Structure-function analysis of delta trafficking, receptor binding and signaling in Drosophila.
The transmembrane proteins Delta and Notch act as ligand and receptor in a conserved signaling pathway required for a variety of cell fate specification events in many organisms. Binding of Delta to Notch results in a proteolytic cascade that releases the Notch intracellular domain, allowing it to participate in transcriptional activation in the nucleus. Recent research has implicated the endocytic and ubiquitylation machinery as essential components of Delta-Notch signaling. Our analysis of chimeric and missense Delta variants has delineated a number of structural requirements for Delta trafficking, receptor binding, and signaling. We find that while the Delta N-terminal domain is necessary and sufficient for binding to Notch, the integrity of the epidermal-growth-factor-like repeat (ELR) 2 is also required for Notch binding. Screening of 117 Delta mutant lines for proteins that exhibit aberrant subcellular trafficking has led to the identification of 18 Delta alleles (DlTD alleles) that encode "trafficking-defective" Delta proteins. We find, unexpectedly, that many DlTD alleles contain missense mutations in ELRs within the Delta extracellular domain. Finally, we find that two DlTD alleles contain lysine missense mutations within the Delta intracellular domain (DeltaICD) that may identify residues important for DeltaICD mono-ubiquitylation and subsequent Delta endocytosis and signaling.
Parks
Annette L
AL
Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Stout
Jane R
JR
Shepard
Scott B
SB
Klueg
Kristin M
KM
Dos Santos
Ana A
AA
Parody
Todd R
TR
Vaskova
Martina
M
Muskavitch
Marc A T
MA
D000595:Amino Acid Sequence; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004705:Endocytosis; D005260:Female; D006031:Glycosylation; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013347:Subcellular Fractions
D029742:Caenorhabditis elegans Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; C064045:delta protein