Molecular probes designed to monitor or perturb signaling events in living cells rely on engineered molecular switches. Here, we show that a kinase-inducible bimolecular switch comprising a kinase-specific substrate and a phosphoamino acid binding domain can be used for acute regulation of cellular events. As a proof of concept, we employed a Protein Kinase A (PKA)-dependent switch and coupled it to a lipid phosphatase to manipulate the level of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) in living cells. PKA activation results in rapid degradation of PI(4,5)P(2). Conversely, when PKA is inhibited, dephosphorylation of the switch leads to the replenishment of PI(4,5)P(2). Thus, this strategy can be used for reversibly controlling enzymatic action in living cells. Furthermore, its genetic encodability and modular design should facilitate the adaptation of this approach to control different cellular activities as a function of phosphorylation-dependent input signals, thereby providing versatile tools for potentially perturbing or rewiring signaling pathways.