PtdIns(4,5)P2 dynamics during endocytosis in yeast. Our results indicate that PtdIns(4,5)P2 levels increase and decline in conjunction with coat and actin assembly and disassembly, respectively. Live-cell image analysis of endocytic protein dynamics in an sjl1
sjl2
mutant, which has elevated PtdIns(4,5)P2 levels, revealed that the endocytic machinery is still able to assemble and disassemble dynamically, albeit nonproductively. The defects in the dynamic behavior of the various endocytic proteins in this double mutant suggest that PtdIns(4,5)P2 turnover is required for multiple stages during endocytic vesicle formation. Furthermore, our results indicate that PtdIns(4,5)P2 turnover may act in coordination with the Ark1/Prk1 protein kinases in stimulating disassembly of the endocytic machinery.
Abbreviations used in this paper: ANTH, AP180 N-terminal homology; Clc, clathrin light chain; PH, pleckstrin homology; PtdIns(4,5)P2, phosphatidylinositol- 4,5-bisphosphate.

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