A glycosphingolipid binding domain controls trafficking and activity of the mammalian notch ligand delta-like 1.
The activity of Notch ligands is tightly regulated by trafficking events occurring both before and after ligand-receptor interaction. In particular endocytosis and recycling have been shown to be required for full signaling activity of the ligands before they encounter the Notch receptor. However little is known about the precise endocytic processes that contribute to ligand internalization. Here we demonstrate that endocytosis contributes to Dll1 signaling activity by preserving the ligand from shedding and degradation. We further show that the glycosphingolipid-binding motif originally identified in Drosophila Notch ligands is conserved in mammals and is necessary for Dll1 internalization. Mutation of its conserved tryptophan residue results in a Dll1 molecule which is rapidly inactivated by shedding and degradation, does not recycle to the cell surface and does not activate Notch signaling. Finally, silencing in the signal-sending cells of glucosylceramide synthase, the enzyme implicated in the initial phase of glycosphingolipid synthesis, down-regulates Notch activation. Our data indicate that glycosphingolipids, by interacting with Dll1, may act as functional co-factors to promote its biological activity.
Unité de Signalisation Moléculaire et Activation Cellulaire, URA CNRS 2582, Institut Pasteur, Paris, France.
Sara Farrah
SF
Heuss
Nadine
N
Tarantino
Jacques
J
Fantini
Delphine
D
Ndiaye-Lobry
Julien
J
Moretti
Alain
A
Israël
Frédérique
F
Logeat
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D020868:Gene Silencing; D005964:Glucosyltransferases / Q000235:genetics; D006028:Glycosphingolipids / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D008563:Membrane Lipids / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability; D021381:Protein Transport; D034622:RNA Interference; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction
D006028:Glycosphingolipids; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D008563:Membrane Lipids; D051880:Receptors, Notch; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase