Distinct phosphorylation states of mammalian CaMKIIß control the induction and maintenance of sleep.

The reduced sleep duration previously observed in Camk2b knockout mice revealed a role for Ca2+/calmodulin-dependent protein kinase II (CaMKII)ß as a sleep-promoting kinase. However, the underlying mechanism by which CaMKIIß supports sleep regulation is largely unknown. Here, we demonstrate that activation or inhibition of CaMKIIß can increase or decrease sleep duration in mice by almost 2-fold, supporting the role of CaMKIIß as a core sleep regulator in mammals. Importantly, we show that this sleep regulation depends on the kinase activity of CaMKIIß. A CaMKIIß mutant mimicking the constitutive-active (auto)phosphorylation state promotes the transition from awake state to sleep state, while mutants mimicking subsequent multisite (auto)phosphorylation states suppress the transition from sleep state to awake state. These results suggest that the phosphorylation states of CaMKIIß differently control sleep induction and maintenance processes, leading us to propose a "phosphorylation hypothesis of sleep" for the molecular control of sleep in mammals.

Cortical parvalbumin neurons are responsible for homeostatic sleep rebound through CaMKII activation.

The homeostatic regulation of sleep is characterized by rebound sleep after prolonged wakefulness, but the molecular and cellular mechanisms underlying this regulation are still unknown. In this study, we show that Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent activity control of parvalbumin (PV)-expressing cortical neurons is involved in homeostatic regulation of sleep in male mice. Prolonged wakefulness enhances cortical PV-neuron activity. Chemogenetic suppression or activation of cortical PV neurons inhibits or induces rebound sleep, implying that rebound sleep is dependent on increased activity of cortical PV neurons. Furthermore, we discovered that CaMKII kinase activity boosts the activity of cortical PV neurons, and that kinase activity is important for homeostatic sleep rebound. Here, we propose that CaMKII-dependent PV-neuron activity represents negative feedback inhibition of cortical neural excitability, which serves as the distributive cortical circuits for sleep homeostatic regulation.