title: Numb independently antagonizes Sanpodo membrane targeting and Notch signaling in Drosophila sensory organ precursor cells.
abstract: In Drosophila, mitotic neural progenitor cells asymmetrically segregate the cell fate determinant Numb in order to block Notch signaling in only one of the two daughter cells. Sanpodo, a membrane protein required for Notch signaling in asymmetrically dividing cells, is sequestered from the plasma membrane to intracellular vesicles in a Numb-dependent way after neural progenitor cell mitosis. However, the significance of Numb-dependent Sanpodo regulation is unclear. In this study, we conducted a structure-function analysis to identify the determinants of Sanpodo targeting in vivo. We identified an NPAF motif in the amino-terminal cytoplasmic tail of Sanpodo, which is conserved among insect Sanpodo homologues. The Sanpodo NPAF motif is predicted to bind directly to the Numb phosphotyrosine-binding domain and is critical for Numb binding in vitro. Deletion or mutation of the NPAF motif results in accumulation of Sanpodo at the plasma membrane in Numb-positive cells in vivo. Genetic analysis of Sanpodo NPAF mutants shows that Numb-dependent Sanpodo endocytic targeting can be uncoupled from Notch signaling regulation. Our findings demonstrate that Sanpodo contains an evolutionarily conserved motif that has been linked to Numb-dependent regulation in vertebrates and further support the model that Numb regulates Notch signaling independently of Sanpodo membrane trafficking in neural progenitor cells.
authors.affiliation: Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Tong
authors.forename: Diana
authors.initials: D
authors.lastname: Zitserman
authors.forename: Ilya
authors.initials: I
authors.lastname: Serebriiskii
authors.forename: Mark
authors.initials: M
authors.lastname: Andrake
authors.forename: Roland
authors.initials: R
authors.lastname: Dunbrack
authors.forename: Fabrice
authors.initials: F
authors.lastname: Roegiers
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D007605:Juvenile Hormones / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism; D008938:Mitosis; D008969:Molecular Sequence Data; D009474:Neurons / Q000502:physiology*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051880:Receptors, Notch / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D029721:Drosophila Proteins; D007605:Juvenile Hormones; D008840:Microfilament Proteins; D051880:Receptors, Notch; C060606:numb protein, Drosophila; C112833:spdo protein, Drosophila