At the cell periphery, a network of actin filaments is involved in the production of clathrin-coated vesicles during endocytosis. Carreno et al. now find that actin dynamics contribute to the formation of clathrin-coated vesicles that carry material from the trans-Golgi network (TGN) to the lysosome. The protein Hip1R, known to be important at the cell surface where it binds to both actin and clathrin, is associated with clathrin-coated vesicles that bud from the TGN. When expression of Hip1R was reduced, Golgi organization was disrupted, and actin that was associated with clathrin-coated vesicles accumulated at the TGN. These effects correlated with a slowing of lysosomal enzyme exit from the Golgi, and inhibition of actin dynamics had a similar effect. Thus, Hip1R and its association with actin appear to be important not only during endocytosis at the cell surface, but also deep within the cell as clathrin-coated vesicles depart the TGN en route to lysosomes. -- SMH
J. Cell Biol. 165, 781 (2004).
