Identification of genes required for secretory granule exocitosis using a reverse genetic approach in Drosophila melanogaster

SEBASTIAN PÉREZ PANDOLFO; MARIANA MELANI; ROCIO VICTORIA DE LA RIVA CARRASCO; WAPPNER, PABLO

Conferencia; Buenos Aires Research Conference on Autophagy; 2017

Secretory glands are made of epithelial cells specialized in massive protein secretion. Secretory cargoes emerge from the Golgi apparatus inside membrane-bound vesicles. These vesicles undergo a process of maturation that includes homotypic fusion, acidification and condensation. Mature vesicles contact the plasma membrane, coat with actin, and release their cargo to the lumen of the gland. Drosophila salivary glands are a useful model to study secretory vesicle biogenesis and exocytosis. Salivary gland cells produce mucins (glue proteins) that are packed in secretory granules, which are exocytosed to the lumen of the gland and later excreted, gluing the prepupa to the substrate. We are studying the mechanism by which zonda, a gene that we recently reported as an early component of the autophagy pathway, regulates this process. Zonda mutant cells fail to secrete glue proteins, which instead, are retained in large granules suggesting that Zonda may be involved in the recognition, tethering or fusion of the granules with the plasma membrane. To identify components that might cooperate with Zonda in this process we perform a screen of candidate genes in which we abrogated the activity of Rabs, SNAREs and exocyst subunits to find those that phenocopy Zonda loss of function. Interestingly, we found that the depletion of RalA, a GTPase related with the exocyst complex, phenocopies Zonda?s loss of function. These observations pave the way to further research to understand the relation between these two proteins during exocitosis.