A fluorescent indicator for tyrosine phosphorylation-based insulin signaling pathways

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Signaling

Background:

• Insulin signaling is a critical pathway regulating glucose metabolism.
• Tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) is a key early event in this pathway.
• Accurate detection of IRS-1 phosphorylation is essential for studying insulin resistance and diabetes.

Purpose of the Study:

• To develop a novel fluorescent indicator for real-time monitoring of tyrosine phosphorylation in insulin signaling.
• To utilize Förster Resonance Energy Transfer (FRET) for sensitive detection of phosphopeptide-protein interactions.
• To establish a tool for quantifying insulin-induced IRS-1 phosphorylation.

Main Methods:

• A FRET pair was constructed using a synthetic phosphopeptide (pY939) derived from IRS-1 and the SH2 domain of PI 3-kinase (SH2N).
• The phosphopeptide and SH2N were labeled with tetramethylrhodamine and fluorescein, respectively.
• Changes in FRET emission spectra were measured to detect the formation and dissociation of the FRET complex in response to phosphopeptide binding.

Main Results:

• The FRET pair demonstrated a decrease in emission at 580 nm and an increase at 520 nm upon dissociation induced by unlabeled phosphopeptide.
• Tyrosine phosphorylation of a substrate peptide (Y939) by insulin receptor was successfully detected using this FRET pair.
• The indicator showed sensitivity to insulin concentrations ranging from approximately 1.0 x 10^-9 to 1.0 x 10^-6 M.

Conclusions:

• The developed FRET pair serves as a competitive fluorescent indicator for tyrosine phosphorylation-based insulin signaling.
• This tool allows for sensitive and quantitative detection of insulin-induced IRS-1 phosphorylation.
• The indicator has potential applications in research on metabolic diseases and drug discovery.