Single Cell Protein Analysis

Zhenning Cao, Chang Lu

The detection of protein translocation (i.e., the movement of intracellular proteins among various subcellular compartments) conventionally relies on imaging and subcellular-fractionation-based techniques that do not generate information on a large cell population with single-cell resolution. Although special flow cytometric tools such as imaging flow cytometry may generate single-cell data on processes such as nucleocytoplasmic transport, such equipment is expensive (thus has limited accessibility) and has low throughput for examining cells due to the reliance on high-speed imaging. Here we describe a protocol for detecting translocation of native proteins using a common flow cytometer which detects fluorescence intensity without imaging. We conduct chemical release of cytosolic proteins and fluorescence immunostaining of a targeted protein. The detected fluorescence intensity is quantitatively correlated to the cytosolic/nuclear localization of the protein at the single cell level. Our technique provides a simple route for studying nucleocytoplasmic transport with single-cell resolution using common flow cytometers.