PLA for visualization and quantification of protein specific pTyr levels. K562 cells probed in in situ PLA with anti-pTyr antibody, 4G10, combined with protein specific antibodies (specified in figure) for control cells (C), cells treated with tyrosine kinase inhibitor (TKI, imatinib) (ABL, SCH, ERK2) and cells treated with tyrosine phosphatase inhibitor (TPI, pervanadate) (PI3K p110β and p85β). A) Visualization by fluorescent pictures: Red dots represent detected pTyr signals, cell nuclei are stained in blue and cytoplasms stained in green. Scale bars 10 μm. B) Quantification: The number of pTyr signals per cell for different proteins are presented in a diagram. Bars represent mean with 95% confidence interval. The PI3K protein (p110β unit) was found sensitive to TPI but not to TKI treatment. The results for the ERK2 protein are enlarged to visualize that there was a significant difference between control and treated cells.