Hiding in plain sight: Uncovering a new function of vitamin A in redox signaling

► PKCδ, p66Shc, cytochrome C and vitamin A form a mitochondrial signal module. ► The PKCδ signalosome senses and adjusts the workload of the respiratory chain. ► The PKCδ signalosome signals the pyruvate dehydrogenase complex to adjust fuel flux. ► Vitamin A serves as co-factor and electron carrier for redox activation of PKCδ.