Dual function C-terminal domain of dynamin-1: Modulation of self-assembly by interaction of the assembly site with SH3 domains

Impairment of endocytosis by mutational targeting of dynamin-1 GTPases can result in paralysis and embryonic lethality. Dynamin-1 assembles at coated pits where it functions to cleave vesicles from donor membranes. Receptor e ndocytosis is modulated by SH3 (src homology 3) domain proteins, which dire ctly bind to dynamin C-terminal proline motif sequences, affecting: both th e dynamin GTPase activity and its recruitment to coated pits. We have deter mined that dynamin-dynamin interactions, which are required for dynamin hel ix formation, involve these same SH3 domain-binding C-terminal proline moti f sequences. Consequently, SH3 domain proteins induce the in vitro disassem bly of dynamin helices. Our results therefore suggest the the dual function of the dynamin C-terminus (involving amino acids 800-840) pel-mits direct regulation of dynamin assembly and function through interaction with SH3 do main proteins, Additionally, the N-terminal GTPase domain plays an importan t role in assembly. Finally, we show that the central PH (pleckstrin homolo gy) domain exerts a strong inhibitory effect on the capacity for dynamin-1 self-assembly.