title: LIN-12/Notch trafficking and regulation of DSL ligand activity during vulval induction in Caenorhabditis elegans.
abstract: A novel mode of crosstalk between the EGFR-Ras-MAPK and LIN-12/Notch pathways occurs during the patterning of a row of vulval precursor cells (VPCs) in Caenorhabditis elegans: activation of the EGFR-Ras-MAPK pathway in the central VPC promotes endocytosis and degradation of LIN-12 protein. LIN-12 downregulation in the central VPC is a prerequisite for the activity of the lateral signal, which activates LIN-12 in neighboring VPCs. Here we characterize cis-acting targeting sequences in the LIN-12 intracellular domain and find that in addition to a di-leucine motif, serine/threonine residues are important for internalization and lysine residues are important for post-internalization trafficking and degradation. We also identify two trans-acting factors that are required for post-internalization trafficking and degradation: ALX-1, a homolog of yeast Bro1p and mammalian Alix and the WWP-1/Su(dx)/Itch ubiquitin ligase. By examining the effects of mutated forms of LIN-12 and reduced wwp-1 or alx-1 activity on subcellular localization and activity of LIN-12, we provide evidence that the lateral signal-inhibiting activity of LIN-12 resides in the extracellular domain and occurs at the apical surface of the VPCs.
authors.affiliation: Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Shaye
authors.forename: Iva
authors.initials: I
authors.lastname: Greenwald
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D005260:Female; D007930:Leucine / Q000378:metabolism; D008024:Ligands; D008239:Lysine / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D021381:Protein Transport / Q000502:physiology; D051880:Receptors, Notch / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013912:Threonine / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000502:physiology; D014844:Vulva / Q000196:embryology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D008024:Ligands; C082460:Lin-12 protein, C elegans; D008565:Membrane Proteins; D051880:Receptors, Notch; C095846:Sur-2 protein, C elegans; D014157:Transcription Factors; C484140:dsl-1 protein, C elegans; D013912:Threonine; D012694:Serine; C413402:wwp-1 protein, C elegans; D044767:Ubiquitin-Protein Ligases; D007930:Leucine; D008239:Lysine