title: Role of recycling, Mindbomb1 association, and exclusion from lipid rafts of δ-like 4 for effective Notch signaling to drive T cell development.
abstract: Intrathymic T cell development is predicated on the Notch1 ligand Delta-like (Dll) 4. However, both Dll4 and Dll1 can support T cell development in vitro. Endocytosis of Dll1 is important for Notch activation, whereas currently there is no evidence for the role of Dll4 endocytosis in T cell development. To elucidate this, we generated Dll4 constructs that modify or inhibit endocytosis. Our results show that targeting the intracellular domain affects Dll4's ability to induce Notch target gene expression, support efficient T cell development, and inhibit B cell development. Dll4 function relies on a combination of factors, which include strong Mindbomb1 (Mib1) association, ubiquitination, and internalization and recycling back to the cell surface, to engage Notch1 effectively. Distinct membrane localization and the Delta/Serrate/Lag2 (DSL) domain were important for Dll4 function. These features are consistent with a "recycling" model, but not in opposition to a "mechano-transduction" model, whereby Dll4 is able to engage Notch and create a pulling force required to activate signaling, leading to the induction of T-lineage development. Taken together, in contrast to Dll1, Dll4 does not localize to lipid rafts and shows stronger association with Mib1 and increased Notch1 uptake, which likely account for its superior ability to induce T cell development.
authors.affiliation: Department of Immunology, University of Toronto and Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada.
authors.forename: Divya K
authors.initials: DK
authors.lastname: Shah
authors.forename: Mahmood
authors.initials: M
authors.lastname: Mohtashami
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Zúñiga-Pflücker
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002135:Calcium-Binding Proteins; D002453:Cell Cycle / Q000235:genetics / Q000276:immunology*; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D005260:Female; D005333:Fetus / Q000166:cytology / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency* / Q000378:metabolism; D008024:Ligands; D021962:Membrane Microdomains / Q000235:genetics* / Q000276:immunology; D008565:Membrane Proteins / Q000172:deficiency* / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D011247:Pregnancy; D051881:Receptor, Notch1 / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054875:Ubiquitination / Q000235:genetics / Q000276:immunology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D008565:Membrane Proteins; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; C470629:MIB1 protein, mouse; D044767:Ubiquitin-Protein Ligases