BACKGROUND: Apelin/APJ system has a wide range of physiological functions,but its intracellular signal transduction,in particular,apelin receptor desensitization,internalization,resensitization degradation,have still no consistent opinion.OBJECTIVE: To construct eukaryotic expression vector expressing human apelin receptor(APJ)tagged to red fluorescent protein(pDsRED-express-C1),and to determine the expression in human embryo kidney 293 cells.METHODS: The plasmid pcDNA3.1-hAPJ was used as a template for PCR amplification of human APJ.Following PCR amplification the PCR product were removed and enzymatic digestion with EcoR I and BamH I.Same enzymes were used to cut vector pDsRED-express-C1.The digestive product was ligated by conventional methods of connection,then transfected into Competent E.coli TOP10.Single clones were picked plasmid extraction,followed by restriction enzyme digestion and finally DNA sequencing.The recombinant plasmid with correct sequencing was transfected into human embryonic kidney cells,PI staining,followed by the observation under a confocal microscope.RESULTS AND CONCLUSION: PCR amplified a 1.2-kb fragment,which was consistent with the expected size of the human APJ.The pDsRed-hAPJ recombinant plasmid was cut into two fragments,one corresponded to the pDsRED-express-C1 vector size,and the other fragment corresponded to APJ target fragment.Confocal microscopy analysis showed that,APJ was expressed mainly in the membrane of human embryo kidney 293 cells.The pDeRed-hAPJ eukaryotic plasmid expression vector was successfully constructed and effective expression of this fusion protein is achieved,which might be instrumental in the study of displacement and intracellular localization of human APJ.