Actin gets Hip at the TGN

A thick mess of cortical actin works intimately with clathrin to assist endocytosis at the plasma membrane, with the actin providing force for vesicle fission, propulsion, or both. Now, Carreno et al. (page 781) show that the less well-known actin around the trans-Golgi network (TGN) also aids in the trafficking of clathrin-coated vesicles from TGN to lysosomes.

The clue for such a link came from studies of Hip1R, a protein that links actin to clathrin-coated endocytic vesicles. When the team knocked down Hip1R expression using RNAi, they found abnormally swollen Golgi cisternae with many extra buds or vesicles stuck to the surface of the TGN. Subsequent fluorescent phalloidin staining of Hip1R-depleted cells also revealed abnormal actin formations at the Golgi surface. Similar actin-based curved structures have also been found when...