Microcystin-LR (MC-LR) is a secondary metabolite produced by cyanobacteria, globally renowned for its potent hepatotoxicity. However, an increasing body of research suggests that it also exhibits ...pronounced neurotoxicity. PP2A is a fundamental intracellular phosphatase that plays a pivotal role in cell development and survival. Although extensive research has focused on the binding of MC-LR to the C subunit of PP2A, few studies have explored the key amino acid sites that can prevent the binding of MC-LR to PP2A-C. Due to the advantages of
(
), such as ease of genetic editing and a short lifespan, we exposed nematodes to MC-LR in a manner that simulated natural exposure conditions based on MC-LR concentrations in natural water bodies (immersion exposure). Our findings demonstrate that MC-LR exerts comprehensive toxicity on nematodes, including reducing lifespan, impairing reproductive capabilities, and diminishing sensory functions. Notably, and for the first time, we observed that MC-LR neurotoxic effects can persist up to the F3 generation, highlighting the significant threat that MC-LR poses to biological populations in natural environments. Furthermore, we identified two amino acid sites (L252 and C278) in PP2A-C through mutations that prevented MC-LR binding without affecting PP2A activity. This discovery was robustly validated through behavioral studies and neuronal calcium imaging using nematodes. In conclusion, we identified two crucial amino acid sites that could prevent MC-LR from binding to PP2A-C, which holds great significance for the future development of MC-LR detoxification drugs.
Cell-cell communication via ligand-receptor signaling is a fundamental feature of complex organs. Despite this, the global landscape of intercellular signaling in mammalian liver has not been ...elucidated. Here we perform single-cell RNA sequencing on non-parenchymal cells isolated from healthy and NASH mouse livers. Secretome gene analysis revealed a highly connected network of intrahepatic signaling and disruption of vascular signaling in NASH. We uncovered the emergence of NASH-associated macrophages (NAMs), which are marked by high expression of triggering receptors expressed on myeloid cells 2 (Trem2), as a feature of mouse and human NASH that is linked to disease severity and highly responsive to pharmacological and dietary interventions. Finally, hepatic stellate cells (HSCs) serve as a hub of intrahepatic signaling via HSC-derived stellakines and their responsiveness to vasoactive hormones. These results provide unprecedented insights into the landscape of intercellular crosstalk and reprogramming of liver cells in health and disease.
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•Heterogeneity and plasticity of non-parenchymal cells in healthy and NASH liver•Landscape of intrahepatic ligand-receptor signaling at single-cell resolution•Emergence of Trem2+ NASH-associated macrophages (NAMs) in mouse and human NASH•Stellakine secretion and contractile response to vasoactive hormones by HSCs
This work illustrates the heterogeneity of liver non-parenchymal cells (NPCs) and their reprogramming during NASH pathogenesis. Using single-cell RNA-sequencing analysis, the authors mapped the landscape of the intrahepatic ligand-receptor signaling network and revealed two fundamental aspects of HSC biology: stellakine secretion and contractile response to vasoactive hormones. Hepatic vascular dysfunction and emergence of Trem2+ NASH-associated macrophages (NAMs) are two conserved features of mouse and human NASH.
Voltage-gated sodium (Na
) channels initiate action potentials. Fast inactivation of Na
channels, mediated by an Ile-Phe-Met motif, is crucial for preventing hyperexcitability and regulating firing ...frequency. Here we present cryo-electron microscopy structure of Na
Eh from the coccolithophore Emiliania huxleyi, which reveals an unexpected molecular gating mechanism for Na
channel fast inactivation independent of the Ile-Phe-Met motif. An N-terminal helix of Na
Eh plugs into the open activation gate and blocks it. The binding pose of the helix is stabilized by multiple electrostatic interactions. Deletion of the helix or mutations blocking the electrostatic interactions completely abolished the fast inactivation. These strong interactions enable rapid inactivation, but also delay recovery from fast inactivation, which is ~160-fold slower than human Na
channels. Together, our results provide mechanistic insights into fast inactivation of Na
Eh that fundamentally differs from the conventional local allosteric inhibition, revealing both surprising structural diversity and functional conservation of ion channel inactivation.
Tissue-tissue communications are integral to organismal aging, orchestrating a body-wide aging process. The brain plays a key role in this process by detecting and processing signals from the ...environment and then communicating them to distal tissues such as the gut to regulate longevity. How this is achieved, however, is poorly understood. Here, using
as a model, we identified two distinct neuroendocrine signaling circuits by which the worm nervous system senses cool and warm environmental temperatures through cool- and warm-sensitive neurons and then signals the gut to extend and shorten life span, respectively. The prolongevity "cool" circuit uses the small neurotransmitters glutamate and serotonin, whereas the anti-longevity "warm" circuit is mediated by insulin-like neuropeptides. Both types of neuroendocrine signals converge on the gut through their cognate receptors to differentially regulate the transcription factor DAF-16/FOXO, leading to opposing outcomes in longevity. Our study illustrates how the brain detects and processes environmental signals to bidirectionally regulate longevity by signaling the gut.
In search of the molecular identities of cold-sensing receptors, we carried out an unbiased genetic screen for cold-sensing mutants in C. elegans and isolated a mutant allele of glr-3 gene that ...encodes a kainate-type glutamate receptor. While glutamate receptors are best known to transmit chemical synaptic signals in the CNS, we show that GLR-3 senses cold in the peripheral sensory neuron ASER to trigger cold-avoidance behavior. GLR-3 transmits cold signals via G protein signaling independently of its glutamate-gated channel function, suggesting GLR-3 as a metabotropic cold receptor. The vertebrate GLR-3 homolog GluK2 from zebrafish, mouse, and human can all function as a cold receptor in heterologous systems. Mouse DRG sensory neurons express GluK2, and GluK2 knockdown in these neurons suppresses their sensitivity to cold but not cool temperatures. Our study identifies an evolutionarily conserved cold receptor, revealing that a central chemical receptor unexpectedly functions as a thermal receptor in the periphery.
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•C. elegans genetic screen identifies the glutamate receptor GLR-3 as a cold receptor•GLR-3 senses cold in a peripheral sensory neuron to trigger cold-avoidance behavior•GLR-3 is a metabotropic cold receptor requiring G proteins to transmit cold signals•The mouse GLR-3 homolog GluK2 acts in DRG sensory neurons to mediate cold sensation
An evolutionarily conserved cold sensor, which is encoded by a glutamate receptor gene, transmits cold signals through G-protein signaling, independent of its channel function.
Many animal tissues/cells are photosensitive, yet only two types of photoreceptors (i.e., opsins and cryptochromes) have been discovered in metazoans. The question arises as to whether unknown types ...of photoreceptors exist in the animal kingdom. LITE-1, a seven-transmembrane gustatory receptor (GR) homolog, mediates UV-light-induced avoidance behavior in C. elegans. However, it is not known whether LITE-1 functions as a chemoreceptor or photoreceptor. Here, we show that LITE-1 directly absorbs both UVA and UVB light with an extinction coefficient 10–100 times that of opsins and cryptochromes, indicating that LITE-1 is highly efficient in capturing photons. Unlike typical photoreceptors employing a prosthetic chromophore to capture photons, LITE-1 strictly depends on its protein conformation for photon absorption. We have further identified two tryptophan residues critical for LITE-1 function. Interestingly, unlike GPCRs, LITE-1 adopts a reversed membrane topology. Thus, LITE-1, a taste receptor homolog, represents a distinct type of photoreceptor in the animal kingdom.
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•LITE-1, a taste receptor homolog, is a bona fide photoreceptor that senses UV light•LITE-1 has a high efficiency of photon capturing•Photoabsorption by LITE-1 relies on its conformation and requires two Trp residues•Introducing such a Trp residue into a related protein promotes photosensitivity
A taste receptor homolog absorbs UV light and mediates avoidance behavior in C. elegans in response to light exposure.
Reactive oxygen species (ROS) are well known to elicit a plethora of detrimental effects on cellular functions by causing damages to proteins, lipids and nucleic acids. Neurons are particularly ...vulnerable to ROS, and nearly all forms of neurodegenerative diseases are associated with oxidative stress. Here, we report the surprising finding that exposing C. elegans to low doses of H
O
promotes, rather than compromises, sensory behavior and the function of sensory neurons such as ASH. This beneficial effect of H
O
is mediated by an evolutionarily conserved peroxiredoxin-p38/MAPK signaling cascade. We further show that p38/MAPK signals to AKT and the TRPV channel OSM-9, a sensory channel in ASH neurons. AKT phosphorylates OSM-9, and such phosphorylation is required for H
O
-induced potentiation of sensory behavior and ASH neuron function. Our results uncover a beneficial effect of ROS on neurons, revealing unexpected complexity of the action of oxidative stressors in the nervous system.
Voltage-gated sodium (Na
) channels mediate a plethora of electrical activities. Na
channels govern cellular excitability in response to depolarizing stimuli. Inactivation is an intrinsic property of ...Na
channels that regulates cellular excitability by controlling the channel availability. The fast inactivation, mediated by the Ile-Phe-Met (IFM) motif and the N-terminal helix (N-helix), has been well-characterized. However, the molecular mechanism underlying Na
channel slow inactivation remains elusive. Here, we demonstrate that the removal of the N-helix of Na
Eh (Na
Eh
) results in a slow-inactivated channel, and present cryo-EM structure of Na
Eh
in a potential slow-inactivated state. The structure features a closed activation gate and a dilated selectivity filter (SF), indicating that the upper SF and the inner gate could serve as a gate for slow inactivation. In comparison to the Na
Eh structure, Na
Eh
undergoes marked conformational shifts on the intracellular side. Together, our results provide important mechanistic insights into Na
channel slow inactivation.
Micronutrients and cell death have a strong relationship and both are essential for human to maintain good body health. Dysregulation of any micronutrients causes metabolic or chronic diseases, ...including obesity, cardiometabolic condition, neurodegeneration, and cancer. The nematode
is an ideal genetic organism for researching the mechanisms of micronutrients in metabolism, healthspan, and lifespan. For example,
is a haem auxotroph, and the research of this special haem trafficking pathway contributes important reference to mammal study. Also,
characteristics including anatomy simply, clear cell lineage, well-defined genetics, and easily differentiated cell forms make it a powerful tool for studying the mechanisms of cell death including apoptosis, necrosis, autophagy, and ferroptosis. Here, we describe the understanding of micronutrient metabolism currently and also sort out the fundamental mechanisms of different kinds of cell death. A thorough understanding of these physiological processes not only builds a foundation for developing better treatments for various micronutrient disorders but also provides key insights into human health and aging.
The sodium-activated Slo2.2 channel is abundantly expressed in the brain, playing a critical role in regulating neuronal excitability. The Na+-binding site and the underlying mechanisms of ...Na+-dependent activation remain unclear. Here, we present cryoelectron microscopy (cryo-EM) structures of human Slo2.2 in closed, open, and inhibitor-bound form at resolutions of 2.6–3.2 Å, revealing gating mechanisms of Slo2.2 regulation by cations and a potent inhibitor. The cytoplasmic gating ring domain of the closed Slo2.2 harbors multiple K+ and Zn2+ sites, which stabilize the channel in the closed conformation. The open Slo2.2 structure reveals at least two Na+-sensitive sites where Na+ binding induces expansion and rotation of the gating ring that opens the inner gate. Furthermore, a potent inhibitor wedges into a pocket formed by pore helix and S6 helix and blocks the pore. Together, our results provide a comprehensive structural framework for the investigation of Slo2.2 channel gating, Na+ sensation, and inhibition.
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•The high-resolution EM structures of hSlo2.2 are shown in the presence and absence of Na+•Multiple cation-binding sites in Slo2.2 and their modulation of Slo2.2 gating are revealed•Possible lipids bind to the inner gate of Slo2.2, which may be involved in channel gating•Inhibitor C23 wedges into a pocket formed by pore helix and S6 helix and blocks the pore
Zhang et al. describe the cryo-EM structures of human Slo2.2 in the closed, open, and inhibitor-bound form at resolutions of 2.6–3.2 Å and propose the molecular mechanisms of Slo2.2 regulation by cations and potent inhibitor Compound 23, which contribute to the understanding of Slo2.2 gating.
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