Notch ligand activity is modulated by glycosphingolipid membrane composition in Drosophila melanogaster

Abstract

Endocytosis of the transmembrane ligands Delta (Dl) and Serrate (Ser) is required for the proper activation of Notch receptors. The E3 ubiquitin ligases Mindbomb1 (Mib1) and Neuralized (Neur) regulate the ubiquitination of Dl and Ser and thereby promote both ligand endocytosis and Notch receptor activation. In this study, we identify the α1,4-N-acetylgalactosaminyltransferase-1 (α4GT1) gene as a gain of function suppressor of Mib1 inhibition. Expression of α4GT1 suppressed the signaling and endocytosis defects of Dl and Ser resulting from the inhibition of mib1 and/or neur activity. Genetic and biochemical evidence indicate that α4GT1 plays a regulatory but nonessential function in Notch signaling via the synthesis of a specific glycosphingolipid (GSL), N5, produced by α4GT1. Furthermore, we show that the extracellular domain of Ser interacts with GSLs in vitro via a conserved GSL-binding motif, raising the possibility that direct GSL–protein interactions modulate the endocytosis of Notch ligands. Together, our data indicate that specific GSLs modulate the signaling activity of Notch ligands.

Deciphering the Glycolipid Code of Alzheimer's and Parkinson's Amyloid Proteins Allowed the Creation of a Universal Ganglioside-Binding Peptide

“…A broad range of SBDs have been identified in phylogenetically-distant proteins including microbial [9], [10], insect [7] and human proteins [11], [13], [14]. These discoveries have enabled to draw a photofit of the SBD, which is typically a looped domain with a central aromatic residue and a basic amino acid at each end [1].…”

Neurofibromatosis-like phenotype in Drosophila caused by lack of glucosylceramide extension

“…One is that the phenotype is caused by lack of elongated GSLs, as these play important roles in cell recognition and signaling by confining signal transduction proteins to selected membrane compartments (4). In addition, elongated GSLs directly interact with membrane proteins that modulate receptor activation via modification of receptor dimerization, recycling, and galectin-mediated clustering (26)(27)(28)(29). Importantly, GlcCer and MacCer are minor components of the GSL repertoire in extracts from Drosophila embryos and larvae because they represent biosynthetic intermediates for elongated GSLs (30).…”

Molecular Basis for the Glycosphingolipid-Binding Specificity of α-Synuclein: Key Role of Tyrosine 39 in Membrane Insertion

“…Overall, these data indicated that the N-terminal parts of α-synuclein and Aβ share a common motif with high structural homology and significant sequence similarity. Since both the 34-45 fragment of α-synuclein [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], the human cellular prion protein PrP (192-209), a 14-mer GM1-binding peptide selected from a phage display library, and Aβ (fragment [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Identical amino acids are indicated in yellow ( ⁎ ) and amino acids of the same class (conserved substitutions such as basic for basic or aromatic for aromatic) in blue (:).…”

“…21 This domain, initially identified in the V3 loop of the HIV-1 surface envelope glycoprotein gp120, 22 has been found later in PrP and Aβ, 10,23 bacterial toxins and adhesins, 24 membrane proteins and receptors, 25,26 and more recently in α-synuclein. 14 So far, the strategy to detect a SBD has been (i) to perform structure similarity searches with the combinatorial extension (CE) method, 10,27 using the prototype HIV-1 gp120 V3 loop as template, or (ii) to look for the presence of short motifs containing the key amino acid residues listed above (aromatic, Gly and/or Pro, basic), especially when the three-dimensional structure of the protein is unknown.…”