Association of Endophilin B1 with Cytoplasmic Vesicles

Abstract

Endophilins are SH3-and BAR domain-containing proteins implicated in membrane remodeling and vesicle formation. Endophilins A1 and A2 promote the budding of endocytic vesicles from the plasma membrane, whereas endophilin B1 has been implicated in vesicle budding from intracellular organelles, including the trans-Golgi network and late endosomes. We previously reported that endophilins A1 and A2 exist almost exclusively as soluble dimers in the cytosol. Here, we present results of fluorescence fluctuation spectroscopy analyses indicating that, in contrast, the majority of endophilin B1 is present in multiple copies on small, highly mobile cytoplasmic vesicles. Formation of these vesicles was enhanced by overexpression of wild-type dynamin 2, but suppressed by expression of a catalytically inactive dynamin 2 mutant. Using dual-color heterospecies partition analysis, we identified the epidermal growth factor receptor on endophilin B1 vesicles. Moreover, a proportion of endophilin B1 vesicles also contained caveolin, whereas clathrin was almost undetectable on those vesicles. These results raise the possibility that endophilin B1 participates in dynamin 2-dependent formation of a population of transport vesicles distinct from those generated by A-type endophilins.

Arc/Arg3.1 has an activity-regulated interaction with PICK1 that results in altered spatial dynamics

“…Recent studies have further supported the role of this interaction in the postsynaptic terminal by demonstrating that Arc can stimulate the polymerization and activity of dynamin 2 and dynamin 3, while presynaptic dynamin 1 was not shown to be affected 9 . Conversely, endophilins are ~40 kDa proteins with C-terminal BAR (Bin/Amphiphysin/Rvs) domains that homodimerize into crescent-shaped structures that induce and stabilize membrane curvature at the necks of budding endocytic vesicles 9 , 14 . The Arc-binding determinant has been localized to residues 218–254 of endophilin which corresponds to the C-terminal of the BAR domain 10 .…”