TRPC1

Upregulation of TRPC1 in microglia promotes neutrophil infiltration after ischemic stroke

Neutrophil infiltration has been linked to worse clinical outcomes after ischemic stroke. Microglia, a key type of immune-competent cell, engage in cross-talk with the infiltrating immune cells in the inflamed brain area, yet the molecular mechanisms involved remain largely unexplored. In this study, we investigated the mechanisms of how canonical transient receptor potential 1 (TRPC1) modulated neutrophil infiltration in male mouse cerebral ischemia and reperfusion injury (CIRI) models. Our findings revealed a notable upregulation of TRPC1 in microglia within both middle cerebral artery occlusion reperfusion (MCAO/R) and in vitro oxygen-glucose deprivation/regeneration (OGD/R) model. Conditional Trpc1 knockdown in microglia markedly reduced infarct volumes and alleviated neurological deficits. Microglia conditional Trpc1 knockdown mice displayed less neutrophil infiltration in peri-infarct area. Trpc1 knockdown microglia exhibited a reduced primed proinflammatory phenotype with less secretion of CC-Chemokines ligand (CCL) 5 and CCL2 after MCAO/R. Blocking CCL5/2 significantly mitigated neutrophil infiltration in microglia/neutrophil transwell co-culture system upon OGD/R condition. Trpc1 knockdown markedly reduced store-operated calcium entry and nuclear factor of activated T-cells c1 (NFATc1) level in OGD/R treated microglia. Overexpression of Nfatc1 reversed the CCL5/2 reducing effect of Trpc1 knockdown, which is mediated by small interfering RNA in BV2 cells upon OGD/R. Our data indicate that upregulation of TRPC1 in microglia stimulates the production of CCL5/2 through the Ca2+/NFATc1 pathway. Upregulated CCL5/2 leads to an increase in neutrophil infiltration into the brain, thereby aggravating reperfusion injury. Our results demonstrate the importance of TRPC1 in microglia-mediated neuroinflammation and suggest a potential means for reducing CIRI induced neurological injury.

Harmonizing Magnetic Mitohormetic Regenerative Strategies: Developmental Implications of a Calcium-Mitochondrial Axis Invoked by Magnetic Field Exposure

Mitohormesis is a process whereby mitochondrial stress responses, mediated by reactive oxygen species (ROS), act cumulatively to either instill survival adaptations (low ROS levels) or to produce cell damage (high ROS levels). The mitohormetic nature of extremely low-frequency electromagnetic field (ELF-EMF) exposure thus makes it susceptible to extraneous influences that also impinge on mitochondrial ROS production and contribute to the collective response. Consequently, magnetic stimulation paradigms are prone to experimental variability depending on diverse circumstances. The failure, or inability, to control for these factors has contributed to the existing discrepancies between published reports and in the interpretations made from the results generated therein. Confounding environmental factors include ambient magnetic fields, temperature, the mechanical environment, and the conventional use of aminoglycoside antibiotics. Biological factors include cell type and seeding density as well as the developmental, inflammatory, or senescence statuses of cells that depend on the prior handling of the experimental sample. Technological aspects include magnetic field directionality, uniformity, amplitude, and duration of exposure. All these factors will exhibit manifestations at the level of ROS production that will culminate as a unified cellular response in conjunction with magnetic exposure. Fortunately, many of these factors are under the control of the experimenter. This review will focus on delineating areas requiring technical and biological harmonization to assist in the designing of therapeutic strategies with more clearly defined and better predicted outcomes and to improve the mechanistic interpretation of the generated data, rather than on precise applications. This review will also explore the underlying mechanistic similarities between magnetic field exposure and other forms of biophysical stimuli, such as mechanical stimuli, that mutually induce elevations in intracellular calcium and ROS as a prerequisite for biological outcome. These forms of biophysical stimuli commonly invoke the activity of transient receptor potential cation channel classes, such as TRPC1.

Targeting transient receptor potential canonical 1 reduces non‑small cell lung cancer chemoresistance and stemness via inhibition of PI3K/AKT signaling

TRPC1 enhances cell proliferation and migration in non-small cell lung cancer (NSCLC); however, its effect on NSCLC chemoresistance and stemness remains to be determined. The aim of the current study was to investigate the effect of TRPC1 on NSCLC chemoresistance and stemness and to determine the underlying mechanism of action. Cisplatin-resistant A549 (A549/CDDP) and H460 (H460/CDDP) cells were first established and were then transfected with negative control small interfering (si)RNA (si-NC) or TRPC1 siRNA (si-TRPC1). Cells were then treated with 740 Y-P, a PI3K/Akt agonist. Subsequently, the sensitivity of A549/CDDP and H460/CDDP cells to CDDP was evaluated. Furthermore, the expression levels of CD133 and CD44, and sphere formation ability were also determined. The results showed that the half-maximal inhibitory concentration (IC₅₀) of CDDP was significantly higher in A549/CDDP cells compared with A549 cells and in H460/CDDP cells compared with H460 cells. TRPC1 silencing decreased the IC₅₀ value of CDDP compared with the si-NC group in A549/CDDP (11.78 vs. 21.58 µM; P<0.01) and H460/CDDP (23.76 vs. 43.11 µM; P<0.05) cells. Additionally, TRPC1 knockdown in both cell lines decreased the number of spheres formed compared with the si-NC group. Furthermore, compared with the si-NC group, A549/CDDP cells transfected with si-TRPC1 exhibited decreased levels of both CD133 (P<0.01) and CD44 (P<0.05). However, only CD133 (P<0.05) was downregulated in TRPC1-depleted H460/CDDP cells compared with the si-NC group. In addition, TRPC1 knockdown repressed PI3K/AKT signaling compared with the si-NC group in both A549/CDDP and H460/CDDP cells (all P<0.05). Finally, cell treatment with 740 Y-P reversed the effect of TRPC1 knockdown on PI3K/AKT signaling, chemoresistance, and cancer stemness in A549/CDDP and H460/CDDP cells (all P<0.05). In conclusion, the results of the current study suggested that targeting TRPC1 could attenuate cancer stemness and chemoresistance via suppression of PI3K/AKT signaling in NSCLC.

Interactions between the Polysialylated Neural Cell Adhesion Molecule and the Transient Receptor Potential Canonical Channels 1, 4, and 5 Induce Entry of Ca2+ into Neurons

The neural cell adhesion molecule (NCAM) plays important functional roles in the developing and mature nervous systems. Here, we show that the transient receptor potential canonical (TRPC) ion channels TRPC1, -4, and -5 not only interact with the intracellular domains of the transmembrane isoforms NCAM140 and NCAM180, but also with the glycan polysialic acid (PSA) covalently attached to the NCAM protein backbone. NCAM antibody treatment leads to the opening of TRPC1, -4, and -5 hetero- or homomers at the plasma membrane and to the influx of Ca²⁺ into cultured cortical neurons and CHO cells expressing NCAM, PSA, and TRPC1 and -4 or TRPC1 and -5. NCAM-stimulated Ca²⁺ entry was blocked by the TRPC inhibitor Pico145 or the bacterial PSA homolog colominic acid. NCAM-stimulated Ca²⁺ influx was detectable neither in NCAM-deficient cortical neurons nor in TRPC1/4- or TRPC1/5-expressing CHO cells that express NCAM, but not PSA. NCAM-induced neurite outgrowth was reduced by TRPC inhibitors and a function-blocking TRPC1 antibody. A characteristic signaling feature was that extracellular signal-regulated kinase 1/2 phosphorylation was also reduced by TRPC inhibitors. Our findings indicate that the interaction of NCAM with TRPC1, -4, and -5 contributes to the NCAM-stimulated and PSA-dependent Ca²⁺ entry into neurons thereby influencing essential neural functions.

Music alleviates pain perception in depression mouse models by promoting the release of glutamate in the hippocampus of mice to act on GRIK5

Objective: To explore the effect of music in pain perception and the molecular mechanism. Methods: Mice were separated to control, music, music + inhibitor, and saline group. Percentage pain reduction of mice in each group was determined. The contents of 5-HT, Glu, and NE in cerebrospinal fluid of mice in the four groups were determined by HPLC. FISH was used to analyze the distribution characteristics of GRIK5 in hippocampal tissues. The protein expressions of GRIK5, NMDA 1, and TRPC1 in the hippocampal tissues were determined via western blot. Results: Mice exposed to music showed a higher percentage of pain reduction compared to model animals, while injection of GRIK5 inhibitor weakened the effect of music. It increased the contents of 5-HT, Glu, and NE in mouse models of depression. The fluorescence signal in music group was significantly stronger than saline group. Music remarkably increased the expression of GRIK5, DLG4, NMDA 1, and TRPC1 proteins when compared with saline group. Conclusion: Music promoted the secretion of Glu. The glutaminergic pathway sensed Glu, subsequently activated GRIK5, DLG4, and NMDA 1 proteins to excite dopaminergic neurons, and finally promoted the production of 5-HT.

The regulatory and modulatory roles of TRP family channels in malignant tumors and relevant therapeutic strategies

Transient receptor potential (TRP) channels are one primary type of calcium (Ca²⁺) permeable channels, and those relevant transmembrane and intracellular TRP channels were previously thought to be mainly associated with the regulation of cardiovascular and neuronal systems. Nowadays, however, accumulating evidence shows that those TRP channels are also responsible for tumorigenesis and progression, inducing tumor invasion and metastasis. However, the overall underlying mechanisms and possible signaling transduction pathways that TRP channels in malignant tumors might still remain elusive. Therefore, in this review, we focus on the linkage between TRP channels and the significant characteristics of tumors such as multi-drug resistance (MDR), metastasis, apoptosis, proliferation, immune surveillance evasion, and the alterations of relevant tumor micro-environment. Moreover, we also have discussed the expression of relevant TRP channels in various forms of cancer and the relevant inhibitors' efficacy. The chemo-sensitivity of the anti-cancer drugs of various acting mechanisms and the potential clinical applications are also presented. Furthermore, it would be enlightening to provide possible novel therapeutic approaches to counteract malignant tumors regarding the intervention of calcium channels of this type.

Dysregulated transient receptor potential channel 1 expression and its correlation with clinical features and survival profile in surgical non-small-cell lung cancer patients

BACKGROUND

Transient receptor potential channel 1 (TRPC1) facilitates the tumor growth, metastasis, and chemoresistance in a series of neoplasms, while its correlation with clinical features and survival profile in NSCLC patients remains elusive. Hence, this study aimed to explore this topic.

METHODS

Totally, 192 NSCLC patients were enrolled. Protein and mRNA expression of TRPC1 in carcinoma tissue and para-carcinoma tissue were evaluated by immunohistochemistry (IHC) assay and reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay, respectively.

RESULTS

Immunohistochemistry score and mRNA expression of TRPC1 were higher in carcinoma tissue compared with para-carcinoma tissue (both p < 0.001). Besides, increased TRPC1 IHC score (p = 0.004) and elevated TRPC1 mRNA overexpression (p = 0.016) were linked with occurrence of LYN metastasis; meanwhile, increased TRPC1 IHC score (p = 0.015) and raised TRPC1 mRNA expression (p = 0.009) were also linked with advanced TNM stage, whereas TRPC1 IHC score and TRPC1 mRNA expression were not correlated with other clinical features (all p > 0.05). Additionally, TRPC1 protein high (p = 0.007) and TRPC1 mRNA high (p = 0.015) were correlated with poor disease-free survival (DFS) but not correlated with overall survival (OS). Moreover, multivariate Cox's proportional hazards regression analysis showed that high TRPC1 protein expression (p = 0.046) and advanced TNM stage (p < 0.001) were independently correlated with poor DFS. However, TRPC1 protein and mRNA expression were not linked with OS (both p > 0.05), while poor differentiation (p = 0.003) and advanced TNM stage (p < 0.001) were independently associated with worse OS.

CONCLUSIONS

TRPC1 is unregulated in NSCLC tissue with its overexpression relating to the occurrence of LYN metastasis and worse DFS in NSCLC patients.

Transient Receptor Potential (TRP) Ion Channels Involved in Malignant Glioma Cell Death and Therapeutic Perspectives

Among the most biologically, thus clinically, aggressive primary brain tumors are found malignant gliomas. Despite recent advances in adjuvant therapies, which include targeted and immunotherapies, after surgery and radio/chemotherapy, the tumor is recurrent and always lethal. Malignant gliomas also contain a pool of initiating stem cells that are highly invasive and resistant to conventional treatment. Ion channels and transporters are markedly involved in cancer cell biology, including glioma cell biology. Transient receptor potential (TRP) ion channels are calcium-permeable channels implicated in Ca²⁺ changes in multiple cellular compartments by modulating the driving force for Ca²⁺ entry. Recent scientific reports have shown that these channels contribute to the increase in glioblastoma aggressiveness, with glioblastoma representing the ultimate level of glioma malignancy. The current review focuses on each type of TRP ion channel potentially involved in malignant glioma cell death, with the ultimate goal of identifying new therapeutic targets to clinically combat malignant gliomas. It thus appears that cannabidiol targeting the TRPV2 type could be such a potential target.

Correlation between classical transient receptor potential channel 1 gene polymorphism and microalbuminuria in patients with primary hypertension

OBJECTIVE

To investigate the correlation between transient receptor potential channel 1 (TRPC1) gene polymorphism and microalbuminuria in patients with primary hypertension. Methods: A total of 468 patients with primary hypertension were admitted to the Department of Hypertension of the First Affiliated Hospital of Xinjiang Medical University from April 2015 to November 2017. According to microalbuminuria, the patients were divided into two groups: high urinary albumin group (EH+mALB group, n = 71) and normal urinary microalbuminuria group (EH group, n = 397). The Sequenom detection technology was used for genotyping the single nucleotide polymorphism (SNP) sites of the TRPC1 gene, such as rs1382688, rs3821647, rs7638459, rs953239, and rs7621642.

RESULTS

(1) No significant differences were detected in gender, smoking history, drinking history, family history, course of hypertension, fasting blood glucose, urea, creatinine, triglyceride, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glycosylated hemoglobin, vitamin D, homocysteine, and cystatin C between the two groups (P > .05). However, age, body mass index (BMI), 24-h mean systolic and diastolic blood pressure, and 24-h average pulse pressure were statistically significant (P < .05). (2) No significant difference was detected in the distribution frequency of the polymorphisms of the TRPC1 gene between the two groups (P > .05), while the genotype, allele, and recessive model of rs7638459 differed significantly difference (P < .05). (3) Logistic regression analysis showed that BMI and rs7638459 CC genotype were the risk factors of increased microalbuminuria in patients with primary hypertension.

CONCLUSION

TRPC1 gene polymorphism is associated with increased microalbuminuria in patients with primary hypertension. The CC genotype of rs7638459 may increase the risk of microalbuminuria in patients with essential hypertension, while BMI and rs7638459 CC genotype may be the risk factors of increased microalbuminuria in patients with primary hypertension.

TRP Channels Interactome as a Novel Therapeutic Target in Breast Cancer

Breast cancer is one of the most frequent cancer types worldwide and the first cause of cancer-related deaths in women. Although significant therapeutic advances have been achieved with drugs such as tamoxifen and trastuzumab, breast cancer still caused 627,000 deaths in 2018. Since cancer is a multifactorial disease, it has become necessary to develop new molecular therapies that can target several relevant cellular processes at once. Ion channels are versatile regulators of several physiological- and pathophysiological-related mechanisms, including cancer-relevant processes such as tumor progression, apoptosis inhibition, proliferation, migration, invasion, and chemoresistance. Ion channels are the main regulators of cellular functions, conducting ions selectively through a pore-forming structure located in the plasma membrane, protein–protein interactions one of their main regulatory mechanisms. Among the different ion channel families, the Transient Receptor Potential (TRP) family stands out in the context of breast cancer since several members have been proposed as prognostic markers in this pathology. However, only a few approaches exist to block their specific activity during tumoral progress. In this article, we describe several TRP channels that have been involved in breast cancer progress with a particular focus on their binding partners that have also been described as drivers of breast cancer progression. Here, we propose disrupting these interactions as attractive and potential new therapeutic targets for treating this neoplastic disease.

Function of the Porcine TRPC1 Gene in Myogenesis and Muscle Growth

In animals, muscle growth is a quantitative trait controlled by multiple genes. Previously, we showed that the transient receptor potential channel 1 (TRPC1) gene was differentially expressed in muscle tissues between pig breeds with divergent growth traits base on RNA-seq. Here, we characterized TRPC1 expression profiles in different tissues and pig breeds and showed that TRPC1 was highly expressed in the muscle. We found two single nucleotide polymorphisms (SNPs) (C-1763T and C-1604T) in TRPC1 that could affect the promoter region activity and regulate pig growth rate. Functionally, we used RNAi and overexpression to illustrate that TRPC1 promotes myoblast proliferation, migration, differentiation, fusion, and muscle hypertrophy while inhibiting muscle degradation. These processes may be mediated by the activation of Wnt signaling pathways. Altogether, our results revealed that TRPC1 might promote muscle growth and development and plays a key role in Wnt-mediated myogenesis.

Control of PTH secretion by the TRPC1 ion channel

Familial hypocalciuric hypercalcemia (FHH) is a genetic condition associated with hypocalciuria, hypercalcemia, and, in some cases, inappropriately high levels of circulating parathyroid hormone (PTH). FHH is associated with inactivating mutations in the gene encoding the Ca2+-sensing receptor (CaSR), a GPCR, and GNA11 encoding G protein subunit α 11 (Gα11), implicating defective GPCR signaling as the root pathophysiology for FHH. However, the downstream mechanism by which CaSR activation inhibits PTH production/secretion is incompletely understood. Here, we show that mice lacking the transient receptor potential canonical channel 1 (TRPC1) develop chronic hypercalcemia, hypocalciuria, and elevated PTH levels, mimicking human FHH. Ex vivo and in vitro studies revealed that TRPC1 serves a necessary and sufficient mediator to suppress PTH secretion from parathyroid glands (PTGs) downstream of CaSR in response to high extracellular Ca2+ concentration. Gα11 physically interacted with both the N- and C-termini of TRPC1 and enhanced CaSR-induced TRPC1 activity in transfected cells. These data identify TRPC1-mediated Ca2+ signaling as an essential component of the cellular apparatus controlling PTH secretion in the PTG downstream of CaSR.

Transient receptor potential canonical 1 channel mediates the mechanical stress‑induced epithelial‑mesenchymal transition of human bronchial epithelial (16HBE) cells

Airway remodeling is a central event in the pathology of chronic obstructive pulmonary disease (COPD) that leads to airway narrowing and subsequently, to increased mechanical pressure. High mechanical pressure can exacerbate airway remodeling. Thus, a treatment regimen aimed at disrupting this high-pressure airway remodeling vicious cycle may improve the prognosis of patients with COPD. Recent studies have demonstrated that mechanical stress induces lung epithelial-mesenchymal transition (EMT), which is commonly present in airway epithelial cells of patients with COPD. As TRPC1 functions as a mechanosensitive channel that mediates non-selective cation entry in response to increased membrane stretch, the present study investigated the role of TRPC1 in the occurrence of EMT induced by mechanical stress. In the present study, the expression of TRPC1 in the bronchial epithelium was examined in vivo by immunohistochemistry. In vitro, human bronchial epithelial (16HBE) cells were subjected to mechanical stretching for up to 48 h, and TRPC1 expression was then examined by RT-qPCR and western blot analysis. In addition, TRPC1 receptor function was assessed by Ca²⁺ imaging and siRNA transfection. EMT was identified using immunofluorescence, western blot analysis and RT-qPCR. It was found that TRPC1 expression was upregulated in patients with COPD and in 16HBE cells subjected to mechanical stretch. The mechanical stress-induced activation of TRPC1 in 16HBE cells increased the intracellular calcium concentration and subsequently decreased the expression of cytokeratin 8 and E-cadherin, and increased the expression of α-smooth muscle actin, indicating the occurrence of EMT. On the whole, the findings of the present study demonstrate that TRPC1 plays a key role in the occurrence of EMT in human lung epithelial cells in response to mechanical stretch; thus, this protein may serve as a novel therapeutic target for progressive airway remodeling in COPD.

Dysfunction of transient receptor potential ion channels as an important pathophysiological mechanism in asthma

Asthma is a chronic heterogeneous disease characterized by chronic inflammation and bronchial hyperreactivity. Neurogenic inflammation is one of the important causes of hyperreactivity. Dysfunction of transient receptor potential (TRP) ion channels underlies the development of neurogenic inflammation, bronchial hyperreactivity and respiratory symptoms of asthma such as bronchospasm and cough. TRP channels are expressed in the respiratory tract. Their activation is mediated by endogenous and exogenous factors involved in the pathogenesis of asthma. The study of functioning and regulation of TRP channels is relevant, as they could be important therapeutic targets for asthma. The aim of the review is to summarize modern ideas about the mechanisms of functioning and regulation of members of the TRP channel superfamily, the role of which in lung pathology and physiology are the best studied.

The involvement of TRP channels in memory formation and task retrieval in a passive avoidance task in one-day old chicks

An increase in the intracellular Ca2+ level in neurons is one of the main steps in the memory formation cascade. The increase results from extracellular Ca2+ influx by activation of ionotropic glutamate receptors and release from intracellular stores by the stimulation of IP3 receptors (IP3Rs) via group I metabotropic glutamate receptors (mGluR1/5). Recent data indicate an additional mechanism resulting in Ca2+ influx into neurons, triggered by intracellular signals that are directly connected to the activation of group I mGluRs. This influx occurs through transient receptor potential (TRP) channels, which are permeable to Na+, K+ and, mainly, Ca2+. These channels are activated by increases in intracellular Ca2+, diacylglycerol (DAC) and inositol 1,4,5-triphosphate (IP3) level resulting from a group I mGluR activation. The aim of the present study was to investigate the participation of TRP channels, especially from TRPC and TRPV groups, in memory consolidation and reconsolidation and memory retrieval processes in a passive avoidance task in one-day old chicks. TRP channels were blocked by the injection of the unspecific channel modulators SKF 96365 (2.5 µl 30 µM/hemisphere) and 2-APB (2.5 µl 10 µM/hemisphere) directly into the intermediate medial mesopallium (IMM) region of the chick brain immediately after initial training or after a reminder. The inhibition of specific TRP channels (TRPV1, TRPV3 or TRPC3) was achieved by the application of selective antibodies. Our results demonstrate that the inhibition of TRP channels by the application of both modulators disrupted memory consolidation, resulting in permanent task amnesia. The inhibition of the TRPV1, TRPC3 and TRPV3 channels by specific antibodies resulted in similar amnesia. Moreover, the inhibition of TRP channels by SKF 96365 and 2-APB at different time points after initial training or after the reminder also resulted in amnesia, indicating the role of TRP channels in memory retrieval. The inhibition of calcium influx through these channels resulted in permanent memory disruption, which suggests that the calcium signal generated by TRP channels is crucial for memory formation and retrieval processes. For the first time, the important role of TRPV3 channels in memory formation was demonstrated.

Transient Receptor Potential Canonical (TRPC) Channels as Modulators of Migration and Invasion

Calcium (Ca²⁺) is perhaps the most versatile signaling molecule in cells. Ca²⁺ regulates a large number of key events in cells, ranging from gene transcription, motility, and contraction, to energy production and channel gating. To accomplish all these different functions, a multitude of channels, pumps, and transporters are necessary. A group of channels participating in these processes is the transient receptor potential (TRP) family of cation channels. These channels are divided into 29 subfamilies, and are differentially expressed in man, rodents, worms, and flies. One of these subfamilies is the transient receptor potential canonical (TRPC) family of channels. This ion channel family comprises of seven isoforms, labeled TRPC1–7. In man, six functional forms are expressed (TRPC1, TRPC3–7), whereas TRPC2 is a pseudogene; thus, not functionally expressed. In this review, we will describe the importance of the TRPC channels and their interacting molecular partners in the etiology of cancer, particularly in regard to regulating migration and invasion.

Focused ultrasound activates voltage-gated calcium channels through depolarizing TRPC1 sodium currents in kidney and skeletal muscle

Pulsed focused ultrasound (pFUS) technology is being developed for clinical neuro/immune modulation and regenerative medicine. Biological signal transduction of pFUS forces can require mechanosensitive or voltage-gated plasma membrane ion channels. Previous studies suggested pFUS is capable of activating either channel type, but their mechanistic relationship remains ambiguous. We demonstrated pFUS bioeffects increased mesenchymal stem cell tropism (MSC) by altering molecular microenvironments through cyclooxygenase-2 (COX2)-dependent pathways. This study explored specific relationships between mechanosensitive and voltage-gated Ca²⁺ channels (VGCC) to initiate pFUS bioeffects that increase stem cell tropism.

Methods: Murine kidneys and hamstring were given pFUS (1.15 or 1.125 MHz; 4MPa peak rarefactional pressure) under ultrasound or magnetic resonance imaging guidance. Cavitation and tissue displacement were measure by hydrophone and ultrasound radiofrequency data, respectively. Elastic modeling was performed from displacement measurements. COX2 expression and MSC tropism were evaluated in the presence of pharmacological ion channel inhibitors or in transient-receptor-potential-channel-1 (TRPC1)-deficient mice. Immunohistochemistry and co-immunoprecipitation examined physical channel relationships. Fluorescent ionophore imaging of cultured C2C12 muscle cells or TCMK1 kidney cells probed physiological interactions.

Results: pFUS induced tissue deformations resulting in kPa-scale forces suggesting mechanical activation of pFUS-induced bioeffects. Inhibiting VGCC or TRPC1 in vivo blocked pFUS-induced COX2 upregulation and MSC tropism to kidneys and muscle. A TRPC1/VGCC complex was observed in plasma membranes. VGCC or TRPC1 suppression blocked pFUS-induced Ca²⁺ transients in TCMK1 and C2C12 cells. Additionally, Ca²⁺ transients were blocked by reducing transmembrane Na⁺ potentials and observed Na⁺ transients were diminished by genetic TRPC1 suppression.

Conclusion: This study suggests that pFUS acoustic radiation forces mechanically activate a Na⁺-containing TRPC1 current upstream of VGCC rather than directly opening VGCC. The electrogenic function of TRPC1 provides potential mechanistic insight into other pFUS techniques for physiological modulation and optimization strategies for clinical implementation.

Role of TRPC1 channels in pressure-mediated activation of airway remodeling

Background

Bronchoconstriction and cough, a characteristic of the asthmatic response, leads to development of compressive stresses in the airway wall. We hypothesized that progressively pathological high mechanical stress could act on mechanosensitive cation channels, such as transient receptor potential channel 1 (TRPC1) and then contributes to airway remodeling.

Methods

We imitate the pathological airway pressure in vitro using cyclic stretch at 10 and 15% elongation. Ca²⁺ imaging was applied to measure the activity of TRPC1 after bronchial epithelial cells exposed to cyclic stretch for 0, 0.5, 1, 1.5, 2, 2.5 h. To further clarify the function of channnel TRPC1 in the process of mechano-transduction in airway remodeling, the experiment in vivo was implemented. The TRPC1 siRNA and budesonide were applied separately to asthmatic models. The morphological changes were measured by HE and Massion method. The expression levels of TRPC1 were evaluated by real-time PCR, western blot and immunohistochemistry. The protein expression level of IL-13, TGF-β₁ and MMP-9 in BALF were measured by ELISA.

Results

The result showed that cyclic stretch for 15% elongation at 1.5 h could maximize the activity of TRPC1 channel. This influx in Ca²⁺ was blocked by TRPC1 siRNA. Higher TRPC1 expression was observed in the bronchial epithelial layer of ovalbumin induced asthmatic models. The knockdown of TRPC1 with TRPC1 siRNA was associated with a hampered airway remodeling process, such as decreased bronchial wall thickness and smooth muscle hypertrophy/hyperplasia, a decreased ECM deposition area and inflammation infiltration around airway wall. Meantime, expression of IL-13, TGF-β₁ and MMP-9 in OVA+TRPC1 siRNA also showed reduced level. TRPC1 intervention treatment showed similar anti-remodeling therapeutic effect with budesonide.

Conclusions

These results demonstrate that most TRPC1 channels expressed in bronchial epithelial cells mediate the mechanotransduction mechanism. TRPC1 inducing abnormal Ca²⁺ signal mediates receptor-stimulated and mechanical stimulus-induced airway remodeling. The inhibition of TRPC1 channel could produce similar therapeutic effect as glucocortisteroid to curb the development of asthmatic airway remodeling.

Inhibition of Polyamine Biosynthesis Reverses Ca2+ Channel Remodeling in Colon Cancer Cells

Store-operated Ca²⁺ entry (SOCE) is the most important Ca²⁺ entry pathway in non-excitable cells. Colorectal cancer (CRC) shows decreased Ca²⁺ store content and enhanced SOCE that correlate with cancer hallmarks and are associated to remodeling of store-operated channels (SOCs). Normal colonic cells display small, Ca²⁺-selective currents driven by Orai1 channels. In contrast, CRC cells display larger, non-selective currents driven by Orai1 and transient receptor potential canonical type 1 channels (TRPC1). Difluoromethylornithine (DFMO), a suicide inhibitor of ornithine decarboxylase (ODC), the limiting step in polyamine biosynthesis, strongly prevents CRC, particularly when combined with sulindac. We asked whether DFMO may reverse SOC remodeling in CRC. We found that CRC cells overexpress ODC and treatment with DFMO decreases cancer hallmarks including enhanced cell proliferation and apoptosis resistance. Consistently, DFMO enhances Ca²⁺ store content and decreases SOCE in CRC cells. Moreover, DFMO abolish selectively the TRPC1-dependent component of SOCs characteristic of CRC cells and this effect is reversed by the polyamine putrescine. Combination of DFMO and sulindac inhibit both SOC components and abolish SOCE in CRC cells. Finally, DFMO treatment inhibits expression of TRPC1 and stromal interaction protein 1 (STIM1) in CRC cells. These results suggest that polyamines contribute to Ca²⁺ channel remodeling in CRC, and DFMO may prevent CRC by reversing channel remodeling.

TRPC1 regulates brown adipose tissue activity in a PPARγ-dependent manner

Brown adipose tissue (BAT) has the unique ability to convert energy stored in the form of triglycerides into heat. This property makes BAT a target tissue to increase energy expenditure and improve systemic metabolic control. TRPC1 is a founding member of the TRP protein family that also includes several temperature sensitive channels. We show that TRPC1 is highly expressed in all adipocyte depots including BAT and that Trpc1-deficient mice are prone to weight gain and manifest reduced metabolic control. We also demonstrate that knockdown of TRPC1 in cultured brown adipocytes leads to a downregulation of several metabolic genes, including UCP1 and PPARγ, as well as upregulation of a BAT-specific thermosensitive channel TRPV2, ultimately resulting in impaired respiratory function. We also show that TRPC1 is a possible target of PPARγ, suggesting that TRPC1 is a downstream component of a mechanism that translates metabolic or environmental stimuli into output in the form of BAT activity. Better understanding of the possible role of TRPC1 and other TRP channels in body temperature regulation and BAT function may help us to develop obesity therapies based on BAT activation.

Activation of TRPC1 Channel by Metabotropic Glutamate Receptor mGluR5 Modulates Synaptic Plasticity and Spatial Working Memory

Group I metabotropic glutamate receptors, in particular mGluR5, have been implicated in various forms of synaptic plasticity that are believed to underlie declarative memory. We observed that mGluR5 specifically activated a channel containing TRPC1, an isoform of the canonical family of transient receptor potential (TRPC) channels highly expressed in CA1-3 regions of the hippocampus. TRPC1 is able to form tetrameric complexes with TRPC4 and/or TRPC5 isoforms. TRPC1/4/5 complexes have recently been involved in the efficiency of synaptic transmission in the hippocampus. We therefore used a mouse model devoid of TRPC1 expression to investigate the involvement of mGluR5-TRPC1 pathway in synaptic plasticity and memory formation. Trpc1^-/- mice showed alterations in spatial working memory and fear conditioning. Activation of mGluR increased synaptic excitability in neurons from WT but not from Trpc1^-/- mice. LTP triggered by a theta burst could not maintain over time in brain slices from Trpc1^-/- mice. mGluR-induced LTD was also impaired in these mice. Finally, acute inhibition of TRPC1 by Pico145 on isolated neurons or on brain slices mimicked the genetic depletion of Trpc1 and inhibited mGluR-induced entry of cations and subsequent effects on synaptic plasticity, excluding developmental or compensatory mechanisms in Trpc1^-/- mice. In summary, our results indicate that TRPC1 plays a role in synaptic plasticity and spatial working memory processes.

ORAI Calcium Channels

In this review article, we discuss the different gene products and translational variants of ORAI proteins and their contribution to the makeup of different native calcium-conducting channels with distinct compositions and modes of activation. We also review the different modes of regulation of these distinct calcium channels and their impact on downstream cellular signaling controlling important physiological functions.

TRP Channel Involvement in Salivary Glands-Some Good, Some Bad

Salivary glands secrete saliva, a mixture of proteins and fluids, which plays an extremely important role in the maintenance of oral health. Loss of salivary secretion causes a dry mouth condition, xerostomia, which has numerous deleterious consequences including opportunistic infections within the oral cavity, difficulties in eating and swallowing food, and problems with speech. Secretion of fluid by salivary glands is stimulated by activation of specific receptors on acinar cell plasma membrane and is mediated by an increase in cytosolic [Ca²⁺] ([Ca²⁺]_i). The increase in [Ca²⁺]_i regulates a number of ion channels and transporters that are required for establishing an osmotic gradient that drives water flow via aquaporin water channels in the apical membrane. The Store-Operated Ca²⁺ Entry (SOCE) mechanism, which is regulated in response to depletion of ER-Ca²⁺, determines the sustained [Ca²⁺]_i increase required for prolonged fluid secretion. Core components of SOCE in salivary gland acinar cells are Orai1 and STIM1. In addition, TRPC1 is a major and non-redundant contributor to SOCE and fluid secretion in salivary gland acinar and ductal cells. Other TRP channels that contribute to salivary flow are TRPC3 and TRPV4, while presence of others, including TRPM8, TRPA1, TRPV1, and TRPV3, have been identified in the gland. Loss of salivary gland function leads to dry mouth conditions, or xerostomia, which is clinically seen in patients who have undergone radiation treatment for head-and-neck cancers, and those with the autoimmune exocrinopathy, Sjögren’s syndrome (pSS). TRPM2 is a unique TRP channel that acts as a sensor for intracellular ROS. We will discuss recent studies reported by us that demonstrate a key role for TRPM2 in radiation-induced salivary gland dysfunction. Further, there is increasing evidence that TRPM2 might be involved in inflammatory processes. These interesting findings point to the possible involvement of TRPM2 in Sjögren’s Syndrome, although further studies will be required to identify the exact role of TRPM2 in this disease.

TRPC1 Deficiency Impairs the Endothelial Progenitor Cell Function via Inhibition of Calmodulin/eNOS Pathway

Endothelial progenitor cells (EPCs) promote angiogenesis and play a pivotal role in endothelial repair and re-endothelialization after vascular injury. Transient receptor potential-canonical1 (TRPC1) has been recently implied to play important roles on EPC function. Here, we studied the role of TRPC1 in regulating EPC function in vivo and in vitro. EPCs were cultured from TRPC1-knockout mice and their controls. In vitro, TRPC1 knockout reduced EPC functional activities, including migration and tube formation. Additionally, calmodulin (CaM)/endothelial nitric oxide synthase (eNOS) signaling activity were downregulated after TRPC1 knockout. Administration of CaM or eNOS inhibitor ameliorated TRPC1 knockout-reduced EPC migration and tube formation. In vivo Matrigel plug assay confirmed that TRPC1 knockout decreased formation of functional blood vessels of EPCs compared with wild-type EPCs. Taken together, these data suggest that TRPC1 is a critical regulator of angiogenesis.

Functional expression of calcium-permeable canonical transient receptor potential 4-containing channels promotes migration of medulloblastoma cells

KEY POINTS

The proton sensing ovarian cancer G protein coupled receptor 1 (OGR1, aka GPR68) promotes expression of the canonical transient receptor potential channel subunit TRPC4 in normal and transformed cerebellar granule precursor (DAOY) cells. OGR1 and TRPC4 are prominently expressed in healthy cerebellar tissue throughout postnatal development and in primary cerebellar medulloblastoma tissues. Activation of TRPC4-containing channels in DAOY cells, but not non-transformed granule precursor cells, results in prominent increases in [Ca2+ ]i and promotes cell motility in wound healing and transwell migration assays. Medulloblastoma cells not arising from granule precursor cells show neither prominent rises in [Ca2+ ]i nor enhanced motility in response to TRPC4 activation unless they overexpressTRPC4. Our results suggest that OGR1 enhances expression of TRPC4-containing channels that contribute to enhanced invasion and metastasis of granule precursor-derived human medulloblastoma.

ABSTRACT

Aberrant intracellular Ca2+ signalling contributes to the formation and progression of a range of distinct pathologies including cancers. Rises in intracellular Ca2+ concentration occur in response to Ca2+ influx through plasma membrane channels and Ca2+ release from intracellular Ca2+ stores, which can be mobilized in response to activation of cell surface receptors. Ovarian cancer G protein coupled receptor 1 (OGR1, aka GPR68) is a proton-sensing Gq -coupled receptor that is most highly expressed in cerebellum. Medulloblastoma (MB) is the most common paediatric brain tumour that arises from cerebellar precursor cells. We found that nine distinct human MB samples all expressed OGR1. In both normal granule cells and the transformed human cerebellar granule cell line DAOY, OGR1 promoted expression of the proton-potentiated member of the canonical transient receptor potential (TRPC) channel family, TRPC4. Consistent with a role for TRPC4 in MB, we found that all MB samples also expressed TRPC4. In DAOY cells, activation of TRPC4-containing channels resulted in large Ca2+ influx and enhanced migration, while in normal cerebellar granule (precursor) cells and MB cells not derived from granule precursors, only small levels of Ca2+ influx and no enhanced migration were observed. Our results suggest that OGR1-dependent increases in TRPC4 expression may favour formation of highly Ca2+ -permeable TRPC4-containing channels that promote transformed granule cell migration. Increased motility of cancer cells is a prerequisite for cancer invasion and metastasis, and our findings may point towards a key role for TRPC4 in progression of certain types of MB.

Maitotoxin Is a Potential Selective Activator of the Endogenous Transient Receptor Potential Canonical Type 1 Channel in Xenopus laevis Oocytes

Maitotoxin (MTX) is the most potent marine toxin known to date. It is responsible for a particular human intoxication syndrome called ciguatera fish poisoning (CFP). Several reports indicate that MTX is an activator of non-selective cation channels (NSCC) in different cell types. The molecular identity of these channels is still an unresolved topic, and it has been proposed that the transient receptor potential (TRP) channels are involved in this effect. In Xenopus laevis oocytes, MTX at picomolar (pM) concentrations induces the activation of NSCC with functional and pharmacological properties that resemble the activity of TRP channels. The purpose of this study was to characterize the molecular identity of the TRP channel involved in the MTX response, using the small interference RNA (siRNA) approach and the two-electrode voltage-clamp technique (TEVC). The injection of a specifically designed siRNA to silence the transient receptor potential canonical type 1 (TRPC1) protein expression abolished the MTX response. MTX had no effect on oocytes, even at doses 20-fold higher compared to cells without injection. Total mRNA and protein levels of TRPC1 were notably diminished. The TRPC4 siRNA did not change the MTX effect, even though it was important to note that the protein level was reduced by the silencing of TRPC4. Our results suggest that MTX could be a selective activator of TRPC1 channels in X. laevis oocytes and a useful pharmacological tool for further studies on these TRP channels.

Neurological and Motor Disorders: TRPC in the Skeletal Muscle

Transient receptor potential canonical (TRPC) channels belong to the large family of TRPs that are mostly nonselective cation channels with a great variety of gating mechanisms. TRPC are composed of seven members that can all be activated downstream of agonist-induced phospholipase C stimulation, but some members are also stretch-activated and/or are part of the store-operated Ca²⁺ entry (SOCE) pathway. Skeletal muscles generate contraction via an explosive increase of cytosolic Ca²⁺ concentration resulting almost exclusively from sarcoplasmic reticulum Ca²⁺ channel opening. Even if neglected for a long time, it is now commonly accepted that Ca²⁺ entry via SOCE and other routes is essential to sustain contractions of the skeletal muscle. In addition, Ca²⁺ influx is required during muscle regeneration, and alteration of the influx is associated with myopathies. In this chapter, we review the implication of TRPC channels at different stages of muscle regeneration, in adult muscle fibers, and discuss their implication in myopathies.

STIM-TRP Pathways and Microdomain Organization: Contribution of TRPC1 in Store-Operated Ca2+ Entry: Impact on Ca2+ Signaling and Cell Function

Store-operated calcium entry (SOCE) is a ubiquitous Ca²⁺ entry pathway that is activated in response to depletion of ER-Ca²⁺ stores and critically controls the regulation of physiological functions in a wide variety of cell types. The transient receptor potential canonical (TRPC) channels (TRPCs 1-7), which are activated by stimuli leading to PIP₂ hydrolysis, were first identified as molecular components of SOCE channels. While TRPC1 was associated with SOCE and regulation of function in several cell types, none of the TRPC members displayed I _CRAC, the store-operated current identified in lymphocytes and mast cells. Intensive search finally led to the identification of Orai1 and STIM1 as the primary components of the CRAC channel. Orai1 was established as the pore-forming channel protein and STIM1 as the ER-Ca²⁺ sensor protein involved in activation of Orai1. STIM1 also activates TRPC1 via a distinct domain in its C-terminus. However, TRPC1 function depends on Orai1-mediated Ca²⁺ entry, which triggers recruitment of TRPC1 into the plasma membrane where it is activated by STIM1. TRPC1 and Orai1 form distinct store-operated Ca²⁺ channels that regulate specific cellular functions. It is now clearly established that regulation of TRPC1 trafficking can change plasma membrane levels of the channel, the phenotype of the store-operated Ca²⁺ current, as well as pattern of SOCE-mediated [Ca²⁺]_i signals. Thus, TRPC1 is activated downstream of Orai1 and modifies the initial [Ca²⁺]_i signal generated by Orai1. This review will highlight current concepts of the activation and regulation of TRPC1 channels and its impact on cell function.

Sphingosine-1-phosphate-activated TRPC1 channel controls chemotaxis of glioblastoma cells

TRP channels are involved in the control of a broad range of cellular functions such as cell proliferation and motility. We investigated the gating mechanism of TRPC1 channel and its role in U251 glioblastoma cells migration in response to chemotaxis by platelet-derived growth factor (PDGF). PDGF induced an influx of Ca²⁺ that was partially inhibited after pretreatment of the cells with SKI-II, a specific inhibitor of sphingosine kinase producing sphingosine-1-P (S1P). S1P by itself also induced an entry of Ca²⁺. Interestingly, PDGF- and S1P-induced entries of Ca²⁺ were lost in siRNA-TRPC1 treated cells. PDGF-induced chemotaxis of U251 cells was dramatically inhibited in cells treated with SKI-II. This effect was almost completely rescued by addition of synthetic S1P. Chemotaxis was also completely lost in siRNA-TRPC1 treated cells and interestingly, the rescue of migration of cells treated with SKI-II by S1P was dependent on the expression of TRPC1. Immunocytochemistry revealed that, in response to PDGF, TRPC1 translocated from inside of the cell to the front of migration (lamellipodes). This effect seemed PI3K dependent as it was inhibited by cell pre-treatment with LY294002, a PI3-kinase inhibitor. Our results thus identify S1P as a potential activator of TRPC1, a channel involved in cell orientation during chemotaxis by PDGF.

Transient Receptor Potential Canonical 1 (TRPC1) Channels as Regulators of Sphingolipid and VEGF Receptor Expression: IMPLICATIONS FOR THYROID CANCER CELL MIGRATION AND PROLIFERATION

The identity of calcium channels in the thyroid is unclear. In human follicular thyroid ML-1 cancer cells, sphingolipid sphingosine 1-phosphate (S1P), through S1P receptors 1 and 3 (S1P1/S1P3), and VEGF receptor 2 (VEGFR2) stimulates migration. We show that human thyroid cells express several forms of transient receptor potential canonical (TRPC) channels, including TRPC1. In TRPC1 knockdown (TRPC1-KD) ML-1 cells, the basal and S1P-evoked invasion and migration was attenuated. Furthermore, the expression of S1P3 and VEGFR2 was significantly down-regulated. Transfecting wild-type ML-1 cells with a nonconducting TRPC1 mutant decreased S1P3 and VEGFR2 expression. In TRPC1-KD cells, receptor-operated calcium entry was decreased. To investigate whether the decreased receptor expression was due to attenuated calcium entry, cells were incubated with the calcium chelator BAPTA-AM (1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). In these cells, and in cells where calmodulin and calmodulin-dependent kinase were blocked pharmacologically, S1P3 and VEGFR2 expression was decreased. In TRPC1-KD cells, both hypoxia-inducible factor 1α expression and the secretion and activity of MMP2 and MMP9 were attenuated, and proliferation was decreased in TRPC1-KD cells. This was due to a prolonged G1 phase of the cell cycle, a significant increase in the expression of the cyclin-dependent kinase inhibitors p21 and p27, and a decrease in the expression of cyclin D2, cyclin D3, and CDK6. Transfecting TRPC1 to TRPC1-KD cells rescued receptor expression, migration, and proliferation. Thus, the expression of S1P3 and VEGFR2 is mediated by a calcium-dependent mechanism. TRPC1 has a crucial role in this process. This regulation is important for the invasion, migration, and proliferation of thyroid cancer cells.

Classical Transient Receptor Potential 1 (TRPC1): Channel or Channel Regulator?

In contrast to other Classical Transient Receptor Potential TRPC channels the function of TRPC1 as an ion channel is a matter of debate, because it is often difficult to obtain substantial functional signals over background in response to over-expression of TRPC1 alone. Along these lines, heterologously expressed TRPC1 is poorly translocated to the plasma membrane as a homotetramer and may not function on its own physiologically, but may rather be an important linker and regulator protein in heteromeric TRPC channel tetramers. However, due to the lack of specific TRPC1 antibodies able to detect native TRPC1 channels in primary cells, identification of functional TRPC1 containing heteromeric TRPC channel complexes in the plasma membrane is still challenging. Moreover, an extended TRPC1 cDNA, which was recently discovered, may seriously question results obtained in heterologous expression systems transfected with shortened cDNA versions. Therefore, this review will focus on the current status of research on TRPC1 function obtained in primary cells and a TRPC1-deficient mouse model.