CSB428H1F FINAL EXAMINATION 2009 ANSWER KEY
#1: Langevin et al.
What is the role of the exocyst complex, specifically Sec5, in delivery of DE-Cad/Arm to the plasma
membrane from the recycling endosome and how do they interact with RE components such as Rab11?
Drosophila Sec5, Sec6 and Sec15 tethers DE-Cad vesicles originating from the RE to lateral
membrane for exocytosis. Sec5 also mediates transcytosis of DE-Cad. In addition, Arm interact with
Sec10 at PM and Arm act as a landmark for DE-Cad delivery. In the absence of Sec5, Sec6 and Sec15
function, DE-Cad accumulates in an enlarged RE.
sec5 mutant notum cells generated using FLP/FRT were analyzed for different intracellular markers to
investigate the nature of the enlarged intracellular compartment. Golgi marker Lava Lamp, late
endosome marker Hepatocyte growth factor-Regulated tyrosine kinase Substrate, early endosome
marker Rab5 was distributed normally in mutant cells. But Rab11 distribution was disrupted in mutant
cells: they were found in large punctate structures with higher intensity of Rab11 and colocalized with
DE-Cad in RE. Additional RE maker Nuclear Fallout confirmed this result. This shows Sec5 is
necessary for the recycling of DE-Cad from RE to the lateral membrane
Investigate possible interaction between components of the exocyst complex with the cell cytoskeleton.
Specifically, MT have been known to play a role in vesicular trafficking, and the authors could
investigate if disruption of MT also disrupts delivery of DE-Cad to lateral membrane and
establishment of AJs. MT could be disrupted by drugs such as nocodazole or knockdown of
#2: Chaung et al.