A single phosphorylation site of SIK3 regulates daily sleep amounts and sleep need in mice

Abstract

Sleep is an evolutionally conserved behavior from vertebrates to invertebrates. The molecular mechanisms that determine daily sleep amounts and the neuronal substrates for homeostatic sleep need remain unknown. Through a large-scale forward genetic screen of sleep behaviors in mice, we previously demonstrated that the Sleepy mutant allele of the Sik3 protein kinase gene markedly increases daily nonrapid-eye movement sleep (NREMS) amounts and sleep need. The Sleepy mutation deletes the in-frame exon 13 encoding a peptide stretch encompassing S551, a known PKA recognition site in SIK3. Here, we demonstrate that single amino acid changes at SIK3 S551 (S551A and S551D) reproduce the hypersomnia phenotype of the Sleepy mutant mice. These mice exhibit increased NREMS amounts and inherently increased sleep need, the latter demonstrated by increased duration of individual NREMS episodes and higher EEG slow-wave activity during NREMS. At the molecular level, deletion or mutation at SIK3 S551 reduces PKA recognition and abolishes 14-3-3 binding. Our results suggest that the evolutionally conserved S551 of SIK3 mediates, together with PKA and 14-3-3, the intracellular signaling crucial for the regulation of daily sleep amounts and sleep need at the organismal level.

A salt-induced kinase (SIK) is required for the metabolic regulation of sleep

“…We were able to test this prediction by studying the function of a KIN-29 protein with a conserved Serine 517 mutated to Alanine ( S9A Fig ). The motivation for making this particular mutant was the observation that a homologous change in the mouse SIK3 gene results in a sleepy phenotype [78]. While we did not observe a sleepy phenotype in the kin-29(S517A) mutants, we found that KIN-29(S517A) mutant protein did not move to the nucleus during lethargus ( Fig 7A-B ); moreover, it did not rescue the sleeping-defective of kin-29 null mutants ( Fig 7C ).…”

The role of the hypothalamus in cortical arousal and sleep homeostasis

“…An alternative possibility is that sleep propensity may be enhanced if some of the strong wake-promoting areas are inhibited, consistent with the idea that sleep represents a default state of a neural network or the whole organism (Bandarabadi et al, 2020;Krueger et al, 2013). Therefore, even if accumulation of sleep need, in some form, occurs across many distributed brain networks (Bridi et al, 2019;Bruning et al, 2019;Honda et al, 2018;Lazarus et al, 2019;Muheim et al, 2019;Noya et al, 2019;Shi and Ueda, 2018;Tatsuki et al, 2016;Williams and Naidoo, 2020), it is likely that state switching is initiated from a relatively limited set of brain circuits, which have the capacity to integrate sleep-wake history related signals with other ecological and homeostatic demands. Whilst the biological substrate of global sleep homeostasis remains unclear, the question of which brain areas are involved in encoding the time spent awake or asleep seems tractable.…”

Forward genetic approach for behavioral neuroscience using animal models

“…3F) or aspartic acid (S551D), mice showed a decreased NREM sleep time similar to Sleepy mutant mice. 228) SIK3 protein variants exhibited decreased binding to 14-3-3 proteins compared with the wild-type SIK3 protein. 228) Although it is unclear whether binding to 14-3-3 protein itself is important for sleep control, changes in the biochemical properties of the SIK3 protein may lead to a reduced waking time.…”