Dynamins are a family of approximately 100-kDa GTPases that are thought to play a pivotal role in the formation of endocytic coated vesicles. There are three dynamin genes in mammals: dynamin I is neuron-specific, dynamin II shows ubiquitous expression, and dynamin III is expressed in testis, brain, and lung. However, most studies on the functions of dynamins to date have been restricted to dynamin I. In the present study, we show that, like dynamin I, dynamin II is involved in receptor-mediated endocytosis. While this study was in progress, Jones et al. [Jones, S.M., Howell, K.E., Henley, J.R., Cao, H., and McNiven, M.A. (1998) Science 279, 573-577] reported that dynamin II is localized in the trans-Golgi network (TGN) and involved in the formation of constitutive transport vesicles and clathrin-coated vesicles from this compartment. However, immunofluorescence analyses and experiments using cells transfected with dominant-negative dynamin II failed to show any evidence for localization of dynamin II in the TGN or for its involvement in vesicle formation from this compartment. Our data thus indicate that dynamin II is involved in endocytosis but not in the formation of transport vesicles from the TGN.
