Apical sorting of chimeric GFP-CUB domains in MDCK cells. The conditioned media were collected from MDCK cells stably expressing chimeric GFP-CUB-V5-His domains (GFP-CUB) and GFP alone (GFP). The constructs are shown in panel A. The proteins secreted into the apical and basolateral domains were determined by mouse anti–V5 IgG for V5-His tagged construct and by mouse anti–GFP IgG (B). The signals on the luminogram were scanned and quantified by NIH ImageJ software. The relative amount (means ± SD, n = 5) of each protein in the conditioned medium collected from the apical domain of the cells was expressed in panel C.