Lijun Kang

Introduction: Neuronal aging is tightly linked to neurodegeneration with dysregulation of GABA (gamma-aminobutyric acid), the primary inhibitory neurotransmitter, contributing to age-associated neuronal impairment. Our prior work demonstrated that restoring the key GABA-synthesizing enzyme UNC-25 (glutamic acid decarboxylase, GAD) in Caenorhabditis elegans AMsh glia mitigates age-related neurodegeneration. This study aims to provide a transcriptomic resource and identify potential pathways associated with glial GABA modulation during neuronal aging. Methods: ASH neurons from day 1 and day 7 nematodes were isolated and FACS-purified (Psra-6::RFP+/Pgpa-4::GFP-) from three distinct groups: Wild-type, unc -25 mutants, unc -25 mutants with AMsh glia-specific UNC-25 rescue. RNA-seq used Illumina NovaSeq (150 bp PE reads, aligned to WormBase WS293). DESeq2 identified DEGs (FDR < 0.05, fold-change ≥ 1); clusterProfiler performed GSEA and pathway enrichment. Comparisons also included AMsh glia vs. ASH neurons in wild young adults. Results: Here, we present transcriptomic data of glutamatergic ASH sensory neurons (a critical target of aging-related neurodegeneration) from three aging groups: wild-type worms, unc -25 (GABA-deficient) mutants, and unc -25 mutants with AMsh glia-specific UNC-25 rescue. Transcriptomic analyses revealed distinct transcriptional profiles across groups. Notably, the Hedgehog signaling pathway and its transcriptional effector TRA-1/GLI, the C. elegans GLI ortholog, were specifically upregulated in the glial rescue group, while the neuroprotective transcription factor HSF-1 was downregulated, suggesting these pathways as potential mediators of glial GABA-associated neuroprotection. We also provide transcriptomic comparisons between AMsh glia and ASH neurons in young worms, laying a foundation for understanding glia-neuron crosstalk. Conclusions: This work establishes a valuable transcriptomic resource for glial GABA-associated ASH neuronal aging and identifies candidate pathways, offering critical molecular insights to dissect age-related neurodegeneration mechanisms and inform potential therapeutic targets.

Thermosensation is evolutionarily conserved for survival, yet the roles of glia in temperature coding and circuit dynamics remain poorly understood. Here, we identify C. elegans AMsh glia as dual-mode thermosensory hubs that autonomously detect temperature fluctuations by co-expressing the heat receptor GCY-28 (guanylate cyclase) and cold receptor GLR-3 (ionotropic glutamate receptor). Thermal changes induce spatiotemporal calcium dynamics in glia, driving GABA release to bidirectionally modulate neural circuits: enhancing AFD-mediated warmth detection through the excitatory receptor EXP-1 and suppressing ASH-dependent cold avoidance via the inhibitory receptor LGC-38. This GABAergic hub-and-spoke architecture regulates a broad range of thermal behaviors, including thermal avoidance, thermal resistance, and thermal preference. These findings establish glia as critical interpreters of environmental cues, highlighting their dual roles as sensors and modulators in sensory processing and providing a paradigm for understanding conserved glial mechanisms in neural circuit dynamics and behavioral plasticity.

Polymodal sensory neurons integrate diverse stimuli for environmental perception, but their modality discrimination mechanisms remain unclear. We focused on Caenorhabditis elegans inner labial type 1 (IL1) neurons, key polymodal neurons mediating mechanical and cold responses, and identified a hierarchical channel system supporting their multimodal function. Specifically, DEG-1 sodium channels are dedicated mechanotransduction receptors; GLR-3 glutamate receptors are the main rapid cold sensors, driving cold-induced calcium signals and behaviors; TRPA-1 bidirectionally modulates mechanical adaptation via calcium signaling and promotes cold-related longevity. This framework reveals a polymodal design logic: dedicated channels (DEG-1/GLR-3) process discrete modalities in parallel for specificity, while TRPA-1 regulates both. Our work provides a molecular blueprint for IL1's precise stimulus processing, offering insights into conserved multimodal integration mechanisms across lineages.

Munc13 plays a crucial role in short-term synaptic plasticity by regulating synaptic vesicle (SV) exocytosis and neurotransmitter release at the presynaptic terminals. However, the intricate mechanisms governing these processes have remained elusive due to the presence of multiple functional domains within Munc13, each playing distinct roles in neurotransmitter release. Here, we report a coordinated mechanism in the Caenorhabditis elegans Munc13 homolog UNC-13 that controls the functional switch of UNC-13 during synaptic transmission. Mutations disrupting the interactions of C1 and C2B with diacylglycerol (DAG) and phosphatidylinositol 4,5-bisphosphate (PIP₂) on the plasma membrane induced the gain-of-function state of UNC-13L, the long UNC-13 isoform, resulting in enhanced SV release. Concurrent mutations in both domains counteracted this enhancement, highlighting the functional interdependence of C1 and C2B. Intriguingly, the individual C1 and C2B domains exhibited significantly stronger facilitation of SV release compared to the presence of both domains, supporting a mutual inhibition of C1 and C2B under basal conditions. Moreover, the N-terminal C2A and X domains exhibited opposite regulation on the functional switch of UNC-13L. Furthermore, we identified the polybasic motif in the C2B domain that facilitates SV release. Finally, we found that disruption of C1 and C2B membrane interaction in UNC-13S, the short isoform, leads to functional switch between gain-of-function and loss-of-function. Collectively, our findings provide a novel mechanism for SV exocytosis wherein UNC-13 undergoes functional switches through the coordination of its major domains, thereby regulating synaptic transmission and short-term synaptic plasticity.

Mechanotransduction channels are widely expressed in both vertebrates and invertebrates, mediating various physiological processes such as touch, hearing and blood-pressure sensing. While previously known mechanotransduction channels in metazoans are primarily cation-selective, we identified Anoctamin-1 (ANOH-1), the C. elegans homolog of mammalian calcium-activated chloride channel ANO1/TMEM16A, as an essential component of a mechanosensory channel complex that contributes to the nose touch mechanosensation in C. elegans. Ectopic expression of either C. elegans or human Anoctamin-1 confers mechanosensitivity to touch-insensitive neurons, suggesting a cell-autonomous role of ANOH-1/ANO1 in mechanotransduction. Additionally, we demonstrated that the mechanosensory function of ANOH-1/ANO1 relies on CIB (calcium- and integrin- binding) proteins. Thus, our results reveal an evolutionarily conserved chloride channel involved in mechanosensory transduction in metazoans, highlighting the importance of anion channels in mechanosensory processes.

Aging‐induced cognitive impairment is associated with a loss of metabolic homeostasis and plasticity. An emerging idea is that targeting key metabolites is sufficient to impact the function of other organisms. Therefore, more metabolism‐targeted therapeutic intervention is needed to improve cognitive impairment. We first conducted untargeted metabolomic analyses and 16S rRNA to identify the aging‐associated metabolic adaption and intestinal microbiome change. Untargeted metabolomic analyses of plasma revealed L‐arginine metabolic homeostasis was altered during the aging process. Impaired L‐arginine metabolic homeostasis was associated with low abundance of intestinal Akkermansia muciniphila ( AKK ) colonization in mice. Long‐term supplementation of AKK outer membranes protein‐Amuc_1100, rescued the L‐arginine level and restored cognitive impairment in aging mice. Mechanically, Amuc_1100 acted directly as a source of L‐arginine and enriched the L‐arginine‐producing bacteria. In aged brain, Amuc_1100 promoted the superoxide dismutase to alleviated oxidation stress, and increased nitric oxide, derivatives of L‐arginine, to improve synaptic plasticity. Meanwhile, L‐arginine repaired lipopolysaccharide‐induced intestinal barrier damage and promoted growth of colon organoid. Our findings indicated that aging‐related cognitive impairment was closely associated with the disorders of L‐arginine metabolism. AKK ‐derived Amuc_1100, as a potential postbiotic, targeting the L‐arginine metabolism, might provide a promising therapeutic strategy to maintain the intestinal homeostasis and cognitive function in aging.

Numerous taste receptors and related molecules have been identified in vertebrates and invertebrates. Otopetrin1 has recently been identified as mammalian sour taste receptor which is essential for acid sensation. However, whether other Otopetrin proteins are involved in PH-sensing remains unknown. In C. elegans, there are eight otopetrin homologous genes but their expression patterns and functions have not been reported so far. Through heterologous expression in HEK293T cells, we found that ceOTOP1a can be activated by acid in NMDG⁺ solution without conventional cations, which generated inward currents and can be blocked by zinc ions. Moreover, we found that Otopetrin channels are widely expressed in numerous tissues, especially in sensory neurons in the nematode. These results suggest that the biophysical characteristics of the Otopetrin channels in nematodes are generally conserved. However, a series of single gene mutations of otopetrins, which were constructed by CRISPR-Cas9 method, did not affect either calcium responses in ASH polymodal sensory neurons to acid stimulation or acid avoidance behaviors, suggesting that Otopetrin channels might have diverse functions among species. This study reveals that nematode Otopetrins are evolutionarily conserved acid-sensitive proton channels, and provides a framework for further revealing the function and mechanisms of Otopetrin channels in both invertebrates and vertebrates.