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Cell and Systems Biology
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CSB428H1F Article #1: Langevin et al.Drosophila Wing Notum Exocyst
Loss of exocyst Sec5, Sec6 and Sec15 in fly epithelia results in DE-Cad/Arm accumulating in
enlarged Rab11 recycling endosome (RE).
Rab11 interact with Sec15 and Arm interacts with Sec10, as Sec15 and Sec10 are located on RE.
The exocyst complex is important for recognition and tethering between vesicle and PM for
polarized transport to apical and basal membranes.
DE-Cad/Arm accumulate intracellularly in sec5
Crb-Sdt, Baz-Par6-aPKC, basolateral Dlg, Scrib and Fas3 was unaffected in Sec5, but DE-Cad, Arm
and D -cat accumulated in apical cytoplasm and around nucleus in punctate structures.
DE-Cad and Arm accumulate in enlarged RE in Sec5
Golgi marker Lva, EE marker Rab5 and LE marker HRS were normal, but Rab11 was distributed in
enlarged punctate structures with higher fluorescence. Some of these large RE were formed by
coalescence of smaller punctate structures. Additional RE marker was also found in higher levels.
DE-Cad and Arm colocalized with RE in WT cells. In sec5 DE-Cad and Arm was excessively
enriched in RE and colocalized with Nuf and Rab11. Even when distribution of Arm or DE-Cad was
normal, Rab11 and Nuf accumulated. Overall the RE is enlarged in sec5 and DE-Cad accumulation
is a consequence of Rab11 and Nuf accumulation in RE.
Sec5 is associated with RE and lateral cortex
In WT cells, Sec5 was found in both punctate structures colocalizing with mostly Rab11 and at cell
cortex where it colocalized with DE-Cad/Arm/AJ. Therefore Sec5 regulates size of RE and
distribution of DE-Cad.
In sec6, Sec5, DE-Cad and Arm accumulated in apical punctate structures and was reduced laterally.
RE was also enlarged and Sec5 structures colocalized with Rab11. Therefore in WT Sec5 may bind
RE before going to cell cortex and both Sec5 and Sec6 regulate the RE.
Sec15 interact with Rab11-GTP (Rab11 is GTPase). Therefore Sec15 is an effector of Rab11 and
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