Dynamin-independent synaptic vesicle retrieval?

A new study proposes that synaptic vesicle endocytosis at a large synaptic terminal is partly independent of dynamin and GTP hydrolysis, suggesting a new mechanism leading to vesicle fission and maintenance of neurotransmission. Among the most astonishing mutants in flies are the temperature-sensitive alleles of shibire. These mutants are paralyzed when their temperature is raised to 30 °C, yet they resume activity rapidly after their return to 25 °C. Their paralysis is mirrored by the trapped endocytic intermediates that decorate vesicle-depleted synapses of shibire mutants at the elevated temperature1. The dynamin GTPase encoded by the shibire gene has since been implicated as being important in endocytic events. Dynamin’s GTPase activity is required to pinch vesicles off the plasma membrane once a critical curvature is reached during endocytosis2. Mutants and biochemicals that inhibit this ‘pinchase ’ activity have become standard tools for assessing the importance of endocytosis at synapses and elsewhere. In the current issue, Xu et al.3 report an elegant set of experiments that led them to propose that at least some components of synaptic vesicle endocytosis operate independently o