Notch receptor–ligand binding and activation: Insights from molecular studies

Abstract

Highlights► We review the high resolution structures of the Notch receptor and ligands. ► Highlight the docking events of Notch receptor and ligand at the cell surface. ► Indicate the future challenges in understanding Notch receptor–ligand interactions.

Development of an optimized synthetic Notch receptor as an in vivo cell–cell contact sensor

“…One of the best characterized RIPdependent signaling molecules is Notch, a membrane receptor with a single transmembrane domain (10). Binding of a ligand to the extracellular domain of Notch induces proteolytic cleavage and release of its intracellular domain (ICD), which translocates to the nucleus and functions as a transcriptional factor (11) (Fig. 1 A and B).…”

“…First, the system is highly compact because it only involves a ligand and a receptor, together with several broadly expressed proteases (12). Second, unlike most other receptors, such as gated ion channels, G-protein-coupled receptors, and receptor tyrosine kinases, Notch is activated through mechanical forces generated by ligand-receptor binding (11,13), such that the binding and activation machinery can be uncoupled to allow rewiring of the system with artificial interacting domains. Third, the ICD of Notch, which mediates downstream effects, can be replaced by other transcriptional factors without affecting its proteolytic activation (14,15).…”

Endocytosis in Notch Signaling Activation

“…Let us now briefly analyze the architecture of Notch receptors and ligands to highlight those structural features that are key factors in endocytosis-mediated signaling activation (reviewed in [80,81]). …”

“…Going from the N-to the C-terminus, mammalian Notch receptors contain five regions ( Fig.1): (i) a variable number of Epidermal growth factor (EGF)-like domains (spanning from 29 to 36 domains in mammals), many of which contain calcium-binding sites (cbEGFlike domains); (ii) three Lin-12-Notch repeats (LNR); (iii) a hydrophobic region for receptor heterodimerization (HD domain), which is cleaved at the S1 site (at 70 amino acids from the transmembrane domain), and which contains the S2 site (at 12 amino acids from the transmembrane domain); (iv) the transmembrane domain, which bears the S3 cleavage site, a substrate for regulated intramembrane proteolysis (RIP) by the presenilin/ -secretase complex to liberate the intracellular domain; (v) the NICD, which contains a RAM domain (for Notch binding to the transcription factor CSL/CBF1/Suppressor of Hairless/Lag-1)), seven ankyrin repeats (ANK), a transcription activation domain (TAD) and a PEST domain (which is implicated in NICD degradation by proteolysis and whose mutation leads to increased receptor stability , a condition that closely correlates with cancer, including some T-cell leukemias) (reviewed in [80]). LNRs, plus the heterodimerization domain, form the so-called negative regulatory region (NRR), which folds onto the S2 cleavage site by means of extensive interdomain interactions [94][95][96][97][98].…”

Stimulation of Notch Signaling in Mouse Osteoclast Precursors

“…The stretching force of ligand binding induces conformational changes in the Notch receptor that facilitate extracellular cleavage of the receptor by TNFalpha converting enzyme (TACE) followed by an intracellular cleavage event mediated by a presenilin-containing gamma-secretase complex (γ-secretase). γ-secretase releases the Notch intracellular domain (NICD) which translocates into the nucleus where it forms a transcriptional activation complex with CBF-1-Su(H)-Lag-1 (CSL), mastermind-like (MAML), and cell type-specific factors to drive expression of target genes 5 .…”