Nitrous oxide (N2O) induces rapid and durable antidepressant effects. The cellular and circuit mechanisms mediating this process are not known. Here we find that a single dose of inhaled N2O induces rapid and specific activation of layer V (L5) pyramidal neurons in the cingulate cortex of rodents exposed to chronic stress conditions. N2O-induced L5 activation rescues a stress-associated hypoactivity state, persists following exposure, and is necessary for its antidepressant-like activity. Although NMDA-receptor antagonism is believed to be a primary mechanism of action for N2O, L5 neurons activate even when NMDA-receptor function is attenuated through both pharmacological and genetic approaches. By examining different molecular and circuit targets, we identify N2O-induced inhibition of calcium-sensitive potassium (SK2) channels as a key molecular interaction responsible for driving specific L5 activity along with ensuing antidepressant-like effects. These results suggest that N2O-induced L5 activation is crucial for its fast antidepressant action and this effect involves novel and specific molecular actions in distinct cortical cell types.
© 2025. The Author(s).

Mitochondria-ER contact sites (MERCS) are vital for mitochondrial dynamics, lipid exchange, Ca2+ homeostasis, and energy metabolism. We examined whether mitochondrial metabolism changes during the cell cycle depend on MERCS dynamics and are regulated by the outer mitochondrial protein mitochondrial rho GTPase 1 (MIRO1). Wound healing was assessed in mice with fibroblast-specific deletion of MIRO1. Wild-type and MIRO1-/- fibroblasts and vascular smooth muscle cells were evaluated for proliferation, cell cycle progression, number of MERCS, distance, and protein composition throughout the cell cycle. Restoration of MIRO1 mutants was used to test the role of MIRO1 domains; Ca2+ transients and mitochondrial metabolism were evaluated using biochemical, immunodetection, and fluorescence techniques. MERCS increased in number during G1/S compared with during G0, which was accompanied by a notable rise in protein-protein interactions involving VDAC1 and IP3R as well as GRP75 and MIRO1 by proximity-ligation assays. Split-GFP ER/mitochondrial contacts of 40 nm also increased. Mitochondrial Ca2+ concentration ([Ca2+]), membrane potential, and ATP levels correlated with the formation of MERCS during the cell cycle. MIRO1 deficiency blocked G1/S progression and the cell-cycle-dependent formation of MERCS and altered ER Ca2+ release and mitochondrial Ca2+ uptake. MIRO1 mutants lacking the Ca2+-sensitive EF hands or the transmembrane domain did not rescue cell proliferation or the formation of MERCS. MIRO1 controls an increase in the number of MERCS during cell cycle progression and increases mitochondrial [Ca2+], driving metabolic activity and proliferation through its EF hands.

Autophagosome formation initiated on the endoplasmic reticulum (ER)-associated omegasome requires LC3. Translational regulation of LC3 biosynthesis is unexplored. Here we demonstrate that LC3 mRNA is recruited to omegasomes by directly binding to the ER transmembrane Sigma-1 receptor (S1R). Cell-based and in vitro reconstitution experiments show that S1R interacts with the 3' UTR of LC3 mRNA and ribosomes to promote LC3 translation. Strikingly, the 3' UTR of LC3 is also required for LC3 protein lipidation, thereby linking the mRNA-3' UTR to LC3 function. An autophagy-defective S1R mutant responsible for amyotrophic lateral sclerosis cannot bind LC3 mRNA or induce LC3 translation. We propose a model wherein S1R de-represses LC3 mRNA via its 3' UTR at the ER, enabling LC3 biosynthesis and lipidation. Because several other LC3-related proteins use the same mechanism, our data reveal a conserved pathway for localized translation essential for autophagosome biogenesis with insights illuminating the molecular basis of a neurodegenerative disease.
Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

Nitrous oxide (N 2 O) induces rapid and durable antidepressant effects in patients suffering from treatment-resistant depression 1,2 . The cellular and circuit mechanisms mediating this process are not known. Here we find that a single dose of inhaled N 2 O induces rapid and specific activation of layer V (L5) pyramidal neurons in the prefrontal cortex of rodents exposed to chronic stress conditions. N 2 O-induced L5 activation rescues a stress-associated hypoactivity state, persists following N 2 O exposure, and is necessary for its antidepressant action. While NMDA-receptor (NMDA-R) antagonism has been N 2 O’s purported mechanism of action, L5 neurons activate independently from NMDA-R function and synaptic activity. By examining different molecular targets controlling excitability and cortical circuit elements, we identify N 2 O-induced inhibition of calcium-sensitive potassium (SK2) channels as a primary molecular interaction responsible for driving both rapid and persistent L5 activity along with its ensuing antidepressant-like effects. These results suggest that N 2 O-induced L5 activation is crucial for its fast antidepressant action and this effect involves novel and specific molecular actions with SK2 channels expressed in specific L5 cell types.

The intestine is responsible for nutrient absorption and orchestrates metabolism in different organs during feeding, a process which is partly controlled by intestine-derived hormones. However, it is unclear whether the intestine plays an important role in metabolism during fasting. Here we have identified a novel hormone, famsin, which is secreted from the intestine and promotes metabolic adaptations to fasting. Mechanistically, famsin is shed from a single-pass transmembrane protein, Gm11437, during fasting and then binds OLFR796, an olfactory receptor, to activate intracellular calcium mobilization. This famsin-OLFR796 signaling axis promotes gluconeogenesis and ketogenesis for energy mobilization, and torpor for energy conservation during fasting. In addition, neutralization of famsin by an antibody improves blood glucose profiles in diabetic models, which identifies famsin as a potential therapeutic target for treating diabetes. Therefore, our results demonstrate that communication between the intestine and other organs by a famsin-OLFR796 signaling axis is critical for metabolic adaptations to fasting.
© 2023. The Author(s) under exclusive licence to Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences.