Genome-wide RNAi screening in C. elegans reveals OXPHOS and pyrimidine synthesis pathways as PKA regulators.

Protein kinase A (PKA) plays a crucial and conserved role in various biological processes across species. Despite its significance, tissue-level regulatory networks controlling PKA activity remain incompletely characterized. In this study, we develop a live animal PKA sensor that can faithfully indicate changes in PKA activity in the intestines of Caenorhabditis elegans (C. elegans). Using complementary genome-wide and intestine-specific RNAi screens, we reveal both intestine-autonomous and non-autonomous regulators of intestinal PKA. Notably, we show that inhibiting mitochondrial oxidative phosphorylation, either through RNAi or chemical treatment, leads to a marked increase in intestinal PKA activity. Additionally, we demonstrate that the pyrimidine synthesis pathway serves as a critical autonomous regulator of PKA in the intestines of C. elegans, operating mechanistically in a cAMP-independent manner. Furthermore, this pathway holds a critical and conserved role in regulating PKA in cultured human cells. Overall, our study uncovers the first set of intestinal PKA regulators in C. elegans, with potential implications for PKA modulation under physiological or pathological conditions across species.