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

Abstract

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 vesicles^2,3. The shibire mutation also affects many tissues outside the nervous system^4–7. 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 dynamin^8,9, 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.