The Experts below are selected from a list of 11157 Experts worldwide ranked by ideXlab platform
Bernd Nilius - One of the best experts on this subject based on the ideXlab platform.
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Vanilloid Transient Receptor Potential Cation Channels : An Overview
Current Pharmaceutical Design, 2008Co-Authors: Rudi Vennekens, Grzegorz Owsianik, Bernd NiliusAbstract:The mammalian branch of the Transient Receptor Potential (TRP) superfamily of cation channels consists of 28 members. They can be subdivided in six main subfamilies: the TRPC (‘Canonical’), TRPV (‘Vanilloid’), TRPM (‘Melastatin’), TRPP (‘Polycystin’), TRPML (‘Mucolipin’) and the TRPA (‘Ankyrin’) group. The TRPV subfamily comprises channels that are critically involved in nociception and thermo-sensing (TRPV1, TRPV2, TRPV3, TRPV4) as well as highly Ca2+ selective channels involved in Ca2+ absorption/ reabsorption in mammals (TRPV5, TRPV6). In this review we summarize fundamental physiological properties of all TRPV members in the light of various cellular functions of these channels and their significance in the systemic context of the mammalian organism.
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molecular determinants of permeation through the cation channel trpm6
Cell Calcium, 2007Co-Authors: Catalin N Topala, Joost G J Hoenderop, Bernd Nilius, Wouter Tiel M Groenestege, Stephanie Thebault, Dennis Van Den Berg, Rene J M BindelsAbstract:TRPM6 and its closest relative TRPM7 are members of the Transient Receptor Potential Melastatin (TRPM) subfamily of cation channels and are known to be Mg2+ permeable. By aligning the sequence of the putative TRPM6 pore with the pore sequences of the other subfamily members, we located in the loop between the fifth and the sixth transmembrane domain, a stretch of amino acids residues, 1028GEIDVC1033, as the potential selectivity filter. Two negatively charged residues, E1024 (conserved in TRPM6, TRPM7, TRPM1 and TRPM3) and D1031 (conserved along the entire TRPM subfamily), were identified as important determinants of cation permeation through TRPM6, because neutralization of both residues into an alanine resulted in non-functional channels. Neutralization of E1029 (conserved in TRPM6, TRPM7, TRPM4 and TRPM5) resulted in channels with increased conductance for Ba2+ and Zn2+, decreased ruthenium red sensitivity and larger pore diameter compared to wild-type TRPM6. Changing the residue I1030 into methionine, resulted in channels with lower conductance for Ni2+, decreased sensitivity to ruthenium red block and reduced pore diameter. Thus, these data demonstrate that amino acid residues E1024, I1030 and D1031 are important for channel function and that subtle amino acid variation in the pore region accounts for TRPM6 permeation properties.
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regulation of transient receptor potential trp channels by phosphoinositides
Pflügers Archiv: European Journal of Physiology, 2007Co-Authors: Tibor Rohacs, Bernd NiliusAbstract:This review summarizes the modulation of transient receptor potential (TRP) channels, by phosphoinositides. TRP channels are characterized by polymodal activation and a surprising complexity of regulation mechanisms. Possibly, most if not all TRP channels are modulated by phosphoinositides. Modulation by phosphatidylinositol 4,5-biphosphate (PIP2) has been shown in detail for TRP vanilloid (TRPV) 1, TRPV5, TRP melastatin (TRPM) 4, TRPM5, TRPM7, TRPM8, TRP polycystin 2, and the Drosophila TPR-like (TRPL) channels. This review describes mechanisms of modulation of TRP channels mainly by PIP2 and discusses some future challenges of this fascinating topic.
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permeation and selectivity of trp channels
Annual Review of Physiology, 2006Co-Authors: Grzegorz Owsianik, Thomas Voets, Karel Talavera, Bernd NiliusAbstract:▪ Abstract Ion channels are pore-forming transmembrane proteins that allow ions to permeate biological membranes. Pore structure plays a crucial role in determining the ion permeation and selectivity properties of particular channels. In the past few decades, efforts have been undertaken to identify key elements of the pore regions of different classes of ion channels. In this review, we summarize current knowledge about permeation and selectivity of channel proteins from the transient receptor potential (TRP) superfamily. Whereas all TRP channels are permeable for cations, only two TRP channels are impermeable for Ca2+ (TRPM4, TRPM5), and two others are highly Ca2+ permeable (TRPV5, TRPV6). Despite the great advances in the TRP channel field during the past decade, only a limited number of reports have dealt with functional characterization of pore properties, biophysical aspects of cation permeation, or description of pore structures of TRP channels. This review gives an overview of available experiment...
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the selectivity filter of the cation channel trpm4
Journal of Biological Chemistry, 2005Co-Authors: Bernd Nilius, Grzegorz Owsianik, Annelies Janssens, Jean Prenen, Chunbo Wang, Michael X Zhu, Thomas VoetsAbstract:Transient receptor potential channel melastatin subfamily (TRPM) 4 and its close homologue, TRPM5, are the only two members of the large transient receptor potential superfamily of cation channels that are impermeable to Ca2+. In this study, we located the TRPM4 selectivity filter and investigated possible structural elements that render it Ca2+-impermeable. Based on homology with known cation channel pores, we identified an acidic stretch of six amino acids in the loop between transmembrane helices TM5 and TM6 (981EDMDVA986) as a potential selectivity filter. Substitution of this six-amino acid stretch with the selectivity filter of TRPV6 (TIIDGP) resulted in a functional channel that combined the gating hallmarks of TRPM4 (activation by Ca2+, voltage dependence) with TRPV6-like sensitivity to block by extracellular Ca2+ and Mg2+ as well as Ca2+ permeation. Neutralization of Glu981 resulted in a channel with normal permeability properties but a strongly reduced sensitivity to block by intracellular spermine. Neutralization of Asp982 yielded a functional channel that exhibited extremely fast desensitization (τ
Thomas Gudermann - One of the best experts on this subject based on the ideXlab platform.
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role of kinase coupled trp channels in mineral homeostasis
Pharmacology & Therapeutics, 2017Co-Authors: Vladimir Chubanov, Lorenz Mittermeier, Thomas GudermannAbstract:Abstract Transient receptor potential (TRP) proteins TRPM6 and TRPM7 are α-kinase-coupled divalent cation-selective channels activated upon a reduction of cytosolic levels of Mg2+ and Mg·ATP. Emerging evidence indicate that one of the main physiological functions of TRPM6 and TRPM7 is maintaining of cellular metabolism of Mg2+ and likely other essential metals such as Ca2+ and Zn2+. Recent experiments with genetic animal models have shown that TRPM6 and TRPM7 are essential for epithelial Mg2+ transport in the placenta and intestine. In addition, mutations in TRPM6 or TRPM7 have been linked to Mg2+ deficiency in humans. However, many key functional aspects of these remarkable proteins as well as mechanisms of the associated channelopathies remain incompletely understood. The present review article highlights the recent significant progress in the field with the focus on the vital roles of TRPM7 and TRPM7 in mineral homeostasis.
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trpm6 and trpm7 differentially contribute to the relief of heteromeric trpm6 7 channels from inhibition by cytosolic mg 2 and mg atp
Scientific Reports, 2017Co-Authors: Silvia Ferioli, Susanna Zierler, Thomas Gudermann, Joanna Zaiserer, Johann Schredelseker, Vladimir ChubanovAbstract:TRPM6 and its homologue TRPM7 are α-kinase-coupled divalent cation-selective channels activated upon reduction of cytosolic levels of Mg2+ and Mg·ATP. TRPM6 is vital for organismal Mg2+ balance. However, mechanistically the cellular role and functional nonredundancy of TRPM6 remain incompletely understood. Comparative analysis of native currents in primary cells from TRPM6- versus TRPM7-deficient mice supported the concept that native TRPM6 primarily functions as a constituent of heteromeric TRPM6/7 channels. However, heterologous expression of the human TRPM6 protein engendered controversial results with respect to channel characteristics including its regulation by Mg2+ and Mg·ATP. To resolve this issue, we cloned the mouse TRPM6 (mTRPM6) cDNA and compared its functional characteristics to mouse TRPM7 (mTRPM7) after heterologous expression. Notably, we observed that mTRPM6 and mTRPM7 differentially regulate properties of heteromeric mTRPM6/7 channels: In the presence of mTRPM7, the extreme sensitivity of functionally expressed homomeric mTRPM6 to Mg2+ is tuned to higher concentrations, whereas mTRPM6 relieves mTRPM7 from the tight inhibition by Mg·ATP. Consequently, the association of mTRPM6 with mTRPM7 allows for high constitutive activity of mTRPM6/7 in the presence of physiological levels of Mg2+ and Mg·ATP, thus laying the mechanistic foundation for constant vectorial Mg2+ transport specifically into epithelial cells.
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Evolutionary determinants of divergent calcium selectivity of TRPM channels
The FASEB Journal, 2007Co-Authors: Michael Mederos Y Schnitzler, Thomas Gudermann, Janine Wäring, Vladimir ChubanovAbstract:The mammalian TRPM gene family can be subdivided into distinct categories of cation channels that are either highly permeable for Ca(2+) (TRPM3/6/7), nonselective (TRPM2/8), or even Ca(2+) impermeable (TRPM4/5). TRPM6/7 are fused to alpha-kinase domains, whereas TRPM2 is linked to an ADP-ribose phosphohydrolase (Nudix domain). At a molecular level, the evolutionary steps that gave rise to the structural and functional TRPM channel diversity remain elusive. Here, we provide phylogenetic evidence that Nudix-linked channels represent an ancestral type of TRPMs that is present in various phyla, ranging from protists to humans. Surprisingly, the pore-forming segments of invertebrate TRPM2-like proteins display high sequence similarity to those of Ca(2+)-selective TRPMs, while human TRPM2 is characterized by a loss of several conserved residues. Using the patch-clamp technique, Ca(2+) imaging, and site-directed mutagenesis, we demonstrate that restoration of only two "ancient" pore residues in human TRPM2 (Q981E/P983Y) significantly increased (approximately 4-fold) its permeability for Ca(2+). Conversely, introduction of a "modern" sequence motif into mouse TRPM7 (E1047Q/Y1049P) resulted in the loss of Ca(2+) permeation and a linear TRPM2-like current-voltage relationship. Overall, our findings provide an integrative view on the evolution of the domain architecture and the structural basis of the distinct ion permeation profiles of TRPM channels.
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hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore forming region of trpm6
Journal of Biological Chemistry, 2007Co-Authors: Vladimir Chubanov, Siegfried Waldegger, Michael Mederos Y Schnitzler, Karl P Schlingmann, Janine Wäring, Jolanta Heinzinger, Silke Kaske, Thomas GudermannAbstract:Abstract Hypomagnesemia with secondary hypocalcemia is an autosomal recessive disorder caused by mutations in the TRPM6 gene. Current experimental evidence suggests that TRPM6 may function in a specific association with TRPM7 by means of heterooligomeric channel complex formation. Here, we report the identification and functional characterization of a new hypomagnesemia with secondary hypocalcemia missense mutation in TRPM6. The affected subject presented with profound hypomagnesemia and hypocalcemia caused by compound heterozygous mutation in the TRPM6 gene: 1208(-1)G > A affecting the acceptor splice site preceding exon 11, and 3050C > G resulting in the amino acid change (P1017R) in the putative pore-forming region of TRPM6. To assess the functional consequences of the P1017R mutation, TRPM6P1017R and wild-type TRPM6 were co-expressed with TRPM7 in Xenopus oocytes and HEK 293 cells, and currents were assessed by two-electrode voltage clamp and whole cell patch clamp measurements, respectively. Co-expression of wild-type TRPM6 and TRPM7 resulted in a significant increase in the amplitude of TRPM7-like currents. In contrast, TRPM6P1017R suppressed TRPM7 channel activity. In line with these observations, TRPM7, containing the corresponding mutation P1040R, displayed a dominant-negative effect upon co-expression with wild-type TRPM7. Confocal microscopy and fluorescence resonance energy transfer recordings demonstrated that the P1017R mutation neither affects assembly of TRPM6 with TRPM7, nor co-trafficking of heteromultimeric channel complexes to the cell surface. We conclude that a functional defect in the putative pore of TRPM6/7 channel complexes is sufficient to impair body magnesium homeostasis.
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hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore forming region of trpm6
Journal of Biological Chemistry, 2007Co-Authors: Vladimir Chubanov, Siegfried Waldegger, Michael Mederos Y Schnitzler, Karl P Schlingmann, Janine Wäring, Jolanta Heinzinger, Silke Kaske, Thomas GudermannAbstract:Abstract Hypomagnesemia with secondary hypocalcemia is an autosomal recessive disorder caused by mutations in the TRPM6 gene. Current experimental evidence suggests that TRPM6 may function in a specific association with TRPM7 by means of heterooligomeric channel complex formation. Here, we report the identification and functional characterization of a new hypomagnesemia with secondary hypocalcemia missense mutation in TRPM6. The affected subject presented with profound hypomagnesemia and hypocalcemia caused by compound heterozygous mutation in the TRPM6 gene: 1208(-1)G > A affecting the acceptor splice site preceding exon 11, and 3050C > G resulting in the amino acid change (P1017R) in the putative pore-forming region of TRPM6. To assess the functional consequences of the P1017R mutation, TRPM6P1017R and wild-type TRPM6 were co-expressed with TRPM7 in Xenopus oocytes and HEK 293 cells, and currents were assessed by two-electrode voltage clamp and whole cell patch clamp measurements, respectively. Co-expression of wild-type TRPM6 and TRPM7 resulted in a significant increase in the amplitude of TRPM7-like currents. In contrast, TRPM6P1017R suppressed TRPM7 channel activity. In line with these observations, TRPM7, containing the corresponding mutation P1040R, displayed a dominant-negative effect upon co-expression with wild-type TRPM7. Confocal microscopy and fluorescence resonance energy transfer recordings demonstrated that the P1017R mutation neither affects assembly of TRPM6 with TRPM7, nor co-trafficking of heteromultimeric channel complexes to the cell surface. We conclude that a functional defect in the putative pore of TRPM6/7 channel complexes is sufficient to impair body magnesium homeostasis.
Vladimir Chubanov - One of the best experts on this subject based on the ideXlab platform.
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role of kinase coupled trp channels in mineral homeostasis
Pharmacology & Therapeutics, 2017Co-Authors: Vladimir Chubanov, Lorenz Mittermeier, Thomas GudermannAbstract:Abstract Transient receptor potential (TRP) proteins TRPM6 and TRPM7 are α-kinase-coupled divalent cation-selective channels activated upon a reduction of cytosolic levels of Mg2+ and Mg·ATP. Emerging evidence indicate that one of the main physiological functions of TRPM6 and TRPM7 is maintaining of cellular metabolism of Mg2+ and likely other essential metals such as Ca2+ and Zn2+. Recent experiments with genetic animal models have shown that TRPM6 and TRPM7 are essential for epithelial Mg2+ transport in the placenta and intestine. In addition, mutations in TRPM6 or TRPM7 have been linked to Mg2+ deficiency in humans. However, many key functional aspects of these remarkable proteins as well as mechanisms of the associated channelopathies remain incompletely understood. The present review article highlights the recent significant progress in the field with the focus on the vital roles of TRPM7 and TRPM7 in mineral homeostasis.
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trpm6 and trpm7 differentially contribute to the relief of heteromeric trpm6 7 channels from inhibition by cytosolic mg 2 and mg atp
Scientific Reports, 2017Co-Authors: Silvia Ferioli, Susanna Zierler, Thomas Gudermann, Joanna Zaiserer, Johann Schredelseker, Vladimir ChubanovAbstract:TRPM6 and its homologue TRPM7 are α-kinase-coupled divalent cation-selective channels activated upon reduction of cytosolic levels of Mg2+ and Mg·ATP. TRPM6 is vital for organismal Mg2+ balance. However, mechanistically the cellular role and functional nonredundancy of TRPM6 remain incompletely understood. Comparative analysis of native currents in primary cells from TRPM6- versus TRPM7-deficient mice supported the concept that native TRPM6 primarily functions as a constituent of heteromeric TRPM6/7 channels. However, heterologous expression of the human TRPM6 protein engendered controversial results with respect to channel characteristics including its regulation by Mg2+ and Mg·ATP. To resolve this issue, we cloned the mouse TRPM6 (mTRPM6) cDNA and compared its functional characteristics to mouse TRPM7 (mTRPM7) after heterologous expression. Notably, we observed that mTRPM6 and mTRPM7 differentially regulate properties of heteromeric mTRPM6/7 channels: In the presence of mTRPM7, the extreme sensitivity of functionally expressed homomeric mTRPM6 to Mg2+ is tuned to higher concentrations, whereas mTRPM6 relieves mTRPM7 from the tight inhibition by Mg·ATP. Consequently, the association of mTRPM6 with mTRPM7 allows for high constitutive activity of mTRPM6/7 in the presence of physiological levels of Mg2+ and Mg·ATP, thus laying the mechanistic foundation for constant vectorial Mg2+ transport specifically into epithelial cells.
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Evolutionary determinants of divergent calcium selectivity of TRPM channels
The FASEB Journal, 2007Co-Authors: Michael Mederos Y Schnitzler, Thomas Gudermann, Janine Wäring, Vladimir ChubanovAbstract:The mammalian TRPM gene family can be subdivided into distinct categories of cation channels that are either highly permeable for Ca(2+) (TRPM3/6/7), nonselective (TRPM2/8), or even Ca(2+) impermeable (TRPM4/5). TRPM6/7 are fused to alpha-kinase domains, whereas TRPM2 is linked to an ADP-ribose phosphohydrolase (Nudix domain). At a molecular level, the evolutionary steps that gave rise to the structural and functional TRPM channel diversity remain elusive. Here, we provide phylogenetic evidence that Nudix-linked channels represent an ancestral type of TRPMs that is present in various phyla, ranging from protists to humans. Surprisingly, the pore-forming segments of invertebrate TRPM2-like proteins display high sequence similarity to those of Ca(2+)-selective TRPMs, while human TRPM2 is characterized by a loss of several conserved residues. Using the patch-clamp technique, Ca(2+) imaging, and site-directed mutagenesis, we demonstrate that restoration of only two "ancient" pore residues in human TRPM2 (Q981E/P983Y) significantly increased (approximately 4-fold) its permeability for Ca(2+). Conversely, introduction of a "modern" sequence motif into mouse TRPM7 (E1047Q/Y1049P) resulted in the loss of Ca(2+) permeation and a linear TRPM2-like current-voltage relationship. Overall, our findings provide an integrative view on the evolution of the domain architecture and the structural basis of the distinct ion permeation profiles of TRPM channels.
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hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore forming region of trpm6
Journal of Biological Chemistry, 2007Co-Authors: Vladimir Chubanov, Siegfried Waldegger, Michael Mederos Y Schnitzler, Karl P Schlingmann, Janine Wäring, Jolanta Heinzinger, Silke Kaske, Thomas GudermannAbstract:Abstract Hypomagnesemia with secondary hypocalcemia is an autosomal recessive disorder caused by mutations in the TRPM6 gene. Current experimental evidence suggests that TRPM6 may function in a specific association with TRPM7 by means of heterooligomeric channel complex formation. Here, we report the identification and functional characterization of a new hypomagnesemia with secondary hypocalcemia missense mutation in TRPM6. The affected subject presented with profound hypomagnesemia and hypocalcemia caused by compound heterozygous mutation in the TRPM6 gene: 1208(-1)G > A affecting the acceptor splice site preceding exon 11, and 3050C > G resulting in the amino acid change (P1017R) in the putative pore-forming region of TRPM6. To assess the functional consequences of the P1017R mutation, TRPM6P1017R and wild-type TRPM6 were co-expressed with TRPM7 in Xenopus oocytes and HEK 293 cells, and currents were assessed by two-electrode voltage clamp and whole cell patch clamp measurements, respectively. Co-expression of wild-type TRPM6 and TRPM7 resulted in a significant increase in the amplitude of TRPM7-like currents. In contrast, TRPM6P1017R suppressed TRPM7 channel activity. In line with these observations, TRPM7, containing the corresponding mutation P1040R, displayed a dominant-negative effect upon co-expression with wild-type TRPM7. Confocal microscopy and fluorescence resonance energy transfer recordings demonstrated that the P1017R mutation neither affects assembly of TRPM6 with TRPM7, nor co-trafficking of heteromultimeric channel complexes to the cell surface. We conclude that a functional defect in the putative pore of TRPM6/7 channel complexes is sufficient to impair body magnesium homeostasis.
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hypomagnesemia with secondary hypocalcemia due to a missense mutation in the putative pore forming region of trpm6
Journal of Biological Chemistry, 2007Co-Authors: Vladimir Chubanov, Siegfried Waldegger, Michael Mederos Y Schnitzler, Karl P Schlingmann, Janine Wäring, Jolanta Heinzinger, Silke Kaske, Thomas GudermannAbstract:Abstract Hypomagnesemia with secondary hypocalcemia is an autosomal recessive disorder caused by mutations in the TRPM6 gene. Current experimental evidence suggests that TRPM6 may function in a specific association with TRPM7 by means of heterooligomeric channel complex formation. Here, we report the identification and functional characterization of a new hypomagnesemia with secondary hypocalcemia missense mutation in TRPM6. The affected subject presented with profound hypomagnesemia and hypocalcemia caused by compound heterozygous mutation in the TRPM6 gene: 1208(-1)G > A affecting the acceptor splice site preceding exon 11, and 3050C > G resulting in the amino acid change (P1017R) in the putative pore-forming region of TRPM6. To assess the functional consequences of the P1017R mutation, TRPM6P1017R and wild-type TRPM6 were co-expressed with TRPM7 in Xenopus oocytes and HEK 293 cells, and currents were assessed by two-electrode voltage clamp and whole cell patch clamp measurements, respectively. Co-expression of wild-type TRPM6 and TRPM7 resulted in a significant increase in the amplitude of TRPM7-like currents. In contrast, TRPM6P1017R suppressed TRPM7 channel activity. In line with these observations, TRPM7, containing the corresponding mutation P1040R, displayed a dominant-negative effect upon co-expression with wild-type TRPM7. Confocal microscopy and fluorescence resonance energy transfer recordings demonstrated that the P1017R mutation neither affects assembly of TRPM6 with TRPM7, nor co-trafficking of heteromultimeric channel complexes to the cell surface. We conclude that a functional defect in the putative pore of TRPM6/7 channel complexes is sufficient to impair body magnesium homeostasis.
Andrea Fleig - One of the best experts on this subject based on the ideXlab platform.
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n myc induced up regulation of trpm6 trpm7 channels promotes neuroblastoma cell proliferation
Oncotarget, 2014Co-Authors: Zheng Zhang, Andrea Fleig, Malika Faouzi, Junhao Huang, Dirk Geerts, Reinhold PennerAbstract:// Zheng Zhang 1,3,* , Malika Faouzi 1,* , Junhao Huang 1 , Dirk Geerts 2 , Haijie Yu 1 , Andrea Fleig 1 and Reinhold Penner 1 1 Center for Biomedical Research, The Queen’s Medical Center, University of Hawaii Cancer Center and John A. Burns School of Medicine, University of Hawaii, Honolulu, U.S.A 2 Department of Pediatric Oncology/Hematology, Erasmus University Medical Center, Dr. Molewaterplein 50, GE Rotterdam, the Netherlands 3 Department of Pharmacology, School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, China * These authors contributed equally to this work Correspondence: Reinhold Penner, email: // Andrea Fleig, email: // Keywords : cancer/magnesium/neuroblastoma/N-Myc/TRPM6/TRPM7 Received : May 28, 2014 Accepted : July 31, 2014 Published : July 31, 2014 Abstract Intracellular levels of the divalent cations Ca 2+ and Mg 2+ are important regulators of cell cycle and proliferation. However, the precise mechanisms by which they are regulated in cancer remain incompletely understood. The channel kinases TRPM6 and TRPM7 are gatekeepers of human Ca 2+ /Mg 2+ metabolism. Here, we investigated the human neuroblastoma cell line SHEP-21N in which the MYCN oncogene (encoding N-Myc) can be reversibly expressed under control of an inducible repressor. We report that N-Myc expression increases cell growth and up-regulates both TRPM6 and TRPM7 expression. Membrane current analyses reveal that endogenous TRPM6/TRPM7 currents exhibit reduced Mg·ATP suppression, increased Mg 2+ sensitivity, and diminished sensitivity to 2-APB inhibition. These properties are consistent with N-Myc-induced increase of heteromeric TRPM7/TRPM6 channels promoting Ca 2+ and Mg 2+ uptake. Genetic suppression of TRPM6/TRPM7 through siRNA inhibits cell proliferation, suggesting that N-Myc can promote neuroblastoma cell proliferation through up-regulation of divalent cation-transporting channels.
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the trpm6 kinase domain determines the mg atp sensitivity of trpm7 m6 heteromeric ion channels
Journal of Biological Chemistry, 2014Co-Authors: Zheng Zhang, Reinhold Penner, Malika Faouzi, Carsten Schmitz, Junhao Huang, Andrea FleigAbstract:The transient receptor potential melastatin member 7 (TRPM7) and member 6 (TRPM6) are divalent cation channel kinases essential for magnesium (Mg2+) homeostasis in vertebrates. It remains unclear how TRPM6 affects divalent cation transport and whether this involves functional homomeric TRPM6 plasma membrane channels or heteromeric channel assemblies with TRPM7. We show that homomeric TRPM6 is highly sensitive to intracellular free Mg2+ and therefore unlikely to be active at physiological levels of [Mg2+]i. Co-expression of TRPM7 and TRPM6 produces heteromeric TRPM7/M6 channels with altered pharmacology and sensitivity to intracellular Mg·ATP compared with homomeric TRPM7. Strikingly, the activity of heteromeric TRPM7/M6 channels is independent of intracellular Mg·ATP concentrations, essentially uncoupling channel activity from cellular energy status. Disruption of TRPM6 kinase phosphorylation activity re-introduces Mg·ATP sensitivity to the heteromeric channel similar to that of TRPM7. Thus, TRPM6 modulates the functionality of TRPM7, and the TRPM6 kinase plays a critical role in tuning the phenotype of the TRPM7·M6 channel complex.
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waixenicin a inhibits cell proliferation through magnesium dependent block of transient receptor potential melastatin 7 trpm7 channels
Journal of Biological Chemistry, 2011Co-Authors: Susanna Zierler, Reinhold Penner, Peter Porzgen, David F Horgen, Zheng Zhang, Andrea FleigAbstract:Transient receptor potential melastatin 7 (TRPM7) channels represent the major magnesium-uptake mechanism in mammalian cells and are key regulators of cell growth and proliferation. They are expressed abundantly in a variety of human carcinoma cells controlling survival, growth, and migration. These characteristics are the basis for recent interest in the channel as a target for cancer therapeutics. We screened a chemical library of marine organism-derived extracts and identified waixenicin A from the soft coral Sarcothelia edmondsoni as a strong inhibitor of overexpressed and native TRPM7. Waixenicin A activity was cytosolic and potentiated by intracellular free magnesium (Mg2+) concentration. Mutating a Mg2+ binding site on the TRPM7 kinase domain reduced the potency of the compound, whereas kinase deletion enhanced its efficacy independent of Mg2+. Waixenicin A failed to inhibit the closely homologous TRPM6 channel and did not significantly affect TRPM2, TRPM4, and Ca2+ release-activated Ca2+ current channels. Therefore, waixenicin A represents the first potent and relatively specific inhibitor of TRPM7 ion channels. Consistent with TRPM7 inhibition, the compound blocked cell proliferation in human Jurkat T-cells and rat basophilic leukemia cells. Based on the ability of the compound to inhibit cell proliferation through Mg2+-dependent block of TRPM7, waixenicin A, or structural analogs may have cancer-specific therapeutic potential, particularly because certain cancers accumulate cytosolic Mg2+.
Thomas Voets - One of the best experts on this subject based on the ideXlab platform.
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permeation and selectivity of trp channels
Annual Review of Physiology, 2006Co-Authors: Grzegorz Owsianik, Thomas Voets, Karel Talavera, Bernd NiliusAbstract:▪ Abstract Ion channels are pore-forming transmembrane proteins that allow ions to permeate biological membranes. Pore structure plays a crucial role in determining the ion permeation and selectivity properties of particular channels. In the past few decades, efforts have been undertaken to identify key elements of the pore regions of different classes of ion channels. In this review, we summarize current knowledge about permeation and selectivity of channel proteins from the transient receptor potential (TRP) superfamily. Whereas all TRP channels are permeable for cations, only two TRP channels are impermeable for Ca2+ (TRPM4, TRPM5), and two others are highly Ca2+ permeable (TRPV5, TRPV6). Despite the great advances in the TRP channel field during the past decade, only a limited number of reports have dealt with functional characterization of pore properties, biophysical aspects of cation permeation, or description of pore structures of TRP channels. This review gives an overview of available experiment...
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the selectivity filter of the cation channel trpm4
Journal of Biological Chemistry, 2005Co-Authors: Bernd Nilius, Grzegorz Owsianik, Annelies Janssens, Jean Prenen, Chunbo Wang, Michael X Zhu, Thomas VoetsAbstract:Transient receptor potential channel melastatin subfamily (TRPM) 4 and its close homologue, TRPM5, are the only two members of the large transient receptor potential superfamily of cation channels that are impermeable to Ca2+. In this study, we located the TRPM4 selectivity filter and investigated possible structural elements that render it Ca2+-impermeable. Based on homology with known cation channel pores, we identified an acidic stretch of six amino acids in the loop between transmembrane helices TM5 and TM6 (981EDMDVA986) as a potential selectivity filter. Substitution of this six-amino acid stretch with the selectivity filter of TRPV6 (TIIDGP) resulted in a functional channel that combined the gating hallmarks of TRPM4 (activation by Ca2+, voltage dependence) with TRPV6-like sensitivity to block by extracellular Ca2+ and Mg2+ as well as Ca2+ permeation. Neutralization of Glu981 resulted in a channel with normal permeability properties but a strongly reduced sensitivity to block by intracellular spermine. Neutralization of Asp982 yielded a functional channel that exhibited extremely fast desensitization (τ
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comparison of functional properties of the ca2 activated cation channels trpm4 and TRPM5 from mice
Cell Calcium, 2005Co-Authors: Nina Ullrich, Rudi Vennekens, Jean Prenen, Guy Droogmans, Thomas Voets, Karel Talavera, Bernd NiliusAbstract:Non-selective cation (NSC) channels activated by intracellular Ca2+ ([Ca2+]i) play an important role in Ca2+ signaling and membrane excitability in many cell types. TRPM4 and TRPM5, two Ca2+-activated cation channels of the TRP superfamily, are potential molecular correlates of NSC channels. We compared the functional properties of mouse TRPM4 and TRPM5 heterologously expressed in HEK 293 cells. Dialyzing cells with different Ca2+ concentrations revealed a difference in Ca2+ sensitivity between TRPM4 and TRPM5, with EC50 values of 20.2+/-4.0 microM and 0.70+/-0.1 microM, respectively. Similarly, TRPM5 activated at lower Ca2+ concentration than TRPM4 when [Ca2+]i was raised by UV uncaging of the Ca2+-cage DMNP-EDTA. Current amplitudes of TRPM4 and TRPM5 were not correlated to the rate of changes in [Ca2+]i. The Ca2+ sensitivity of both channels was strongly reduced in inside-out patches, resulting in approximately 10-30 times higher EC50 values than under whole-cell conditions. Currents through TRPM4 and TRPM5 deactivated at negative and activated at positive potentials with similar kinetics. Both channels were equally sensitive to block by intracellular spermine. TRPM4 displayed a 10-fold higher affinity for block by flufenamic acid. Importantly, ATP4- blocked TRPM4 with high affinity (IC50 of 0.8+/-0.1 microM), whereas TRPM5 is insensitive to ATP4- at concentrations up to 1 mM.
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decavanadate modulates gating of trpm4 cation channels
The Journal of Physiology, 2004Co-Authors: Bernd Nilius, Annelies Janssens, Jean Prenen, Thomas Voets, Guy DroogmansAbstract:We have tested the effects of decavanadate (DV), a compound known to interfere with ATP binding in ATP-dependent transport proteins, on TRPM4, a Ca(2+)-activated, voltage-dependent monovalent cation channel, whose activity is potently blocked by intracellular ATP(4-). Application of micromolar Ca(2+) concentrations to the cytoplasmic side of inside-out patches led to immediate current activation followed by rapid current decay, which can be explained by an at least 30-fold decreased apparent affinity for Ca(2+). Subsequent application of DV (10 microm) strongly affected the voltage-dependent gating of the channel, resulting in large sustained currents over the voltage range between -180 and +140 mV. The effect of DV was half-maximal at a concentration of 1.9 microm. The Ca(2+)- and voltage-dependent gating of the channel was well described by a sequential kinetic scheme in which Ca(2+) binding precedes voltage-dependent gating. The effects of DV could be explained by an action on the voltage-dependent closing step. Surprisingly, DV did not antagonize the effect of ATP(4-) on TRPM4, but caused a nearly 10-fold increase in the sensitivity of the ATP(4-) block. TRPM5, which is the most homologous channel to TRPM4, was not modulated by DV. The effect of DV was lost in a TRPM4 chimera in which the C-terminus was substituted with that of TRPM5. Deletion of a cluster in the C-terminus of TRPM4 containing positively charged amino acid residues with a high homology to part of the decavanadate binding site in SERCA pumps, completely abolished the DV effect but also accelerated desensitization. Deletion of a similar site in the N-terminus had no effects on DV responses. These results indicate that the C-terminus of TRPM4 is critically involved in mediating the DV effects. In conclusion, decavanadate modulates TRPM4, but not TRPM5, by inhibiting voltage-dependent closure of the channel.
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molecular determinants of permeation through the cation channel trpv4
Journal of Biological Chemistry, 2002Co-Authors: Thomas Voets, Joris Vriens, Annelies Janssens, Jean Prenen, Hiroyuki Watanabe, Ulrich Wissenbach, Matthias Bodding, Guy DroogmansAbstract:TRPM6 and its closest relative TRPM7 are members of the Transient Receptor Potential Melastatin (TRPM) subfamily of cation channels and are known to be Mg 2+ permeable. By aligning the sequence of the putative TRPM6 pore with the pore sequences of the other subfamily members, we located in the loop between the fifth and the sixth transmembrane domain, a stretch of amino acids residues, 1028 GEIDVC 1033 , as the potential selectivity filter. Two negatively charged residues, E 1024 (conserved in TRPM6, TRPM7, TRPM1 and TRPM3) and D 1031 (conserved along the entire TRPM subfamily), were identified as important determinants of cation permeation through TRPM6, because neutralization of both residues into an alanine resulted in non-functional channels. Neutralization of E 1029 (conserved in TRPM6, TRPM7, TRPM4 and TRPM5) resulted in channels with increased conductance for Ba 2+ and Zn 2+ , decreased ruthenium red sensitivity and larger pore diameter compared to wild-type TRPM6. Changing the residue I 1030 into methionine, resulted in channels with lower conductance for Ni 2+ , decreased sensitivity to ruthenium red block and reduced pore diameter. Thus, these data demonstrate that amino acid residues E 1024 ,I 1030 and D 1031 are important for channel function and that subtle amino acid variation in the pore region accounts for TRPM6 permeation properties.
