The TRP superfamily of cation channels

Genome-wide characterization of the TRP gene family and transcriptional expression profiles under different temperatures in gecko Hemiphyllodactylus yunnanensis

Temperature is closely linked to the life history of organisms, and thus thermoception is an important sensory mechanism. Transient receptor potential (TRP) ion channels are the key mediators of thermal sensation. In this study, we analyzed the sequence characteristics of TRPs in gecko Hemiphyllodactylus yunnanensis and compared the phylogenetic relationships of TRP family members among different Squamata species. In addition, we sequenced the transcriptome of skin and brain tissues of H. yunnanensis exposed to 12 °C (cold), 20 °C (cool), 28 °C (warm), and 36 °C (hot). The results showed that a total of 591 TRPs were identified in the genomes of 21 Squamate species, and these genes were classified into six subfamilies. Among them, 26 TRP genes were identified in H. yunnanensis and distributed on 13 chromosomes. Overall, TRP genes were conserved in squamates. Based on the transcriptome results, we found a total of 9 TRP genes expressed in the brain and skin of H. yunnanensis, of which six TRP genes were under positive selection. TRPP1L2, TRPP1L3, and TRPV1 were involved in heat-sensitive responses (> 36 °C), and TRPV3, TRPA1, and TRPM8 were involved in cold-sensitive responses (< 20 °C). TRPM8 and TRPP1L2 were important cold and heat sensors in H. yunnanensis, respectively.

Brg1 and RUNX1 synergy in regulating TRPM4 channel in mouse cardiomyocytes

Background

Transient Receptor Potential Melastatin 4 (TRPM4), a non-selective cation channel, plays a critical role in cardiac conduction abnormalities. Brg1, an ATP-dependent chromatin remodeler, is essential for regulating gene expression in both heart development and disease. Our previous studies demonstrated Brg1 impacted on cardiac sodium/potassium channels and electrophysiological stability, its influence on TRPM4 expression and function remained unexplored.

Methods

We investigated the role of Brg1 in regulating TRPM4 expression and function through overexpression and knockdown experiments in mouse cardiomyocytes and TRPM4-overexpressing HEK293 cells by western blot, qPCR, immunofluorescence staining and patch clamp techniques. Cardiomyocytes were exposed to hypoxia for 12 h to mimic cardiac stress, and Brg1 inhibition was performed to assess its impact on TRPM4 under hypoxia. Bioinformatic analyses (STRING and JASPAR databases), Co-immunoprecipitation (Co-IP), dual luciferase reporter assays, and Chromatin Immunoprecipitation (ChIP) were employed to study the interaction between Brg1, RUNX1, and TRPM4 transcription regulation.

Results

Brg1 positively regulated TRPM4 expression in mouse cardiomyocytes and modulated TRPM4 current in TRPM4-overexpressing HEK293 cells. Brg1 inhibition markedly diminishes TRPM4's hyperexpression in cardiomyocytes exposed to hypoxia. Integrative analyses utilizing STRNG databases and Protein Data Bank unveiled a putative interaction between Brg1 and the transcription factor RUNX1, and we substantiated the interaction between Brg1 and RUNX1. Several binding sites of RUNX1 with the TRPM4 promoter region were predicted by the JASPAR database, and empirical validation substantiated Brg1 modulated TRPM4 promoter activity via RUNX1 engagement. ChIP confirmed that Brg1 interacted with RUNX1 forming a transcriptional complex that located in TRPM4 promoter.

Conclusion

Our study demonstrated that Brg1 and RUNX1 formed a transcriptional complex that modulated TRPM4 expression and function, especially under hypoxic conditions. These findings provided new insights into TRPM4 regulation and highlighted its potential as a therapeutic target for cardiac hypoxia-related disorders.

Recent advances on the structure and the function relationships of the TRPV4 ion channel

The members of the superfamily of Transient Receptor Potential (TRP) ion channels are physiologically important molecules that have been studied for many years and are still being intensively researched. Among the vanilloid TRP subfamily, the TRPV4 ion channel is an interesting protein due to its involvement in several essential physiological processes and in the development of various diseases. As in other proteins, changes in its function that lead to the development of pathological states, have been closely associated with modification of its regulation by different molecules, but also by the appearance of mutations which affect the structure and gating of the channel. In the last few years, some structures for the TRPV4 channel have been solved. Due to the importance of this protein in physiology, here we discuss the recent progress in determining the structure of the TRPV4 channel, which has been achieved in three species of animals (Xenopus tropicalis, Mus musculus, and Homo sapiens), highlighting conserved features as well as key differences among them and emphasizing the binding sites for some ligands that play crucial roles in its regulation.

Gut symbiont-derived anandamide promotes reward learning in honeybees by activating the endocannabinoid pathway

Polyunsaturated fatty acids (PUFAs) are dietary components participating in neurotransmission and cell signaling. Pollen is a source of PUFAs for honeybees, and disruptions in dietary PUFAs reduce the cognitive performance of honeybees. We reveal that gut bacteria of honeybees contribute to fatty acid metabolism, impacting reward learning. Gut bacteria possess Δ-6 desaturases that mediate fatty acid elongation and compensate for the absence of honeybee factors required for fatty acid metabolism. Colonization with Gilliamella apicola, but not a mutant lacking the Δ-6 desaturase FADS2, increases the production of anandamide (AEA), a ligand of the endocannabinoid system, and alters learning and memory. AEA activates the Hymenoptera-specific transient receptor AmHsTRPA in astrocytes, which induces Ca2+ influx and regulates glutamate re-uptake of glial cells to enhance reward learning. These findings illuminate the roles of gut symbionts in host fatty acid metabolism and the impacts of endocannabinoid signaling on the reward system of social insects.

TRPC6 is ubiquitously present in lymphatic tissues: A study using samples from body donors

Transient receptor potential canonical channel 6 (TRPC6) is a non-selective cation channel that is activated by diacylglycerol. It belongs to the TRP superfamily, is expressed in numerous tissues and has been shown to be associated with diseases, such as focal segmental glomerulosclerosis, idiopathic pulmonary arterial hypertension and cardiac hypertrophy. The investigation of the channel in human lymphoid tissues has thus far been limited to mRNA analysis or the western blotting of isolated lymphoid cell lines. The present study aimed to detect the channel in human lymphoid tissue using immunohistochemistry. For this purpose, lymphatic tissues were obtained from body donors. The lymphatic organs analyzed included the lymph nodes, spleen, palatine tonsil, gut-associated lymphoid tissues (ileum and vermiform appendix) and thymus. A total of 102 samples were obtained and processed for hematoxylin and eosin (H&E) staining. The H&E staining method was employed to identify five samples with good morphology. In total, three samples of the palatine tonsil of patients were included. Immunostaining was carried out using a knockout-validated anti-TRPC6 antibody. As shown by the results, using immunohistochemical staining, the presence of TRPC6 was confirmed in all the analyzed lymphatic tissue samples. Lymphocytes in lymph nodes, spleen, palatine tonsil, thymus, and gut-associated lymphatic tissues in ileum and vermiform appendix exhibited a positive staining signal. The follicle-associated epithelium of the palatine tonsil, ileum and appendix also demonstrated staining. Vessels of the lymphatic organs, particularly the trabecular arteries of the spleen, the submucosal vessels of the appendix and ileum, as well as the high endothelial venules in the palatine tonsils and lymphatic vessels of the lymph nodes expressed TRPC6 protein. TRPC6 in follicles may be involved in the immune response. TRPC6 in high endothelial venules suggests a role in leukocyte migration. The role of TRPC6 and other channels of the TRP family in lymphatic organs warrant further investigations to elucidate whether TRP channels are a pharmacological target.

Mechanosensitive ion channels in glaucoma pathophysiology

Force sensing is a fundamental ability that allows cells and organisms to interact with their physical environment. The eye is constantly subjected to mechanical forces such as blinking and eye movements. Furthermore, elevated intraocular pressure (IOP) can cause mechanical strain at the optic nerve head, resulting in retinal ganglion cell death (RGC) in glaucoma. How mechanical stimuli are sensed and affect cellular physiology in the eye is unclear. Recent studies have shown that mechanosensitive ion channels are expressed in many ocular tissues relevant to glaucoma and may influence IOP regulation and RGC survival. Furthermore, variants in mechanosensitive ion channel genes may be associated with risk for primary open angle glaucoma. These findings suggest that mechanosensitive channels may be important mechanosensors mediating cellular responses to pressure signals in the eye. In this review, we focus on mechanosensitive ion channels from three major channel families-PIEZO, two-pore potassium and transient receptor potential channels. We review the key properties of these channels, their effects on cell function and physiology, and discuss their possible roles in glaucoma pathophysiology.

Functions of TRPs in retinal tissue in physiological and pathological conditions

The Transient Receptor Potential (TRP) constitutes a family of channels subdivided into seven subfamilies: Ankyrin (TRPA), Canonical (TRPC), Melastatin (TRPM), Mucolipin (TRPML), no-mechano-potential C (TRPN), Polycystic (TRPP), and Vanilloid (TRPV). Although they are structurally similar to one another, the peculiarities of each subfamily are key to the response to stimuli and the signaling pathway that each one triggers. TRPs are non-selective cation channels, most of which are permeable to Ca2+, which is a well-established second messenger that modulates several intracellular signaling pathways and is involved in physiological and pathological conditions in various cell types. TRPs depolarize excitable cells by increasing the influx of Ca2+, Na+, and other cations. Most TRP families are activated by temperature variations, membrane stretching, or chemical agents and, therefore, are defined as polymodal channels. All TPRs are expressed, at some level, in the central nervous system (CNS) and ocular-related structures, such as the retina and optic nerve (ON), except the TRPP in the ON. TRPC, TRPM, TRPV, and TRPML are found in the retinal pigmented cells, whereas only TRPA1 and TRPM are detected in the uvea. Accordingly, several studies have focused on the search to unravel the role of TRPs in physiological and pathological conditions related to the eyes. Thus, this review aims to shed light on endogenous and exogenous modulators, triggered cell signaling pathways, and localization and roles of each subfamily of TRP channels in physiological and pathological conditions in the retina, optic nerve, and retinal pigmented epithelium of vertebrates.

Latest Insights into the In Vivo Studies in Murine Regarding the Role of TRP Channels in Wound Healing-A Review

Wound healing involves physical, chemical and immunological processes. Transient receptor potential (TRP) and other ion channels are implicated in epidermal re-epithelization. Ion movement across ion channels can induce transmembrane potential that leads to transepithelial potential (TEP) changes. TEP is present in epidermis surrounding the lesion decreases and induces an endogenous direct current generating an epithelial electric field (EF) that could be implicated in wound re-epithelialization. TRP channels are involved in the activation of immune cells during mainly the inflammatory phase of wound healing. The aim of the study was to review the mechanisms of ion channel involvement in wound healing in in vivo experiments in murine (mice, rats) and how can this process be influenced. This review used the latest results published in scientific journals over the last year and this year to date (1 January 2023-31 December 3000) in order to include the in-press articles. Some types of TRP channels, such as TRPV1, TRPV3 and TRPA1, are expressed in immune cells and can be activated by inflammatory mediators. The most beneficial effects in wound healing are produced using agonists of TRPV1, TRPV4 and TRPA1 channels or by inhibiting with antagonists, antisense oligonucleotides or knocking down TRPV3 and TRPM8 channels.

TRPV4 affects visual signals in photoreceptors and rod bipolar cells

Introduction

Mechanical sensitive channels expressed in mammalian retinas are effectors of elevated pressure stresses, but it is unclear how their activation affects visual function in pressure-related retinal disorders.

Methods

This study investigated the role of the transient potential channel vanilloid TRPV4 in photoreceptors and rod bipolar cells (RBCs) with immunohistochemistry, confocal microscopy, electroretinography (ERG), and patch-clamp techniques.

Results

TRPV4 immunoreactivity (IR) was found in the outer segments of photoreceptors, dendrites and somas of PKCα-positive RBCs and other BCs, plexiform layers, and retinal ganglion cells (RGCs) in wild-type mice. TRPV4-IR was largely diminished in the retinas of homozygous TRPV4 transgenic mice. Genetically suppressing TRPV4 expression moderately but significantly enhanced the amplitude of ERG a- and b-waves evoked by scotopic and mesopic lights (0.55 to 200 Rh*rod-1 s-1) and photopic lights (105-106 Rh*rod-1 s-1) compared to wild-type mice in fully dark-adapted conditions. The implicit time evoked by dim lights (0.55 to 200 Rh*rod-1 s-1) was significantly decreased for b-waves and elongated for a-waves in the transgenic mice. ERG b-wave evoked by dim lights is primarily mediated by RBCs, and under voltage-clamp conditions, the latency of the light-evoked cation current in RBCs of the transgenic mice was significantly shorter compared to wild-type mice. About 10% of the transgenic mice had one eye undeveloped, and the percentage was significantly higher than in wild-type mice.

Conclusions

The data indicates that TRPV4 involves ocular development and is expressed and active in outer retinal neurons, and interventions of TRPV4 can variably affect visual signals in rods, cones, RBCs, and cone ON BCs.

Function and mechanism of action of the TRPV1 channel in the development of triple-negative breast cancer

Transient receptor potential channel subfamily vanilloid 1 (TRPV1) is a member of the transient receptor potential family of nonselective cationic transmembrane channel proteins that are involved in the regulation of calcium homeostasis. It is expressed in various tumor types and has been implicated in the regulation of cancer growth, metastasis, apoptosis, and cancer-related pain. TRPV1 is highly expressed in triple-negative breast cancer (TNBC), and both its agonists and antagonists may exert anti-cancer effects. In this review, we provide an overview of the effect of TRPV1 on TNBC development and its influence on immunotherapy in an attempt to facilitate the development of future treatment strategies.

The Variety of Mechanosensitive Ion Channels in Retinal Neurons

Alterations in intraocular and external pressure critically involve the pathogenesis of glaucoma, traumatic retinal injury (TRI), and other retinal disorders, and retinal neurons have been reported to express multiple mechanical-sensitive channels (MSCs) in recent decades. However, the role of MSCs in visual functions and pressure-related retinal conditions has been unclear. This review will focus on the variety and functional significance of the MSCs permeable to K+, Na+, and Ca2+, primarily including the big potassium channel (BK); the two-pore domain potassium channels TRAAK and TREK; Piezo; the epithelial sodium channel (ENaC); and the transient receptor potential channels vanilloid TRPV1, TRPV2, and TRPV4 in retinal photoreceptors, bipolar cells, horizontal cells, amacrine cells, and ganglion cells. Most MSCs do not directly mediate visual signals in vertebrate retinas. On the other hand, some studies have shown that MSCs can open in physiological conditions and regulate the activities of retinal neurons. While these data reasonably predict the crossing of visual and mechanical signals, how retinal light pathways deal with endogenous and exogenous mechanical stimulation is uncertain.

Transient Receptor Potential Channels in Sensory Mechanisms of the Lower Urinary Tract

BACKGROUND

Urine storage and excretion require a network of interactions in the urinary tract and the central nervous system, which is mediated by a reservoir of water in the bladder and the outlet to the bladder neck, urethra, and external urethral sphincter. Through communicating and coordinating each other, micturition system eventually showed a switch-like activity pattern.

SUMMARY

At cervicothoracic and lumbosacral spine, the spinal reflex pathway of the lower urinary tract (LUT) received mechanosensory input from the urothelium to regulate the bladder contraction activity, thereby controlled urination voluntarily. Impairment of above-mentioned any level could result in lower urinary tract dysfunction, placed a huge burden on patients and society. Specific expression of purinergic receptors and transient receptor potential (TRP) channels are thought to play an important role in urinary excretion in the LUT.

KEY MESSAGES

This article reviewed the knowledge about the voiding reflex and described the role and function of TRP channels during voiding.

Calcium and Neural Stem Cell Proliferation

Intracellular calcium plays a pivotal role in central nervous system (CNS) development by regulating various processes such as cell proliferation, migration, differentiation, and maturation. However, understanding the involvement of calcium (Ca2+) in these processes during CNS development is challenging due to the dynamic nature of this cation and the evolving cell populations during development. While Ca2+ transient patterns have been observed in specific cell processes and molecules responsible for Ca2+ homeostasis have been identified in excitable and non-excitable cells, further research into Ca2+ dynamics and the underlying mechanisms in neural stem cells (NSCs) is required. This review focuses on molecules involved in Ca2+ entrance expressed in NSCs in vivo and in vitro, which are crucial for Ca2+ dynamics and signaling. It also discusses how these molecules might play a key role in balancing cell proliferation for self-renewal or promoting differentiation. These processes are finely regulated in a time-dependent manner throughout brain development, influenced by extrinsic and intrinsic factors that directly or indirectly modulate Ca2+ dynamics. Furthermore, this review addresses the potential implications of understanding Ca2+ dynamics in NSCs for treating neurological disorders. Despite significant progress in this field, unraveling the elements contributing to Ca2+ intracellular dynamics in cell proliferation remains a challenging puzzle that requires further investigation.

Transient Receptor Potential Canonical 5 (TRPC5): Regulation of Heart Rate and Protection against Pathological Cardiac Hypertrophy

TRPC5 is a non-selective cation channel that is expressed in cardiomyocytes, but there is a lack of knowledge of its (patho)physiological role in vivo. Here, we examine the role of TRPC5 on cardiac function under basal conditions and during cardiac hypertrophy. Cardiovascular parameters were assessed in wild-type (WT) and global TRPC5 knockout (KO) mice. Despite no difference in blood pressure or activity, heart rate was significantly reduced in TRPC5 KO mice. Echocardiography imaging revealed an increase in stroke volume, but cardiac contractility was unaffected. The reduced heart rate persisted in isolated TRPC5 KO hearts, suggesting changes in basal cardiac pacing. Heart rate was further investigated by evaluating the reflex change following drug-induced pressure changes. The reflex bradycardic response following phenylephrine was greater in TRPC5 KO mice but the tachycardic response to SNP was unchanged, indicating an enhancement in the parasympathetic control of the heart rate. Moreover, the reduction in heart rate to carbachol was greater in isolated TRPC5 KO hearts. To evaluate the role of TRPC5 in cardiac pathology, mice were subjected to abdominal aortic banding (AAB). An exaggerated cardiac hypertrophy response to AAB was observed in TRPC5 KO mice, with an increased expression of hypertrophy markers, fibrosis, reactive oxygen species, and angiogenesis. This study provides novel evidence for a direct effect of TRPC5 on cardiac function. We propose that (1) TRPC5 is required for maintaining heart rate by regulating basal cardiac pacing and in response to pressure lowering, and (2) TRPC5 protects against pathological cardiac hypertrophy.

TRPM5 activation depends on a synergistic effect of calcium and PKC phosphorylation

Transient receptor potential melastatin 5 (TRPM5) is a calcium-activated monovalent-specific ion channel involved in insulin secretion and taste transduction, making it an attractive target for drug development in various pathologies. While TRPM5 activation involves ligand binding to Gq/G-protein coupled receptors (GPCR) and subsequent elevation of intracellular calcium levels, recent reports suggest the need for additional molecular determinants. Hence, the mechanism of TRPM5 activation remains to be elucidated. Here, we show that PKC phosphorylation and the elevation of intracellular Ca2+ levels are required for TRPM5 activation, with PKC phosphorylation being crucial for channel-evoked currents, primarily at physiological membrane potentials. In contrast, physiological relevant calcium levels alone only induce TRPM5 activation at positive voltages. Our findings highlight the necessity of coordinated intracellular calcium release and PKC phosphorylation for TRPM5 activation. Thus, our results suggest that regulation of PKC activity could be a promising therapeutic target for diseases associated with TRPM5 modulation.

Molecular and structural basis of the dual regulation of the polycystin-2 ion channel by small-molecule ligands

Mutations in the PKD2 gene, which encodes the polycystin-2 (PC2, also called TRPP2) protein, lead to autosomal dominant polycystic kidney disease (ADPKD). As a member of the transient receptor potential (TRP) channel superfamily, PC2 functions as a non-selective cation channel. The activation and regulation of the PC2 channel are largely unknown, and direct binding of small-molecule ligands to this channel has not been reported. In this work, we found that most known small-molecule agonists of the mucolipin TRP (TRPML) channels inhibit the activity of the PC2_F604P, a gain-of-function mutant of the PC2 channel. However, two of them, ML-SA1 and SF-51, have dual regulatory effects, with low concentration further activating PC2_F604P, and high concentration leading to inactivation of the channel. With two cryo-electron microscopy (cryo-EM) structures, a molecular docking model, and mutagenesis results, we identified two distinct binding sites of ML-SA1 in PC2_F604P that are responsible for activation and inactivation, respectively. These results provide structural and functional insights into how ligands regulate PC2 channel function through unusual mechanisms and may help design compounds that are more efficient and specific in regulating the PC2 channel and potentially also for ADPKD treatment.

TRPM channels in health and disease

Different cell channels and transporters tightly regulate cytoplasmic levels and the intraorganelle distribution of cations. Perturbations in these processes lead to human diseases that are frequently associated with kidney impairment. The family of melastatin-related transient receptor potential (TRPM) channels, which has eight members in mammals (TRPM1-TRPM8), includes ion channels that are highly permeable to divalent cations, such as Ca2+, Mg2+ and Zn2+ (TRPM1, TRPM3, TRPM6 and TRPM7), non-selective cation channels (TRPM2 and TRPM8) and monovalent cation-selective channels (TRPM4 and TRPM5). Three family members contain an enzymatic protein moiety: TRPM6 and TRPM7 are fused to α-kinase domains, whereas TRPM2 is linked to an ADP-ribose-binding NUDT9 homology domain. TRPM channels also function as crucial cellular sensors involved in many physiological processes, including mineral homeostasis, blood pressure, cardiac rhythm and immunity, as well as photoreception, taste reception and thermoreception. TRPM channels are abundantly expressed in the kidney. Mutations in TRPM genes cause several inherited human diseases, and preclinical studies in animal models of human disease have highlighted TRPM channels as promising new therapeutic targets. Here, we provide an overview of this rapidly evolving research area and delineate the emerging role of TRPM channels in kidney pathophysiology.

Molecular details of ruthenium red pore block in TRPV channels

Transient receptor potential vanilloid (TRPV) channels play a critical role in calcium homeostasis, pain sensation, immunological response, and cancer progression. TRPV channels are blocked by ruthenium red (RR), a universal pore blocker for a wide array of cation channels. Here we use cryo-electron microscopy to reveal the molecular details of RR block in TRPV2 and TRPV5, members of the two TRPV subfamilies. In TRPV2 activated by 2-aminoethoxydiphenyl borate, RR is tightly coordinated in the open selectivity filter, blocking ion flow and preventing channel inactivation. In TRPV5 activated by phosphatidylinositol 4,5-bisphosphate, RR blocks the selectivity filter and closes the lower gate through an interaction with polar residues in the pore vestibule. Together, our results provide a detailed understanding of TRPV subfamily pore block, the dynamic nature of the selectivity filter and allosteric communication between the selectivity filter and lower gate.

Taste shaped the use of botanical drugs

The perception of taste and flavour (a combination of taste, smell, and chemesthesis), here also referred to as chemosensation, enables animals to find high-value foods and avoid toxins. Humans have learned to use unpalatable and toxic substances as medicines, yet the importance of chemosensation in this process is poorly understood. Here, we generate tasting-panel data for botanical drugs and apply phylogenetic generalised linear mixed models to test whether intensity and complexity of chemosensory qualities as well as particular tastes and flavours can predict ancient Graeco-Roman drug use. We found chemosensation to be strongly predictive of therapeutic use: botanical drugs with high therapeutic versatility have simple yet intense tastes and flavours, and 21 of 22 chemosensory qualities predicted at least one therapeutic use. In addition to the common notion of bitter tasting medicines, we also found starchy, musky, sweet, and soapy drugs associated with versatility. In ancient Greece and Rome, illness was thought to arise from imbalance in bodily fluids or humours, yet our study suggests that uses of drugs were based on observed physiological effects that are often consistent with modern understanding of chemesthesis and taste receptor pharmacology.

The Multifaceted Functions of TRPV4 and Calcium Oscillations in Tissue Repair

The transient receptor potential vanilloid 4 (TRPV4) specifically functions as a mechanosensitive ion channel and is responsible for conveying changes in physical stimuli such as mechanical stress, osmotic pressure, and temperature. TRPV4 enables the entry of cation ions, particularly calcium ions, into the cell. Activation of TRPV4 channels initiates calcium oscillations, which trigger intracellular signaling pathways involved in a plethora of cellular processes, including tissue repair. Widely expressed throughout the body, TRPV4 can be activated by a wide array of physicochemical stimuli, thus contributing to sensory and physiological functions in multiple organs. This review focuses on how TRPV4 senses environmental cues and thereby initiates and maintains calcium oscillations, critical for responses to organ injury, tissue repair, and fibrosis. We provide a summary of TRPV4-induced calcium oscillations in distinct organ systems, along with the upstream and downstream signaling pathways involved. In addition, we delineate current animal and disease models supporting TRPV4 research and shed light on potential therapeutic targets for modulating TRPV4-induced calcium oscillation to promote tissue repair while reducing tissue fibrosis.

Identification of transient receptor potential channel genes from the swimming crab, Portunus Trituberculatus, and their expression profiles under acute temperature stress

BACKGROUND

Temperature is an important environment factor that is critical to the survival and growth of crustaceans. However, the mechanisms by which crustaceans detect changes in temperature are still unclear. The transient receptor potential (TRP) channels are non-selective cation channels well known for properties in temperature sensation. However, comprehensive understandings on TRP channels as well as their temperature sensing functions are still lacking in crustaceans.

RESULTS

In this study, a total of 26 TRP genes were identified in the swimming crab, Portunus trituberculatus, which can be classified into TRPA, TRPC, TRPP, TRPM, TRPML, TRPN and TRPV. Tissue expression analysis revealed a wide distribution of these TRP genes in P. trituberculatus, and antennules, neural tissues, and ovaries were the most commonly expressed tissues. To investigate the responsiveness of TRP genes to the temperature change, 18 TRPs were selected to detect their expression after high and low temperature stress. The results showed that 12 TRPs showed induced gene expression in both high and low temperature groups, while 3 were down-regulated in the low temperature group, and 3 showed no change in expression in either group.

CONCLUSIONS

This study characterized the TRP family genes in P. trituberculatus, and explored their involvement in response to temperature stress. Our results will enhance overall understanding of crustacean TRP channels and their possible functions.

Targeting TRP channels: recent advances in structure, ligand binding, and molecular mechanisms

Transient receptor potential (TRP) channels are a large and diverse family of transmembrane ion channels that are widely expressed, have important physiological roles, and are associated with many human diseases. These proteins are actively pursued as promising drug targets, benefitting greatly from advances in structural and mechanistic studies of TRP channels. At the same time, the complex, polymodal activation and regulation of TRP channels have presented formidable challenges. In this short review, we summarize recent progresses toward understanding the structural basis of TRP channel function, as well as potential ligand binding sites that could be targeted for therapeutics. A particular focus is on the current understanding of the molecular mechanisms of TRP channel activation and regulation, where many fundamental questions remain unanswered. We believe that a deeper understanding of the functional mechanisms of TRP channels will be critical and likely transformative toward developing successful therapeutic strategies targeting these exciting proteins. This endeavor will require concerted efforts from computation, structural biology, medicinal chemistry, electrophysiology, pharmacology, drug safety and clinical studies.

The Role of TRPM7 in Oncogenesis

This review summarizes the current understanding of the role of transient receptor potential melastatin-subfamily member 7 (TRPM7) channels in the pathophysiology of neoplastic diseases. The TRPM family represents the largest and most diverse group in the TRP superfamily. Its subtypes are expressed in virtually all human organs playing a central role in (patho)physiological events. The TRPM7 protein (along with TRPM2 and TRPM6) is unique in that it has kinase activity in addition to the channel function. Numerous studies demonstrate the role of TRPM7 chanzyme in tumorigenesis and in other tumor hallmarks such as proliferation, migration, invasion and metastasis. Here we provide an up-to-date overview about the possible role of TRMP7 in a broad range of malignancies such as tumors of the nervous system, head and neck cancers, malignant neoplasms of the upper gastrointestinal tract, colorectal carcinoma, lung cancer, neoplasms of the urinary system, breast cancer, malignant tumors of the female reproductive organs, prostate cancer and other neoplastic pathologies. Experimental data show that the increased expression and/or function of TRPM7 are observed in most malignant tumor types. Thus, TRPM7 chanzyme may be a promising target in tumor therapy.

TRPC3 signalling contributes to the biogenesis of extracellular vesicles

Extracellular vesicles (EVs) contribute to a wide range of pathological processes including cancer progression, yet the molecular mechanisms underlying their biogenesis remain incompletely characterized. The development of tetraspanin-based pHluorin reporters has enabled the real-time analysis of EV release at the plasma membrane. Here, we employed CD81-pHluorin to investigate mechanisms of EV release in ovarian cancer (OC) cells and report a novel role for the Ca2+-permeable transient receptor potential (TRP) channel TRPC3 in EV-mediated communication. We found that specific activation of TRPC3 increased Ca2+ signalling in SKOV3 cells and stimulated an immediate increase in EV release. Ca2+-stimulants histamine and ionomycin likewise induced EV release, and imaging analysis revealed distinct stimulation-dependent temporal and spatial release dynamics. Interestingly, inhibition of TRPC3 attenuated histamine-stimulated Ca2+-entry and EV release, indicating that TRPC3 is likely to act downstream of histamine signalling in EV biogenesis. Furthermore, we found that direct activation of TRPC3 as well as the application of EVs derived from TRPC3-activated cells increased SKOV3 proliferation. Our data provides insights into the molecular mechanisms and dynamics underlying EV release in OC cells, proposing a key role for TRPC3 in EV biogenesis.

The versatility of the putative transient receptor potential ion channels in regulating the calcium signaling in Aspergillus nidulans

IMPORTANCE

Transient receptor potential (TRP) ion channels are evolutionarily conserved integral membrane proteins with non-selective ion permeability, and they are widely distributed in mammals and single-cell yeast and serve as crucial mediators of sensory signals. However, the relevant information concerning TRP channels in Aspergillus nidulans remains inadequately understood. In this study, by gene deletion, green fluorescent protein tagging, and cytosolic Ca2+ transient monitoring techniques, the biological functions of three potential TRP channels (TrpA, TrpB, and TrpC) have been explored for which they play distinct and multiple roles in hyphal growth, conidiation, responsiveness to external stress, and regulation of intracellular Ca2+ homeostasis. The findings of this study on the functions of potential TRP channels in A. nidulans may serve as a valuable reference for understanding the roles of TRP homologs in industrial or medical strains of Aspergillus, as well as in other filamentous fungi.

Regulatory mechanisms controlling store-operated calcium entry

Calcium influx through plasma membrane ion channels is crucial for many events in cellular physiology. Cell surface stimuli lead to the production of inositol 1,4,5-trisphosphate (IP3), which binds to IP3 receptors (IP3R) in the endoplasmic reticulum (ER) to release calcium pools from the ER lumen. This leads to the depletion of ER calcium pools, which has been termed store depletion. Store depletion leads to the dissociation of calcium ions from the EF-hand motif of the ER calcium sensor Stromal Interaction Molecule 1 (STIM1). This leads to a conformational change in STIM1, which helps it to interact with the plasma membrane (PM) at ER:PM junctions. At these ER:PM junctions, STIM1 binds to and activates a calcium channel known as Orai1 to form calcium release-activated calcium (CRAC) channels. Activation of Orai1 leads to calcium influx, known as store-operated calcium entry (SOCE). In addition to Orai1 and STIM1, the homologs of Orai1 and STIM1, such as Orai2/3 and STIM2, also play a crucial role in calcium homeostasis. The influx of calcium through the Orai channel activates a calcium current that has been termed the CRAC current. CRAC channels form multimers and cluster together in large macromolecular assemblies termed "puncta". How CRAC channels form puncta has been contentious since their discovery. In this review, we will outline the history of SOCE, the molecular players involved in this process, as well as the models that have been proposed to explain this critical mechanism in cellular physiology.

Functional dynamics and allosteric modulation of TRPA1

The cation channel TRPA1 is a potentially important drug target, and characterization of TRPA1 functional dynamics might help guide structure-based drug design. Here, we present results from long-timescale molecular dynamics simulations of TRPA1 with an allosteric activator, allyl isothiocyanate (AITC), in which we observed spontaneous transitions from a closed, non-conducting channel conformation into an open, conducting conformation. Based on these transitions, we propose a gating mechanism in which movement of a regulatory TRP-like domain allosterically translates into pore opening in a manner reminiscent of pore opening in voltage-gated ion channels. In subsequent experiments, we found that mutations that disrupt packing of the S4-S5 linker-TRP-like domain and the S5 and S6 helices also affected channel activity. In simulations, we also observed A-967079, a known allosteric inhibitor, binding between helices S5 and S6, suggesting that A-967079 may suppress activity by stabilizing a non-conducting pore conformation-a finding consistent with our proposed gating mechanism.

An update on mechanisms of pruritus and their potential treatment in primary cutaneous T-cell lymphoma

Primary cutaneous T-cell lymphomas (CTCL), which include mycosis fungoides (MF) and Sézary syndrome (SS), are a group of lymphoproliferative disorders characterized by clonal accumulation of neoplastic T-lymphocytes in the skin. Severe pruritus, one of the most common and distressing symptoms in primary CTCL, can significantly impair emotional well-being, physical functioning, and interpersonal relationships, thus greatly reducing quality of life. Unfortunately, effectively managing pruritus remains challenging in CTCL patients as the underlying mechanisms are, as of yet, not fully understood. Previous studies investigating the mechanisms of itch in CTCL have identified several mediators and their corresponding antagonists used for treatment. However, a comprehensive overview of the mediators and receptors contributing to pruritus in primary CTCL is lacking in the current literature. Here, we summarize and review the mediators and receptors that may contribute to pruritus in primary CTCL to explore the mechanisms of CTCL pruritus and identify effective therapeutic targets using the PubMed and Web of Science databases. Studies were included if they described itch mediators and receptors in MF and SS. Overall, the available data suggest that proteases (mainly tryptase), and neuropeptides (particularly Substance P) may be of greatest interest. At the receptor level, cytokine receptors, MRGPRs, and TRP channels are most likely important. Future drug development efforts should concentrate on targeting these mediators and receptors for the treatment of CTCL pruritus.

Ouabain's Influence on TRPV4 Channels of Epithelial Cells: An Exploration of TRPV4 Activity, Expression, and Signaling Pathways

Ouabain, a substance originally obtained from plants, is now classified as a hormone because it is produced endogenously in certain animals, including humans. However, its precise effects on the body remain largely unknown. Previous studies have shown that ouabain can influence the phenotype of epithelial cells by affecting the expression of cell-cell molecular components and voltage-gated potassium channels. In this study, we conducted whole-cell clamp assays to determine whether ouabain affects the activity and/or expression of TRPV4 channels. Our findings indicate that ouabain has a statistically significant effect on the density of TRPV4 currents (dITRPV4), with an EC50 of 1.89 nM. Regarding treatment duration, dITRPV4 reaches its peak at around 1 h, followed by a subsequent decline and then a resurgence after 6 h, suggesting a short-term modulatory effect related to on TRPV4 channel activity and a long-term effect related to the promotion of synthesis of new TRPV4 channel units. The enhancement of dITRPV4 induced by ouabain was significantly lower in cells seeded at low density than in cells in a confluent monolayer, indicating that the action of ouabain depends on intercellular contacts. Furthermore, the fact that U73122 and neomycin suppress the effect caused by ouabain in the short term suggests that the short-term induced enhancement of dITRPV4 is due to the depletion of PIP2 stores. In contrast, the fact that the long-term effect is inhibited by PP2, wortmannin, PD, FR18, and IKK16 suggests that cSrc, PI3K, Erk1/2, and NF-kB are among the components included in the signaling pathways.

Insect transient receptor potential vanilloid channels as potential targets of insecticides

Chordotonal organs are miniature sensory organs present in insects. Chordotonal organs depend on transient receptor potential (TRP) channels. Transient receptor potential vanilloid (TRPV) channels are the only TRPs identified that can act as targets of insecticides. By binding with TRPV channels, insecticides targeting the chordotonal organs trigger the inflow of calcium ions, resulting in abnormal function of the chordotonal organ to achieve the goal of eliminating pests. TRPV channels are highly expressed in various developmental stages and tissue parts of insects and play an important role in the whole life history of insects. In this review, we will discuss the structure and types of TRPV channels as well as their genetic relationships in different species. We also systematically reviewed the recent progress of TRPV channels as insecticide targets, demonstrating that TRPV channels can be used as the target of new high-efficiency insecticides.

Temperature activated transient receptor potential ion channels from Antarctic fishes

Antarctic notothenioid fishes (cryonotothenioids) live in waters that range between -1.86°C and an extreme maximum +4°C. Evidence suggests these fish sense temperature peripherally, but the molecular mechanism of temperature sensation in unknown. Previous work identified transient receptor potential (TRP) channels TRPA1b, TRPM4 and TRPV1a as the top candidates for temperature sensors. Here, cryonotothenioid TRPA1b and TRPV1a are characterized using Xenopus oocyte electrophysiology. TRPA1b and TRPV1a showed heat-evoked currents with Q10s of 11.1 ± 2.2 and 20.5 ± 2.4, respectively. Unexpectedly, heat activation occurred at a threshold of 22.9 ± 1.3°C for TRPA1b and 32.1 ± 0.6°C for TRPV1a. These fish have not experienced such temperatures for at least 15 Myr. Either (1) another molecular mechanism underlies temperature sensation, (2) these fishes do not sense temperatures below these thresholds despite having lethal limits as low as 5°C, or (3) native cellular conditions modify the TRP channels to function at relevant temperatures. The effects of osmolytes, pH, oxidation, phosphorylation, lipids and accessory proteins were tested. No conditions shifted the activity range of TRPV1a. Oxidation in combination with reduced cholesterol significantly dropped activation threshold of TRPA1b to 11.3 ± 2.3°C, it is hypothesized the effect may be due to lipid raft disruption.

Therapeutic Potential of Cannabinoids in Glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. To date, intraocular pressure (IOP) is the only modifiable risk factor in glaucoma treatment, but even in treated patients, the disease can progress. Cannabinoids, which have been known to lower IOP since the 1970s, have been shown to have beneficial effects in glaucoma patients beyond their IOP-lowering properties. In addition to the classical cannabinoid receptors CB1 and CB2, knowledge of non-classical cannabinoid receptors and the endocannabinoid system has increased in recent years. In particular, the CB2 receptor has been shown to mediate anti-inflammatory, anti-apoptotic, and neuroprotective properties, which may represent a promising therapeutic target for neuroprotection in glaucoma patients. Due to their vasodilatory effects, cannabinoids improve blood flow to the optic nerve head, which may suggest a vasoprotective potential and counteract the altered blood flow observed in glaucoma patients. The aim of this review was to assess the available evidence on the effects and therapeutic potential of cannabinoids in glaucoma patients. The pharmacological mechanisms underlying the effects of cannabinoids on IOP, neuroprotection, and ocular hemodynamics have been discussed.

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca²⁺, Mg²⁺, Na⁺, K⁺, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.

Alleviation of thermal nociception depends on heat-sensitive neurons and a TRP channel in the brain

Acute avoidance of dangerous temperatures is critical for animals to prevent or minimize injury. Therefore, surface receptors have evolved to endow neurons with the capacity to detect noxious heat so that animals can initiate escape behaviors. Animals including humans have evolved intrinsic pain-suppressing systems to attenuate nociception under some circumstances. Here, using Drosophila melanogaster, we uncovered a new mechanism through which thermal nociception is suppressed. We identified a single descending neuron in each brain hemisphere, which is the center for suppression of thermal nociception. These Epi neurons, for Epione-the goddess of soothing of pain-express a nociception-suppressing neuropeptide Allatostatin C (AstC), which is related to a mammalian anti-nociceptive peptide, somatostatin. Epi neurons are direct sensors for noxious heat, and when activated they release AstC, which diminishes nociception. We found that Epi neurons also express the heat-activated TRP channel, Painless (Pain), and thermal activation of Epi neurons and the subsequent suppression of thermal nociception depend on Pain. Thus, while TRP channels are well known to sense noxious temperatures to promote avoidance behavior, this work reveals the first role for a TRP channel for detecting noxious temperatures for the purpose of suppressing rather than enhancing nociception behavior in response to hot thermal stimuli.

TRiPPing the sensors: The osmosensing pathway of Polycystin 2

Mutations to polycystin-2 (PC2), a non-selective cation permeant transient receptor potential channel, results in polycystic kidney disease (PKD). Despite the disease relevance of PC2, the physiological agonist that activates PC2 has remained elusive. As one of the earliest symptoms in PKD is a urine concentrating deficiency, we hypothesized that shifts in osmolarity experienced by the collecting duct cells would activate PC2 and loss of PC2 would prevent osmosensing. We found that mice with inducible PC2 knocked out (KO) in renal tubules had dilute urine. Hyperosmotic stimuli induced a rise in endoplasmic reticulum (ER)-mediated cytosolic calcium which was absent in PC2 KO mice and PC2 KO cells. A pathologic point mutation that prevents ion flux through PC2 inhibited the calcium rise, pointing to the centrality of PC2 in the osmotic response. To understand how an extracellular stimulus activated ER-localized PC2, we examined microtubule-ER dynamics, and found that the osmotically induced calcium increase was preceded by microtubule destabilization. This was due to a novel interaction between PC2 and the microtubule binding protein MAP4 that tethers the microtubules to the ER. Finally, disruption of the MAP4-PC2 interaction prevented incorporation of the water channel aquaporin 2 following a hyperosmotic challenge, in part explaining the dilute urine. Our results demonstrate that MAP4-dependent microtubule stabilization of ER-resident PC2 is required for PC2 to participate in the osmosensing pathway. Moreover, osmolarity represents a bona fide physiological stimulus for ER-localized PC2 and loss of PC2 in renal epithelial cells impairs osmosensing ability and urine concentrating capacity.

Molecular architecture of the Gαi-bound TRPC5 ion channel

G-protein coupled receptors (GPCRs) and ion channels serve as key molecular switches through which extracellular stimuli are transformed into intracellular effects, and it has long been postulated that ion channels are direct effector molecules of the alpha subunit of G-proteins (Gα). However, no complete structural evidence supporting the direct interaction between Gα and ion channels is available. Here, we present the cryo-electron microscopy structures of the human transient receptor potential canonical 5 (TRPC5)-Gαi3 complexes with a 4:4 stoichiometry in lipid nanodiscs. Remarkably, Gαi3 binds to the ankyrin repeat edge of TRPC5 ~ 50 Å away from the cell membrane. Electrophysiological analysis shows that Gαi3 increases the sensitivity of TRPC5 to phosphatidylinositol 4,5-bisphosphate (PIP2), thereby rendering TRPC5 more easily opened in the cell membrane, where the concentration of PIP2 is physiologically regulated. Our results demonstrate that ion channels are one of the direct effector molecules of Gα proteins triggered by GPCR activation-providing a structural framework for unraveling the crosstalk between two major classes of transmembrane proteins: GPCRs and ion channels.

The diverse effects of pathogenic point mutations on ion channel activity of a gain-of-function polycystin-2

Autosomal dominant polycystic kidney disease is caused by mutations in PKD1 or PKD2 genes. The latter encodes polycystin-2 (PC2, also known as TRPP2), a member of the transient receptor potential ion channel family. Despite most pathogenic mutations in PKD2 being truncation variants, there are also many point mutations, which cause small changes in protein sequences but dramatic changes in the in vivo function of PC2. How these mutations affect PC2 ion channel function is largely unknown. In this study, we systematically tested the effects of 31 point mutations on the ion channel activity of a gain-of-function PC2 mutant, PC2_F604P, expressed in Xenopus oocytes. The results show that all mutations in the transmembrane domains and channel pore region, and most mutations in the extracellular tetragonal opening for polycystins domain, are critical for PC2_F604P channel function. In contrast, the other mutations in the tetragonal opening for polycystins domain and most mutations in the C-terminal tail cause mild or no effects on channel function as assessed in Xenopus oocytes. To understand the mechanism of these effects, we have discussed possible conformational consequences of these mutations based on the cryo-EM structures of PC2. The results help gain insight into the structure and function of the PC2 ion channel and the molecular mechanism of pathogenesis caused by these mutations.

Co-exposure to particulate matter and humidity increases blood pressure in hypertensive mice via the TRPV4-cPLA2-COX2 pathway

Epidemiological studies have demonstrated that particulate matter (PM) can induce or exacerbate hypertension. High relative humidity has been associated with elevated blood pressure in certain regions. However, the coupling effect of humidity and PM on elevated blood pressure and the underlying mechanisms remain unknown. Herein, we aimed to explore the effects of exposure to PM and/or high relative humidity on hypertension, as well as elucidate underlying mechanisms. Male C57/BL6 mice were intraperitoneally administered N^G-nitro-L-arginine methyl ester (L-NAME) to establish a hypertensive mouse model. The hypertensive mice were exposed to PM (0.15 mg/kg/day) and/or different relative humidities (45/90%) for eight weeks. Histopathological changes, systolic blood pressure (SBP), endothelial-derived contracting factors (thromboxane B₂ [TXB₂], Prostaglandin F2α [PGF_2α], endothelin-1 [ET-1], and angiotensin II [Ang II]), and relaxing factors (prostaglandin I₂ [PGI₂] and nitric oxide [NO]) were measured to assess the effects of PM exposure and humidity on hypertension in mice. Levels of transient receptor potential vanilloid 4 (TRPV4), cytosolic phospholipase A₂ (cPLA₂), and cyclooxygenase 2 (COX2) were measured to explore their potential mechanisms. Herein, exposure to 90% relative humidity or PM alone had a slight but insignificant effect on hypertension. However, pathological changes and elevated blood pressure were markedly exacerbated following exposure to PM and 90% relative humidity. Levels of PGF_2α, TXB₂, and ET-1 were significantly increased, whereas the PGI₂ level was substantially decreased. HC-067047-mediated blockade of TRPV4 suppressed TRPV4, cPLA₂, and COX2 expression and effectively alleviated the increased blood pressure induced by exposure to PM and 90% relative humidity. These results indicate that 90% relative humidity and PM can activate the TRPV4-cPLA₂-COX2 ion channel in the aorta, altering the endothelial-derived contracting and relaxing factors and enhancing blood pressure in hypertensive mice.

Xerostomia and Its Cellular Targets

Xerostomia, the subjective feeling of a dry mouth associated with dysfunction of the salivary glands, is mainly caused by radiation and chemotherapy, various systemic and autoimmune diseases, and drugs. As saliva plays numerous essential roles in oral and systemic health, xerostomia significantly reduces quality of life, but its prevalence is increasing. Salivation mainly depends on parasympathetic and sympathetic nerves, and the salivary glands responsible for this secretion move fluid unidirectionally through structural features such as the polarity of acinar cells. Saliva secretion is initiated by the binding of released neurotransmitters from nerves to specific G-protein-coupled receptors (GPCRs) on acinar cells. This signal induces two intracellular calcium (Ca2+) pathways (Ca2+ release from the endoplasmic reticulum and Ca2+ influx across the plasma membrane), and this increased intracellular Ca2+ concentration ([Ca2+]i) causes the translocation of the water channel aquaporin 5 (AQP5) to the apical membrane. Consequently, the GPCR-mediated increased [Ca2+]i in acinar cells promotes saliva secretion, and this saliva moves into the oral cavity through the ducts. In this review, we seek to elucidate the potential of GPCRs, the inositol 1,4,5-trisphosphate receptor (IP3R), store-operated Ca2+ entry (SOCE), and AQP5, which are essential for salivation, as cellular targets in the etiology of xerostomia.

Vitamin C Modes of Action in Calcium-Involved Signaling in the Brain

Vitamin C (ascorbic acid) is well known for its potent antioxidant properties, as it can neutralize ROS and free radicals, thereby protecting cellular elements from oxidative stress. It predominantly exists as an ascorbate anion and after oxidation to dehydroascorbic acid and further breakdown, is removed from the cells. In nervous tissue, a progressive decrease in vitamin C level or its prolonged deficiency have been associated with an increased risk of disturbances in neurotransmission, leading to dysregulation in brain function. Therefore, understanding the regulatory function of vitamin C in antioxidant defence and identification of its molecular targets deserves more attention. One of the key signalling ions is calcium and a transient rise in its concentration is crucial for all neuronal processes. Extracellular Ca²⁺ influx (through specific ion channels) or Ca²⁺ release from intracellular stores (endoplasmic reticulum, mitochondria) are precisely controlled. Ca²⁺ regulates the functioning of the CNS, including growth, development, myelin formation, synthesis of catecholamines, modulation of neurotransmission and antioxidant protection. A growing body of evidence indicates a unique role for vitamin C in these processes. In this short review, we focus on vitamin C in the regulation of calcium-involved pathways under physiological and stress conditions in the brain.

Analysis of Potential Genes and Economic Parameters Associated with Growth and Heat Tolerance in Sheep (Ovis aries)

This study explored the potential genes and economic factors that might be associated with growth and heat tolerance in two sheep breeds. Data on growth performance from the third month to six months of age were obtained based on records. In comparison to Aboudeleik lambs, Barki lambs developed considerably greater starting body weight, final body weight, final body weight gain, daily weight gain, and percentage increase in BW/month. Single nucleotide polymorphisms (SNPs) were found between lambs of the two breeds using PCR-DNA sequencing of CAST, LEP, MYLK4, MEF2B, STAT5A, TRPV1, HSP90AB1, HSPB6, HSF1, ST1P1, and ATP1A1 genes. Lambs from each breed were divided into groups based on detected SNPs in genes related to growth. The least squares means of the differentiated groups revealed a significant correlation of detected SNPs with growth and heat tolerance attributes (p ≤ 0.05). Barki lambs elicited greater total variable costs, total costs, total return, and net return values. The Barki sheep provided the best economic efficiency value when comparing the percentage difference between net profit and economic efficiency. Together with economic considerations, SNPs found may be used as proxies for marker-assisted selection of the best breed of sheep for traits related to growth and heat tolerance.

Involvement of TRPM7 in Alcohol-Induced Damage of the Blood-Brain Barrier in the Presence of HIV Viral Proteins

Ethanol (EtOH) exerts its effects through various protein targets, including transient receptor potential melastatin 7 (TRPM7) channels, which play an essential role in cellular homeostasis. We demonstrated that TRPM7 is expressed in rat brain microvascular endothelial cells (rBMVECs), the major cellular component of the blood-brain barrier (BBB). Heavy alcohol drinking is often associated with HIV infection, however mechanisms underlying alcohol-induced BBB damage and HIV proteins, are not fully understood. We utilized the HIV-1 transgenic (HIV-1Tg) rat to mimic HIV-1 patients on combination anti-retroviral therapy (cART) and demonstrated TRPM7 expression in rBMVECs wass lower in adolescent HIV-1Tg rats compared to control animals, however control and HIV-1Tg rats expressed similar levels at 9 weeks, indicating persistent presence of HIV-1 proteins delayed TRPM7 expression. Binge exposure to EtOH (binge EtOH) decreased TRPM7 expression in control rBMVECs in a concentration-dependent manner, and abolished TRPM7 expression in HIV-1Tg rats. In human BMVECs (hBMVECs), TRPM7 expression was downregulated after treatment with EtOH, HIV-1 proteins, and in combination. Next, we constructed in vitro BBB models using BMVECs and found TRPM7 antagonists enhanced EtOH-mediated BBB integrity changes. Our study demonstrated alcohol decreased TRPM7 expression, whereby TRPM7 could be involved in the mechanisms underlying BBB alcohol-induced damage in HIV-1 patients on cART.

The Biology of Lysosomes: From Order to Disorder

Since its discovery in 1955, the understanding of the lysosome has continuously increased. Once considered a mere waste removal system, the lysosome is now recognised as a highly crucial cellular component for signalling and energy metabolism. This notable evolution raises the need for a summarized review of the lysosome's biology. As such, throughout this article, we will be compiling the current knowledge regarding the lysosome's biogenesis and functions. The comprehension of this organelle's inner mechanisms is crucial to perceive how its impairment can give rise to lysosomal disease (LD). In this review, we highlight some examples of LD fine-tuned mechanisms that are already established, as well as others, which are still under investigation. Even though the understanding of the lysosome and its pathologies has expanded through the years, some of its intrinsic molecular aspects remain unknown. In order to illustrate the complexity of the lysosomal diseases we provide a few examples that have challenged the established single gene-single genetic disorder model. As such, we believe there is a strong need for further investigation of the exact abnormalities in the pathological pathways in lysosomal disease.

Subunit composition, molecular environment, and activation of native TRPC channels encoded by their interactomes

In the mammalian brain TRPC channels, a family of Ca²⁺-permeable cation channels, are involved in a variety of processes from neuronal growth and synapse formation to transmitter release, synaptic transmission and plasticity. The molecular appearance and operation of native TRPC channels, however, remained poorly understood. Here, we used high-resolution proteomics to show that TRPC channels in the rodent brain are macro-molecular complexes of more than 1 MDa in size that result from the co-assembly of the tetrameric channel core with an ensemble of interacting proteins (interactome). The core(s) of TRPC1-, C4-, and C5-containing channels are mostly heteromers with defined stoichiometries for each subtype, whereas TRPC3, C6, and C7 preferentially form homomers. In addition, TRPC1/C4/C5 channels may co-assemble with the metabotropic glutamate receptor mGluR1, thus guaranteeing both specificity and reliability of channel activation via the phospholipase-Ca²⁺ pathway. Our results unveil the subunit composition of native TRPC channels and resolve the molecular details underlying their activation.

Detection of TRPM6 and TRPM7 Proteins in Normal and Diseased Cardiac Atrial Tissue and Isolated Cardiomyocytes

Magnesium-sensitive transient receptor potential melastatin (TRPM) ion channels, TRPM6 and TRPM7, are present in several organs, but their roles in the heart remain unclear. Therefore, here, we studied the expression patterns of TRPM6 and TRPM7 in normal and diseased myocardium. Cardiac atrial tissue and cardiomyocytes were obtained from healthy pigs and undiseased human hearts as well as from hearts of patients with ischemic heart disease (IHD) or atrial fibrillation (AF). Immunofluorescence and ELISA were used to detect TRP proteins. TRPM6 and TRPM7 immunofluorescence signals, localized at/near the cell surface or intracellularly, were detected in pig and human atrial tissues. The TRP channel modulators carvacrol (CAR, 100 µM) or 2-aminoethoxydiphenyl borate (2-APB, 500 µM) decreased the TRPM7 signal, but enhanced that of TRPM6. At a higher concentration (2 mM), 2-APB enhanced the signals of both proteins. TRPM6 and TRPM7 immunofluorescence signals and protein concentrations were increased in atrial cells and tissues from IHD or AF patients. TRPM6 and TRPM7 proteins were both detected in cardiac atrial tissue, with relatively similar subcellular localization, but distinctive drug sensitivity profiles. Their upregulated expression in IHD and AF suggests a possible role of the channels in cardiac atrial disease.

The mechanism of ginger and its processed products in the treatment of estradiol valerate coupled with oxytocin-induced dysmenorrhea in mice via regulating the TRP ion channel-mediated ERK1/2/NF-κB signaling pathway

Ginger (Rhizoma zingiberis, RZ) has been used as a food, spice, supplement, flavoring agent, and as an edible herbal medicine. It is characterized by its pungency and aroma, and is rich in nutrients with remarkable pharmacological effects. It is used in traditional medicine clinics to treat diseases and symptoms, such as colds, headache, and primary dysmenorrhea (PD). In China, a variety of processed products of RZ are used as herbal medicines, such as baked ginger (BG) or ginger charcoal (GC) to treat different diseases and symptoms. However, the molecular mechanism of the therapeutic effect of RZ and its processed products (RZPPs, including BG or GC) against PD has not been well characterized. Moreover, whether the transient receptor potential (TRP) ion channels are involved in this process is not clear. In the present study, UHPLC-Q-TOF MS was adopted to analyse the differential quality markers (DQMs) between RZ and RZPPs. In addition, differential metabolomics (DMs) was acquired between RZ- and RZPPs-treated estradiol valerate coupled with an oxytocin-induced PD mouse uterus using untargeted metabolomics (UM). A correlation analysis between DQMs and DMs was also conducted. Benzenoids, lipids, and lipid-like molecules were the main DQMs between RZ and RZPPs. RZ and RZPPs were found to improve the pathological status of the uterus of a PD mouse, with significantly decreased serum levels of E2, PGF2α, TXB2 and remarkably increased levels of PROG and 6-keto-PGF1α. Moreover, RZ and RZPPs alleviated PD in mice via regulating the TRP ion channel-mediated ERK1/2/NF-κB signaling pathway. Our results indicate that the therapeutic effect of RZ and RZPPs against PD may be mediated by regulating the TRP ion channel-mediated ERK1/2/NF-κB signaling pathway, and provide a reference for the development of new dietary supplements or medicines.

Positive interaction between ASH and ASK sensory neurons accelerates nociception and inhibits behavioral adaptation

Central and peripheral sensory neurons tightly regulate nociception and avoidance behavior. The peripheral modulation of nociception provides more veridical and instantaneous information for animals to achieve rapid, more fine-tuned and concentrated behavioral responses. In this study, we find that positive interaction between ASH and ASK sensory neurons is essential for the fast-rising phase of ASH Ca²⁺ responses to noxious copper ions and inhibits the adaption of avoiding Cu²⁺. We reveal the underlying neuronal circuit mechanism. ASK accelerates the ASH Ca²⁺ responses by transferring cGMP through gap junctions. ASH excites ASK via a disinhibitory neuronal circuit composed of ASH, AIA, and ASK. Avoidance adaptation depends on the slope rate of the rising phase of ASH Ca²⁺ responses. Thus, in addition to amplitude, sensory kinetics is significant for sensations and behaviors, especially for sensory and behavioral adaptations.

The past and future of transient receptor potential: A scientometric analysis

BACKGROUND

Thermoreceptors include TRPV1 and TRPM8. TRPV1 and TRPM8 are TRP channels. TRP ion channels are widely expressed in many different tissues and cell types, and are involved in different physiological processes. Research on the structure and basic physiological functions of TRPV1 is relatively perfect, and the relationship between the pathogenesis of other members of the TRP family and specific diseases and TRPV1 remains to be explored in depth.

METHODS

Articles regarding TRP were culled from the Web of Science Core Collection, and knowledge maps were generated using the CiteSpace software.

RESULTS

In total, 19,862 articles were included. The number of published articles on this topic has rapidly increased since 2000, with more than 1000 articles published per year by 2020. MAKOTO TOMINAGA was the author with the most articles. The countries with the most articles were the United States and China. However, the number of articles in the U.S. was 3 times that in China. The organizations that publish the most articles are Harvard University in the US and Seoul Natl University in South Korea. TRP and the pathogenesis of diseases, such as neuropathy and stroke, are hotspots of current research.

CONCLUSION

To our knowledge, this is the first study to provide an overview of the literature on TRP. Research on TRPs is developing rapidly.

Calcium-Permeable Channels Cooperation for Rheumatoid Arthritis: Therapeutic Opportunities

Rheumatoid arthritis is a common autoimmune disease that results from the deposition of antibodies–autoantigens in the joints, leading to long-lasting inflammation. The main features of RA include cartilage damage, synovial invasion and flare-ups of intra-articular inflammation, and these pathological processes significantly reduce patients’ quality of life. To date, there is still no drug target that can act in rheumatoid arthritis. Therefore, the search for novel drug targets has become urgent. Due to their unique physicochemical properties, calcium ions play an important role in all cellular activities and the body has evolved a rigorous calcium signaling system. Calcium-permeable channels, as the main operators of calcium signaling, are widely distributed in cell membranes, endoplasmic reticulum membranes and mitochondrial membranes, and mediate the efflux and entry of Ca2+. Over the last century, more and more calcium-permeable channels have been identified in human cells, and the role of this large family of calcium-permeable channels in rheumatoid arthritis has gradually become clear. In this review, we briefly introduce the major calcium-permeable channels involved in the pathogenesis of RA (e.g., acid-sensitive ion channel (ASIC), transient receptor potential (TRP) channel and P2X receptor) and explain the specific roles and mechanisms of these calcium-permeable channels in the pathogenesis of RA, providing more comprehensive ideas and targets for the treatment of RA.