Early requirement of the exocyst complex in the biogenesis of secretory granules of Drosophila melanogaster salivary glands

ROCIO V. DE LA RIVA CARRASCO; SUAREZ SOFIA; WAPPNER PABLO; SUAREZ SOFIA; WAPPNER PABLO; SEBASTIAN PEREZ PANDOLFO; MELANI MARIANA; SEBASTIAN PEREZ PANDOLFO; MELANI MARIANA; ROCIO V. DE LA RIVA CARRASCO

Congreso; X meeting of the Latin American Society for Developmental Biology; 2019

Glands and exocrine tissues relay on exocytosis to release their content into the blood or target organs. Exocytosis involves the biogenesis and maturation of an exocytic vesicle that buds from the Golgi apparatus, as well as the correct routing of the vesicle to the apical surface of the cell and its fusion with the plasma membrane (PM)to achieve the secretion of the cargo to the extracellular medium. The salivary glands of Drosophila melanogaster are a great model to study this process. During their development, salivary glands turn on the synthesis of mucins that are stored in vesicles named secretory granules (SG). SG are secreted at pupariation allowing the pupa to adhere to the substrate. Through a genetic screen we identified that the exocyst is required for SG exocytosis. The exocyst is an evolutionary conserved hetero-octameric complex whose primary function is to mediate the tethering of secretory vesicles to the PM. In the salivary glands we found an earlier function: the biogenesis of SG. The abrogation of the exocystproduces very small SG, suggesting a defect in SG maturation. We also detect that GFP- musin is trapped within a network, suggesting that exocytic vesicles cannot bud from the Golgi apparatus. Markers of mature SG are not recruited to exocyst-knock down SG further indicating a defect in their maturation. We will analyze Golgi and late endosome markers as well as other markers of SG maturation in order to define the early function of the exocyst in exocytosis.