title: Endocytosis-mediated downregulation of LIN-12/Notch upon Ras activation in Caenorhabditis elegans.
abstract: The coordination of signals from different pathways is important for cell fate specification during animal development. Here, we define a novel mode of crosstalk between the epidermal growth factor receptor/Ras/mitogen-activated protein kinase cascade and the LIN-12/Notch pathway during Caenorhabditis elegans vulval development. Six vulval precursor cells (VPCs) are initially equivalent but adopt different fates as a result of an inductive signal mediated by the Ras pathway and a lateral signal mediated by the LIN-12/Notch pathway. One consequence of activating Ras is a reduction of LIN-12 protein in P6.p (ref. 2), the VPC believed to be the source of the lateral signal. Here we identify a 'downregulation targeting signal' (DTS) in the LIN-12 intracellular domain, which encompasses a di-leucine-containing endocytic sorting motif. The DTS seems to be required for internalization of LIN-12, and on Ras activation it might mediate altered endocytic routing of LIN-12, leading to downregulation. We also show that if LIN-12 is stabilized in P6.p, lateral signalling is compromised, indicating that LIN-12 downregulation is important in the appropriate specification of cell fates in vivo.
authors.affiliation: Department of Genetics and Development, and Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Shaye
authors.forename: Iva
authors.initials: I
authors.lastname: Greenwald
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000196:embryology / Q000201:enzymology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D019070:Cell Lineage; D015536:Down-Regulation; D004705:Endocytosis; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D015801:Helminth Proteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D051880:Receptors, Notch; D015398:Signal Transduction; D014844:Vulva / Q000166:cytology / Q000196:embryology / Q000201:enzymology / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; C082460:Lin-12 protein, C elegans; D008565:Membrane Proteins; D051880:Receptors, Notch; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins