Basic study on SH2 domain of Grb2 as a molecular probe for detection of RTK activation

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• Receptor tyrosine kinases (RTKs), including epidermal growth factor receptor (EGFR), are crucial in cancer development when abnormally activated.
• Targeting RTK activation is a key strategy for cancer diagnosis and therapy.

Purpose of the Study:

• To engineer a molecular imaging probe for detecting activated RTKs.
• To utilize the Grb2 SH2 domain as a probe component for cancer characterization.
• To assess the probe's ability to monitor RTK activation and kinase inhibitor effects.

Main Methods:

• The Grb2 SH2 domain was genetically modified (fused with TAT, flag, and tyrosine residue) to create a cell-penetrant probe (TSF).
• TSF cellular uptake, stability, and localization were analyzed in EGFR-expressing cells.
• TSF binding to phosphorylated-EGFR and its response to epidermal growth factor (EGF) stimulation and a tyrosine kinase inhibitor (Tyrphostin AG1478) were evaluated.

Main Results:

• TSF successfully entered EGFR-expressing cells and bound to phosphorylated-EGFR, with binding increasing upon EGF stimulation.
• TSF co-localized with EGFR in activated cells and showed distinct cytosolic dot localization in non-activated cells.
• EGFR activation extended TSF cellular retention time, which was reduced by Tyrphostin AG1478 treatment.

Conclusions:

• The Grb2 SH2 domain is a promising binding component for developing probes to detect activated RTKs.
• This probe can potentially characterize cancers based on RTK activation status.
• The probe is effective in evaluating the impact of kinase inhibitors on RTK activation.