The exocyst component Sec5 is present on endocytic vesicles in the oocyte of Drosophila melanogaster.
The exocyst is an octameric complex required for polarized secretion. Some components of the exocyst are found on the plasma membrane, whereas others are recruited to Golgi membranes, suggesting that exocyst assembly tethers vesicles to their site of fusion. We have found that in Drosophila melanogaster oocytes the majority of the exocyst component Sec5 is unexpectedly present in clathrin-coated pits and vesicles at the plasma membrane. In oocytes, the major substrate for clathrin-dependent endocytosis is the vitellogenin receptor Yolkless. A truncation mutant of Sec5 (sec5(E13)) allows the formation of normally sized oocytes but with greatly reduced yolk uptake. We find that in sec5(E13) oocytes Yolkless accumulates aberrantly in late endocytic compartments, indicating a defect in the endocytic cycling of the receptor. An analogous truncation of the yeast SEC5 gene results in normal secretion but a temperature-sensitive defect in endocytic recycling. Thus, the exocyst may act in both Golgi to plasma membrane traffic and endocytic cycling, and hence in oocytes is recruited to clathrin-coated pits to facilitate the rapid recycling of Yolkless.
Sommer
Bernhard
B
Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, England, UK.
Oprins
Adrian
A
Rabouille
Catherine
C
Munro
Sean
S
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D022163:Clathrin-Coated Vesicles / Q000378:metabolism / Q000648:ultrastructure; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism* / Q000648:ultrastructure; D004527:Egg Proteins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005260:Female; D008565:Membrane Proteins / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009865:Oocytes / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D022161:Transport Vesicles / Q000378:metabolism* / Q000648:ultrastructure
D029721:Drosophila Proteins; D004527:Egg Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; C103131:SEC5 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C502950:Sec5 protein, Drosophila; C030474:vitellogenin receptor