This would be straightforward: activation of sleep-promoting CaMKII is mediated by the increased neuronal spikes presumably associated with the awake state. Factors that may transduce the wake-associated information to the kinase are not limited to the synaptic input. Several monoamines working as excitatory neuromodulators (e.g., norepinephrine or dopamine) that promote wakefulness (Fuller et al., 2011) may also alter the activity of CaMKII by modulating the excitability of neurons. The SIK family is controlled by the multisite phosphorylation caused by elevated cAMP and subsequent activation of PKA. The neuronal cAMP level is modulated by several G protein-coupled receptors, including receptors of the excitatory monoamine neuromodulators. Although PKA has been known to mediate an awake-promoting effect caused by octopamine neurotransmitter in Drosophila (Hendricks et al., 2001; Crocker et al., 2010), the PKA-SIK pathway in mammals might be involved in the sleep-promoting effect of neurotransmitters which activates the cAMP in cortical neurons. On the other hand, ERK is activated by a wide range of cell signaling from cell differentiation to cell death (Coulthard et al., 2009). A potential pathway related to sleep control is stress-induced activation of ERK, which may be triggered by sleep deprivation that is known to be associated with the elevation of inflammatory responses (Clinton et al., 2011). If a part of these signals activates the sleep-promoting kinases, the kinases may bridge the cellular signaling to the induction of sleep.
results demonstrated that both perturbations similarly increase phosphorylated proteins without much increase in the amount of total (non-phosphorylated) protein; indeed, the researchers have a series of phosphorylated proteins, named as the sleep-need-index-phosphoproteins (SNIPPs), that increase in both sleep-deprived and the Sleepy mice. Many SNIPPs are involved in the synaptic regulation and, interestingly, include CaMKII. CaMKII activation during sleep deprivation may simply be due to increased synaptic input during the wake period, but similar activation of CaMKII in the Sleepy mice with short awake duration strongly suggests that CaMKII activity is associated with an increased need for sleep.
In particular, SIK3 appears to induce a similar phosphoproteomic profile to that caused by sleep deprivation, and the dynamics of CaMKII activation correlate well with the expected accumulation of sleep need. These results imply that kinases transduce and store cumulative neuronal activity as the phosphorylation status of their substates, including the phosphorylation status of the kinases themselves. In this view, the molecular entity of sleepiness is, at least in part, protein phosphorylation: we shall call this idea a phosphorylation hypothesis of molecular sleepiness–the kinase-centric understanding of sleep-wake transition may integrate the molecular mechanism of sleepiness and physiological functions of sleep to control protein activity
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from more paywalled article that went beyond SIK3/CaMKII:
we identified PKA as a wake-promoting kinase and PP1 and calcineurin were identified as sleep-promoting phosphatases in mammals. A recent proteomics approach, which quantified changes in the relative abundance of each protein at the postsynaptic density (PSD) from the mouse cortex and hippocampus during awake and sleep phases, revealed a relative increase in both catalytic and regulatory subunits of PKA components during the wake phase compared with several other PSD proteins1. Furthermore, motif analysis of the phos-
1 phopeptide predicted enriched PKA activity in the wake phase , which
suggests that PKA activity is dynamically controlled by the sleep–wake cycle. A subsequently conducted time-course phosphoproteomics analysis3 demonstrated that PKA is activated at the end of the light (sleep) phase.
Overall, our results characterize PP1 as a sleep-promoting phosphatase functioning at excitatory post-synapses. The sleep-promoting function remained evident even under forced awakening conditions. That is, Ppp1r9b KO mice demonstrated increased awake duration induction following a cage change (Extended Data Fig. 6h). By contrast, mice expressing the sleep-promoting PSD95–PPP1CAT320A or PSD95–PPP1CCT311A mutation showed reduced awake duration induction after cage change
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why does PKA (subunits (Prkar1a, Prkar1b, *Prkar2a *and Prkar2b) have so many regulatory subunits
The multiple regulatory (R) subunits of Protein Kinase A (PKA) serve several important biological functions:
- Tissue-Specific Expression:
- Different tissues need different PKA regulation
- R1a is ubiquitous
- R1b is enriched in brain and nervous tissue
- R2a is found in reproductive tissues
- R2b is prominent in brain and adipose tissue
- Different Biochemical Properties:
- Varying sensitivities to cAMP
- Different binding affinities to A-Kinase Anchoring Proteins (AKAPs)
- Different phosphorylation sites
- Distinct subcellular localization patterns
- Evolutionary Advantages:
- Allows fine-tuned responses to different signals
- Provides redundancy for critical signaling pathways
- Enables tissue-specific regulation
- Permits complex spatiotemporal control
- Different Types of Regulation:
- R1 units typically provide baseline regulation
- R2 units often handle more dynamic responses
- Different degradation rates
- Varying responses to cellular conditions
This diversity enables precise control of PKA signaling across different cellular contexts and physiological conditions.
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AC
"*PPP1CB *and *PPP1CC *also required the PSD95 fusion protein to pro- duce an increase in sleep duration (Extended Data Fig. 5c–f,j–m). The sleep-promoting function of gain-of-function PSD95–*PPP1CAT320A *was attributed to the increase in NREM sleep compared with the loss-of-function PSD95–PPP1CAH248K" how does this work?
Let me break this down:
This is describing how different forms of PPP1C (a protein phosphatase) affect sleep when fused to PSD95:
- Basic components:
- PPP1C variants (PPP1CB and PPP1CC)
- PSD95 (a scaffolding protein in synapses)
- Two PPP1CA mutations:
- T320A (gain-of-function)
- H248K (loss-of-function)
- The findings:
- PPP1CB and PPP1CC needed to be fused to PSD95 to increase sleep
- PSD95-PPP1CA T320A (more active) increased NREM sleep
- PSD95-PPP1CA H248K (less active) had less effect on sleep
- Mechanism likely involves:
- PSD95 targeting the phosphatase to synapses
- PPP1C then modifies synaptic proteins
- This affects synaptic strength/function
- These changes influence sleep/wake circuits
Would you like me to explain more about how phosphatases regulate synaptic function or how this might mechanistically affect sleep?
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AC
why do Ppp1r9b KO mice sleep less?
Ppp1r9b (also known as Spinophilin/Neurabin-2) knockout mice sleep less because:
- Spinophilin’s normal role:
- Targets PP1 (protein phosphatase 1) to dendritic spines
- Regulates synaptic plasticity
- Modulates receptor trafficking/function
- Particularly affects glutamate receptor regulation
- Without Spinophilin:
- PP1 targeting to synapses is disrupted
- This likely alters synaptic strength
- May affect sleep-promoting circuits
- Could disrupt normal synaptic homeostasis during sleep
The relationship makes sense because:
- PP1 is a major regulator of synaptic plasticity
- Sleep is tightly linked to synaptic regulation
- Spinophilin helps localize this regulation to the right place
However, since this involves complex sleep regulation pathways and knockout studies, I should note that I may be simplifying some of the mechanisms. The exact pathway from Spinophilin loss to reduced sleep might involve additional factors.
CopyRetry
AC
why do PSD95-fused PPP1CA(H248K) or PPP1CA(T320A). sleep more
Let me break down how these PSD95-PPP1CA fusions affect sleep:
- PSD95 fusion effect:
- PSD95 targets PPP1CA directly to synaptic sites
- This creates highly localized phosphatase activity
- More precise control than natural targeting
- The mutations:
- H248K is typically loss-of-function for PPP1CA
- T320A is typically gain-of-function for PPP1CA
- When fused to PSD95, both increase sleep
- Likely mechanism:
- Direct synaptic targeting overrides normal regulation
- Forces phosphatase activity at synapses regardless of mutation
- May alter synaptic strength in sleep-promoting circuits
- Could bypass normal Spinophilin-dependent targeting
This suggests that the key factor might be the forced synaptic localization via PSD95 fusion, rather than just the phosphatase activity level.
Would you like me to explain more about how phosphatase localization affects synaptic function?
