Transient Receptor Potential C6 Research Articles

A novel gain-of-function mutation in transient receptor potential C6 that causes podocytes injury.

Podocyte injury plays a vital role in focal segmental glomerulosclerosis (FSGS), and apoptosis is one of its mechanisms. The transient receptor potential channel 6 (TRPC6) is highly expressed in podocytes and mutations mediate podocyte injury. We found TRPC6 gene mutation (N110S) was a new mutation and pathogenic in the preliminary clinical work. The purpose of this study was to investigate the potential mechanism of mutation in TRPC6 (TRPC6-N110S) in the knock-in gene mouse model and in immortalized mouse podocytes (MPC5). Transmission electron microscopy was used to evaluate renal injury morphology. We measured 24-hour urinary albumin-to-creatinine ratios and major biochemical parameters such as serum albumin, urea nitrogen, and total cholesterol. The results of CCK-8 assay and apoptosis experiments showed that the TRPC6-N110S overexpression group had slower proliferative activity and increased apoptosis than the control group. FluO-3 assay revealed increased calcium influx in the TRPC6-N110S overexpression group. Podocin level was decreased in TRPC6-N110S group, while TRPC6 and desmin levels were increased in TRPC6-N110S group. The 24 h uACR at 6 weeks was significantly higher in the pure-zygotes group than in the WT and heterozygotes groups, and this difference was found at 8 and 10 weeks.TRPC6 levels showed no significant difference between homozygote and WT mice. Compared to homozygote group, expression of podocin and nephrin were increased in WT, but levels of desmin was decreased in WT. Our results suggest that this new mutation causes podocyte injury probably by enhancing calcium influx and podocyte apoptosis, accompanied by increased proteinuria and decreased expression of nephrin and podocin.

Gal-3 (Galectin-3) and KCa3.1 Mediate Heterogeneous Cell Coupling and Myocardial Fibrogenesis Driven by βAR (β-Adrenoceptor) Activation.

Heart failure is associated with sympatho-βAR (β-adrenoceptor) activation and cardiac fibrosis. Gal-3 (galectin-3) and KCa3.1 channels that are upregulated in diverse cells of diseased heart are implicated in mediating myocardial inflammation and fibrosis. It remains unclear whether Gal-3 interacts with KCa3.1 leading to cardiac fibrosis in the setting of βAR activation. We tested the effect of KCa3.1 blocker TRAM-34 on cardiac fibrosis and inflammation in cardiac-restricted β2-TG (β2AR overexpressed transgenic) mice and determined KCa3.1 expression in β2-TG×Gal-3-/- mouse hearts. Mechanisms of KCa3.1 in mediating Gal-3 induced fibroblast activation were studied ex vivo. Expression of Gal-3 and KCa3.1 was elevated in β2-TG hearts. Gal-3 gene deletion in β2-TG mice decreased KCa3.1 expression in inflammatory cells but not in fibroblasts. Treatment of β2-TG mice with TRAM-34 for 1 or 2 months significantly ameliorated cardiac inflammation and fibrosis and reduced Gal-3 level. In cultured fibroblasts, Gal-3 upregulated KCa3.1 expression and channel currents with enhanced membrane potential and Ca2+ entry through TRPV4 (transient receptor potential V4) and TRPC6 (transient receptor potential C6) channels leading to fibroblast activation. In conclusion, βAR stimulation promotes Gal-3 production that upregulates KCa3.1 channels in noncardiomyocyte cells and activates KCa3.1 channels in fibroblasts leading to hyperpolarization of membrane potential and Ca2+ entry via TRP channels. Gal-3-KCa3.1 signaling mobilizes diverse cells facilitating regional inflammation and fibroblast activation and hence myocardial fibrosis.

Study on the role of transient receptor potential C6 channels in esophageal squamous cell carcinoma radiosensitivity.

To study the effect of transient receptor potential C6 (TRPC6) channels on esophageal squamous cell carcinoma (ESCC) cell lines Eca109 cell cycle and to confirm whether TRPC6 channel is candidate radiosensitivity in vitro and in vivo. We chose Eca109 cell line with a strong TRPC6 channels expression. Cell cycle was investigated after TRPC6 channel inhibitor SKF96365 treated with a 5 µM concentration. According to the results of cell cycle, radiation was performed. CCK-8 test was used to test the cell proliferation. Then we performed the same study in vivo. Total of 40 male nude mice were randomly divided into four groups as follows: SKF96365, radio, combined radio-SKF96365 and control. In SKF96365 group, 20 mg/kg 5 µM SKF96365 was injected into the abdominal cavity of the nude mice at day 5-11. In radiation group, the nude mice received radiotherapy 2 Gy per day at day 7-11. In combined radio-SKF96365 group, 20 mg/kg 5 µM SKF96365 was injected into the abdominal cavity of the nude mice at day 5-11 and 2 Gy radiotherapy was delivered to the tumor site at day 7-11. In control group, nude mice were injected saline into the abdominal cavity at day 5-11. General states of health were observed, the tumor size in volume was measured with calipers two times every week. Six weeks after seeding, mice were sacrificed by neck-break. The tumor size was measured in volume with caliper and in weigh with scale. Treatment with SKF96365 substantially increased the percentage of Eca109 cells in the G2/M phase and reduced that in G0/G1 phase in a time-dependent manner. Most of the cells (85.26%), 24 h after SKF96365 treatment were arrested in the G2/M phase. CCK-8 test showed that Eca109 ESCC cells received both SKF96365 and radiation showed the worst ability of cell proliferation. The same result was obtained in vivo. Nude mice received combined radio-SKF96365 showed the smallest tumor size and volume. TRPC6 plays an important role in development of esophageal cancer, and SKF96365 may increase the sensitivity of radiotherapy. TRPC6 may become a new radiotherapy target in esophageal cancer.

TRPC6 and kidney disease: sclerosing more than just glomeruli?

Fibrosis is a common response to injury but can also perpetuate tissuedysfunction. Transient receptor potential C6 (TRPC6) is implicated incardiac and skin healing via regulation of myofibroblast differentiation. Wu etal. now demonstrate a role for TRPC6 in renal fibrosis, via a mechanism that also relies on TRPC3 and is antagonized by soluble klotho. Modulation of TRPC3/6 activity may provide a means of dampening the fibrotic response involved in chronic kidney disease progression.

Hyperforin activates gene transcription involving transient receptor potential C6 channels

Hypericum perforatum is one of the most prominent medical plants. Hyperforin, a main ingredient of H. perforatum, has been shown to activate transient receptor potential canonical C6 (TRPC6) channels. Alternatively, it has been proposed that hyperforin functions as a protonophore in a TRPC6-independent manner. Here, we show that hyperforin stimulation activates the transcription factor AP-1 in HEK293 cells expressing TRPC6 (T6.11 cells), but did not substantially change the AP-1 activity in HEK293 cells lacking TRPC6. We identified the AP-1 binding site as a hyperforin-responsive element. AP-1 is composed of the transcription factors c-Jun and c-Fos, or other members of the c-Jun and c-Fos families of proteins. Hyperforin stimulation increased c-Jun and c-Fos promoter activities in T6.11 cells and induced an upregulation of c-Jun and c-Fos biosynthesis. The analysis of the c-Fos promoter revealed that the cAMP-response element also functions as a hyperforin-responsive element. Hyperforin-induced upregulation of AP-1 in T6.11 cells was attenuated by preincubation of the cells with either pregnenolone or progesterone, indicating that gene regulation via TRPC6 is under control of hormones or hormonal precursors. The signal transduction of hyperforin-induced AP-1 gene transcription required an influx of Ca2+ ions into the cells, the activation of MAP kinases, and the activation of the transcription factors c-Jun and ternary complex factor. We conclude that hyperforin regulates gene transcription via activation of TRPC6 channels, involving stimulus-regulated protein kinases and stimulus-responsive transcription factors. The fact that hyperforin regulates gene transcription may explain many of the intracellular alterations induced by this compound.

Cytochrome P450-Derived Epoxyeicosatrienoic Acids and Pulmonary Hypertension: Central Role of Transient Receptor Potential C6 Channels

Hypoxia induces the constriction of pulmonary resistance arteries, which results in the redistribution of blood from poor to better ventilated areas, thus optimizing its oxygenation. Many different oxygen-sensing mechanisms have been proposed to regulate this process, including cytochrome P450 enzymes. These enzymes, which convert substrates such as arachidonic acid into bioactive epoxides (the epoxyeicosatrienoic acids [EETs]), are highly expressed in the lung as is the soluble epoxide hydrolase which metabolizes the epoxides to their less active diols. The EETs play a well-documented role as endothelium-derived vasodilators in the systemic vasculature, but in the pulmonary circulation, they are generated in vascular smooth muscle cells and potentiate vasoconstriction. Preventing the breakdown of 11,12-EET by the inhibition or genetic deletion of the soluble epoxide hydrolase strongly augments the response to hypoxia. Mechanistically, 11,12-EET potentiates the contractile response by recruiting transient receptor potential C6 channels to caveolae. Indeed, neither 11,12-EET nor hypoxia is able to elicit pulmonary vasoconstriction in TRPC6 knockout mice. The cytochrome and soluble epoxide hydrolase enzymes are also implicated in the vascular remodeling associated with chronic hypoxia and pulmonary hypertension. Thus, targeting this pathway may be in an attractive new therapeutic approach to treat this incapacitating disease.

Upregulation of TRPC1 in the development of cardiac hypertrophy

The importance of Ca 2+ entry in the cardiac hypertrophic response is well documented, but the actual Ca 2+ entry channels remain unknown. Transient receptor potential (TRP) proteins are thought to form either homo- or heteromeric Ca 2+ entry channels that are involved in the proliferation and differentiation of various cells. The purpose of this study was to explore the potential involvement of TRP channels in the development of cardiac hypertrophy. The mRNA and protein expression of several TRP channel subunits were evaluated using hearts from abdominal aortic-banded (AAB) rats. Although TRPs C1, C3, C5, and C6 were constitutively expressed, only TRPC1 expression was significantly increased in the hearts of AAB rats compared to sham-operated rats. Using primary cultures of neonatal rat cardiomyocytes, we detected increases in the expression of TRPC1, brain natriuretic peptide (BNP), and atrial natriuretic factor (ANF), as well as increases in store-operated Ca 2+ entry (SOCE) and cell surface area, following endothelin-1 (ET-1) treatment. Silencing of the TRPC1 gene via small interfering RNA (siRNA) attenuated SOCE and prevented ET-1-, angiotensin-II (AT II)-, and phenylephrine (PE)-induced cardiac hypertrophy. In HEK 293T cells, overexpression of TRPC1 augmented SOCE, leading to an increase in nuclear factor of activated T cells (NFAT) promoter activity, while co-transfection with dominant-negative forms of TRPC1 suppressed it. In conclusion, TRPC1 functions in Ca 2+ influx, and its upregulation is involved in the development of cardiac hypertrophy; moreover, it plays an important role in the regulation of the signaling pathways that govern cardiac hypertrophy. These findings establish TRPC1 as a functionally important regulator of cardiac hypertrophy.

Point:Counterpoint: Hypoxic pulmonary vasoconstriction is/is not mediated by increased production of reactive oxygen species

This series of debates was initiated for the Journal of Applied Physiology because we believe an important means of searching for truth is through debate where contradictory viewpoints are put forward. This dialectic process whereby a thesis is advanced, then opposed by an antithesis, with a

Expression of transient receptor potential C6 and related transient receptor potential family members in human airway smooth muscle and lung tissue.

Elevation of the intracellular free Ca(2+) concentration regulates many functional responses in airway smooth muscle, including contraction, proliferation, adhesion, and cell survival. This increase in calcium can be achieved by a release from internal stores (sarcoplasmic reticulum) and/or entry across the cell membrane from the extracellular environment. The molecular identity of this calcium influx pathway in human airway smooth muscle (HASM) remains unclear. Functional studies using Fluo 4-loaded HASM suggest the presence of a histamine H(1) receptor-activated Ca(2+) entry pathway with characteristics similar to those seen with transient receptor potential (TRP) family homologs. Using a range of molecular and cell biological approaches we defined the expression pattern of transient receptor potential classics (TRPC) homologs in airway cells and tissue. Here we show that HASM and human bronchial epithelial cells both express TRPC1, -4, and -6, with HASM also expressing TRPC3 at the mRNA level. Identification of TRPC6 protein by western blot and confocal microscopy indicated that the protein is localized in specific cell types, suggesting that it plays an important role in regulating key functions in airway cells. These data demonstrate the expression of a range of TRPC homologs in the airway and the presence of a functional Ca(2+) entry pathway with characteristics typical of TRPC family members. TRPC homologs may provide an important novel target for the treatment of airway disease.