Executioner caspase is proximal to Fasciclin 3 which facilitates non-lethal activation inDrosophilaolfactory receptor neurons

Abstract

AbstractExecutioner caspases are activated by initiator caspases, resulting in lethal and non-lethal cellular outcomes. Despite the identification of numerous caspase-dependent non-lethal cellular processes (CDPs), the molecular mechanism that enables precise regulation of the non-lethal functions of executioner caspases remains unclear. Here, we conducted a comprehensive analysis of endogenous proximal proteins ofDrosophilaexecutioner caspasesin vivousing TurboID. We discovered that in the adult brain, the executioner caspase Drice is primarily proximal to membrane proteins, including the cell adhesion molecule Fasciclin 3 (Fas3). Notably, Drice is proximal to the specific alternative splicing isoforms of Fas3G. To investigate whether Fas3 modulates caspase activity, we developed a Gal4-Manipulated Area-Specific CaspaseTracker/CasExpress (MASCaT) system for highly sensitive monitoring of non-lethal caspase activity near membrane compartments. Using MASCaT, we demonstrated that Fas3 promoted caspase activation near membrane compartments in olfactory receptor neurons without killing them. Activation regulates innate olfactory attraction behavior. Collectively, our findings suggest that the proximal proteins of executioner caspases provide a compartmentalized platform for non-lethal caspase activation and function.Author SummaryCaspases are Cysteine-ASPartic acid proteASEs which are primarily involved in cell death. In addition, caspases play versatile non-lethal (non-cell death) roles in a wide range of cell types including neurons. However, the molecular mechanism that enables the precise regulation of non-lethal activation and functions remains unclear. Here, we focused on the proximal proteins of caspases as potential regulators of non-lethal activation. By comprehensively analyzing the proximal proteins of caspases in the adultDrosophilabrain using TurboID, we discovered that caspases are primarily proximal to membrane proteins rather than to cytosolic proteins. By developing a genetic tool that enables highly sensitive monitoring of non-lethal caspase activity near membrane compartments, we found that proximal proteins facilitate non-lethal caspase activation in olfactory receptor neurons. Importantly, non-lethal caspase activation in olfactory receptor neurons affects organismal innate attraction behavior. Our research suggests that a compartmentalized platform established by proximal proteins enables precise regulation of non-lethal caspase activation and function.