The Rise in Tubular pH during Hypercalciuria Exacerbates Calcium Stone Formation.

In calcium nephrolithiasis (CaNL), most calcium kidney stones are identified as calcium oxalate (CaOx) with variable amounts of calcium phosphate (CaP), where CaP is found as the core component. The nucleation of CaP could be the first step of CaP+CaOx (mixed) stone formation. High urinary supersaturation of CaP due to hypercalciuria and an elevated urine pH have been described as the two main factors in the nucleation of CaP crystals. Our previous in vivo findings (in mice) show that transient receptor potential canonical type 3 (TRPC3)-mediated Ca2+ entry triggers a transepithelial Ca2+ flux to regulate proximal tubular (PT) luminal [Ca2+], and TRPC3-knockout (KO; -/-) mice exhibited moderate hypercalciuria and microcrystal formation at the loop of Henle (LOH). Therefore, we utilized TRPC3 KO mice and exposed them to both hypercalciuric [2% calcium gluconate (CaG) treatment] and alkalineuric conditions [0.08% acetazolamide (ACZ) treatment] to generate a CaNL phenotype. Our results revealed a significant CaP and mixed crystal formation in those treated KO mice (KOT) compared to their WT counterparts (WTT). Importantly, prolonged exposure to CaG and ACZ resulted in a further increase in crystal size for both treated groups (WTT and KOT), but the KOT mice crystal sizes were markedly larger. Moreover, kidney tissue sections of the KOT mice displayed a greater CaP and mixed microcrystal formation than the kidney sections of the WTT group, specifically in the outer and inner medullary and calyceal region; thus, a higher degree of calcifications and mixed calcium lithiasis in the kidneys of the KOT group was displayed. In our effort to find the Ca2+ signaling pathophysiology of PT cells, we found that PT cells from both treated groups (WTT and KOT) elicited a larger Ca2+ entry compared to the WT counterparts because of significant inhibition by the store-operated Ca2+ entry (SOCE) inhibitor, Pyr6. In the presence of both SOCE (Pyr6) and ROCE (receptor-operated Ca2+ entry) inhibitors (Pyr10), Ca2+ entry by WTT cells was moderately inhibited, suggesting that the Ca2+ and pH levels exerted sensitivity changes in response to ROCE and SOCE. An assessment of the gene expression profiles in the PT cells of WTT and KOT mice revealed a safeguarding effect of TRPC3 against detrimental processes (calcification, fibrosis, inflammation, and apoptosis) in the presence of higher pH and hypercalciuric conditions in mice. Together, these findings show that compromise in both the ROCE and SOCE mechanisms in the absence of TRPC3 under hypercalciuric plus higher tubular pH conditions results in higher CaP and mixed crystal formation and that TRPC3 is protective against those adverse effects.

TRPC4 aggravates hypoxic pulmonary hypertension by promoting pulmonary endothelial cell apoptosis.

Pulmonary hypertension (PH) is a devastating disease that lacks effective treatment options and is characterized by severe pulmonary vascular remodeling. Pulmonary arterial endothelial cell (PAEC) dysfunction drives the initiation and pathogenesis of pulmonary arterial hypertension. Canonical transient receptor potential (TRPC) channels, a family of Ca2+-permeable channels, play an important role in various diseases. However, the effect and mechanism of TRPCs on PH development have not been fully elucidated. Among the TRPC family members, TRPC4 expression was markedly upregulated in PAECs from hypoxia combined with SU5416 (HySu)-induced PH mice and monocrotaline (MCT)-treated PH rats, as well as in hypoxia-exposed PAECs, suggesting that TRPC4 in PAECs may participate in the occurrence and development of PH. In this study, we aimed to investigate whether TRPC4 in PAECs has an aggravating effect on PH and elucidate the molecular mechanisms. We observed that hypoxia treatment promoted PAEC apoptosis through a caspase-12/endoplasmic reticulum stress (ERS)-dependent pathway. Knockdown of TRPC4 attenuated hypoxia-induced apoptosis and caspase-3/caspase-12 activity in PAECs. Accordingly, adeno-associated virus (AAV) serotype 6-mediated pulmonary endothelial TRPC4 silencing (AAV6-Tie-shRNA-TRPC4) or TRPC4 antagonist suppressed PH progression as evidenced by reduced right ventricular systolic pressure (RVSP), pulmonary vascular remodeling, PAEC apoptosis and reactive oxygen species (ROS) production. Mechanistically, unbiased RNA sequencing (RNA-seq) suggested that TRPC4 deficiency suppressed the expression of the proapoptotic protein sushi domain containing 2 (Susd2) in hypoxia-exposed mouse PAECs. Moreover, TRPC4 activated hypoxia-induced PAEC apoptosis by promoting Susd2 expression. Therefore, inhibiting TRPC4 ameliorated PAEC apoptosis and hypoxic PH in animals by repressing Susd2 signaling, which may serve as a therapeutic target for the management of PH.

Biomass fuels related-PM2.5 promotes lung fibroblast-myofibroblast transition through PI3K/AKT/TRPC1 pathway.

Emerging evidence has suggested that exposure to PM2.5 is a significant contributing factor to the development of chronic obstructive pulmonary disease (COPD). However, the underlying biological effects and mechanisms of PM2.5 in COPD pathology remain elusive. In this study, we aimed to investigate the implication and regulatory effect of biomass fuels related-PM2.5 (BRPM2.5) concerning the pathological process of fibroblast-to-myofibroblast transition (FMT) in the context of COPD. In vivo experimentation revealed that exposure to biofuel smoke was associated with airway inflammation in rats. After 4 weeks of exposure, there was inflammation in the small airways, but no significant structural changes in the airway walls. However, after 24 weeks, airway remodeling occurred due to increased collagen deposition, myofibroblast proliferation, and tracheal wall thickness. In vitro, cellular immunofluorescence results showed that with stimulation of BRPM2.5 for 72 h, the cell morphology of fibroblasts changed significantly, most of the cells changed from spindle-shaped to star-shaped irregular, α-SMA stress fibers appeared in the cytoplasm and the synthesis of type I collagen increased. The collagen gel contraction experiment showed that the contractility of fibroblasts was enhanced. The expression level of TRPC1 in fibroblasts was increased. Specific siRNA-TRPC1 blocked BRPM2.5-induced FMT and reduced cell contractility. Additionally, specific siRNA-TRPC1 resulted in a decrease in the augment of intracellular Ca2+ concentration ([Ca2+]i) induced by BRPM2.5. Notably, it was found that the PI3K inhibitor, LY294002, inhibited enhancement of AKT phosphorylation level, FMT occurrence, and elevation of TRPC1 protein expression induced by BRPM2.5. The findings indicated that BRPM2.5 is capable of inducing the FMT, with the possibility of mediation by PI3K/AKT/TRPC1. These results hold potential implications for the understanding of the molecular mechanisms involved in BRPM2.5-induced COPD and may aid in the development of novel therapeutic strategies for pathological conditions characterized by fibrosis.

TRPC3 Is Downregulated in Primary Hyperparathyroidism.

Transient receptor potential canonical sub-family channel 3 (TRPC3) is considered to play a critical role in calcium homeostasis. However, there are no established findings in this respect with regard to TRPC6. Although the parathyroid gland is a crucial organ in calcium household regulation, little is known about the protein distribution of TRPC channels-especially TRPC3 and TRPC6-in this organ. Our aim was therefore to investigate the protein expression profile of TRPC3 and TRPC6 in healthy and diseased human parathyroid glands. Surgery samples from patients with healthy parathyroid glands and from patients suffering from primary hyperparathyroidism (pHPT) were investigated by immunohistochemistry using knockout-validated antibodies against TRPC3 and TRPC6. A software-based analysis similar to an H-score was performed. For the first time, to our knowledge, TRPC3 and TRPC6 protein expression is described here in the parathyroid glands. It is found in both chief and oxyphilic cells. Furthermore, the TRPC3 staining score in diseased tissue (pHPT) was statistically significantly lower than that in healthy tissue. In conclusion, TRPC3 and TRPC6 proteins are expressed in the human parathyroid gland. Furthermore, there is strong evidence indicating that TRPC3 plays a role in pHPT and subsequently in parathyroid hormone secretion regulation. These findings ultimately require further research in order to not only confirm our results but also to further investigate the relevance of these channels and, in particular, that of TRPC3 in the aforementioned physiological functions and pathophysiological conditions.

Phenotypical, genotypical and pathological characterization of the moonwalker mouse, a model of ataxia.

We performed a comprehensive study of the morphological, functional, and genetic features of moonwalker (MWK) mice, a mouse model of spinocerebellar ataxia caused by a gain of function of the TRPC3 channel. These mice show numerous behavioral symptoms including tremor, altered gait, circling behavior, impaired motor coordination, impaired motor learning and decreased limb strength. Cerebellar pathology is characterized by early and almost complete loss of unipolar brush cells as well as slowly progressive, moderate loss of Purkinje cell (PCs). Structural damage also includes loss of synaptic contacts from parallel fibers, swollen ER structures, and degenerating axons. Interestingly, no obvious correlation was observed between PC loss and severity of the symptoms, as the phenotype stabilizes around 2 months of age, while the cerebellar pathology is progressive. This is probably due to the fact that PC function is severely impaired much earlier than the appearance of PC loss. Indeed, PC firing is already impaired in 3 weeks old mice. An interesting feature of the MWK pathology that still remains to be explained consists in a strong lobule selectivity of the PC loss, which is puzzling considering that TRPC is expressed in every PC. Intriguingly, genetic analysis of MWK cerebella shows, among other alterations, changes in the expression of both apoptosis inducing and resistance factors possibly suggesting that damaged PCs initiate specific cellular pathways that protect them from overt cell loss.

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

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

Ca2+ Depletion in the ER Causes Store-Operated Ca2+ Entry via the TRPC6 Channel in Mouse Brown Adipocytes.

beta3-adrenergic activation causes Ca2+ release from the mitochondria and subsequent Ca2+ release from the endoplasmic reticulum (ER), evoking store-operated Ca2+ entry (SOCE) due to Ca2+ depletion from the ER in mouse brown adipocytes. In this study, we investigated how Ca2+ depletion from the ER elicits SOCE in mouse brown adipocytes using fluorometry of intracellular Ca2+ concentration ([Ca2+]i). The administration of cyclopiazonic acid (CPA), a reversible sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) pump blocker in the ER, caused an increase in [Ca2+]i. Moreover, CPA induced SOCE was suppressed by the administration of a Ca2+ free Krebs solution and the transient receptor potential canonical 6 (TRPC6) selective blockers 2-APB, ML-9 and GsMTx-4 but not Pico145, which blocks TRPC1/4/5. Administration of TRPC6 channel agonist 1-oleoyl-2-acetyl-sn-glycerol (OAG) and flufenamic acid elicited Ca2+ entry. Moreover, our RT-PCR analyses detected mRNAs for TRPC6 in brown adipose tissues. In addition, western blot analyses showed the expression of the TRPC6 protein. Thus, TRPC6 is one of the Ca2+ pathways involved in SOCE. These modes of Ca2+ entry provide the basis for heat production via activation of Ca2+-dependent dehydrogenase and the expression of uncoupling protein 1 (UCP1). Enhancing thermogenic metabolism in brown adipocytes may serve as broad therapeutic utility to reduce obesity and metabolic syndrome.

Porcine transient receptor potential channel 1 (TRPC1) regulates muscle growth via the Wnt/ß-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 ß-catenin expression and promoted myogenesis, which was partly reversed by inhibitors of ß-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/ß-catenin and non-canonical Wnt/Ca2+ pathways.

The IGF2BP2-lncRNA TRPC7-AS1 axis promotes hepatocellular carcinoma cell proliferation and invasion.

Hepatocellular carcinoma(HCC) is one of the most common tumors in the world. Human insulin-like growth factor 2(IGF2) mRNA binding protein 2(IGF2BP2) plays an important role in the progression of hepatocellular carcinoma. Additionally, long non-coding RNA(lncRNA) has been confirmed as a key regulator of hepatocellular carcinoma occurrence. However, the function of TRPC7-AS1 has not been verified in hepatocellular carcinoma. The research results revealed that high IGF2BP2 expression was associated with a decreased survival rate in patients with hepatocellular carcinoma. Furthermore, IGF2BP2 knockdown inhibited and IGF2BP2 overexpression promoted the cell proliferation and invasion of hepatocellular carcinoma cells. The research illuminated that IGF2BP2 regulated the expression of TRPC7-AS1, and a correlation was observed between IGF2BP2 and TRPC7-AS1 expression. TRPC7-AS1 silencing repressed and its overexpression promoted the progression of hepatocellular carcinoma. After silencing or overexpressing TRPC7-AS1, the expression of the high-mobility group AT-hook 2 (HMGA2) gene decreased or increased, respectively. IGF2BP2 enhanced the expression of TRPC7-AS1 and thus affected the expression of HMGA2, thereby promoting hepatocellular carcinoma progression.

Endothelial cell Orai1 is essential for endothelium-dependent contraction of mouse carotid arteries in normotensive and hypertensive mice.

Endothelium-dependent contraction (EDC) exists in blood vessels of normotensive animals, but is exaggerated in hypertension. An early signal in EDC is cytosolic Ca2+ rise in endothelial cells. In this study we investigated the functional role of Orai1, a major endothelial cell Ca2+ entry channel, in EDC. Hypertension model was established in WT mice by intake of L-NNA in the drinking water (0.5 g/L) for 4 weeks or osmotic pump delivery of Ang II (1.5 mg·kg-1·d-1) for 2 weeks. In TRPC5 KO mice, the concentration of L-NNA and Ang II were increased to 1 g/L or 2 mg·kg-1·d-1, respectively. Arterial segments were prepared from carotid arteries and aortas, and EDC was elicited by acetylcholine in the presence of Nω-nitro-L-arginine methyl ester. We showed that low concentration of acetylcholine (3-30 nM) initiated relaxation in phenylephrine-precontracted carotid arteries of both normotensive and hypertensive mice, while high concentration of acetylcholine (0.1-2 µM) induced contraction. Application of selective Orai1 inhibitors AnCoA4 (100 µM) or YM58483 (400 nM) had no effect on ACh-induced relaxation but markedly reduced acetylcholine-induced EDC. We found that EDC was increased in hypertensive mice compared with that of normotensive mice, which was associated with increased Orai1 expression in endothelial cells of hypertensive mice. Compared to TRPC5 and TRPV4, which were also involved in EDC, endothelial cell Orai1 had relatively greater contribution to EDC than either TRPC5 or TRPV4 alone. We identified COX-2, followed by PGF2α, PGD2 and PGE2 as the downstream signals of Orai1/TRPC5/TRPV4. In conclusion, Orai1 coordinates together with TRPC5 and TRPV4 in endothelial cells to regulate EDC responses. This study demonstrates a novel function of Orai1 in EDC in both normotensive and hypertensive mice, thus providing a general scheme about the control of EDC by Ca2+-permeable channels.

Discovery of N-alkyl-N-benzyl thiazoles as novel TRPC antagonists for the treatment of glioblastoma multiforme.

Glioblastoma multiforme represents a substantial clinical challenge. Transient receptor potential channel (TRPC) antagonists might provide new therapeutic options for this aggressive cancer. In this study, a series of N-alkyl-N-benzoyl and N-alkyl-N-benzyl thiazoles were designed and prepared using a scaffold-hopping strategy and evaluated as TRPC6 antagonists. This resulted in the discovery of 15g, a potent TRPC antagonist that exhibited suitable inhibitory micromolar activities against TRPC3, TRPC4, TRPC5, TPRC6, and TRPC7 and displayed noteworthy anti-glioblastoma efficacy in vitro against U87 cell lines. In addition, 15g featured an acceptable pharmacokinetic profile and exhibited better in vivo potency (25 mg/kg/d) than the frontline therapeutic agent temozolomide (50 mg/kg/d) in xenograft models. Taken together, the TRPC antagonist 15g represents a promising lead compound for developing new anti-glioblastoma agents.

MiR-138-5p Inhibits Thyroid Cancer Cell Growth and Stemness by Targeting TRPC5/Wnt/ß-Catenin Pathway.

MicroRNAs play a key role in the pathogenesis of many types of cancer, including thyroid cancer (TC). MiR-138-5p has been confirmed to be abnormally expressed in TC tissues. However, the role of miR-138-5p in TC progression and its potential molecular mechanism need to be further explored. In this study, quantitative real-time PCR was used to examine miR-138-5p and TRPC5 expression, and western blot analysis was performed to examine the protein levels of TRPC5, stemness-related markers, and Wnt pathway-related markers. Dual-luciferase reporter assay was used to assess the interaction between miR-138-5p and TRPC5. Cell proliferation, stemness, and apoptosis were examined using colony formation assay, sphere formation assay, and flow cytometry. Our data showed that miR-138-5p could target TRPC5 and its expression was negatively correlated with TRPC5 expression in TC tumor tissues. MiR-138-5p decreased proliferation, stemness, and promoted gemcitabine-induced apoptosis in TC cells, and this effect could be reversed by TRPC5 overexpression. Moreover, TRPC5 overexpression abolished the inhibitory effect of miR-138-5p on the activity of Wnt/ß-catenin pathway. In conclusion, our data showed that miR-138-5p suppressed TC cell growth and stemness via the regulation of TRPC5/Wnt/ß-catenin pathway, which provided some guidance for studying the potential function of miR-138-5p in TC progression.

Trpc6 knockout protects against renal fibrosis by restraining the CN­NFAT2 signaling pathway in T2DM mice.

Diabetic kidney disease (DKD), one of the common complications of type­2 diabetes mellitus (T2DM), has become the principal cause of end­stage kidney disease. Transient receptor potential channel 6 (TRPC6), one of non­selective cation channels with significant calcium­permeability, is associated with renal fibrosis. However, the mechanism of TRPC6 in T2DM­induced renal fibrosis is still not entirely understood. The present study explored the potential mechanism of Trpc6 knockout in T2DM­induced renal fibrosis in Trpc6­/­ mice. The results showed that Trpc6 knockout inhibited the loss of body weight and the increase of fasting blood glucose (FBG) and significantly improved renal dysfunction and glomerular fibrosis in T2DM mice. The present study also indicated that Trpc6 knockout significantly lowered the expression of phosphorylated (p­)SMAD2/3, TGF­ß, calcineurin (CN), nuclear factor of activated T­cell (NFAT)2 and Nod­like receptor (NLR) 3 inflammasome­associated proteins. Calcium imaging results revealed that Trpc6 knockdown could decrease the levels of [Ca2+]i and inhibited calcium homeostasis imbalance. Moreover, it was found that knockout of Trpc6 had no significant influence on lipid disposition and reactive oxygen species generation in the kidney cortex. The present study suggested that knockout of Trpc6 may alleviate glomerular fibrosis and delay DKD progression by reducing [Ca2+]i overload and inhibiting the CN­NFAT2 pathway in T2DM mice.

The Multifunctional TRPC6 Protein: Significance in the Field of Cardiovascular Studies.

Cardiovascular disease is the leading cause of death, medical complications, and healthcare costs. Although recent advances have been in treating cardiovascular disorders linked with a reduced ejection fraction, acutely decompensate cardiac failure remains a significant medical problem. The transient receptor potential cation channel (TRPC6) family responds to neurohormonal and mechanical stress, playing critical roles in cardiovascular diseases. Therefore, TRP C6 channels have great promise as therapeutic targets. Numerous studies have investigated the roles of TRP C6 channels in pain neurons, highlighting their significance in cardiovascular research. The TRPC6 protein exhibits a broad distribution in various organs and tissues, including the brain, nerves, heart, blood vessels, lungs, kidneys, gastrointestinal tract, and other bodily structures. Its activation can be triggered by alterations in osmotic pressure, mechanical stimulation, and diacylglycerol. Consequently, TRPC6 plays a significant role in the pathophysiological mechanisms underlying diverse diseases within living organisms. A recent study has indicated a strong correlation between the disorder known as TRPC6 and the development of cardiovascular diseases. Consequently, investigations into the association between TRPC6 and cardiovascular diseases have gained significant attention in the scientific community. This review explores the most recent developments in the recognition and characterization of TRPC6. Additionally, it considers the field's prospects while examining how TRPC6 might be altered and its clinical applications.

ß-Arrestin pathway activation by selective ATR1 agonism promotes calcium influx in podocytes, leading to glomerular damage.

Angiotensin receptor blockers (ARBs) are the first-line treatment for hypertension; they act by inhibiting signaling through the angiotensin 1 receptor (AT1R). Recently, a novel biased AT1R agonist, TRV120027 (TRV), which selectively activates the ß-arrestin cascade and blocks the G-protein-coupled receptor pathway has been proposed as a potential blood pressure medication. Here, we explored the effects of TRV and associated ß-arrestin signaling in podocytes, essential cells of the kidney filter. We used human podocyte cell lines to determine ß-arrestin's involvement in calcium signaling and cytoskeletal reorganization and Dahl SS rats to investigate the chronic effects of TRV administration on glomerular health. Our experiments indicate that the TRV-activated ß-arrestin pathway promotes the rapid elevation of intracellular Ca2+ in a dose-dependent manner. Interestingly, the amplitude of ß-arrestin-mediated Ca2+ influx was significantly higher than the response to similar Ang II concentrations. Single-channel analyses show rapid activation of transient receptor potential canonical (TRPC) channels following acute TRV application. Furthermore, the pharmacological blockade of TRPC6 significantly attenuated the ß-arrestin-mediated Ca2+ influx. Additionally, prolonged activation of the ß-arrestin pathway in podocytes resulted in pathological actin cytoskeleton rearrangements, higher apoptotic cell markers, and augmented glomerular damage. TRV-activated ß-arrestin signaling in podocytes may promote TRPC6 channel-mediated Ca2+ influx, foot process effacement, and apoptosis, possibly leading to severe defects in glomerular filtration barrier integrity and kidney health. Under these circumstances, the potential therapeutic application of TRV for hypertension treatment requires further investigation to assess the balance of the benefits versus possible deleterious effects and off-target damage.

Selective Activation of a TRPC6 Ion Channel Over TRPC3 by Metalated Type-B Polycyclic Polyprenylated Acylphloroglucinols.

Selective modulation of TRPC6 ion channels is a promising therapeutic approach for neurodegenerative diseases and depression. A significant advancement showcases the selective activation of TRPC6 through metalated type-B PPAP, termed PPAP53. This success stems from PPAP53's 1,3-diketone motif facilitating metal coordination. PPAP53 is water-soluble and as potent as hyperforin, the gold standard in this field. In contrast to type-A, type-B PPAPs offer advantages such as gram-scale synthesis, easy derivatization, and long-term stability. Our investigations reveal PPAP53 selectively binding to the C-terminus of TRPC6. Although cryoelectron microscopy has resolved the majority of the TRPC6 structure, the binding site in the C-terminus remained unresolved. To address this issue, we employed state-of-the-art artificial-intelligence-based protein structure prediction algorithms to predict the missing region. Our computational results, validated against experimental data, indicate that PPAP53 binds to the 777LLKL780-region of the C-terminus, thus providing critical insights into the binding mechanism of PPAP53.

Pico145 inhibits TRPC4-mediated mICAT and postprandial small intestinal motility.

In intestinal smooth muscle cells, receptor-operated TRPC4 are responsible for the majority of muscarinic receptor cation current (mICAT), which initiates cholinergic excitation-contraction coupling. Our aim was to examine the effects of the TRPC4 inhibitor Pico145 on mICAT and Ca2+ signalling in mouse ileal myocytes, and on intestinal motility. Ileal myocytes freshly isolated from two month-old male BALB/c mice were used for patch-clamp recordings of whole-cell currents and for intracellular Ca2+ imaging using Fura-2. Functional assessment of Pico145's effects was carried out by standard in vitro tensiometry, ex vivo video recordings and in vivo postprandial intestinal transit measurements using carmine red. Carbachol (50 µM)-induced mICAT was strongly inhibited by Pico145 starting from 1 pM. The IC50 value for the inhibitory effect of Pico145 on this current evoked by intracellularly applied GTPγS (200 µM), and thus lacking desensitisation, was found to be 3.1 pM, while carbachol-induced intracellular Ca2+ rises were inhibited with IC50 of 2.7 pM. In contrast, the current activated by direct TRPC4 agonist (-)-englerin A was less sensitive to the action of Pico145 that caused only ∼43 % current inhibition at 100 pM. The inhibitory effect developed rather slowly and it was potentiated by membrane depolarisation. In functional assays, Pico145 produced concentration-dependent suppression of both spontaneous and carbachol-evoked intestinal smooth muscle contractions and delayed postprandial intestinal transit. Thus, Pico145 is a potent GI-active small-molecule which completely inhibits mICAT at picomolar concentrations and which is as effective as trpc4 gene deficiency in in vivo intestinal motility tests.

Role of Neuronal TRPC6 Channels in Synapse Development, Memory Formation and Animal Behavior.

The transient receptor potential cation channel, subfamily C, member 6 (TRPC6), has been believed to adjust the formation of an excitatory synapse. The positive regulation of TRPC6 engenders synapse enlargement and improved learning and memory in animal models. TRPC6 is involved in different synaptoprotective signaling pathways, including antagonism of N-methyl-D-aspartate receptor (NMDAR), activation of brain-derived neurotrophic factor (BDNF) and postsynaptic store-operated calcium entry. Positive regulation of TRPC6 channels has been repeatedly shown to be good for memory formation and storage. TRPC6 is mainly expressed in the hippocampus, particularly in the dentate granule cells, cornu Ammonis 3 (CA3) pyramidal cells and gamma-aminobutyric acid (GABA)ergic interneurons. It has been observed that TRPC6 agonists have a great influence on animal behavior including memory formation and storage The purpose of this review is to collect the available information on the role of TRPC6 in memory formation in various parts of the brain to understand how TRPC6-specific pharmaceutical agents will affect memory in distinct parts of the central nervous system (CNS).

Calcium transport and sensing in TRPC channels - New insights into a complex feedback regulation.

Canonical TRP (TRPC) channels are a still enigmatic family of signaling molecules with multimodal sensing features. These channels enable Ca2+ influx through the plasma membrane to control a diverse range of cellular functions. Based on both regulatory- and recently uncovered structural features, TRPC channels are considered to coordinate Ca2+ and other divalent cations not only within the permeation path but also at additional sensory sites. Analysis of TRPC structures by cryo-EM identified multiple regulatory ion binding pockets. With this review, we aim at an overview and a critical discussion of the current concepts of divalent sensing by TRPC channels.