Comparison of Two Transmembrane Proteins as Fusion Partner for Protein Expression on the Surface of Cell

In many cases the expression of a soluble protein on the cell surface is desirable for the study of a functional protein, more applications of a protein, or investigation of protein-protein interaction. The expression of a soluble protein on the surface of a cell is often achieved by genetically linking it to the extracellular fragment of a transmembrane partner. In this study, the myc epitope was linked with the N terminal of transmembrane proteins either A2TM or ΔLNGFR, amplified by overlapping PCR. The plasmids expressing fusion protein were transfected into 293FT cells and the expression of target proteins was evaluated by fluorescent microscopy, flow cytometry, and Western blot. The results of flow cytometry revealed that both A2TM and ΔLNGFR were expressed on the cell surface, but A2TM could only be detected with a high copy number. Western blotting showed that the expression level of ΔLNGFR was significant and protein was heavily glycosylated. By contrast, the expression of A2TM was hardly detected. The results indicated that glycosylated ΔLNGFR was a good candidate partner for the expression of a soluble protein on the cell surface.