Abstract
This protocol describes how to measure interaction between Notch receptors and their ligands by cell-based assay using Dynabeads. We have used the protocol to determine binding capacity between Notch1-transfected HEK293T cells and ligand-coated Dynabeads. Expression of Eogt in Notch1-expressing cells promoted binding toward DLL4-coated beads, but not JAG1-coated beads. The Notch-ligand assay using Dynabeads suggested that Eogt facilitates DLL4-Notch1 interaction (Sawaguchi et al., 2017).
Keywords: Notch, Ligand binding assay, Dynabeads, Dll4-Fc
Background
The Notch signal pathway regulates many types of cellular events such as proliferation, cell fate determination, and cellular differentiation in all metazoans (Mumm and Kopan, 2000). To initiate Notch signaling, extracellular domains of Notch receptors engage their ligands, Delta like (DLL) ligands or Jagged (JAG) ligands, presented on opposing cells. Epidermal growth factor (EGF)-like domains of Notch receptors are critical for the ligand binding and modified by specific glycans including O-fucose, O-glucose, and O-GlcNAc glycans (Stanley and Okajima, 2010). Some of these glycans serve as regulators of Notch signaling pathway by modulating physical interaction between Notch receptors and ligands (Moloney et al., 2000). To investigate whether O-GlcNAc regulates Notch-ligand interaction, we developed a novel Dynabeads-based Notch-ligand binding assay. In this assay, Notch receptors expressed on HEK293T cells are incubated with Dynabeads Protein A coated with DLL4-Fc or JAG1-Fc. Unlike soluble ligands used for other binding assay, direction of Notch ligands is fixed on the beads so that they behave like ligand-expressing cells. Thus, the detected binding represents trans-binding rather than cis-binding, which occurs when Notch receptors and their ligands are expressed in the same cells. This assay demonstrated that O-GlcNAc modification of Notch1 by Eogt potentiates Notch1 binding to DLL4 without affecting JAG1 binding (Sawaguchi et al., 2017).
Materials and Reagents
Equipment
Procedure
Data analysis
In the previously published experiments (Sawaguchi et al., 2017), data were shown as mean ± SD from three independent experiments. In each experiment, 50 GFP-positive cells are analyzed. Welch’s t-test was used.
Notes
This protocol provides high reproducibility. Counting 50 GFP-positive cells gives low variability in most experiments.
Recipes
Acknowledgments
This protocol was modified from the previously published article (Sawaguchi et al., 2017). This work was supported by Japan Society for the Promotion of Science grants # JP15K15064 to TO and MO, #JP26110709 to TO, #JP26291020 to TO, #JP15K18502 to MO, #JP16J00004 to MO; Takeda Science Foundation to TO; Japan Foundation for Applied Enzymology to TO; YOKOYAMA Foundation for Clinical Pharmacology #YRY-1612 to MO.
References
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