Dynamin-like protein encoded by the Drosophila shibire gene associated with vesicular traffic

TEMPERATURE-sensitive paralysis is the most striking defect of adult Drosophila carrying the shibire mutation1. This is believed to be due to a reversible block of endocytosis, which prevents membrane cycling and thus depletes synaptic vesicles2,3. The shibire mutation also affects many tissues outside the nervous system4–7. We have now mapped and characterized the shibire gene. A 275-kilobase yeast artificial chromosome was subcloned into cosmids, among which the gene was then located by analysing with restriction-fragment length polymorphisms. A 15-kilobase fragment of wild-type DNA rescues the mutant phenotype and the sequence of two mutant alleles show differences with wild type, demonstrating that we have isolated the shibire gene. The gene encodes a protein that is highly similar to rat dynamin8,9, 69% of the amino-acid sequence is identical. Dynamin is a GTP-driven mechanochemical enzyme related to mammalian mx-proteins10 and to the yeast vpsl gene product11. Because the shibire gene product and dynamin have extensive similarity, we propose that they are cognate homologues. Dynamin causes microtubules to slide along each other in vitro12 and in extracts it is associated with a distinct, but so far uncharacterized, membrane fraction13. In light of the shibire phenotype, we suggest that these proteins provide the motor for vesicular transport during endocytosis.