Abstract
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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Amino Acid Motifs / genetics
-
Animals
-
Calcium-Binding Proteins / genetics
-
Calcium-Binding Proteins / metabolism*
-
Cell Membrane / genetics
-
Cell Membrane / metabolism
-
Drosophila Proteins / genetics
-
Drosophila Proteins / metabolism*
-
Drosophila melanogaster
-
Endocytosis / physiology*
-
Endoplasmic Reticulum / genetics
-
Endoplasmic Reticulum / metabolism*
-
Intercellular Signaling Peptides and Proteins / genetics
-
Intercellular Signaling Peptides and Proteins / metabolism*
-
Jagged-1 Protein
-
Membrane Proteins / genetics
-
Membrane Proteins / metabolism*
-
Protein Binding
-
Protein Processing, Post-Translational / physiology*
-
Protein Structure, Tertiary / genetics
-
Receptor, Notch1 / genetics
-
Receptor, Notch1 / metabolism
-
Serrate-Jagged Proteins
-
Signal Transduction / genetics
-
Signal Transduction / physiology*
-
Transcriptional Activation / genetics
-
Ubiquitin / genetics
-
Ubiquitin / metabolism
-
Ubiquitin-Protein Ligases / genetics
-
Ubiquitin-Protein Ligases / metabolism*
Substances
-
Calcium-Binding Proteins
-
Drosophila Proteins
-
Intercellular Signaling Peptides and Proteins
-
Jagged-1 Protein
-
Membrane Proteins
-
Receptor, Notch1
-
Ser protein, Drosophila
-
Serrate-Jagged Proteins
-
Ubiquitin
-
Ubiquitin-Protein Ligases
-
neur protein, Drosophila