A bioluminescent capsule was designed for illuminating cell signaling and protein localization. The capsule consists of four components, namely, a secretion peptide (SP), a luciferase body, a cargo protein (or peptide), and a membrane-localization signal (MLS). Any functional proteins sandwiched between the luciferase body and MLS may be cartable to the plasma membrane (PM), where the capsule waits for outer signals and quickly releases the embedded luciferase in response to the signals. With this strategy of locating the capsule in the PM, the bioluminescence intensity was greatly prolonged and strengthened. A staurosporine (STS)-activated apoptosis signaling was efficiently imaged with the capsule carrying a DEVD peptide. Other functional proteins, such as fluorescent proteins and luciferases, were efficiently transported to the membrane by the capsule. A 60-nm-red-shifted bioluminescence was observed with a capsule fused with other luciferases or fluorescent proteins in living cells. This study gives a new insight regarding how to illuminate cellular signals with bioluminescence in living mammalian cells.