Stimulation of transient receptor potential M3 (TRPM3) channels increases interleukin-8 gene promoter activity involving AP-1 and extracellular signal-regulated protein kinase

Prognostic and immunological significance of calcium-related gene signatures in renal clear cell carcinoma

Background: Calcium signaling is implicated in multiple processes including immune response that important in tumor progression. Kidney renal clear cell carcinoma (KIRC) is the most frequent histological type of renal cell carcinoma with up to a third of cases develop metastases. As a result of a lack of in-depth understanding of the mechanisms underlying KIRC, treatment options have been limited. Here, we aim to comprehensively investigate the landscape of Ca²⁺ channels, pumps and exchangers in KIRC patients. Methods: The mRNA expression profiles and gene variations of 58 calcium-related genes (CRGs) in KIRC patients and normal control cases were downloaded from TCGA database. CRGs-related risk score was constructed to quantify calcium patterns by using least absolute shrinkage and selection operator (LASSO) regression. The prognostic value, biological functions, immune landscape and therapeutic sensitivities based on CRGs-related risk score were then evaluated using multiple methods. Finally, key gene of CRGs was identified by weighted gene co-expression network analysis (WGCNA). TCGA-CPTAC, GSE53757 datasets, as well as human tissues were used for validation. Results: KIRC patients had significant differences in CRG expression, prognosis, and biological functions between two CRG clusters. CRGs-related risk score was then determined. The prognosis, tumor mutation burden, immune cell infiltration, immune checkpoints, and the response of targeted inhibitors were remarkably different between high and low CRGs-related risk subtypes. CRGs-related high-risk subtype was characterized by immunosuppressive microenvironment with poor prognosis. Meanwhile, several targeted drugs showed distinct sensitivity between CRGs-related risk subtypes. Finally, TRPM3 was identified as a key CRG based on risk score in KIRC patients. TRPM3 mRNA and protein expression were significantly lower in KIRC tumors than in normal controls. Low TRPM3 expression was associated with poor prognosis in KIRC patients. Conclusion: Our study highlighted the promising prognostic value of CRGs in KIRC tumors. The evaluation of CRGs-related risk score will contribute to predicting prognosis and clinical therapy in KIRC patients.

TRPM3-Induced Gene Transcription Is under Epigenetic Control

Transient receptor potential M3 (TRPM3) cation channels regulate numerous biological functions, including gene transcription. Stimulation of TRPM3 channels with pregnenolone sulfate activates stimulus-responsive transcription factors, which bind to short cognate sequences in the promoters of their target genes. In addition, coregulator proteins are involved that convert the chromatin into a configuration that is permissive for gene transcription. In this study, we determined whether TRPM3-induced gene transcription requires coactivators that change the acetylation pattern of histones. We used compound A485, a specific inhibitor of the histone acetyltransferases CBP and p300. In addition, the role of bromodomain proteins that bind to acetylated lysine residues of histones was analyzed. We used JQ1, an inhibitor of bromodomain and extra terminal domain (BET) family proteins. The results show that both compounds attenuated the activation of AP-1 and CREB-regulated gene transcription following stimulation of TRPM3 channels. Inhibition of CBP/p300 and BET proteins additionally reduced the transcriptional activation potential of the transcription factors c-Fos and Elk-1. Transcriptional upregulation of the interleukin-8 gene was attenuated by A485 and JQ1, indicating that proinflammatory cytokine expression is controlled by CBP/p300 and bromodomain proteins. We conclude that TRPM3-induced signaling involves transcriptional coactivators and acetyl-lysine-bound bromodomain proteins for activating gene transcription.

Chromatin-embedded reporter genes: Quantification of stimulus-induced gene transcription

Receptors and ion channels expressed on the cell surface ensure proper communication between the cells and the environment. In multicellular organism, stimulus-regulated gene transcription is the basis for communication with the environment allowing individual cells to respond to stimuli such as nutrients, chemical stressors and signaling molecules released by other cells of the organism. Hormones, cytokines, and mitogens bind to receptors and ion channels and induce intracellular signaling cascades involving second messengers, kinases, phosphatases, and changes in the concentration of particular ions. Ultimately, the signaling cascades reach the nucleus. Transcription factors are activated that respond to cellular stimulation and induce changes in gene transcription. Investigating stimulus-transcription coupling combines cell biology with genetics. In this review, we discuss the molecular biology of stimulus-induced transcriptional activators and their responsiveness to extracellular and intracellular signaling molecules and to epigenetic regulators. Stimulus-induced gene expression is measured by several methods, including detection of nuclear translocation of transcription factors, phosphorylation or DNA binding. In this article, we emphasize that the most reliable method to directly measure transcriptional activation involves the use of chromatin-embedded reporter genes.

Ca2+ Microdomains, Calcineurin and the Regulation of Gene Transcription

Ca²⁺ ions function as second messengers regulating many intracellular events, including neurotransmitter release, exocytosis, muscle contraction, metabolism and gene transcription. Cells of a multicellular organism express a variety of cell-surface receptors and channels that trigger an increase of the intracellular Ca²⁺ concentration upon stimulation. The elevated Ca²⁺ concentration is not uniformly distributed within the cytoplasm but is organized in subcellular microdomains with high and low concentrations of Ca²⁺ at different locations in the cell. Ca²⁺ ions are stored and released by intracellular organelles that change the concentration and distribution of Ca²⁺ ions. A major function of the rise in intracellular Ca²⁺ is the change of the genetic expression pattern of the cell via the activation of Ca²⁺-responsive transcription factors. It has been proposed that Ca²⁺-responsive transcription factors are differently affected by a rise in cytoplasmic versus nuclear Ca²⁺. Moreover, it has been suggested that the mode of entry determines whether an influx of Ca²⁺ leads to the stimulation of gene transcription. A rise in cytoplasmic Ca²⁺ induces an intracellular signaling cascade, involving the activation of the Ca²⁺/calmodulin-dependent protein phosphatase calcineurin and various protein kinases (protein kinase C, extracellular signal-regulated protein kinase, Ca²⁺/calmodulin-dependent protein kinases). In this review article, we discuss the concept of gene regulation via elevated Ca²⁺ concentration in the cytoplasm and the nucleus, the role of Ca²⁺ entry and the role of enzymes as signal transducers. We give particular emphasis to the regulation of gene transcription by calcineurin, linking protein dephosphorylation with Ca²⁺ signaling and gene expression.

TRPM Channels in Human Diseases

The transient receptor potential melastatin (TRPM) subfamily belongs to the TRP cation channels family. Since the first cloning of TRPM1 in 1989, tremendous progress has been made in identifying novel members of the TRPM subfamily and their functions. The TRPM subfamily is composed of eight members consisting of four six-transmembrane domain subunits, resulting in homomeric or heteromeric channels. From a structural point of view, based on the homology sequence of the coiled-coil in the C-terminus, the eight TRPM members are clustered into four groups: TRPM1/M3, M2/M8, M4/M5 and M6/M7. TRPM subfamily members have been involved in several physiological functions. However, they are also linked to diverse pathophysiological human processes. Alterations in the expression and function of TRPM subfamily ion channels might generate several human diseases including cardiovascular and neurodegenerative alterations, organ dysfunction, cancer and many other channelopathies. These effects position them as remarkable putative targets for novel diagnostic strategies, drug design and therapeutic approaches. Here, we review the current knowledge about the main characteristics of all members of the TRPM family, focusing on their actions in human diseases.

Circular RNA hsa_circ_0054537 sponges miR-130a-3p to promote the progression of renal cell carcinoma through regulating cMet pathway

Renal cell carcinoma (RCC) is one of the most common tumors of the urinary system, seriously impacting public health. CircRNAs have been indicated as potentially critical mediators in tumorigenesis and cancer progression. However, their specific role in the metastasis of RCC remains unclear. In present study, we identified that miR-130a-3p presented aberrantly low-level in RCC cells. Furthermore, it was demonstrated that upregulated miR-130a-3p suppressed the proliferation and migration of cell and promoted cell apoptosis in RCC. Then we predicted the underlyingly upstream modulator of miR-130a-3p was a novel circRNA hsa_circ_0054537, which exhibited dysregulated in RCC cells. Subsequently, we confirmed the direct interaction between hsa_circ_0054537 and miR-130a-3p by RNA pulldown assay. Additionally, luciferase assay confirmed the correlation between hsa_circ_0054537 and miR-130a-3p at the transcriptional level. We also found hsa_circ_0054537 could affect the tumorigenesis through binding to miR-130a-3p competitively. In addition, we identified the target of miR-130a-3p was oncogene cMet, which could be co-controlled by hsa_circ_0054537 and miR-130a-3p. In conclusion, we demonstrated that circRNA hsa_circ_0054537 functioned as a competitive endogenous RNA to regulate cMet expression via sponging miR-130a-3p in renal cancer.

TRPM3_miR-204: a complex locus for eye development and disease

First discovered in a light-sensitive retinal mutant of Drosophila, the transient receptor potential (TRP) superfamily of non-selective cation channels serve as polymodal cellular sensors that participate in diverse physiological processes across the animal kingdom including the perception of light, temperature, pressure, and pain. TRPM3 belongs to the melastatin sub-family of TRP channels and has been shown to function as a spontaneous calcium channel, with permeability to other cations influenced by alternative splicing and/or non-canonical channel activity. Activators of TRPM3 channels include the neurosteroid pregnenolone sulfate, calmodulin, phosphoinositides, and heat, whereas inhibitors include certain drugs, plant-derived metabolites, and G-protein subunits. Activation of TRPM3 channels at the cell membrane elicits a signal transduction cascade of mitogen-activated kinases and stimulus response transcription factors. The mammalian TRPM3 gene hosts a non-coding microRNA gene specifying miR-204 that serves as both a tumor suppressor and a negative regulator of post-transcriptional gene expression during eye development in vertebrates. Ocular co-expression of TRPM3 and miR-204 is upregulated by the paired box 6 transcription factor (PAX6) and mutations in all three corresponding genes underlie inherited forms of eye disease in humans including early-onset cataract, retinal dystrophy, and coloboma. This review outlines the genomic and functional complexity of the TRPM3_miR-204 locus in mammalian eye development and disease.

Stimulation of TRPM3 channels increases the transcriptional activation potential of Elk-1 involving cytosolic Ca2+, extracellular signal-regulated protein kinase, and calcineurin

Stimulation of transient receptor potential M3 (TRPM3) channels with the steroid pregnenolone sulfate increases the transcriptional activation potential of Elk-1, a transcription factor that regulates serum response element-mediated transcription. Here, we show that an influx of Ca²⁺ ions into the cells is essential for the activation of Elk-1 following stimulation of TRPM3. Using genetically encoded Ca²⁺ buffers, we show that a rise in cytoplasmic Ca²⁺ is required for the upregulation of the transcriptional activation potential of Elk-1, while buffering of Ca²⁺ in the nucleus had no inhibitory effect on the transcriptional activity of Elk-1. Pharmacological and genetic experiments showed that extracellular signal-regulated protein kinase (ERK1/2) functions as signal transducer connecting TRPM3 channels with the Elk-1 transcription factor. Accordingly, dephosphorylation of ERK1/2 in the nucleus by MAP kinase phosphatase attenuated TRPM3-mediated Elk-1 activation. Moreover, we show that the Ca²⁺/calmodulin-dependent protein phosphatase calcineurin is part of a shut-off-device for the signaling cascade connecting TRPM3 channels with the activation of Elk-1. The fact that TRPM3 channel stimulation activates Elk-1 connects TRPM3 with the biological functions of Elk-1, including the regulation of proliferation, differentiation, survival, transcription, and cell migration.

The Role of TRP Channels in the Metastatic Cascade

A dysregulated cellular Ca2+ homeostasis is involved in multiple pathologies including cancer. Changes in Ca2+ signaling caused by altered fluxes through ion channels and transporters (the transportome) are involved in all steps of the metastatic cascade. Cancer cells thereby "re-program" and "misuse" the cellular transportome to regulate proliferation, apoptosis, metabolism, growth factor signaling, migration and invasion. Cancer cells use their transportome to cope with diverse environmental challenges during the metastatic cascade, like hypoxic, acidic and mechanical cues. Hence, ion channels and transporters are key modulators of cancer progression. This review focuses on the role of transient receptor potential (TRP) channels in the metastatic cascade. After briefly introducing the role of the transportome in cancer, we discuss TRP channel functions in cancer cell migration. We highlight the role of TRP channels in sensing and transmitting cues from the tumor microenvironment and discuss their role in cancer cell invasion. We identify open questions concerning the role of TRP channels in circulating tumor cells and in the processes of intra- and extravasation of tumor cells. We emphasize the importance of TRP channels in different steps of cancer metastasis and propose cancer-specific TRP channel blockade as a therapeutic option in cancer treatment.