Transient Receptor Potential Channel 1 Expression Research Articles

The Xanthine Derivative KMUP-1 Inhibits Hypoxia-Induced TRPC1 Expression and Store-Operated Ca2+ Entry in Pulmonary Arterial Smooth Muscle Cells.

Exposure to hypoxia results in the development of pulmonary arterial hypertension (PAH). An increase in the intracellular Ca2+ concentration ([Ca2+]i) in pulmonary artery smooth muscle cells (PASMCs) is a major trigger for pulmonary vasoconstriction and proliferation. This study investigated the mechanism by which KMUP-1, a xanthine derivative with phosphodiesterase inhibitory activity, inhibits hypoxia-induced canonical transient receptor potential channel 1 (TRPC1) protein overexpression and regulates [Ca2+]i through store-operated calcium channels (SOCs). Ex vivo PASMCs were cultured from Sprague-Dawley rats in a modular incubator chamber under 1% O2/5% CO2 for 24 h to elucidate TRPC1 overexpression and observe the Ca2+ release and entry. KMUP-1 (1 μM) inhibited hypoxia-induced TRPC family protein encoded for SOC overexpression, particularly TRPC1. KMUP-1 inhibition of TRPC1 protein was restored by the protein kinase G (PKG) inhibitor KT5823 (1 μM) and the protein kinase A (PKA) inhibitor KT5720 (1 μM). KMUP-1 attenuated protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 1 μM)-upregulated TRPC1. We suggest that the effects of KMUP-1 on TRPC1 might involve activating the cyclic guanosine monophosphate (cGMP)/PKG and cyclic adenosine monophosphate (cAMP)/PKA pathways and inhibiting the PKC pathway. We also used Fura 2-acetoxymethyl ester (Fura 2-AM, 5 μM) to measure the stored calcium release from the sarcoplasmic reticulum (SR) and calcium entry through SOCs in hypoxic PASMCs under treatment with thapsigargin (1 μM) and nifedipine (5 μM). In hypoxic conditions, store-operated calcium entry (SOCE) activity was enhanced in PASMCs, and KMUP-1 diminished this activity. In conclusion, KMUP-1 inhibited the expression of TRPC1 protein and the activity of SOC-mediated Ca2+ entry upon SR Ca2+ depletion in hypoxic PASMCs.

Porcine transient receptor potential channel 1 (TRPC1) regulates muscle growth via the Wnt/β-catenin and Wnt/Ca2+ pathways

Transient receptor potential canonical (TRPC) channels allow the intracellular entry of Ca2+ and play important roles in several physio-pathological processes. In this study, we constructed transgenic mice expressing porcine TRPC1 (Tg-pTRPC1) to verify the effects of TRPC1 on skeletal muscle growth and elucidate the underlying mechanism. Porcine TRPC1 increased the muscle mass, fiber cross-sectional area, and exercise endurance of mice and accelerated muscle repair and regeneration. TRPC1 overexpression enhanced β-catenin expression and promoted myogenesis, which was partly reversed by inhibitors of β-catenin. TRPC1 facilitated the accumulation of intracellular Ca2+ and nuclear translocation of the NFATC2/NFATC2IP complex involved in the Wnt/Ca2+ pathway, promoting muscle growth. Paired related homeobox 1 (Prrx1) promoted the expression of TRPC1, NFATC2, and NFATC2IP that participate in the regulation of muscle growth. Taken together, our findings indicate that porcine TRPC1 promoted by Prrx1 could regulate muscle development through activating the canonical Wnt/β-catenin and non-canonical Wnt/Ca2+ pathways.

Cereblon-mediated TRPC1 degradation regulates Ca2+ influx in the heart

•This study investigated how cereblon (CRBN), a substrate receptor of the E3 ubiquitin ligase complex that selectively degrades ion channels, targets cardiac transient receptor potential channel 1 (TRPC1).•Physiologically, CRBN ablation upregulated TRPC1 expression.•Mechanistically, the CRBN Lon domain directly interacts with the C- and N-terminals of TRPC1.•Increasing CRBN levels enhanced TRPC1 ubiquitination and proteasomal degradation.•TRPC1 overexpression in HEK293-CRBN KO cells enhanced TRPC1 current density and Ca2+ transients.•Pathologically, cardiac TRPC1 expression in CRBN-deficient mice was increased during ex vivo ischemic/reperfusion.•Targeting the CRBN-TRPC1 axis may serve as a novel therapeutic approach to address cardiac disease.

Aberrant TRPC1 expression reflects stromal cervical invasion, lymphovascular invasion, elevated FIGO stage, and poor survival in resectable endometrial carcinoma patients.

BackgroundTransient receptor potential channel 1 (TRPC1) promotes tumor growth and metastasis in endometrial carcinoma (EC) cell lines, whereas its clinical role in EC management remains unclear. Therefore, this study aimed to investigate the association of TRPC1 protein expression with the clinical features and survival of EC patients, then was further validated by TRPC1 mRNA measurement and data from The Human Protein Atlas.MethodsTRPC1 protein expression in tumor tissues and normal endometria of 176 resectable EC patients was determined using immunohistochemistry. Besides, TRPC1 mRNA expression of partial patients (n = 80) was detected using RT‐qPCR. Additionally, survival data from The Human Protein Atlas (derived from The Cancer Genome Atlas [TCGA]) was analyzed.ResultsTRPC1 protein expression was up‐regulated in tumor tissue compared with normal endometrium (p < 0.001). Up‐regulated TRPC1 protein expression was associated with stromal cervical invasion (p = 0.044), lymphovascular invasion (p = 0.032), and increased federation of gynecology and obstetrics (FIGO) stage (p = 0.005). Tumor TRPC1 protein high was linked with shortened accumulating disease‐free survival (DFS) (p = 0.009) and overall survival (OS) (p = 0.026), which were also confirmed by multivariate Cox's regression analysis (both p < 0.050). Further, TRPC1 mRNA validation disclosed that TRPC1 mRNA high was related to shortened accumulating DFS (p = 0.038) and exhibited a correlating trend with declined OS (lacked statistical significance) (p = 0.162). Meanwhile, survival analysis on the data from The Human Protein Atlas (derived from TCGA) also exhibited that TRPC1 mRNA high was correlated with reduced accumulating OS (p < 0.001).ConclusionOur findings support TRPC1 as a prognostic biomarker in resectable EC patients.

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

BackgroundTransient 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.MethodsTotally, 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.ResultsImmunohistochemistry 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.ConclusionsTRPC1 is unregulated in NSCLC tissue with its overexpression relating to the occurrence of LYN metastasis and worse DFS in NSCLC patients.

Thioredoxin-1 regulates calcium homeostasis in MPP+ /MPTP-induced Parkinson's disease models.

Disturbance in calcium (Ca2+ ) homeostasis has been involved in a variety of neuropathological conditions including Parkinson's disease (PD). The Ca2+ channel, transient receptor potential channel 1 (TRPC1), plays a protective role in regulating entry of Ca2+ activated by store depletion of Ca2+ in endoplasmic reticulum (ER). We have showed that thioredoxin-1 (Trx-1) plays a role in suppressing ER stress in PD. However, whether Trx-1 regulates TRPC1 expression in PD is still unknown. In the present study, we demonstrated that treatment of 1-methyl-4-phenylpyridinum ion (MPP+ ) significantly reduced the expression of TRPC1 in PC12 cells, which was restored by Trx-1 overexpression, and further decreased significantly by Trx-1 siRNA. Moreover, we found that Ca2+ entered into the cells was decreased by MPP+ in PC 12 cells, which was restored by Trx-1 overexpression, and further decreased by Trx-1 siRNA. MPP+ significantly increased calcium-dependent cysteine protease calpain1 expression in PC12 cells, which was suppressed by Trx-1 overexpression. Calpain1 expression was increased by Trx-1 siRNA or SKF96365, an inhibitor of TRPC1. Moreover, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) decreased TRPC1 expression in the substantia nigra pars compacta region (SNpc), which was restored in mice overexpressing Trx-1, and further decreased in mice of knockdown Trx-1. Inversely, the expression of calpain1 was increased by MPTP, which was suppressed in mice overexpressing Trx-1, and further increased in mice of knockdown Trx-1. In conclusion, Trx-1 regulates the Ca2+ entry through regulating TRPC1 expression after treatment of MPP+ /MPTP.

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.

Expression of TRPC1 and SBEM protein in breast cancer tissue and its relationship with clinicopathological features and prognosis of patients.

This study investigated the relationship of the expression of transient receptor potential channel 1 (TRPC1), small breast epithelial mucin (SBEM) in breast cancer tissues with clinical pathological features and prognosis of patients. Altogether 50 patients with breast cancer who were treated in Weifang People's hospital from April 2017 to November 2018 were selected, and the mRNA and protein differences of TRPC1 and SBEM in breast cancer patients and normal breast cancer tissues were detected by qRT-PCR and Western blot. Spearman test was used for correlation analysis. Logistic univariate and multivariate analysis were performed on the risk factors related to breast cancer metastasis in breast cancer patients. The expression of TRPC1 and SBEM in breast cancer tissues was significantly higher than that in normal breast tissues (P<0.001). The mRNA expression of TRPC1, SBEM and protein was not related to age, tumor size and tissue grade of breast cancer patients, but related to TNM stage, clinical stage and lymph node metastasis (P<0.001). The relative expression of TRPC1 was positively correlated with clinical stage of breast cancer (r=0.992, P<0.001). The relative expression of SBEM was positively correlated with the clinical stage of breast cancer (r=0.853, P<0.001). The relative expression of TRPC1 was positively correlated with TNM staging of breast cancer (r=0.860, P<0.001). The relative expression of SBEM was positively correlated with TNM staging of breast cancer (r=0.880, P<0.001). Multivariate conditional Logistic regression analysis showed that TNM staging, TRPC1, SBEM were independent risk factors for malignant breast cancer metastasis. On the contrary, expression of TRPC1 and SBEM in breast cancer tissues was up-regulated. TRPC1 and SBEM may be involved in the process of breast cancer occurrence, development and metastasis, and can be used as potential tissue biomarkers in diagnosis of breast cancer metastasis and disease assessment.

Effect of selective inhibition or activation of PGE2 EP1 receptor on glomerulosclerosis.

Prostaglandin E2 (PGE2) is involved in numerous physiological and pathological processes of the kidney via its four receptors. A previous study has suggested that a defect in the PGE2 receptor 1 (EP1) gene markedly suppressed the transforming growth factor-β1 (TGF-β1)-induced mesangial cell (MC) proliferation and extracellular matrix aggregation. Therefore, the present study aimed to adopt a pharmacological method of specifically suppressing or activating the EP1 receptor to further verify and demonstrate these results. The EP1 receptor antagonist SC-19220 and EP1 receptor agonist 17-phenyl-trinor-PGE2 ethyl amide (17-pt-PGE2) were selectively used to treat five-sixths nephrectomy renal fibrosis model mice and TGF-β1-stimulated MCs. An Alpha screen PGE2 assay kit, flow cytometry, western blotting and immunohistochemical techniques were adopted to perform in vivo and in vitro experiments. The present results suggested that compared with the control group, the selective EP1 receptor antagonist SC-19220 improved renal function, markedly reduced the plasma blood urea nitrogen and creatinine levels (P<0.05) and alleviated glomerulosclerosis (P<0.05). By contrast, the EP1 receptor agonist 17-pt-PGE2 aggravated renal dysfunction and glomerulosclerosis (P<0.05). To verify the renal protection mechanisms mediated by suppression of the EP1 receptor, the expression levels of endoplasmic reticulum stress (ERS)-related proteins, including chaperone glucose-regulated protein 78 (GRP78), transient receptor potential channel 1 (TRPC1) and protein kinase R-like endoplasmic reticulum kinase (PERK), were further evaluated histologically. The expression of GRP78, TRPC1 and PERK in the antagonist treatment group were markedly downregulated (P<0.05), whereas those in the agonist treatment group were upregulated (P<0.05). The present in vitro experiments demonstrated that, compared with the control group, the EP1 receptor antagonist suppressed the expression of GRP78, TRPC1 and PERK (P<0.05), reduced the production of PGE2 (P<0.05) and decreased the MC apoptosis rate (P<0.05), thus alleviating TGF-β1-stimulated MC injury. Consequently, consistent with previous results, selectively antagonizing the EP1 receptor improved renal function and mitigated glomerulosclerosis, and its potential mechanism might be associated with the suppression of ERS.

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

BackgroundBronchoconstriction 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.MethodsWe 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.ResultsThe 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.ConclusionsThese 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.

MicroRNA-135a is involved in podocyte injury in a transient receptor potential channel 1-dependent manner.

Transient receptor potential (TRP) cation channels are essential for normal cellular physiology, and their abnormal expression may lead to a number of disorders, including podocytopathy. Therefore, it is crucial to understand the mechanisms underlying the regulation of TRP channels. In the present study, microRNA (miR)-135a was found to be upregulated in patients with focal segmental glomerulosclerosis and mice treated with adriamycin (ADR). In cultured podocytes, transforming growth factor (TGF)-β and ADR were found to promote miR-135a expression. Conversely, TRP channel 1 (TRPC1) protein levels were markedly downregulated in podocytes from mice treated with ADR, as well as in cultured podocytes treated with ADR and TGF-β. Ectopic expression of miR-135a led to severe podocyte injury and disarray of the podocyte cytoskeleton, whereas podocyte-specific expression of TRPC1 was able to reverse the pathological effects of miR-135a in cultured podocytes. Moreover, using Luciferase reporter assays and western blot analysis, TRPC1 was identified as a target gene of miR-135a. To the best of our knowledge, this is the first study to demonstrate the role of TRPC1 in the development of podocyte injury and disorders of the podocyte cytoskeleton, which may contribute to the development of novel therapeutics for podocyte injury-associated kidney diseases.

CD5 expression promotes IL-10 production through activation of the MAPK/Erk pathway and upregulation of TRPC1 channels in B lymphocytes.

CD5 is constitutively expressed on T cells and a subset of mature normal and leukemic B cells in patients with chronic lymphocytic leukemia (CLL). Important functional properties are associated with CD5 expression in B cells, including signal transducer and activator of transcription 3 activation, IL-10 production and the promotion of B-lymphocyte survival and transformation. However, the pathway(s) by which CD5 influences the biology of B cells and its dependence on B-cell receptor (BCR) co-signaling remain unknown. In this study, we show that CD5 expression activates a number of important signaling pathways, including Erk1/2, leading to IL-10 production through a novel pathway independent of BCR engagement. This pathway is dependent on extracellular calcium (Ca2+) entry facilitated by upregulation of the transient receptor potential channel 1 (TRPC1) protein. We also show that Erk1/2 activation in a subgroup of CLL patients is associated with TRPC1 overexpression. In this subgroup of CLL patients, small inhibitory RNA (siRNA) for CD5 reduces TRPC1 expression. Furthermore, siRNAs for CD5 or for TRPC1 inhibit IL-10 production. These findings provide new insights into the role of CD5 in B-cell biology in health and disease and could pave the way for new treatment strategies for patients with B-CLL.

Role of the ER stress in prostaglandin E2/E-prostanoid 2 receptor involved TGF-β1-induced mice mesangial cell injury.

This study aims to investigate the relationship between prostaglandin E2 E-prostanoid 2 receptor (EP2) and Endoplasmic reticulum (ER) stress in transforming growth factor-β1 (TGF-β1)-induced mouse glomerular mesangial cells (MCs) injury. We cultured primary WT, EP2(-/-) MCs (EP2 deleted), and adenovirus-EP2-infected WT MCs (EP2 overexpressed). PCR, Western blot, flow cytometry, and immunohistochemical technique were used in in vitro and in vivo experiments. We found that TGF-β1-induced PGE2 synthesis decreased in EP2-deleted MCs and increased in EP2-overexpressed MCs. EP2 deficiency in these MCs augmented the coupling of TGF-β1 to ER stress-associated proteins [chaperone glucose-regulated protein 78 (GRP78), transient receptor potential channel 1 (TRPC1), and transient receptor potential channel 4 (TRPC4)], and upregulation of EP2 showed no significant change of GRP78, but augmented the expression of TRPC1, while TRPC4 expression was downregulated in comparison to normal MCs. In addition, EP2 deficiency in MCs augmented TGF-β1-induced fibronectin (FN), cyclooxygenase-2 (COX2), and CyclinD1 expression. Silencing of EP2 also strengthened TGF-β1-induced extracellular-signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Flow Cytometry showed that silencing of EP2 significantly promoted the apoptosis of MCs. In contrast, EP2 overexpression reversed the effects of EP2 deficiency. 8weeks after 5/6 nephrectomy (Nx), blood urea nitrogen and creatinine concentrations were significantly increased in EP2(-/-) 5/6Nx mice as compared to those of WT 5/6Nx mice. The pathological changes in kidney of EP2(-/-) mice were markedly aggravated compared with WT mice. Immunohistochemical analysis showed significant augment of TRPC4 and ORP150 in the kidney of EP2(-/-) mice compared with WT mice. Considering all the findings, it is suggested that increased expression of EP2 may prevent TGF-β1-induced MCs damage through ER stress regulatory pathway.

Expression Patterns of TRPC1 in Cortical Lesions from Patients with Focal Cortical Dysplasia.

Focal cortical dysplasia (FCD) is known as a common cause of chronic refractory epilepsy, but the underlying mechanisms of the factors that lead to FCD-related epilepsy are unclear. Previous studies have shown that canonical transient receptor potential channels (TRPCs) might be involved in the process of epileptogenesis. Canonical transient receptor potential channel 1 (TRPC1), which is ubiquitously expressed in the brain, has been shown to be involved in epileptiform bust firing in knockout mice. In this study, we examined the expression of TRPC1 in FCD type Ia (FCDIa), FCD type IIa (FCDIIa), and FCD type IIb (FCDIIb) surgical specimens from patients and age-matched autopsy control samples. Real-time quantitative PCR and western blotting indicated that TRPC1 mRNA and protein levels were increased in FCDIa, FCDIIa, and FCDIIb samples compared to control samples. Immunohistochemistry results revealed that TRPC1 was mainly distributed in microcolumns, dysmorphic neurons, and balloon cells. Further double immunofluorescent staining showed that TRPC1 was co-localized with glutamatergic and GABAergic markers. Taken together, our results demonstrate that the overexpression and specific cellular location of TRPC1 might be related to the epileptogenesis of FCD.

Upregulation of canonical transient receptor potential channel in the pulmonary arterial smooth muscle of a chronic thromboembolic pulmonary hypertension rat model.

Chronic ligation of the left main pulmonary artery (PA) results in pulmonary vascular remodeling and sustained vasoconstriction. This method has been used to generate a postobstructive pulmonary vasculopathy model to mimic severe chronic thromboembolic pulmonary hypertension (CTEPH). The aim of this study was to examine the cellular and molecular mechanisms underlying CTEPH and to provide evidence for potential treatments. The CTEPH rat model was induced by surgical left PA ligation (LPAL). Right ventricular systolic pressure (RVSP), lung histochemistry and plasma D-dimer measurements were carried out to evaluate the model. A fluorescence microscope was used to measure the basal intracellular Ca(2+) concentration ([Ca(2+)]i) and store-operated Ca(2+) entry (SOCE) in rat distal pulmonary arterial smooth muscle cells through a Fura-2 fluorescence-based method. The expression of the canonical transient receptor potential channel 1 (TRPC1) and TRPC6 was determined by western blotting and real-time quantitative PCR in isolated distal pulmonary arteries (PA). At the time points of 2 and 5 weeks postsurgery, the RVSP showed significant increases in the LPAL groups in comparison with the respective control groups. LPAL also led to right ventricular hypertrophy (RVH), distal pulmonary arterial remodeling in unobstructed territories and persistently higher plasma D-dimer levels. Increases of the basal [Ca(2+)]i and SOCE in LPAL were associated with a clear upregulation of TRPC1 and TRPC6 expression in the distal PA. Our study demonstrated that LPAL successfully reproduced the vascular tone changes that mimic CTEPH pathogenesis. In this model, the increased RVSP and RVH are likely related to enhanced SOCE and upregulated TRPC1 and TRPC6 expression levels in the distal PA.

A Reciprocal Shift in Transient Receptor Potential Channel 1 (TRPC1) and Stromal Interaction Molecule 2 (STIM2) Contributes to Ca2+ Remodeling and Cancer Hallmarks in Colorectal Carcinoma Cells

We have investigated the molecular basis of intracellular Ca(2+) handling in human colon carcinoma cells (HT29) versus normal human mucosa cells (NCM460) and its contribution to cancer features. We found that Ca(2+) stores in colon carcinoma cells are partially depleted relative to normal cells. However, resting Ca(2+) levels, agonist-induced Ca(2+) increases, store-operated Ca(2+) entry (SOCE), and store-operated currents (ISOC) are largely enhanced in tumor cells. Enhanced SOCE and depleted Ca(2+) stores correlate with increased cell proliferation, invasion, and survival characteristic of tumor cells. Normal mucosa cells displayed small, inward Ca(2+) release-activated Ca(2+) currents (ICRAC) mediated by ORAI1. In contrast, colon carcinoma cells showed mixed currents composed of enhanced ICRAC plus a nonselective ISOC mediated by TRPC1. Tumor cells display increased expression of TRPC1, ORAI1, ORAI2, ORAI3, and STIM1. In contrast, STIM2 protein was nearly depleted in tumor cells. Silencing data suggest that enhanced ORAI1 and TRPC1 contribute to enhanced SOCE and differential store-operated currents in tumor cells, whereas ORAI2 and -3 are seemingly less important. In addition, STIM2 knockdown decreases SOCE and Ca(2+) store content in normal cells while promoting apoptosis resistance. These data suggest that loss of STIM2 may underlie Ca(2+) store depletion and apoptosis resistance in tumor cells. We conclude that a reciprocal shift in TRPC1 and STIM2 contributes to Ca(2+) remodeling and tumor features in colon cancer.

Ammonium increases Ca(2+) signalling and up-regulates expression of TRPC1 gene in astrocytes in primary cultures and in the in vivo brain.

Rapid rise in ammonium concentration in the brain is the major pathogenic factor in hepatic encephalopathy that is manifested by state of confusion, forgetfulness and irritability, psychotic symptoms, delusions, lethargy, somnolence and, in the terminal stages, coma. Primary cultures of mouse astrocytes were used to investigate effects of chronic treatment (3 days) with ammonium chloride (ammonium) at 3 mM, this being a relevant concentration for hepatic encephalopathy condition, on metabotropic receptor agonist-induced increases in free cytosolic Ca(2+) concentration [(Ca(2+))i], measured with fura-2 based microfluorimetry and on store-operated Ca(2+) entry (SOCE) activated following treatment with the SERCA inhibitor thapsigargin. The agonists used were the β-adrenergic agonist isoproterenol, the α2-adrenergic agonist dexmedetomidine, the InsP3 receptor (InsP3R) agonist adenophostin A and ryanodine receptor agonist 4-Chloro-m-cresol (4-CMC). Agonist-induced [Ca(2+)]i responses were significantly increased in astrocytes chronically exposed to ammonium. Similarly, the SOCE, meditated by the transient receptor potential channel 1 (TRPC1), was significantly augmented. The ammonium-induced increase in SOCE was a result of an up-regulation of mRNA and protein expression of TRPC1 in astrocytes. Increase in TRPC1 expression and in SOCE were both prevented by ouabain antagonist canrenone. Similar up-regulation of TRPC1 gene expression was found in the brain of adult mice subjected to intraperitoneal injection of urease for 3 days. In transgenic mice tagged with an astrocyte-specific or a neurone-specific markers and treated with intraperitoneal injections of urease for 3 days, the fluorescence-activated cell sorting of neurones and astrocytes demonstrated that TRPC1 mRNA expression was up-regulated in astrocytes, but not in neurones.

Neurotoxin-induced ER stress in mouse dopaminergic neurons involves downregulation of TRPC1 and inhibition of AKT/mTOR signaling

Individuals with Parkinson's disease (PD) experience a progressive decline in motor function as a result of selective loss of dopaminergic (DA) neurons in the substantia nigra. The mechanism(s) underlying the loss of DA neurons is not known. Here, we show that a neurotoxin that causes a disease that mimics PD upon administration to mice, because it induces the selective loss of DA neurons in the substantia nigra, alters Ca²⁺ homeostasis and induces ER stress. In a human neuroblastoma cell line, we found that endogenous store-operated Ca²⁺ entry (SOCE), which is critical for maintaining ER Ca²⁺ levels, is dependent on transient receptor potential channel 1 (TRPC1) activity. Neurotoxin treatment decreased TRPC1 expression, TRPC1 interaction with the SOCE modulator stromal interaction molecule 1 (STIM1), and Ca²⁺ entry into the cells. Overexpression of functional TRPC1 protected against neurotoxin-induced loss of SOCE, the associated decrease in ER Ca²⁺ levels, and the resultant unfolded protein response (UPR). In contrast, silencing of TRPC1 or STIM1 increased the UPR. Furthermore, Ca²⁺ entry via TRPC1 activated the AKT pathway, which has a known role in neuroprotection. Consistent with these in vitro data, Trpc1⁻/⁻ mice had an increased UPR and a reduced number of DA neurons. Brain lysates of patients with PD also showed an increased UPR and decreased TRPC1 levels. Importantly, overexpression of TRPC1 in mice restored AKT/mTOR signaling and increased DA neuron survival following neurotoxin administration. Overall, these results suggest that TRPC1 is involved in regulating Ca²⁺ homeostasis and inhibiting the UPR and thus contributes to neuronal survival.

Transient Receptor Potential Channel 1 (TRPC1) Reduces Calcium Permeability in Heteromeric Channel Complexes

Specific biological roles of the classical transient receptor potential channel 1 (TRPC1) are still largely elusive. To investigate the function of TRPC1 proteins in cell physiology, we studied heterologously expressed TRPC1 channels and found that recombinant TRPC1 subunits do not form functional homomeric channels. Instead, by electrophysiological analysis TRPC1 was shown to form functional heteromeric, receptor-operated channel complexes with TRPC3, -4, -5, -6, and -7 indicating that TRPC1 proteins can co-assemble with all members of the TRPC subfamily. In all TRPC1-containing heteromers, TRPC1 subunits significantly decreased calcium permeation. The exchange of select amino acids in the putative pore-forming region of TRPC1 further reduced calcium permeability, suggesting that TRPC1 subunits contribute to the channel pore. In immortalized immature gonadotropin-releasing hormone neurons endogenously expressing TRPC1, -2, -5, and -6, down-regulation of TRPC1 resulted in increased calcium permeability and elevated basal cytosolic calcium concentrations. We did not observe any involvement of TRPC1 in store-operated cation influx. Notably, TRPC1 suppressed the migration of gonadotropin-releasing hormone neurons without affecting cell proliferation. Conversely, in TRPC1 knockdown neurons, specific migratory properties like distance covered, locomotion speed, and directionality were increased. These findings suggest a novel regulatory mechanism relying on the expression of TRPC1 and the subsequent formation of heteromeric TRPC channel complexes with reduced calcium permeability, thereby fine-tuning neuronal migration.

Evidence that TRPC1 is involved in hippocampal glutamate-induced cell death

Massive neuronal activation by glutamate can result in an excessive rise in cytoplasmic calcium, a process ultimately leading to neuronal death. We have investigated the role of the transient receptor potential channel 1 (TRPC1) in mediating glutamate-induced neuron death. We show that 2-APB (a blocker of store-operated Ca 2+ entry) dramatically reduces glutamate-induced cell death in hippocampal organotypic slice cultures and that glutamate-induced toxicity is accompanied by an increase in TRPC1 expression. RNAi mediated knock-down of TRPC1 in slice cultures prevented glutamate-induced cell death, indicating that TRPC1 plays a prominent role in calcium entry following exposure to glutamate. Thus, TRPC1 may represent a promising target for pharmacological interventions to prevent or reduce glutamate-induced neuronal damage.