Nat. Cell Biol. 15, 967–977 (2013); published online 14 July 2013; corrected after print 28 August 2013

In the version of this Article originally published, there was an error in Fig. 8e. The arrow beside ARF in green should have been pointing up and the arrow beside ARF in red should have been pointing down. This has been corrected in the HTML and PDF versions of the Article.