Regulated endocytic routing modulates wingless signaling in Drosophila embryos

Embryos have evolved various strategies to confine the action of secreted s ignals. Using an HRP-Wingless fusion protein to track the fate of endocytos ed Wingless, we show that degradation by targeting to lysosomes is one such strategy. Wingless protein is specifically degraded at the posterior of ea ch stripe of wingless transcription, even under conditions of over-expressi on. If lysosomal degradation is compromised genetically or chemically, exce ss Wingless accumulates and ectopic signaling ensues. In the wild-type, Win gless degradation is slower at the anterior than at the posterior. This fol lows in part from the segmental activation of signaling by the epidermal gr owth factor receptor, which accelerates Wingless degradation at the posteri or, thus leading to asymmetrical Wingless signaling along the anterior-post erior axis.