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Ultrasound has been used to non-invasively manipulate neuronal functions in humans and other animals. However, this approach is limited as it has been challenging to target specific cells within the brain or body. Here, we identify human Transient Receptor Potential A1 ( hs TRPA1) as a candidate that confers ultrasound sensitivity to mammalian cells. Ultrasound-evoked gating of hs TRPA1 specifically requires its N-terminal tip region and cholesterol interactions; and target cells with an intact actin cytoskeleton, revealing elements of the sonogenetic mechanism. Next, we use calcium imaging and electrophysiology to show that hs TRPA1 potentiates ultrasound-evoked responses in primary neurons. Furthermore, unilateral expression of hs TRPA1 in mouse layer V motor cortical neurons leads to c-fos expression and contralateral limb responses in response to ultrasound delivered through an intact skull. Collectively, we demonstrate that hs TRPA1-based sonogenetics can effectively manipulate neurons within the intact mammalian brain, a method that could be used across species. Ultrasound can be used to non-invasively control neuronal functions. Here the authors report the use of human Transient receptor potential ankyrin 1 ( hs TRPA1) to achieve ultrasound sensitivity in mammalian cells, and show that it can be used to manipulate neurons in the mammalian brain.

The view of the lysosome as the terminal end of cellular catabolic pathways has been challenged by recent studies showing a central role of this organelle in the control of cell function. Here we show that a lysosomal Ca 2+ signalling mechanism controls the activities of the phosphatase calcineurin and of its substrate TFEB, a master transcriptional regulator of lysosomal biogenesis and autophagy. Lysosomal Ca 2+ release through mucolipin 1 (MCOLN1) activates calcineurin, which binds and dephosphorylates TFEB, thus promoting its nuclear translocation. Genetic and pharmacological inhibition of calcineurin suppressed TFEB activity during starvation and physical exercise, while calcineurin overexpression and constitutive activation had the opposite effect. Induction of autophagy and lysosomal biogenesis through TFEB required MCOLN1-mediated calcineurin activation. These data link lysosomal calcium signalling to both calcineurin regulation and autophagy induction and identify the lysosome as a hub for the signalling pathways that regulate cellular homeostasis. Medina, Ballabio and colleagues report that calcium release from the lysosome stimulates calcineurin, which dephosphorylates and activates TFEB. These findings reveal a central role for calcium signalling in autophagy and lysosome homeostasis.

The Transient Receptor Potential Ankyrin 1 channel (TRPA1), is a member of the large TRP family of ion channels, and functions as a Ca 2+ permeable non-selective cation channel in many different cell processes, ranging from sensory to homeostatic tasks. TRPA1 is highly conserved across the animal kingdom. The only mammalian TRPA subfamily member, TRPA1, is widely expressed in neuronal (e.g. sensory dorsal root and trigeminal ganglia neurons)- and in non-neuronal cells (e.g. epithelial cells, hair cells). It exhibits 14–19 amino-( N -)terminal ankyrin repeats, an unusual structural feature. The TRPA1 channel is activated by noxious cold (<17 °C) as well as by a plethora of chemical compounds that includes not only electrophilic compounds and oxidants that can modify, in an alkylative or oxidative fashion, nucleophilic cysteine residues in the channel’s N -terminus, but also compounds that do not covalently bind to the channel proteins (e.g. menthol, nifedipin). Based on localization and functional properties, TRPA1 is considered a key player in acute and chronic (neuropathic) pain and inflammation. Moreover, its role in the (patho)physiology of nearly all organ systems is anticipated, and will be discussed along with the potential of TRPA1 as a drug target for the management of various pathological conditions.

The structure of mouse transient receptor potential mucolipin 1 (TRPML1), a cation channel located within endosomal and lysosomal membranes, is resolved using single-particle electron cryo-microscopy. Closing in on ion channels Numerous ion channels sit in the membranes of intracellular organelles and are responsible for maintaining concentration gradients and ionic signalling. The transient receptor potential mucolipin (TRPML) channels are Ca( II )-releasing channels that are crucial to endolysosomal function. While TRPML channels regulate physiological processes including membrane trafficking and exocytosis, mutations of TRPML1 cause the lysosomal storage disorder mucolipidosis type IV. Three papers in this issue of Nature report the structure of TRPML channels by cryo-electron microscopy. Seok-Yong Lee and colleagues report the structure of TRPML3, while studies from teams led by Xiaochun Li and Youxing Jiang present the structure of TRPML1. Together, these studies reveal the open and closed states of the TRPML family, indicating the regulatory mechanisms of these channels. As with most TRP channels, TRPML can be gated by specific lipids, and these studies provide insights into substrate binding and channel activation. Transient receptor potential mucolipin 1 (TRPML1) is a cation channel located within endosomal and lysosomal membranes. Ubiquitously expressed in mammalian cells 1 , 2 , its loss-of-function mutations are the direct cause of type IV mucolipidosis, an autosomal recessive lysosomal storage disease 3 , 4 , 5 , 6 . Here we present the single-particle electron cryo-microscopy structure of the mouse TRPML1 channel embedded in nanodiscs. Combined with mutagenesis analysis, the TRPML1 structure reveals that phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P 2 ) binds to the N terminus of the channel—distal from the pore—and the helix–turn–helix extension between segments S2 and S3 probably couples ligand binding to pore opening. The tightly packed selectivity filter contains multiple ion-binding sites, and the conserved acidic residues form the luminal Ca 2+ -blocking site that confers luminal pH and Ca 2+ modulation on channel conductance. A luminal linker domain forms a fenestrated canopy atop the channel, providing several luminal ion passages to the pore and creating a negative electrostatic trap, with a preference for divalent cations, at the luminal entrance. The structure also reveals two equally distributed S4–S5 linker conformations in the closed channel, suggesting an S4–S5 linker-mediated PtdInsP 2 gating mechanism among TRPML channels 7 , 8 .

Key Points The role of transient receptor potential (TRP) channels is best understood in the pain area. As TRP channels are expressed on peripheral nociceptors, where pain is generated, it is hoped that TRP channel blockers will be devoid of the side effects that limit the use of analgesic agents that act on the central nervous system. Several TRP cation channel subfamily V, member 1 (TRPV1) antagonists have advanced to clinical trials, but their side effects (which include hyperthermia and impaired noxious heat detection) have prevented any compounds from progressing beyond Phase II clinical trials. TRPV3 antagonists have shown efficacy in models of neuropathic and inflammatory pain, and one antagonist has entered Phase I clinical trials. An autosomal dominant mutation in the gene that encodes TRP cation channel subfamily A, member 1 (TRPA1) causes familial episodic pain syndrome. Indeed, TRPA1 antagonists have been shown to reduce cold hypersensitivity in rodent models of neuropathic pain without altering normal cold sensation in naive animals. Several TRP channels (such as TRPV1, TRPV4 and TRP cation channel subfamily M, member 8 (TRPM8)) are expressed in the urinary bladder, where they presumably function as sensors of stretch and chemical irritation. TRPV1 and TRPV4 antagonists improve bladder function in rodent models of cystitis. Populations of non-neuronal cells within the skin express many different types of TRP channels that are implicated in the regulation of several key cutaneous functions including skin-derived pruritus, proliferation, differentiation and inflammatory processes. TRPA1 and TRPV1 serve as polymodal sensors in the mammalian respiratory tract that integrate varied inflammatory, oxidant and hazardous irritant stimuli to produce noxious sensations (for example, breathlessness, the urge to cough and nasopharyngeal pain) and respiratory reflexes such as coughing. Several TRP channels — including members of TRP cation channel subfamily C (TRPC) and TRPV — influence the process of gas exchange by regulating airflow, blood flow and airway permeability. Mutations in at least six of the 28 members of the TRP channel superfamily are associated with heritable genetic diseases in humans. These mutations have implicated TRP channels in many pathophysiological states and expanded our understanding of the physiological role of these channels. The role of TRP channels in the brain remains to be elucidated, but it seems to be clear that some members of the superfamily are involved in neuronal excitability and neurotransmitter release. Genetic deletion of TRPC5 leads to an anxiolytic phenotype, whereas a point mutation in TRPC3 leads to ataxia. TRP channels also serve important functions in other diseases that are not fully explored in this Review. For example, cancer and metabolic diseases will be particularly interesting to watch in the future. Transient receptor potential (TRP) channels are a diverse family of cation channels. Here, the authors discuss recent developments in this area, highlight recent developments and setbacks in the field of pain research and analyse TRP channels as targets for skin, pulmonary and urological disorders. Transient receptor potential (TRP) cation channels have been among the most aggressively pursued drug targets over the past few years. Although the initial focus of research was on TRP channels that are expressed by nociceptors, there has been an upsurge in the amount of research that implicates TRP channels in other areas of physiology and pathophysiology, including the skin, bladder and pulmonary systems. In addition, mutations in genes encoding TRP channels are the cause of several inherited diseases that affect a variety of systems including the renal, skeletal and nervous system. This Review focuses on recent developments in the TRP channel-related field, and highlights potential opportunities for therapeutic intervention.

Atopic dermatitis (AD) is a multifaceted, chronic relapsing inflammatory skin disease that affects people of all ages. It is characterized by chronic eczema, constant pruritus, and severe discomfort. AD often progresses from mild annoyance to intractable pruritic inflammatory lesions associated with exacerbated skin sensitivity. The T helper-2 (Th2) response is mainly linked to the acute and subacute phase, whereas Th1 response has been associated in addition with the chronic phase. IL-17, IL-22, TSLP, and IL-31 also play a role in AD. Transient receptor potential (TRP) cation channels play a significant role in neuroinflammation, itch and pain, indicating neuroimmune circuits in AD. However, the Th2-driven cutaneous sensitization of TRP channels is underappreciated. Emerging findings suggest that critical Th2-related cytokines cause potentiation of TRP channels, thereby exaggerating inflammation and itch sensation. Evidence involves the following: (i) IL-13 enhances TRPV1 and TRPA1 transcription levels; (ii) IL-31 sensitizes TRPV1 via transcriptional and channel modulation, and indirectly modulates TRPV3 in keratinocytes; (iii) The Th2-cytokine TSLP increases TRPA1 synthesis in sensory neurons. These changes could be further enhanced by other Th2 cytokines, including IL-4, IL-25, and IL-33, which are inducers for IL-13, IL-31, or TSLP in skin. Taken together, this review highlights that Th2 cytokines potentiate TRP channels through diverse mechanisms under different inflammatory and pruritic conditions, and link this effect to distinct signaling cascades in AD. This review strengthens the notion that interrupting Th2-driven modulation of TRP channels will inhibit transition from acute to chronic AD, thereby aiding the development of effective therapeutics and treatment optimization.

Receptors implicated in cough hypersensitivity are transient receptor potential vanilloid 1 (TRPV1), transient receptor potential cation channel, Subfamily A, Member 1 (TRPA1) and acid sensing ion channel receptor 3 (ASIC3). Respiratory viruses, such as respiratory syncytial virus (RSV) and measles virus (MV) may interact directly and/or indirectly with these receptors on sensory nerves and epithelial cells in the airways. We used in vitro models of sensory neurones (SHSY5Y or differentiated IMR-32 cells) and human bronchial epithelium (BEAS-2B cells) as well as primary human bronchial epithelial cells (PBEC) to study the effect of MV and RSV infection on receptor expression. Receptor mRNA and protein levels were examined by qPCR and flow cytometry, respectively, following infection or treatment with UV inactivated virus, virus-induced soluble factors or pelleted virus. Concentrations of a range of cytokines in resultant BEAS-2B and PBEC supernatants were determined by ELISA. Up-regulation of TRPV1, TRPA1 and ASICS3 expression occurred by 12 hours post-infection in each cell type. This was independent of replicating virus, within the same cell, as virus-induced soluble factors alone were sufficient to increase channel expression. IL-8 and IL-6 increased in infected cell supernatants. Antibodies against these factors inhibited TRP receptor up-regulation. Capsazepine treatment inhibited virus induced up-regulation of TRPV1 indicating that these receptors are targets for treating virus-induced cough.

Cation channels of the transient receptor potential (TRP) family serve important physiological roles by opening in response to diverse intra- and extracellular stimuli that regulate their lower or upper gates. Despite extensive studies, the mechanism coupling these gates has remained obscure. Previous structures have failed to resolve extracellular loops, known in the TRPV subfamily as ‘pore turrets’, which are proximal to the upper gates. We established the importance of the pore turret through activity assays and by solving structures of rat TRPV2, both with and without an intact turret at resolutions of 4.0 Å and 3.6 Å, respectively. These structures resolve the full-length pore turret and reveal fully open and partially open states of TRPV2, both with unoccupied vanilloid pockets. Our results suggest a mechanism by which physiological signals, such as lipid binding, can regulate the lower gate and couple to the upper gate through a pore-turret-facilitated mechanism.

Mechanotransduction channels studied to date are mainly involved with sensing noxious mechanical stimuli; here NOMPC, a member of the TRP ion channel family, is identified as a pore-forming subunit of an ion channel essential to the sensation of gentle touch in Drosophila . The gentle touch of the fruitfly Like vertebrates, Drosophila can perform mechanical sensing, such as gravity sensing, hearing, proprioception, mechanical nociception and gentle-touch sensation. The mechanotransduction channels studied to date are mostly involved in sensing noxious stimuli. Now Yuh Nung Jan and colleagues identify NOMPC—a member of the transient receptor potential family of ion channels—as a pore-forming subunit of an ion channel essential to the sensation of gentle touch in Drosophila . Functional studies suggest that different mechanosensitive channels may be used to sense gentle touch and noxious mechanical stimuli. Touch sensation is essential for behaviours ranging from environmental exploration to social interaction; however, the underlying mechanisms are largely unknown 1 . In Drosophila larvae, two types of sensory neurons, class III and class IV dendritic arborization neurons, tile the body wall. The mechanotransduction channel PIEZO in class IV neurons is essential for sensing noxious mechanical stimuli but is not involved in gentle touch 2 . On the basis of electrophysiological-recording, calcium-imaging and behavioural studies, here we report that class III dendritic arborization neurons are touch sensitive and contribute to gentle-touch sensation. We further identify NOMPC (No mechanoreceptor potential C), a member of the transient receptor potential (TRP) family of ion channels, as a mechanotransduction channel for gentle touch. NOMPC is highly expressed in class III neurons and is required for their mechanotransduction. Moreover, ectopic NOMPC expression confers touch sensitivity to the normally touch-insensitive class IV neurons. In addition to the critical role of NOMPC in eliciting gentle-touch-mediated behavioural responses, expression of this protein in the Drosophila S2 cell line also gives rise to mechanosensitive channels in which ion selectivity can be altered by NOMPC mutation, indicating that NOMPC is a pore-forming subunit of a mechanotransduction channel. Our study establishes NOMPC as a bona fide mechanotransduction channel that satisfies all four criteria proposed for a channel to qualify as a transducer of mechanical stimuli 3 and mediates gentle-touch sensation. Our study also suggests that different mechanosensitive channels may be used to sense gentle touch versus noxious mechanical stimuli.

To mediate the degradation of biomacromolecules, lysosomes must traffic towards cargo-carrying vesicles for subsequent membrane fusion or fission. Mutations of the lysosomal Ca 2+ channel TRPML1 cause lysosomal storage disease (LSD) characterized by disordered lysosomal membrane trafficking in cells. Here we show that TRPML1 activity is required to promote Ca 2+ -dependent centripetal movement of lysosomes towards the perinuclear region (where autophagosomes accumulate) following autophagy induction. ALG-2, an EF-hand-containing protein, serves as a lysosomal Ca 2+ sensor that associates physically with the minus-end-directed dynactin–dynein motor, while PtdIns(3,5)P 2 , a lysosome-localized phosphoinositide, acts upstream of TRPML1. Furthermore, the PtdIns(3,5)P 2 –TRPML1–ALG-2–dynein signalling is necessary for lysosome tubulation and reformation. In contrast, the TRPML1 pathway is not required for the perinuclear accumulation of lysosomes observed in many LSDs, which is instead likely to be caused by secondary cholesterol accumulation that constitutively activates Rab7–RILP-dependent retrograde transport. Ca 2+ release from lysosomes thus provides an on-demand mechanism regulating lysosome motility, positioning and tubulation. Following autophagy induction, lysosomes move to the perinuclear region. Xu and colleagues delineate a pathway involving PtdIns(3,5)P 2 -mediated activation of the TRPML1 channel and the Ca 2+ sensor ALG-2 in this process.