Sleep intensity is adjusted by the length of previous awake time, and under tight homeostatic control by protein phosphorylation. Here, we establish microglia as a new cellular component of the sleep homeostasis circuit. Using quantitative phosphoproteomics of the mouse frontal cortex, we demonstrate that microgliaspecific deletion of TNFa perturbs thousands of phosphorylation sites during the sleep period. Substrates of microglial TNFa comprise sleep-related kinases such as MAPKs and MARKs, and numerous synaptic proteins, including a subset whose phosphorylation status encodes sleep need and determines sleep duration. As a result, microglial TNFa loss attenuates the build-up of sleep need, as measured by electroencephalogram slow-wave activity and prevents immediate compensation for loss of sleep. Our data suggest that microglia control sleep homeostasis by releasing TNFa which acts on neuronal circuitry through dynamic control of phosphorylation.

Microglia sense the changes in their environment. How microglia actively translate these changes into suitable cues to adapt brain physiology is unknown. We reveal an activity-dependent regulation of cortical inhibitory synapses plasticity by microglia, driven by purinergic signaling acting on P2RX7 and mediated by microglia-derived TNFα. We demonstrate that sleep induces this microglia-dependent inhibitory plasticity by promoting synaptic enrichment of GABAARs. We further show that in turn, microglia-specific depletion of TNFα alters slow waves during NREM sleep and blunts sleep-dependent memory consolidation. Together, our results reveal that microglia orchestrate sleep-intrinsic plasticity of inhibitory synapses, ultimately sculpting sleep slow waves and memory.

The time we spend asleep is adjusted to previous time spent awake, and therefore believed to be under tight homeostatic control. Here, we establish microglia as a new cellular component of the sleep homeostat circuit. By using quantitative phosphoproteomics we demonstrate that microglia-derived TNFα controls thousands of phosphorylation sites during the sleep period. Substrates of microglial TNFα comprise sleep-promoting kinases and numerous synaptic proteins, including a subset whose phosphorylation status codes sleep need and determines sleep duration. As a result, lack of microglial TNFα attenuates the build-up of sleep need, as measured by slow wave activity, and prevents immediate compensation for loss of sleep. Together, we propose that microglia control sleep homeostasis by releasing TNFα that acts at the neuronal circuitry through dynamic control of phosphorylation. attenuates the build-up of sleep need, as measured by slow wave activity, and prevents immediate compensation for loss of sleep. Together, we propose that microglia control sleep homeostasis by releasing TNFα that acts at the neuronal circuitry through dynamic control of phosphorylation.