Development of novel affinity reagents for detecting protein tyrosine phosphorylation based on superbinder SH2 domain in tumor cells

Tyrosine phosphorylation, as a hallmark in cellular signal transduction, is important for a diverse array of cellular processes, such as proliferation, metabolism, motility, and survival. Aberrant tyrosine phosphorylation plays a causal role in many diseases, especially the Cancer. Detecting protein phosphorylation status in the Cancer cells or tissues is vital for assessing the pathological phase, discovering the Cancer biomarkers, and identifying the drug targets. However, the common biochemical detection methods remain through anti-pTyr Antibodies, which are known to have limited sensitivity, poor reproducibility and high cost. Recent studies have proved that superbinder SH2 domain is a good replacement of anti-pTyr Antibodies for the specific enrichment of pTyr Peptides in phosphoproteomics analysis. In this work, we exploited a series of affinity reagents based on superbinder SH2 derived from Src protein for detecting the pTyr-containing proteins to replace anti-pY Antibodies in immunoblotting and immunofluorescence techniques. The excellent performance of HRP-sSH2 and EGFP-sSH2 was verified by the analysis of several different tumor cell samples and was compared with most commonly used commercial Antibodies. EGFP-sSH2-(Arg)₉ might be applied as the probe for direct fluorescence imaging in live cells via efficiently penetrating cell membranes and specifically binding with pTyr proteins. In summary, we have developed three novel, convenient, sensitive, and cost-effective affinity reagents that would have wide applications in protein tyrosine phosphorylation analysis for the tumor research and clinical diagnosis.