Motoring microvillar membrane

Just as intestines constantly shed gut cells, so too may gut cells shed their brush border membranes. On page 671, McConnell and Tyska show that microvillar myosin-1a pulls membrane for shedding along the core actin bundle.

Myosin-1a was first seen in micrographs 30 years ago bridging the actin bundle and the overlying membrane in microvilli. But it was not until 1989 that myosin-1a was characterized as an actin plus end–directed motor. Its potential as an active motor in the microvillus, rather than mere structural element, was overlooked until now.

A motor is useful in isolated brush borders, which dramatically shear off their membranes from the base to the tip of the microvillar stalks when fed ATP. McConnell and Tyska find that this actin...