Role of conserved intracellular motifs in Serrate signalling, cis-inhibition and endocytosis.
Notch is the receptor in a signalling pathway that operates in a diverse spectrum of developmental processes. Its ligands (e.g. Serrate) are transmembrane proteins whose signalling competence is regulated by the endocytosis-promoting E3 ubiquitin ligases, Mindbomb1 and Neuralized. The ligands also inhibit Notch present in the same cell (cis-inhibition). Here, we identify two conserved motifs in the intracellular domain of Serrate that are required for efficient endocytosis. The first, a dileucine motif, is dispensable for trans-activation and cis-inhibition despite the endocytic defect, demonstrating that signalling can be separated from bulk endocytosis. The second, a novel motif, is necessary for interactions with Mindbomb1/Neuralized and is strictly required for Serrate to trans-activate and internalise efficiently but not for it to inhibit Notch signalling. Cis-inhibition is compromised when an ER retention signal is added to Serrate, or when the levels of Neuralized are increased, and together these data indicate that cis-inhibitory interactions occur at the cell surface. The balance of ubiquitinated/unubiquitinated ligand will thus affect the signalling capacity of the cell at several levels.
Glittenberg
Marcus
M
Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK.
Pitsouli
Chrysoula
C
Garvey
Clare
C
Delidakis
Christos
C
Bray
Sarah
S
D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster; D004705:Endocytosis / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D000072100:Jagged-1 Protein; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000235:genetics; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D029721:Drosophila Proteins; D036341:Intercellular Signaling Peptides and Proteins; D000072100:Jagged-1 Protein; D008565:Membrane Proteins; D051881:Receptor, Notch1; C000606278:Ser protein, Drosophila; D000072099:Serrate-Jagged Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; C071006:neur protein, Drosophila