The syndapin protein family: linking membrane trafficking with the cytoskeleton.

Syndapins--also called PACSINs--are highly conserved Src-homology 3 (SH3)-domain-containing proteins that seem to exist in all multicellular eukaryotes. They interact with the large GTPase dynamin and several other proteins implicated in vesicle trafficking. Syndapin-dynamin complexes appear to play an important role in vesicle fission at different donor membranes, including the plasma membrane (endocytosis) and Golgi membranes. In addition, syndapins are implicated in later steps of vesicle cycling in neuronal and non-neuronal cells. Syndapins also interact with N-WASP, a potent activator of the Arp2/3 complex that forms a critical part of the actin polymerization machinery. Syndapin oligomers can thereby couple bursts of actin polymerization with the vesicle fission step involving dynamins. This allows newly formed vesicles to move away from the donor membrane driven by actin polymerization. Syndapins also engage in additional interactions with molecules involved in several signal transduction pathways, producing crosstalk at the interface between membrane trafficking and the cytoskeleton. Given the distinct expression patterns of the different syndapins and their splice forms, these proteins could have isoform-specific functions.