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PIP₂ in endocytosis

The breakdown of PI(4,5)P2 by a phosphatase (green) allows endocytosis (red) to complete.

Sites of endocytosis are enriched in PI(4,5)P₂, but its removal is required for endocytosis to be completed, report Sun et al. (page 355).

The membrane minor phospholipid PI(4,5)P₂ has long been implicated in endocytosis. Many endocytotic proteins contain binding sites for it, and, without this binding, endocytosis is impaired. Evidence for the enrichment of PI(4,5)P₂ at sites of endocytosis, however, has been lacking. The team used a PI(4,5)P₂- binding domain, tagged with a fluorescent protein, to follow the dynamics of PI(4,5)P₂ during endocytosis in live cells.

They show that PI(4,5)P₂ is present in patches on the membrane and that these patches move into the cell over time and disappear. To confirm this inward movement was indeed endocytosis, the team used a second fluorescently labeled endocytosis coat protein and showed that the two colors colocalized.

The disappearance of PI(4,5)P₂ coincided with the recruitment of phosphoinositide phosphatase, which is known to break down PI(4,5)P₂. In cells in which PI(4,5)P₂ breakdown was impaired, the team saw abnormal membrane invaginations that are thought to be the sites of multiple attempts and failures at endocytosis.

Indeed, without PI(4,5)P₂ turnover, the endocytotic machinery still arrived at the membrane patches but hung around for longer without completing their job. It thus appears that the breakdown of PI(4,5)P₂ is required for the scission of endocytotic vesicles.

Ruth Williams

ruth.williams{at}rockefeller.edu

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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
J. Cell Biol. 2007 177: 355-367. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF, 943K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Williams, R. Search for Related Content PubMed Articles by Williams, R. Related Collections Related Article Social Bookmarking                            What's this?