We have identified a cell signaling pathway required for preventing ectopic photoreceptor cell recruitment. The signaling cells require the activity of a deubiquitinating enzyme, called Fat facets (Faf). The function of Faf in these cells is to remove a ubiquitin (Ub) chain from a protein called Liquid facets (Lqf). As the Ub chain targets Lqf for proteasomal degradation, Faf activity increases the level of Lqf in the signaling cells. Lqf is a Drosophila homolog of epsin, a vertebrate endocytosis complex protein. The finding that Lqf is the key substrate of Faf in the Drosophila eye shows that an endocytic protein can be a target for the control of a cell communication event critical to cell determination. My talk will be about the most recent data about the function of Lqf in endocytosis, and other components of Faf/Lqf signaling pathway.