Biology subjects

Sokabe, T.

Publications and source records attributed to Sokabe, T..

4 recordsLinked to original sources

bioRxiv2025

Heat-off responses of epidermal cells sensitize Drosophila larvae to noxious inputs

Perception of external thermal stimuli is critical to animal survival, and although an animals skin is the largest contact surface for thermal inputs, contributions of skin cells to noxious temperature sensing have not been extensively explored. Here, we show that exposure to heat transiently sensitizes Drosophila larvae to subsequent noxious stimuli. This sensitization is induced by prior stimulation of epidermal cells but not nociceptors, suggesting that epidermal cells modulate nociceptor function in response to heat exposure. Indeed, we found that Drosophila epidermal cells are intrinsically thermosensitive, exhibiting robust heat-off responses following warming to noxious temperatures as well as responses to cooling below comfortable temperatures. Further, we found that epidermal heat-off calcium responses involve influx of extracellular calcium and require the store-operated calcium channel Orai and its activator Stim. Finally, epidermal heat-off responses and heat-evoked nociceptive sensitization exhibit similar temperature dependencies, and we found that Stim and Orai are required in epidermal cells for heat-evoked nociceptive sensitization. Hence, epidermal thermosensory responses provide a form of adaptive sensitization to facilitate noxious heat avoidance.

neuroscience↗

bioRxiv2025

Alternative Splicing in TRPA1 Drives Sensory Adaptation to Electrophiles in Drosophilids

Behaviors are among the first traits to evolve as animals enter new niches, but their molecular bases are poorly understood. To address this gap, we used the mustard-feeding drosophilid fly Scaptomyza flava, which feeds on toxic Brassicales plants like wasabi that produce noxious, electrophilic isothiocyanates (ITCs or mustard oils). We found that S. flava exhibits dramatically reduced behavioral sensitivity to allyl isothiocyanate (AITC) compared to its microbe-feeding relatives Scaptomyza pallida and Drosophila melanogaster. We hypothesized that molecular evolution of the "wasabi receptor" TRPA1, known to detect ITCs in flies, could explain this loss of aversion. Our experiments revealed three interconnected evolutionary genetic changes consistent with this hypothesis. First, TRPA1 was expressed in labellar tissues of S. flava at the lowest levels among the three species, at a nearly four-fold lower level than in D. melanogaster. Second, S. flava expressed a higher proportion of TRPA1 splice variants previously reported to be less sensitive to chemical stimulus. Third, we identified amino acid substitutions in S. flava that could influence the structure of intracellular domains of TRPA1. To test the functional salience of these mechanisms in vitro and in vivo, we validated TRPA1 splicing isoforms using Xenopus oocyte electrophysiology and the GAL4/UAS system in D. melanogaster. Single TRPA1 isoform electrophysiology in vitro revealed evolution of the channel in the S. flava lineage towards reduced electrophile sensitivity. Ectopic expression of S. flava TRPA1 in D. melanogaster also consistently conferred weaker AITC sensitivity in vivo than expression of its orthologues, although this did not fully recapitulate differences in wild-type phenotypes between species, suggesting other molecular mechanisms were involved. To address this, we explored the consequences of isoform co-expression using oocyte electrophysiology. We found that enrichment of electrophile-insensitive TRPA1 splicing isoforms as observed in the salient S. flava sensory organs additively reduced cellular responses to AITC, which could further contribute to reduced electrophile aversion. Our findings illuminate how expression differences, protein structural changes, and especially alternative splicing, together can drive sensory evolution as animals behaviorally adapt to toxic new niches.

evolutionary biology↗

bioRxiv2023

Ether phospholipids modulate somatosensory responses by tuning multiple receptor functions in Drosophila

Transient receptor potential (TRP) and PIEZO channels are known receptors for physical stimuli, such as temperature and mechanical touch, respectively, in sensory nerves. As these receptors are localized in the plasma membrane, the modulation of sensory receptor activity by plasma membrane lipids has recently attracted attention. In this study, we focused on ether phospholipids (ePLs), which are abundant in neurons, and analyzed their role in somatosensation using Drosophila as a model. Reduced mechanosensory behavior was observed with ePL synthesizing gene knockout or knockdown in mechano-sensitive PIEZO-expressing neurons. The activation of PIEZO channels was significantly augmented in the presence of ePLs. Furthermore, we observed that ePLs modulate the thermosensory behavior and reduce thermal threshold of the thermosensitive TRPA1 channels. Finally, we revealed that ePLs affect membrane tension and lipid order of the plasma membrane in culture cells. Our study identified ePLs as a modulator of multiple somatosensation modalities in Drosophila, which underscore the significance of functional interaction between membrane lipid and sensory channel proteins.

molecular biology↗

bioRxiv2021

Light-induction of endocannabinoids and activation of Drosophila TRPC channels

Drosophila phototransduction represents a classical model for signaling cascades that culminate with activation of TRP channels. TRP and TRPL are the canonical TRP (TRPC) channels, which are gated by light stimulation of rhodopsin and engagement of Gq and phospholipase C{beta} (PLC). Despite decades of investigation, the mechanism of TRP activation in photoreceptor cells is unresolved. Here, using a combination of genetics, lipidomics and Ca2+ imaging, we found that light increased the levels of an abundant endocannabinoid, 2-linoleoyl glycerol (2-LG) in vivo. The elevation in 2-LG strictly depended on the PLC encoded by norpA. Moreover, this endocannabinoid upregulated TRPC-dependent Ca2+ influx in a heterologous expression system and in dissociated ommatidia from compound eyes. We propose that 2-LG is a physiologically relevant endocannabinoid that activates TRPC channels in photoreceptor cells.

neuroscience↗