Drosophila Rolling Blackout Displays Lipase Domain-Dependent and -Independent Endocytic Functions Downstream of Dynamin

作者：Vijayakrishnan Niranjana; Phillips Scott E; Broadie Kendal^*

来源：Traffic, 2010, 11(12): 1567-1578.

DOI：10.1111/j.1600-0854.2010.01117.x

• endocytosis
• endosome
• Garland cell
• giant fiber circuit
• neuromuscular junction
• serine esterase
• shibire
• synaptic vesicle

Drosophila temperature-sensitive rolling blackout (rbots) mutants display a total block of endocytosis in non-neuronal cells and a weaker, partial defect at neuronal synapses. RBO is an integral plasma membrane protein and is predicted to be a serine esterase. To determine if lipase activity is required for RBO function, we mutated the catalytic serine 358 to alanine in the G-X-S-X-G active site, and assayed genomic rescue of rbo mutant non-neuronal and neuronal phenotypes. The rboS358A mutant is unable to rescue rbo null 100% embryonic lethality, indicating that the lipase domain is critical for RBO essential function. Likewise, the rboS358A mutant cannot provide any rescue of endocytic blockade in rbots Garland cells, showing that the lipase domain is indispensable for non-neuronal endocytosis. In contrast, rbots conditional paralysis, synaptic transmission block and synapse endocytic defects are all fully rescued by the rboS358A mutant, showing that the RBO lipase domain is dispensable in neuronal contexts. We identified a synthetic lethal interaction between rbots and the well-characterized dynamin GTPase conditional shibire (shits1) mutant. In both non-neuronal cells and neuronal synapses, shits1; rbots phenocopies shits1 endocytic defects, indicating that dynamin and RBO act in the same pathway, with dynamin functioning upstream of RBO. We conclude that RBO possesses both lipase domain-dependent and scaffolding functions with differential requirements in non-neuronal versus neuronal endocytosis mechanisms downstream of dynamin GTPase activity.

• 出版日期2010-12