The University of Tokyo finds that mammalian sleep−wake cycles are regulated by phosphorylation and dephosphorylation enzymes

A research group led by Professor Hiroki Ueda (also a Team Leader of the RIKEN Center for Biosystems Dynamics Research), Graduate Students Yimeng Wang and Siyu Cao, and Lecturer Koji Ode of the Graduate School of Medicine at the University of Tokyo has announced their research results in mice showing that protein kinase A (PKA), a phosphorylation enzyme, promotes wakefulness, while the dephosphorylation enzymes protein phosphatase 1 (PP1) and calcineurin antagonize PKA to promote sleep. The results are expected to contribute to the elucidation of the mechanism of sleepiness and the development of therapeutic methods for diseases that cause sleep disorders. The work was published in the international journal Nature on November 6.

While sleep is an essential physiological phenomenon conserved in animals with nervous systems, the mechanisms that regulate the amount of sleep per day remain unknown. Neurodegenerative diseases and other brain disorders are known to commonly cause sleep disturbances. Previously, the research group reported that sleep was induced by CaMKII, a protein kinase, in mice. Meanwhile, protein kinases that promote wakefulness or suppress sleep were unknown.

In this study, the research group focused on PKA. PKA has been reported to promote wakefulness in fruit flies (Drosophila spp.) and fragment non-rapid eye movement sleep in mammals. PKA comprises a catalytic subunit responsible for kinase activity and a regulatory subunit that suppresses the enzyme activity. Experiments, including the creation of mice in which the genes for each subunit of PKA were knocked out, showed that the promotion of PKA activity resulted in reduced sleep pressure.

Next, based on the hypothesis that dephosphorylation enzymes that antagonize wake-promoting kinases may promote sleep, they generated and analyzed knockout mice for each of the 34 phosphatase genes expressed in the brain. As a result, sleep pressure was decreased in knockout mice of a regulatory subunit of the dephosphorylation enzyme PP1, "Ppp1r9b." Thus, PP1 was found to promote sleep.

Since PKA was reported to work at the excitatory post-synapse, they investigated the effects of localization and delocalization of PKA and found that sleep duration and other parameters were affected only by localization. The localization to the same site was also found to be important for PP1. They also showed the decreased sleep duration and other effects of postnatal knockout of calcineurin, a phosphatase whose genetic defect is lethal, in mice using their improved gene editing technology.

This result indicates that calcineurin promotes sleep. Furthermore, they examined whether PKA and PP1/calcineurin had competitive effects against each other and found that the wake-promoting effects of PKA were counteracted by the sleep-promoting effects of PP1 or calcineurin, confirming a competitive relationship between PKA and PP1 or calcineurin.

Journal Information
Publication: Nature
Title: Postsynaptic competition between calcineurin and PKA regulates mammalian sleep-wake cycles
DOI: 10.1038/s41586-024-08132-2