Abstract: The present invention relates generally to methods to monitor the transport of proteins through the secretory pathway, and methods to monitor ER stress. In particular, the present invention relates to methods to monitor, in real-time, the processing of protein through the secretory pathway, which can be monitored both at a subcellular level by florescence visualization and quantitatively by detecting the secreted luciferase reporter protein. The present invention also relates to methods to assess biological processes in cells, in particular the secretory pathway and ER stress, as well as methods to identify agents which augment or inhibit the secretory pathway and/or ER stress. The present invention also relates to compositions and nucleic constructs encoding a secreted luciferase-fluorescent protein conjugate for methods to monitor protein trafficking in the cell by simultaneous detection of fluorescence and luciferase secretion.