The Experts below are selected from a list of 11622 Experts worldwide ranked by ideXlab platform
Rhian M. Touyz - One of the best experts on this subject based on the ideXlab platform.
-
TRPM7, Magnesium, and Signaling.
International journal of molecular sciences, 2019Co-Authors: Zhiguo Zou, Francisco J. Rios, Augusto C. Montezano, Rhian M. TouyzAbstract:The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed chanzyme that possesses an ion channel permeable to the divalent cations Mg2+, Ca2+, and Zn2+, and an α-kinase that phosphorylates downstream substrates. TRPM7 and its homologue TRPM6 have been implicated in a variety of cellular functions and is critically associated with intracellular signaling, including receptor tyrosine kinase (RTK)-mediated pathways. Emerging evidence indicates that growth factors, such as EGF and VEGF, signal through their RTKs, which regulate activity of TRPM6 and TRPM7. TRPM6 is primarily an epithelial-associated channel, while TRPM7 is more ubiquitous. In this review we focus on TRPM7 and its association with growth factors, RTKs, and downstream kinase signaling. We also highlight how interplay between TRPM7, Mg2+ and signaling kinases influences cell function in physiological and pathological conditions, such as cancer and preeclampsia.
-
dysregulation of renal transient receptor potential melastatin 6 7 but not paracellin 1 in aldosterone induced hypertension and kidney damage in a model of hereditary hypomagnesemia
Journal of Hypertension, 2011Co-Authors: Alvaro Yogi, Andrzej Mazur, Glaucia E. Callera, Sarah E. O'connor, Rita C. Tostes, Ying He, Jose Correa, Rhian M. TouyzAbstract:RATIONALE: Hyperaldosteronism, important in hypertension, is associated with electrolyte alterations, including hypomagnesemia, through unknown mechanisms. OBJECTIVE: To test whether aldosterone influences renal Mg(2+) transporters, (transient receptor potential melastatin (TRPM) 6, TRPM7, paracellin-1) leading to hypomagnesemia, hypertension and target organ damage and whether in a background of magnesium deficiency, this is exaggerated. METHODS AND RESULTS: Aldosterone effects in mice selectively bred for high-normal (MgH) or low (MgL) intracellular Mg(2+) were studied. Male MgH and MgL mice received aldosterone (350 μg/kg per day, 3 weeks). SBP was elevated in MgL. Aldosterone increased blood pressure and albuminuria and increased urinary Mg(2+) concentration in MgH and MgL, with greater effects in MgL. Activity of renal TRPM6 and TRPM7 was lower in vehicle-treated MgL than MgH. Aldosterone increased activity of TRPM6 in MgH and inhibited activity in MgL. TRPM7 and paracellin-1 were unaffected by aldosterone. Aldosterone-induced albuminuria in MgL was associated with increased renal fibrosis, increased oxidative stress, activation of mitogen-activated protein kinases and nuclear factor-NF-κB and podocyte injury. Mg(2+) supplementation (0.75% Mg(2+)) in aldosterone-treated MgL normalized plasma Mg(2+), increased TRPM6 activity and ameliorated hypertension and renal injury. Hence, in a model of inherited hypomagnesemia, TRPM6 and TRPM7, but not paracellin-1, are downregulated. Aldosterone further decreased TRPM6 activity in hypomagnesemic mice, a phenomenon associated with hypertension and kidney damage. Such effects were prevented by Mg(2+) supplementation. CONCLUSION: Amplified target organ damage in aldosterone-induced hypertension in hypomagnesemic conditions is associated with dysfunctional Mg(2+)-sensitive renal TRPM6 channels. Novel mechanisms for renal effects of aldosterone and insights into putative beneficial actions of Mg(2+), particularly in hyperaldosteronism, are identified.
-
transient receptor potential melastatin 7 TRPM7 cation channels magnesium and the vascular system in hypertension
Circulation, 2011Co-Authors: Alvaro Yogi, Glaucia E. Callera, Rita C. Tostes, Tayze T Antunes, Rhian M. TouyzAbstract:Decreased Mg(2+) concentration has been implicated in altered vascular reactivity, endothelial dysfunction and structural remodeling, processes important in vascular changes and target organ damage associated with hypertension. Unlike our knowledge of other major cations, mechanisms regulating cellular Mg(2+) handling are poorly understood. Until recently little was known about protein transporters controlling transmembrane Mg(2+) influx. However, new research has uncovered a number of genes and proteins identified as transmembrane Mg(2+) transporters, particularly transient receptor potential melastatin (TRPM) cation channels, TRPM6 and TRPM7. Whereas TRPM6 is found primarily in epithelial cells, TRPM7 is ubiquitously expressed. Vascular TRPM7 has been implicated as a signaling kinase involved in vascular smooth muscle cell growth, apoptosis, adhesion, contraction, cytoskeletal organization and migration, and is modulated by vasoactive agents, pressure, stretch and osmotic changes. Emerging evidence suggests that vascular TRPM7 function might be altered in hypertension. The present review discusses the importance of Mg(2+) in vascular biology in hypertension and focuses on transport systems, mainly TRPM7, that might play a role in the control of vascular Mg(2+) homeostasis. Elucidation of the relationship between the complex systems responsible for regulation of Mg(2+) homeostasis, the role of TRPM7 in vascular signaling, and the cardiovascular impact will be important for understanding the clinical implications of hypomagnesemia in cardiovascular disease.
-
Dysregulation of renal transient receptor potential melastatin 6/7 but not paracellin-1 in aldosterone-induced hypertension and kidney damage in a model of hereditary hypomagnesemia
Journal of Hypertension, 2011Co-Authors: Alvaro Yogi, Glaucia E. Callera, Sarah E. O'connor, Jose W. Correa, Rita C. Tostes, André Mazur, Rhian M. TouyzAbstract:Rationale Hyperaldosteronism, important in hypertension, is associated with electrolyte alterations, including hypomagnesemia, through unknown mechanisms. Objective To test whether aldosterone influences renal Mg(2+) transporters, (transient receptor potential melastatin (TRPM) 6, TRPM7, paracellin-1) leading to hypomagnesemia, hypertension and target organ damage and whether in a background of magnesium deficiency, this is exaggerated. Methods and results Aldosterone effects in mice selectively bred for high-normal (MgH) or low (MgL) intracellular Mg(2+) were studied. Male MgH and MgL mice received aldosterone (350 mu g/kg per day, 3 weeks). SBP was elevated in MgL. Aldosterone increased blood pressure and albuminuria and increased urinary Mg(2+) concentration in MgH and MgL, with greater effects in MgL. Activity of renal TRPM6 and TRPM7 was lower in vehicle-treated MgL than MgH. Aldosterone increased activity of TRPM6 in MgH and inhibited activity in MgL. TRPM7 and paracellin-1 were unaffected by aldosterone. Aldosterone-induced albuminuria in MgL was associated with increased renal fibrosis, increased oxidative stress, activation of mitogen-activated protein kinases and nuclear factor-NF-kappa B and podocyte injury. Mg(2+) supplementation (0.75% Mg(2+)) in aldosterone-treated MgL normalized plasma Mg(2+), increased TRPM6 activity and ameliorated hypertension and renal injury. Hence, in a model of inherited hypomagnesemia, TRPM6 and TRPM7, but not paracellin-1, are downregulated. Aldosterone further decreased TRPM6 activity in hypomagnesemic mice, a phenomenon associated with hypertension and kidney damage. Such effects were prevented by Mg(2+) supplementation. Conclusion Amplified target organ damage in aldosterone-induced hypertension in hypomagnesemic conditions is associated with dysfunctional Mg(2+)-sensitive renal TRPM6 channels. Novel mechanisms for renal effects of aldosterone and insights into putative beneficial actions of Mg(2+), particularly in hyperaldosteronism, are identified. J Hypertens 29: 1400-1410 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.
-
downregulation of renal TRPM7 and increased inflammation and fibrosis in aldosterone infused mice effects of magnesium
Hypertension, 2008Co-Authors: Bruno Sontia, Augusto C. Montezano, Tamara M Paravicini, Fatiha Tabet, Rhian M. TouyzAbstract:Hyperaldosteronism is associated with hypertension, cardiovascular fibrosis, and electrolyte disturbances, including hypomagnesemia. Mechanisms underlying aldosterone-mediated Mg 2+ changes are unclear, but the novel Mg 2+ transporters TRPM6 and TRPM7 may be important. We examined whether aldosterone influences renal TRPM6/7 and the TRPM7 downstream target annexin-1 and tested the hypothesis that Mg 2+ administration ameliorates aldosterone-induced cardiovascular and renal injury and prevents aldosterone-associated hypertension. C57B6 mice were studied (12 weeks, n=8 to 9/group); (1) control group (0.2% dietary Mg 2+ ), (2) Mg 2+ group (0.75% dietary Mg 2+ ), (3) aldosterone group (Aldo, 400 μg/kg/min and 0.9% NaCl drinking water), and (4) Aldo+Mg 2+ group. Blood pressure was unaltered by aldosterone and was similar in all groups throughout the experiment. Serum Na + was increased and serum K + and Mg 2+ decreased in the Aldo group. Aldo mice had hypomagnesuria and proteinuria, and renal, cardiac, and aortic fibrosis, which were normalized by Mg 2+ supplementation. Renal and cardiovascular expression of interleukin-6, VCAM1 and COX2 was increased in the Aldo group. Magnesium attenuated renal and cardiac interleukin-6 content and decreased renal VCAM1 and cardiac COX2 expression ( P P 2+ increased mRNA expression of TRPM6 and TRPM7, it had no effect on TRPM7 and annexin-1 protein content. Our data demonstrate that aldosterone mediates blood pressure–independent renal and cardiovascular fibrosis and inflammation through Mg 2+ -sensitive pathways. We suggest that altered Mg 2+ metabolism in hyperaldosteronism may relate to TRPM7 downregulation and that Mg 2+ protects against cardiovascular and renal damaging actions of aldosterone.
Thomas Gudermann - One of the best experts on this subject based on the ideXlab platform.
-
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.
-
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.
-
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.
-
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.
-
A critical role of TRPM channel-kinase for human magnesium transport.
The Journal of Physiology, 2005Co-Authors: Karl Peter Schlingmann, Thomas GudermannAbstract:Hereditary disorders of magnesium homeostasis comprise a heterogenous group of diseases mainly affecting the renal conservation of magnesium. In the past few years, genetic studies in affected individuals disclosed the first molecular components of epithelial magnesium transport: the tight junction protein paracellin-1 (claudin-16) was discovered as a key player in paracellular magnesium and calcium reabsorption in the thick ascending limb of Henle's loop and the γ-subunit was identified as a component of renal Na+–K+-ATPase critical for transcellular magnesium reabsorption in the distal convoluted tubule. However, the molecular identity of proteins directly involved in cellular magnesium transport remained largely unknown until a series of recent studies highlighted the critical role of two members of the transient receptor potential (TRP) family, for body magnesium homeostasis. TRPM6 and TRPM7 belong to the melastatin-related TRPM subfamily of TRP channels whose eight members exhibit a significant diversity in domain structure as well as cation selectivity and activation mechanisms. Both proteins share the unique feature of an atypical kinase domain at their C-terminus for which they have been termed ‘chanzymes’ (channels plus enzymes). Whereas electrophysiological and biochemical analyses identified TRPM7 as an important player in cellular magnesium homeostasis, the critical role of TRPM6 for epithelial magnesium transport emerged from the discovery of loss-of-function mutations in patients with a severe form of hereditary hypomagnesaemia called primary hypomagnesaemia with secondary hypocalcaemia or HSH. The aim of this review is to summarize the data emerging from molecular genetic, biochemical and electrophysiological studies on these fascinating two new proteins combining ion channel and enzyme functions/properties.
Vladimir Chubanov - One of the best experts on this subject based on the ideXlab platform.
-
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.
-
TRPM7.
Handbook of experimental pharmacology, 2014Co-Authors: Andrea Fleig, Vladimir ChubanovAbstract:The channel kinases TRPM6 and TRPM7 are fusion proteins with an ion transport domain and an enzymatically active kinase domain. TRPM7 has been found in every mammalian tissue investigated to date. The two-in-one protein structure, the ubiquitous expression profile, and the protein's unique biophysical characteristics that enable divalent ion transport involve TRPM7 in a plethora of (patho)physiological processes. With its prominent role in cellular and systemic magnesium homeostasis, TRPM7 emerges as a key player in embryonic development, global ischemia, cardiovascular disease, and cancer.
-
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.
-
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.
-
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.
Bernd Nilius - One of the best experts on this subject based on the ideXlab platform.
-
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.
-
The Selectivity Filter of the Cation Channel TRPM4
The Journal of biological chemistry, 2005Co-Authors: Bernd Nilius, Annelies Janssens, Jean Prenen, Chunbo Wang, Grzegorz Owsianik, Michael X Zhu, Thomas VoetsAbstract:Abstract 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 < 5 s), possibly indicating destabilization of the pore. Neutralization of Asp984 resulted in a non-functional channel with a dominant negative phenotype when coexpressed with wild type TRPM4. Combined neutralization of all three acidic residues resulted in a functional channel whose voltage dependence was shifted toward very positive potentials. Substitution of Gln977 by a glutamate, the corresponding residue in divalent cation-permeable TRPM channels, altered the monovalent cation permeability sequence and resulted in a pore with moderate Ca2+ permeability. Our findings delineate the selectivity filter of TRPM channels and provide the first insight into the molecular basis of monovalent cation selectivity.
-
molecular determinants of permeation through the cation channel trpv4
Journal of Biological Chemistry, 2002Co-Authors: Thomas Voets, Annelies Janssens, Jean Prenen, Joris Vriens, Hiroyuki Watanabe, Ulrich Wissenbach, Matthias Bodding, Guy Droogmans, Bernd NiliusAbstract: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.
B.a. Miller - One of the best experts on this subject based on the ideXlab platform.
-
The Role of TRP Channels in Oxidative Stress-induced Cell Death
The Journal of Membrane Biology, 2006Co-Authors: B.a. MillerAbstract:The transient receptor potential (TRP) protein superfamily is a diverse group of voltage-independent calcium-permeable cation channels expressed in mammalian cells. These channels have been divided into six subfamilies, and two of them, TRPC and TRPM, have members that are widely expressed and activated by oxidative stress. TRPC3 and TRPC4 are activated by oxidants, which induce Na^+ and Ca^2+ entry into cells through mechanisms that are dependent on phospholipase C. TRPM2 is activated by oxidative stress or TNFα, and the mechanism involves production of ADP-ribose, which binds to an ADP-ribose binding cleft in the TRPM2 C-terminus. Treatment of HEK 293T cells expressing TRPM2 with H_2O_2 resulted in Ca^2+ influx and increased susceptibility to cell death, whereas coexpression of the dominant negative isoform TRPM2-S suppressed H_2O_2-induced Ca^2+ influx, the increase in [Ca^2+]_i, and onset of apoptosis. U937-ecoR monocytic cells expressing increased levels of TRPM2 also exhibited significantly increased [Ca^2+]_i and increased apoptosis after treatment with H_2O_2 or TNFα. A dramatic increase in caspase 8, 9, 3, 7, and PARP cleavage was observed in TRPM2-expressing cells, demonstrating a downstream mechanism through which cell death is mediated. Inhibition of endogenous TRPM2 function through three approaches, depletion of TRPM2 by RNA interference, blockade of the increase in [Ca^2+]_i through TRPM2 by calcium chelation, or expression of the dominant negative splice variant TRPM2-S protected cell viability. H_2O_2 and amyloid β-peptide also induced cell death in primary cultures of rat striatal cells, which endogenously express TRPM2. TRPM7 is activated by reactive oxygen species/nitrogen species, resulting in cation conductance and anoxic neuronal cell death, which is rescued by suppression of TRPM7 expression. TRPM2 and TRPM7 channels are physiologically important in oxidative stress-induced cell death.
-
The Role of TRP Channels in Oxidative Stress-induced Cell Death
The Journal of Membrane Biology, 2006Co-Authors: B.a. MillerAbstract:The transient receptor potential (TRP) protein superfamily is a diverse group of voltage-independent calcium-permeable cation channels expressed in mammalian cells. These channels have been divided into six subfamilies, and two of them, TRPC and TRPM, have members that are widely expressed and activated by oxidative stress. TRPC3 and TRPC4 are activated by oxidants, which induce Na^+ and Ca^2+ entry into cells through mechanisms that are dependent on phospholipase C. TRPM2 is activated by oxidative stress or TNFα, and the mechanism involves production of ADP-ribose, which binds to an ADP-ribose binding cleft in the TRPM2 C-terminus. Treatment of HEK 293T cells expressing TRPM2 with H_2O_2 resulted in Ca^2+ influx and increased susceptibility to cell death, whereas coexpression of the dominant negative isoform TRPM2-S suppressed H_2O_2-induced Ca^2+ influx, the increase in [Ca^2+]_i, and onset of apoptosis. U937-ecoR monocytic cells expressing increased levels of TRPM2 also exhibited significantly increased [Ca^2+]_i and increased apoptosis after treatment with H_2O_2 or TNFα. A dramatic increase in caspase 8, 9, 3, 7, and PARP cleavage was observed in TRPM2-expressing cells, demonstrating a downstream mechanism through which cell death is mediated. Inhibition of endogenous TRPM2 function through three approaches, depletion of TRPM2 by RNA interference, blockade of the increase in [Ca^2+]_i through TRPM2 by calcium chelation, or expression of the dominant negative splice variant TRPM2-S protected cell viability. H_2O_2 and amyloid β-peptide also induced cell death in primary cultures of rat striatal cells, which endogenously express TRPM2. TRPM7 is activated by reactive oxygen species/nitrogen species, resulting in cation conductance and anoxic neuronal cell death, which is rescued by suppression of TRPM7 expression. TRPM2 and TRPM7 channels are physiologically important in oxidative stress-induced cell death.
