Regulated exocytosis in Drosophila melanogaster requires Zonda: a novel role for a transmembrane immunophilin.

ROMERO, NURIA M.; MELANI, MARIANA; PEREZ PANDOLFO ; KATZ, MAXIMILIANO J.; DE LA RIVA-CARRASCO, ROCÍO V.; WAPPNER, PABLO

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

Exocytosis is a fundamental process not only for cellular homeostasis but also for short and long distance communication between cells. Regulated exocytosis allows the coordinated and synchronized development of organs and tissues by the release of hormones and neuropeptides. We are characterizing the function of a membrane immunophilin named Zonda in regulated exocytosis. We determined that Zonda is required for exocytosis to occur in different secretory tissues such as the ring gland, the IPCs and the salivary glands. The salivary gland of Drosophila?s larvae is an exceptional model to study regulated exocytosis. It produces mucins that are packed into secretory granules (SG) that after a hormonal stimuli release their content to the glandular lumen. For exocytosis to occur, the SG gets in contact with the plasma membrane, and its content is pushed into the lumen by the contraction of an actin-myosin contractile cage. Nevertheless, the molecular components responsible for directioning, tethering and fusion of the SG with the plasma membrane are unknown. We found that Zonda is required specifically for fusion between the SG and the plasma membrane. We carried out an RNAi screen in which we interfered 57 genes looking for potential Zonda interactors. We identified that the small GTPase RalA phenocopies Zonda. Moreover, Zonda?s overexpression rescues the exocytosis defects generated by loss of RalA. We are currently exploring the mechanism by which Zonda and RalA might work together.