SNX1 hugs the curves

A sorting protein uses the coincidence of a lipid signal and membrane curving to direct its tubulation activity to the correct compartment, as shown by Jez Carlton, Peter Cullen (University of Bristol, UK), and colleagues. Relatives of this sorting nexin, SNX1, may control trafficking to and from a number of intracellular compartments.

SNX1 chooses its home via two membrane-binding domains. One targeting domain is the PX domain, which is known to bind to the endosomal phosphoinositide, PI3P. The second is a BAR domain, which was shown to target a fly protein to highly curved membranes and tubulate them.

Cullen's group shows that these domains combine to put mammalian SNX1 on the tubular portion of early endosomes (which also have less curved vesicular domains). This placement was needed to recycle...