Endocytic internalization routes required for delta/notch signaling.
The internalization of transmembrane receptors from the cell surface plays a central role in signal regulation. Receptor internalization can occur through different routes; however, because of the difficulty in selectively blocking these routes in vivo, their roles in signaling are poorly understood. Here we use null mutations in Drosophila dynamin, clathrin, and AP-2 adaptor subunits to analyze internalization requirements for the Delta ligand and its receptor, Notch. Bulk Notch is internalized via AP-2-dependent endocytosis, but signaling by Notch requires AP-2-independent clathrin-dependent endocytosis, highlighting a distinction between Notch endocytic routes required for degradation versus signaling activation. Signaling by Delta requires dynamin, but whether this generates a pulling force of Delta on Notch or allows for Delta entry into a recycling pathway to gain signaling competence is widely debated. Surprisingly, we show that signaling by Delta in germline cells can occur by clathrin-independent endocytosis, when endosomal entry is blocked, and when activity of Rab11 or its effectors is reduced, suggesting that Delta need not pass through a recognized recycling pathway to achieve signaling competence. The absolute requirement for dynamin-dependent endocytosis but not endosomal entry or Rab11 activity supports "pulling force" rather than "recycling" models for Delta activation.
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720-3200, USA.
Sarah L
SL
Windler
David
D
Bilder
D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D002966:Clathrin / Q000235:genetics / Q000502:physiology; D004330:Drosophila / Q000235:genetics / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D034281:Dynamins / Q000235:genetics / Q000502:physiology; D004705:Endocytosis / Q000235:genetics / Q000502:physiology*; D017344:Genes, Insect; D005816:Genetic Complementation Test; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000502:physiology*; D009154:Mutation; D051880:Receptors, Notch / Q000502:physiology*; D015398:Signal Transduction
D033962:Adaptor Protein Complex 2; D002966:Clathrin; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C497759:N protein, Drosophila; D051880:Receptors, Notch; C064045:delta protein; D034281:Dynamins; C439628:shi protein, Drosophila