101
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Beck A, Speicher T, Stoerger C, Sell T, Dettmer V, Jusoh SA, Abdulmughni A, Cavalié A, Philipp SE, Zhu MX, Helms V, Wissenbach U, Flockerzi V. Conserved gating elements in TRPC4 and TRPC5 channels. J Biol Chem 2013; 288:19471-83. [PMID: 23677990 DOI: 10.1074/jbc.m113.478305] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
TRPC4 and TRPC5 proteins share 65% amino acid sequence identity and form Ca(2+)-permeable nonselective cation channels. They are activated by stimulation of receptors coupled to the phosphoinositide signaling cascade. Replacing a conserved glycine residue within the cytosolic S4-S5 linker of both proteins by a serine residue forces the channels into an open conformation. Expression of the TRPC4G503S and TRPC5G504S mutants causes cell death, which could be prevented by buffering the Ca(2+) of the culture medium. Current-voltage relationships of the TRPC4G503S and TRPC5G504S mutant ion channels resemble that of fully activated TRPC4 and TRPC5 wild-type channels, respectively. Modeling the structure of the transmembrane domains and the pore region (S4-S6) of TRPC4 predicts a conserved serine residue within the C-terminal sequence of the predicted S6 helix as a potential interaction site. Introduction of a second mutation (S623A) into TRPC4G503S suppressed the constitutive activation and partially rescued its function. These results indicate that the S4-S5 linker is a critical constituent of TRPC4/C5 channel gating and that disturbance of its sequence allows channel opening independent of any sensor domain.
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Affiliation(s)
- Andreas Beck
- Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany.
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102
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Suzuki T, Notomi T, Miyajima D, Mizoguchi F, Hayata T, Nakamoto T, Hanyu R, Kamolratanakul P, Mizuno A, Suzuki M, Ezura Y, Izumi Y, Noda M. Osteoblastic differentiation enhances expression of TRPV4 that is required for calcium oscillation induced by mechanical force. Bone 2013; 54:172-8. [PMID: 23314072 DOI: 10.1016/j.bone.2013.01.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 12/21/2012] [Accepted: 01/02/2013] [Indexed: 11/29/2022]
Abstract
Mechanical stress is known to alter bone mass and the loss of force stimuli leads to reduction of bone mass. However, molecules involved in this phenomenon are incompletely understood. As mechanical force would affect signaling events in cells, we focused on a calcium channel, TRPV4 regarding its role in the effects of force stimuli on calcium in osteoblasts. TRPV4 expression levels were enhanced upon differentiation of osteoblasts in culture. We found that BMP-2 treatment enhanced TRPV4 gene expression in a dose dependent manner. BMP-2 effects on TRPV4 expression were suppressed by inhibitors for transcription and new protein synthesis. In these osteoblasts, a TRPV4-selective agonist, 4α-PDD, enhanced calcium signaling and the effects of 4α-PDD were enhanced in differentiated osteoblasts compared to the control cells. Fluid flow, as a mechanical stimulation, induced intracellular calcium oscillation in wild type osteoblasts. In contrast, TRPV4 deficiency suppressed calcium oscillation significantly even when the cells were subjected to fluid flow. These data suggest that TRPV4 is involved in the flow-induced calcium signaling in osteoblasts.
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Affiliation(s)
- Takafumi Suzuki
- Department of Molecular Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Japan
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103
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Siskind CE, Panchal S, Smith CO, Feely SME, Dalton JC, Schindler AB, Krajewski KM. A review of genetic counseling for Charcot Marie Tooth disease (CMT). J Genet Couns 2013; 22:422-36. [PMID: 23604902 DOI: 10.1007/s10897-013-9584-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 03/20/2013] [Indexed: 02/07/2023]
Abstract
Charcot Marie Tooth disease (CMT) encompasses the inherited peripheral neuropathies. While four genes have been found to cause over 90 % of genetically identifiable causes of CMT (PMP22, GJB1, MPZ, MFN2), at least 51 genes and loci have been found to cause CMT when mutated, creating difficulties for clinicians to find a genetic subtype for families. Here, the classic features of CMT as well as characteristic features of the most common subtypes of CMT are described, as well as methods for narrowing down the possible subtypes. Psychosocial concerns particular to the CMT population are identified. This is the most inclusive publication for CMT-specific genetic counseling.
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Affiliation(s)
- Carly E Siskind
- Neurosciences Department, Stanford Hospital and Clinics, 300 Pasteur Dr., Stanford, CA 94305, USA.
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104
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Nilius B, Voets T. The puzzle of TRPV4 channelopathies. EMBO Rep 2013; 14:152-63. [PMID: 23306656 DOI: 10.1038/embor.2012.219] [Citation(s) in RCA: 218] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 12/10/2012] [Indexed: 11/09/2022] Open
Abstract
Hereditary channelopathies, that is, mutations in channel genes that alter channel function and are causal for the pathogenesis of the disease, have been described for several members of the transient receptor potential channel family. Mutations in the TRPV4 gene, encoding a polymodal Ca(2+) permeable channel, are causative for several human diseases, which affect the skeletal system and the peripheral nervous system, with highly variable phenotypes. In this review, we describe the phenotypes of TRPV4 channelopathies and overlapping symptoms. Putative mechanisms to explain the puzzle, and how mutations in the same region of the channel cause different diseases, are discussed and experimental approaches to tackle this surprising problem are suggested.
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Affiliation(s)
- Bernd Nilius
- KU Leuven, Department of Cellular & Molecular Medicine, Laboratory of Ion Channel Research, Campus Gasthuisberg, Leuven, Belgium.
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105
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Witting N, Duno M, Born AP, Vissing J. LGMD2L with bone affection: overlapping phenotype of dominant and recessive ANO5-induced disease. Muscle Nerve 2012; 46:829-30. [PMID: 23055322 DOI: 10.1002/mus.23440] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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106
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Henry SP, Liang S, Akdemir KC, de Crombrugghe B. The postnatal role of Sox9 in cartilage. J Bone Miner Res 2012; 27:2511-25. [PMID: 22777888 PMCID: PMC3502666 DOI: 10.1002/jbmr.1696] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 06/05/2012] [Accepted: 06/22/2012] [Indexed: 11/09/2022]
Abstract
Sox9 is an essential transcription factor for the differentiation of the chondrocytic lineage during embryonic development. To test whether Sox9 continues to play a critical role in cartilaginous tissues in the adult mice, we used an inducible, genetic strategy to disrupt the Sox9 gene postnatally in these tissues. The postnatal inactivation of Sox9 led to stunted growth characterized by decreased proliferation, increased cell death, and dedifferentiation of growth plate chondrocytes. Upon postnatal Sox9 inactivation in the articular cartilage, the sulfated proteoglycan and aggrecan content of the uncalcified cartilage were rapidly depleted and the degradation of aggrecan was accompanied by higher ADAMTS5 immunostaining and increased detection of the aggrecan neoepitope, NITEGE. In spite of the severe loss of Collagen 2a1 mRNA, the Collagen II protein persisted in the articular cartilage, and no histopathological signs of osteoarthritis were observed. The homeostasis of the intervertebral disk (IVD) was dramatically altered upon Sox9 depletion, resulting in disk compression and subsequent degeneration. Inactivation of Sox9 in the IVD markedly reduced the expression of several genes encoding extracellular matrix proteins, as well as some of the enzymes responsible for their posttranslational modification. Furthermore, the loss of Sox9 in the IVD decreased the expression of cytokines, cell-surface receptors, and ion channels, suggesting that Sox9 coordinates a large genetic program that is instrumental for the proper homeostasis of the cells contained in the IVD postnatally. Our results indicate that Sox9 has an essential role in the physiological control of cartilaginous tissues in adult mice. © 2012 American Society for Bone and Mineral Research.
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Affiliation(s)
- Stephen P Henry
- Department of Genetics, The University of Texas M.D. Anderson Cancer Center; Houston, TX, USA.
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107
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Masuyama R. Activation of TRPV4 promotes osteoclasts differentiation. Arthritis Res Ther 2012. [PMCID: PMC3332484 DOI: 10.1186/ar3643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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108
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O'Conor CJ, Griffin TM, Liedtke W, Guilak F. Increased susceptibility of Trpv4-deficient mice to obesity and obesity-induced osteoarthritis with very high-fat diet. Ann Rheum Dis 2012. [PMID: 23178209 DOI: 10.1136/annrheumdis-2012-202272] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE To test the hypotheses that: (1) the transient receptor potential vanilloid 4 (TRPV4) ion channel is protective in the obesity model of osteoarthritis (OA), resulting in more severe obesity-induced OA in Trpv4 knockout (Trpv4(-/-)) mice; and (2) loss of TRPV4 alters mesodermal stem cell differentiation. METHODS Male Trpv4(-/-) and wild-type (Trpv4(+/+)) mice were fed a control or high-fat diet (10% kcal and 60% kcal from fat, respectively) for 22 weeks, at which time spontaneous cage activity and severity of knee OA were evaluated. In addition, the adipogenic, osteogenic and chondrogenic potential of bone marrow-derived (MSC) and adipose-derived (ASC) stem cells from Trpv4(-/-) and Trpv4(+/+) mice were compared. RESULTS A high-fat diet significantly increased knee OA scores and reduced spontaneous cage activity in Trpv4(-/-) mice, while also increasing weight gain and adiposity. MSCs from Trpv4(-/-) mice had decreased adipogenic and osteogenic differentiation potential versus Trpv4(+/+) MSCs. ASCs from Trpv4(-/-) mice had increased adipogenic and osteogenic and reduced chondrogenic differentiation potential versus Trpv4(+/+) ASCs. CONCLUSIONS Pan-Trpv4(-/-) mice develop more severe OA with high-fat feeding, potentially due to more severe diet-induced obesity. The altered differentiation potential of Trpv4(-/-) progenitor cells may reflect the importance of this ion channel in the maintenance and turnover of mesodermally-derived tissues.
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Affiliation(s)
- Christopher J O'Conor
- Department of Orthopaedic Surgery, Duke University Medical Center, 375 MSRB, Box 3093, Durham, NC 27710, USA
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109
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Nishimura R, Hata K, Ono K, Takashima R, Yoshida M, Yoneda T. Regulation of endochondral ossification by transcription factors. J Oral Biosci 2012. [DOI: 10.1016/j.job.2012.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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110
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Bang S, Yoo S, Yang TJ, Cho H, Hwang SW. Nociceptive and pro-inflammatory effects of dimethylallyl pyrophosphate via TRPV4 activation. Br J Pharmacol 2012; 166:1433-43. [PMID: 22300296 DOI: 10.1111/j.1476-5381.2012.01884.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Sensory neuronal and epidermal transient receptor potential ion channels (TRPs) serve an important role as pain sensor molecules. While many natural and synthetic ligands for sensory TRPs have been identified, little is known about the endogenous activator for TRPV4. Recently, we reported that endogenous metabolites produced by the mevalonate pathway regulate the activities of sensory neuronal TRPs. Here, we show that dimethylallyl pyrophosphate (DMAPP), a substance produced by the same pathway is an activator of TRPV4. EXPERIMENTAL APPROACH We examined the effects of DMAPP on sensory TRPs using Ca²⁺ imaging and whole-cell electrophysiology experiments with a heterologous expression system (HEK293T cells transfected with individual TRP channels), cultured sensory neurons and keratinocytes. We then evaluated nociceptive behavioural and inflammatory changes upon DMAPP administration in mice in vivo. KEY RESULTS In the HEK cell heterologous expression system, cultured sensory neurons and keratinocytes, µM concentrations of DMAPP activated TRPV4. Agonistic and antagonistic potencies of DMAPP for other sensory TRP channels were examined and activation of TRPV3 by camphor was found to be inhibited by DMAPP. In vivo assays, intraplantar injection of DMAPP acutely elicited nociceptive flinches that were prevented by pretreatment with TRPV4 blockers, indicating that DMAPP is a novel pain-producing molecule through TRPV4 activation. Further, DMAPP induced acute inflammation and noxious mechanical hypersensitivities in a TRPV4-dependent manner. CONCLUSIONS AND IMPLICATIONS Overall, we found a novel sensory TRP acting metabolite and suggest that its use may help to elucidate the physiological role of TRPV4 in nociception and associated inflammation.
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Affiliation(s)
- S Bang
- Korea University Graduate School of Medicine, Seoul, Korea
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111
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Yiu EM, Ryan MM. Genetic axonal neuropathies and neuronopathies of pre-natal and infantile onset. J Peripher Nerv Syst 2012; 17:285-300. [DOI: 10.1111/j.1529-8027.2012.00412.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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112
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Masuyama R, Mizuno A, Komori H, Kajiya H, Uekawa A, Kitaura H, Okabe K, Ohyama K, Komori T. Calcium/calmodulin-signaling supports TRPV4 activation in osteoclasts and regulates bone mass. J Bone Miner Res 2012; 27:1708-21. [PMID: 22492541 DOI: 10.1002/jbmr.1629] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Osteoclast differentiation is critically dependent on calcium (Ca(2+)) signaling. Transient receptor potential vanilloid 4 (TRPV4), mediates Ca(2+) influx in the late stage of osteoclast differentiation and thereby regulates Ca(2+) signaling. However, the system-modifying effect of TRPV4 activity remains to be determined. To elucidate the mechanisms underlying TRPV4 activation based on osteoclast differentiation, TRPV4 gain-of-function mutants were generated by the amino acid substitutions R616Q and V620I in TRPV4 and were introduced into osteoclast lineage in Trpv4 null mice to generate Trpv4(R616Q/V620I) transgenic mice. As expected, TRPV4 activation in osteoclasts increased the number of osteoclasts and their resorption activity, thereby resulting in bone loss. During in vitro analysis, Trpv4(R616Q/V620I) osteoclasts showed activated Ca(2+)/calmodulin signaling compared with osteoclasts lacking Trpv4. In addition, studies of Trpv4(R616Q/V620I) mice that lacked the calmodulin-binding domain indicated that bone loss due to TRPV4 activation was abrogated by loss of interactions between Ca(2+)/calmodulin signaling and TRPV4. Finally, modulators of TRPV4 interactions with the calmodulin-binding domain were investigated by proteomic analysis. Interestingly, nonmuscle myosin IIa was identified by liquid chromatography-tandem mass spectroscopy (LC-MS/MS) analysis, which was confirmed by immunoblotting following coimmunoprecipitation with TRPV4. Furthermore, myosin IIa gene silencing significantly reduced TRPV4 activation concomitant with impaired osteoclast maturation. These results indicate that TRPV4 activation reciprocally regulates Ca(2+)/calmodulin signaling, which involves an association of TRPV4 with myosin IIa, and promotes sufficient osteoclast function.
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Affiliation(s)
- Ritsuko Masuyama
- Department of Cell Biology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
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113
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Oates EC, Reddel S, Rodriguez ML, Gandolfo LC, Bahlo M, Hawke SH, Lamandé SR, Clarke NF, North KN. Autosomal dominant congenital spinal muscular atrophy: a true form of spinal muscular atrophy caused by early loss of anterior horn cells. ACTA ACUST UNITED AC 2012; 135:1714-23. [PMID: 22628388 DOI: 10.1093/brain/aws108] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Autosomal dominant congenital spinal muscular atrophy is characterized by predominantly lower limb weakness and wasting, and congenital or early-onset contractures of the hip, knee and ankle. Mutations in TRPV4, encoding a cation channel, have recently been identified in one large dominant congenital spinal muscular atrophy kindred, but the genetic basis of dominant congenital spinal muscular atrophy in many families remains unknown. It has been hypothesized that differences in the timing and site of anterior horn cell loss in the central nervous system account for the variations in clinical phenotype between different forms of spinal muscular atrophy, but there has been a lack of neuropathological data to support this concept in dominant congenital spinal muscular atrophy. We report clinical, electrophysiology, muscle magnetic resonance imaging and histopathology findings in a four generation family with typical dominant congenital spinal muscular atrophy features, without mutations in TRPV4, and in whom linkage to other known dominant neuropathy and spinal muscular atrophy genes has been excluded. The autopsy findings in the proband, who died at 14 months of age from an unrelated illness, provided a rare opportunity to study the neuropathological basis of dominant congenital spinal muscular atrophy. There was a reduction in anterior horn cell number in the lumbar and, to a lesser degree, the cervical spinal cord, and atrophy of the ventral nerve roots at these levels, in the absence of additional peripheral nerve pathology or abnormalities elsewhere along the neuraxis. Despite the young age of the child at the time of autopsy, there was no pathological evidence of ongoing loss or degeneration of anterior horn cells suggesting that anterior horn cell loss in dominant congenital spinal muscular atrophy occurs in early life, and is largely complete by the end of infancy. These findings confirm that dominant congenital spinal muscular atrophy is a true form of spinal muscular atrophy caused by a loss of anterior horn cells localized to lumbar and cervical regions early in development.
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Affiliation(s)
- Emily C Oates
- Institute for Neuroscience and Muscle Research, Children's Hospital at Westmead, Locked Bag 4001, Westmead, New South Wales, 2145, Australia
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114
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Inada H, Procko E, Sotomayor M, Gaudet R. Structural and biochemical consequences of disease-causing mutations in the ankyrin repeat domain of the human TRPV4 channel. Biochemistry 2012; 51:6195-206. [PMID: 22702953 PMCID: PMC3413242 DOI: 10.1021/bi300279b] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The TRPV4 calcium-permeable cation channel plays important
physiological
roles in osmosensation, mechanosensation, cell barrier formation,
and bone homeostasis. Recent studies reported that mutations in TRPV4,
including some in its ankyrin repeat domain (ARD), are associated
with human inherited diseases, including neuropathies and skeletal
dysplasias, probably because of the increased constitutive activity
of the channel. TRPV4 activity is regulated by the binding of calmodulin
and small molecules such as ATP to the ARD at its cytoplasmic N-terminus.
We determined structures of ATP-free and -bound forms of human TRPV4-ARD
and compared them with available TRPV-ARD structures. The third inter-repeat
loop region (Finger 3 loop) is flexible and may act as a switch to
regulate channel activity. Comparisons of TRPV-ARD structures also
suggest an evolutionary link between ARD structure and ATP binding
ability. Thermal stability analyses and molecular dynamics simulations
suggest that ATP increases stability in TRPV-ARDs that can bind ATP.
Biochemical analyses of a large panel of TRPV4-ARD mutations associated
with human inherited diseases showed that some impaired thermal stability
while others weakened ATP binding ability, suggesting molecular mechanisms
for the diseases.
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Affiliation(s)
- Hitoshi Inada
- Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
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115
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Nishimura G, Lausch E, Savarirayan R, Shiba M, Spranger J, Zabel B, Ikegawa S, Superti-Furga A, Unger S. TRPV4-associated skeletal dysplasias. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2012; 160C:190-204. [PMID: 22791502 DOI: 10.1002/ajmg.c.31335] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dominant mutations in the TRPV4 gene result in a bone dysplasia family and form a continuous phenotypic spectrum that includes, in decreasing severity, lethal, and nonlethal metatropic dysplasia (MD), spondylometaphyseal dysplasia Kozlowski type (SMDK), and autosomal dominant brachyolmia. Several rare variant phenotypes that have some overlap but deviate in some ways from the general pattern have also been described. The known variant phenotypes are spondyloepiphyseal dysplasia Maroteaux type (Pseudo-Morquio type 2), parastremmatic dysplasia, and familial digital arthropathy with brachydactyly. Interestingly, different TRPV4 mutations have been associated with dominantly inherited neurologic disorders such as congenital spinal muscular atrophy and hereditary motor and sensory neuropathy. Finally, a small number of patients have been identified in whom a TRPV4 mutation results in a phenotype combining skeletal dysplasia with peripheral neuropathy. The TRPV4 gene encodes a regulated calcium channel implicated in multiple and diverse cellular processes. Over 50 different TRPV4 mutations have been reported, with two codons appearing to be mutational hot spots: P799 in exon 15, mostly associated with MD, and R594 in exon 11, associated with SMDK. While most pathogenic mutations tested so far result in activation of the calcium channel in vitro, the mechanisms through which TRPV4 activation results in skeletal dysplasia and/or peripheral neuropathy remain unclear and the genotype-phenotype correlations in this group of disorders remains somewhat mysterious. Since the phenotypic expression of most mutations seems to be relatively constant, careful clinical and radiographic assessment is useful in directing molecular analysis.
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Affiliation(s)
- Gen Nishimura
- Génétique Médicale, CHUV, Av. Decker 2, 1011 Lausanne, Switzerland
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116
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TRPV4 axonal neuropathy spectrum disorder. J Clin Neurosci 2012; 19:927-33. [DOI: 10.1016/j.jocn.2011.12.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 12/18/2011] [Indexed: 11/21/2022]
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117
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Butenko O, Dzamba D, Benesova J, Honsa P, Benfenati V, Rusnakova V, Ferroni S, Anderova M. The increased activity of TRPV4 channel in the astrocytes of the adult rat hippocampus after cerebral hypoxia/ischemia. PLoS One 2012; 7:e39959. [PMID: 22761937 PMCID: PMC3384594 DOI: 10.1371/journal.pone.0039959] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 05/30/2012] [Indexed: 02/03/2023] Open
Abstract
The polymodal transient receptor potential vanilloid 4 (TRPV4) channel, a member of the TRP channel family, is a calcium-permeable cationic channel that is gated by various stimuli such as cell swelling, low pH and high temperature. Therefore, TRPV4-mediated calcium entry may be involved in neuronal and glia pathophysiology associated with various disorders of the central nervous system, such as ischemia. The TRPV4 channel has been recently found in adult rat cortical and hippocampal astrocytes; however, its role in astrocyte pathophysiology is still not defined. In the present study, we examined the impact of cerebral hypoxia/ischemia (H/I) on the functional expression of astrocytic TRPV4 channels in the adult rat hippocampal CA1 region employing immunohistochemical analyses, the patch-clamp technique and microfluorimetric intracellular calcium imaging on astrocytes in slices as well as on those isolated from sham-operated or ischemic hippocampi. Hypoxia/ischemia was induced by a bilateral 15-minute occlusion of the common carotids combined with hypoxic conditions. Our immunohistochemical analyses revealed that 7 days after H/I, the expression of TRPV4 is markedly enhanced in hippocampal astrocytes of the CA1 region and that the increasing TRPV4 expression coincides with the development of astrogliosis. Additionally, adult hippocampal astrocytes in slices or cultured hippocampal astrocytes respond to the TRPV4 activator 4-alpha-phorbol-12,-13-didecanoate (4αPDD) by an increase in intracellular calcium and the activation of a cationic current, both of which are abolished by the removal of extracellular calcium or exposure to TRP antagonists, such as Ruthenium Red or RN1734. Following hypoxic/ischemic injury, the responses of astrocytes to 4αPDD are significantly augmented. Collectively, we show that TRPV4 channels are involved in ischemia-induced calcium entry in reactive astrocytes and thus, might participate in the pathogenic mechanisms of astroglial reactivity following ischemic insult.
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Affiliation(s)
- Olena Butenko
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
- Second Medical Faculty, Charles University, Prague, Czech Republic
| | - David Dzamba
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
- Second Medical Faculty, Charles University, Prague, Czech Republic
| | - Jana Benesova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
- Second Medical Faculty, Charles University, Prague, Czech Republic
| | - Pavel Honsa
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
- Second Medical Faculty, Charles University, Prague, Czech Republic
| | - Valentina Benfenati
- Institute for the Study of Nanostructured Material, National Research Council, Bologna, Italy
| | - Vendula Rusnakova
- Laboratory of Gene Expression, Institute of Biotechnology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Stefano Ferroni
- Department of Human and General Physiology, University of Bologna, Bologna, Italy
| | - Miroslava Anderova
- Department of Cellular Neurophysiology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
- * E-mail:
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118
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Denadai-Souza A, Martin L, de Paula MAV, de Avellar MCW, Muscará MN, Vergnolle N, Cenac N. Role of transient receptor potential vanilloid 4 in rat joint inflammation. ACTA ACUST UNITED AC 2012; 64:1848-58. [DOI: 10.1002/art.34345] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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119
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Fiorillo C, Moro F, Brisca G, Astrea G, Nesti C, Bálint Z, Olschewski A, Meschini MC, Guelly C, Auer-Grumbach M, Battini R, Pedemonte M, Romano A, Menchise V, Biancheri R, Santorelli FM, Bruno C. TRPV4 mutations in children with congenital distal spinal muscular atrophy. Neurogenetics 2012; 13:195-203. [PMID: 22526352 DOI: 10.1007/s10048-012-0328-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 03/29/2012] [Indexed: 01/15/2023]
Abstract
Inherited disorders characterized by motor neuron loss and muscle weakness are genetically heterogeneous. The recent identification of mutations in the gene encoding transient receptor potential vanilloid 4 (TRPV4) in distal spinal muscular atrophy (dSMA) prompted us to screen for TRPV4 mutations in a small group of children with compatible phenotype. In a girl with dSMA and vocal cord paralysis, we detected a new variant (p.P97R) localized in the cytosolic N-terminus of the TRPV4 protein, upstream of the ankyrin-repeat domain, where the great majority of disease-associated mutations reside. In another child with congenital dSMA, in this case associated with bone abnormalities, we detected a previously reported mutation (p.R232C). Functional analysis of the novel p.P97R mutation in a heterologous system demonstrated a loss-of-function mechanism. Protein localization studies in muscle, skin, and cultured skin fibroblasts from both patients showed normal protein expression. No TRPV4 mutations were detected in four children with dSMA without bone or vocal cord involvement. Adding to the clinical and molecular heterogeneity of TRPV4-associated diseases, our results suggest that molecular testing of the TRPV4 gene is warranted in cases of congenital dSMA with bone abnormalities and vocal cord paralysis.
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Affiliation(s)
- Chiara Fiorillo
- Neuromuscular Unit, IRCCS Stella Maris, Via dei Giacinti 2, 56028 Pisa, Italy.
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Cho TJ, Matsumoto K, Fano V, Dai J, Kim OH, Chae JH, Yoo WJ, Tanaka Y, Matsui Y, Takigami I, Monges S, Zabel B, Shimizu K, Nishimura G, Lausch E, Ikegawa S. TRPV4-pathy manifesting both skeletal dysplasia and peripheral neuropathy: a report of three patients. Am J Med Genet A 2012; 158A:795-802. [PMID: 22419508 DOI: 10.1002/ajmg.a.35268] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 01/16/2012] [Indexed: 01/17/2023]
Abstract
Heterozygous missense mutations of transient receptor potential vanilloid 4 channel (TRPV4) cause a spectrum of skeletal disorders, including brachyolmia, spondylometaphyseal dysplasia Kozlowski type, metatropic dysplasia, parastremmatic dysplasia, and spondyloepimetaphyseal dysplasia Maroteaux type. Similarly, heterozygous missense mutations of TRPV4 cause a spectrum of peripheral neuropathy, including hereditary motor and sensory neuropathy type IIC, congenital spinal muscular atrophy, and scapuloperoneal spinal muscular atrophy. There are no apparent differences in the amino acid positions affected or type of change predicted by the TRPV4 mutations responsible for the two disease spectrums; nevertheless, no fundamental phenotypic overlap has been shown between the two spectrums. Here, we report on three patients who had both skeletal dysplasia and peripheral neuropathy caused by heterozygous TRPV4 missense mutations. The skeletal and neurologic phenotypes of these patients covered the wide spectrum of reported TRPV4-pathies (disease caused by TRPV4 mutations). The molecular data are complementary, proving that "neuropathic" mutations can cause skeletal dysplasia but also the "skeletopathic" mutations can lead to neuropathies. Our findings suggest that pathogenic mechanisms of TRPV4-pathies in skeletal and nervous systems are not always mutually exclusive and provide further evidence that there is no clear genotype-phenotype correlation for either spectrum. Co-occurrence of skeletal dysplasia and degenerative neuropathy should be kept in mind in clinical practice including diagnostic testing, surgical evaluation, and genetic counseling.
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Affiliation(s)
- Tae-Joon Cho
- Division of Pediatric Orthopaedics, Seoul National University Children's Hospital, Seoul, Korea
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121
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Gailly P. TRP channels in normal and dystrophic skeletal muscle. Curr Opin Pharmacol 2012; 12:326-34. [PMID: 22349418 DOI: 10.1016/j.coph.2012.01.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 01/31/2012] [Accepted: 01/31/2012] [Indexed: 01/29/2023]
Abstract
TRP proteins constitute non-selective cation-permeable ion channels, most of which are permeable to Ca²⁺. In skeletal muscle, several isoforms of the TRPC (Canonical), TRPV (Vanilloid) and TRPM (Melastatin) subfamilies are expressed. In particular, TRPC1, C3 and C6, TRPV2 and V4, TRPM4 and TRPM7 have been consistently found in cultured myoblasts or in adult muscles. These channels seem to directly or indirectly respond to membrane stretch or to Ca²⁺ stores depletion; some isoforms might also constitute unregulated Ca²⁺ leak channels. Their function is largely unknown. TRPC1 and C3 have been involved in muscle development, in particular in myoblasts migration and differentiation. TRPC1 and V4 might allow a basal influx of Ca²⁺ at rest. Their lack has consequences on muscle fatigue. TRPV2 seems to be stretch-sensitive. It localizes mainly in intracellular pools at rest, and translocates to the plasma membrane upon IGF-1 stimulation. TRP channels seem to be involved in the pathophysiology of muscle disorders. In particular in Duchenne muscular dystrophy, the lack of the cytoskeletal protein dystrophin induces a disregulation of several ion channels leading to an abnormal influx of Ca²⁺. We discuss here, the possible involvement of TRP channels in this abnormal influx of Ca²⁺.
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Affiliation(s)
- Philippe Gailly
- Laboratory of Cell Physiology, Institute of Neuroscience, Université catholique de Louvain, 55 av. Hippocrate, B1.55.12, 1200 Brussels, Belgium.
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122
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Nishimura R, Hata K, Matsubara T, Wakabayashi M, Yoneda T. Regulation of bone and cartilage development by network between BMP signalling and transcription factors. J Biochem 2012; 151:247-54. [PMID: 22253449 DOI: 10.1093/jb/mvs004] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Bone morphogenetic protein(s) (BMP) are very powerful cytokines that induce bone and cartilage formation. BMP also stimulate osteoblast and chondrocyte differentiation. During bone and cartilage development, BMP regulates the expression and/or the function of several transcription factors through activation of Smad signalling. Genetic studies revealed that Runx2, Osterix and Sox9, all of which function downstream of BMP, play essential roles in bone and/or cartilage development. In addition, two other transcription factors, Msx2 and Dlx5, which interact with BMP signalling, are involved in bone and cartilage development. The importance of these transcription factors in bone and cartilage development has been supported by biochemical and cell biological studies. Interestingly, BMP is regulated by several negative feedback systems that appear necessary for fine-tuning of bone and cartilage development induced by BMP. Thus, BMP harmoniously regulates bone and cartilage development by forming network with several transcription factors.
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Affiliation(s)
- Riko Nishimura
- Department of Molecular and Cellular Biochemistry, Osaka University Graduate School of Dentistry.
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123
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124
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Lieben L, Carmeliet G. The Involvement of TRP Channels in Bone Homeostasis. Front Endocrinol (Lausanne) 2012; 3:99. [PMID: 22934090 PMCID: PMC3422722 DOI: 10.3389/fendo.2012.00099] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 07/31/2012] [Indexed: 12/11/2022] Open
Abstract
Calcium and bone homeostasis are intimately related. On the one hand, bone relies on a sufficient supply of calcium to maintain its structural and mechanical properties and thus largely depends on calcium absorption in the intestine and calcium reabsorption in the kidney. On the other hand, bone serves as a calcium reserve from which calcium is mobilized to maintain normal calcium levels in blood. A negative external calcium balance will therefore at all times impair skeletal integrity. In addition to the external calcium balance, skeletal homeostasis also depends on the proper differentiation and functioning of bone cells, which relies for a large part on intracellular Ca(2+) signaling. Members of the transient receptor potential (TRP) family of ion channels affect skeletal homeostasis by mediating processes involved in the extracellular as well as intracellular Ca(2+) balance, including intestinal calcium absorption (TRPV6), renal calcium reabsorption (TRPV5), and differentiation of osteoclasts (TRPV1, TRPV2, TRPV4, TRPV5), chondrocytes (TRPV4), and possibly osteoblasts (TRPV1). In this review, we will give a brief overview of the systemic calcium homeostasis and the intracellular Ca(2+) signaling in bone cells with special focus on the TRP channels involved in these processes.
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Affiliation(s)
- Liesbet Lieben
- Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, Katholieke Universiteit LeuvenLeuven, Belgium
| | - Geert Carmeliet
- Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, Katholieke Universiteit LeuvenLeuven, Belgium
- *Correspondence: Geert Carmeliet, Clinical and Experimental Endocrinology, Katholieke Universiteit Leuven, Herestraat 49, O & N1, bus 902, 3000 Leuven, Belgium. e-mail:
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125
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Nemec SF, Cohn DH, Krakow D, Funari VA, Rimoin DL, Lachman RS. The importance of conventional radiography in the mutational analysis of skeletal dysplasias (the TRPV4 mutational family). Pediatr Radiol 2012; 42:15-23. [PMID: 21863289 DOI: 10.1007/s00247-011-2229-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Revised: 07/12/2011] [Accepted: 07/26/2011] [Indexed: 12/25/2022]
Abstract
The spondylo and spondylometaphyseal dysplasias (SMDs) are characterized by vertebral changes and metaphyseal abnormalities of the tubular bones, which produce a phenotypic spectrum of disorders from the mild autosomal-dominant brachyolmia to SMD Kozlowski to autosomal-dominant metatropic dysplasia. Investigations have recently drawn on the similar radiographic features of those conditions to define a new family of skeletal dysplasias caused by mutations in the transient receptor potential cation channel vanilloid 4 (TRPV4). This review demonstrates the significance of radiography in the discovery of a new bone dysplasia family due to mutations in a single gene.
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Affiliation(s)
- Stefan F Nemec
- International Skeletal Dysplasia Registry, Medical Genetics Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, PACT Suite 400, Los Angeles, CA 90048, USA.
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Jang Y, Jung J, Kim H, Oh J, Jeon JH, Jung S, Kim KT, Cho H, Yang DJ, Kim SM, Kim IB, Song MR, Oh U. Axonal neuropathy-associated TRPV4 regulates neurotrophic factor-derived axonal growth. J Biol Chem 2011; 287:6014-24. [PMID: 22187434 DOI: 10.1074/jbc.m111.316315] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Spinal muscular atrophy and hereditary motor and sensory neuropathies are characterized by muscle weakness and atrophy caused by the degenerations of peripheral motor and sensory nerves. Recent advances in genetics have resulted in the identification of missense mutations in TRPV4 in patients with these hereditary neuropathies. Neurodegeneration caused by Ca(2+) overload due to the gain-of-function mutation of TRPV4 was suggested as the molecular mechanism for the neuropathies. Despite the importance of TRPV4 mutations in causing neuropathies, the precise role of TRPV4 in the sensory/motor neurons is unknown. Here, we report that TRPV4 mediates neurotrophic factor-derived neuritogenesis in developing peripheral neurons. TRPV4 was found to be highly expressed in sensory and spinal motor neurons in early development as well as in the adult, and the overexpression or chemical activation of TRPV4 was found to promote neuritogenesis in sensory neurons as well as PC12 cells, whereas its knockdown and pharmacologic inhibition had the opposite effect. More importantly, nerve growth factor or cAMP treatment up-regulated the expression of phospholipase A(2) and TRPV4. Neurotrophic factor-derived neuritogenesis appears to be regulated by the phospholipase A(2)-mediated TRPV4 pathway. These findings show that TRPV4 mediates neurotrophic factor-induced neuritogenesis in developing peripheral nerves. Because neurotrophic factors are essential for the maintenance of peripheral nerves, these findings suggest that aberrant TRPV4 activity may lead to some types of pathology of sensory and motor nerves.
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Affiliation(s)
- Yongwoo Jang
- Sensory Research Center, College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea
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127
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Mutations in TRPV4 cause an inherited arthropathy of hands and feet. Nat Genet 2011; 43:1142-6. [DOI: 10.1038/ng.945] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/24/2011] [Indexed: 11/09/2022]
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128
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Unger S, Lausch E, Stanzial F, Gillessen-Kaesbach G, Stefanova I, Di Stefano CM, Bertini E, Dionisi-Vici C, Nilius B, Zabel B, Superti-Furga A. Fetal akinesia in metatropic dysplasia: The combined phenotype of chondrodysplasia and neuropathy? Am J Med Genet A 2011; 155A:2860-4. [PMID: 21964829 DOI: 10.1002/ajmg.a.34268] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 07/15/2011] [Indexed: 11/08/2022]
Abstract
Dominant mutations in the receptor calcium channel gene TRPV4 have been associated with a family of skeletal dysplasias (metatropic dysplasia, pseudo-Morquio type 2, spondylometaphyseal dysplasia, Kozlowski type, brachyolmia, and familial digital arthropathy) as well as with dominantly inherited neuropathies (hereditary motor and sensory neuropathy 2C, scapuloperoneal spinal muscular atrophy, and congenital distal spinal muscular atrophy). While there is phenotypic overlap between the various members of each group, the two groups were considered to be totally separate with the former being strictly a structural skeletal condition and the latter group being confined to the peripheral nervous system. We report here on fetal akinesia as the presenting feature of severe metatropic dysplasia, suggesting that certain TRPV4 mutations can cause both a skeletal and a neuropathic phenotype. Three cases were detected on prenatal ultrasound because of absent movements in the second trimester. Case 4 presented with multiple joint contractures and absent limb movements at birth and was diagnosed with "fetal akinesia syndrome". Post-interruption and post-natal X-rays showed typical features of metatropic dysplasia in all four. Sequencing of the TRPV4 gene confirmed the presence of de novo heterozygous mutations predicting G78W (Case 1), T740I (Cases 2 and 3), and K276E (Case 4). Although some degree of restriction of movements is not uncommon in fetuses with skeletal dysplasia, akinesia as leading sign is unusual and suggests that certain TRPV4 mutations produce both chondrodysplasia and a peripheral neuropathy resulting in a severe "overlap" phenotype.
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Affiliation(s)
- Sheila Unger
- Service of Medical Genetics, University of Lausanne, Lausanne, Switzerland.
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129
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Abstract
Transient receptor potential channels, of the vanilloid subtype (TRPV), act as sensory mediators, being activated by endogenous ligands, heat, mechanical and osmotic stress. Within the vasculature, TRPV channels are expressed in smooth muscle cells, endothelial cells, as well as in peri-vascular nerves. Their varied distribution and polymodal activation properties make them ideally suited to a role in modulating vascular function, perceiving and responding to local environmental changes. In endothelial cells, TRPV1 is activated by endocannabinoids, TRPV3 by dietary agonists and TRPV4 by shear stress, epoxyeicosatrienoic acids (EETs) and downstream of Gq-coupled receptor activation. Upon activation, these channels contribute to vasodilation via nitric oxide, prostacyclin and intermediate/small conductance potassium channel-dependent pathways. In smooth muscle, TRPV4 is activated by endothelial-derived EETs, leading to large conductance potassium channel activation and smooth muscle hyperpolarization. Conversely, smooth muscle TRPV2 channels contribute to global calcium entry and may aid constriction. TRPV1 and TRPV4 are expressed in sensory nerves and can cause vasodilation through calcitonin gene-related peptide and substance P release as well as mediating vascular function via the baroreceptor reflex (TRPV1) or via increasing sympathetic outflow during osmotic stress (TRPV4). Thus, TRPV channels play important roles in the regulation of normal and pathological cellular function in the vasculature.
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Affiliation(s)
- R L Baylie
- Department of Pharmacology, University of Vermont College of Medicine, Burlington, USA.
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130
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Moran MM, McAlexander MA, Bíró T, Szallasi A. Transient receptor potential channels as therapeutic targets. Nat Rev Drug Discov 2011; 10:601-20. [PMID: 21804597 DOI: 10.1038/nrd3456] [Citation(s) in RCA: 421] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Transient receptor potential (TRP) cation channels have been among the most aggressively pursued drug targets over the past few years. Although the initial focus of research was on TRP channels that are expressed by nociceptors, there has been an upsurge in the amount of research that implicates TRP channels in other areas of physiology and pathophysiology, including the skin, bladder and pulmonary systems. In addition, mutations in genes encoding TRP channels are the cause of several inherited diseases that affect a variety of systems including the renal, skeletal and nervous system. This Review focuses on recent developments in the TRP channel-related field, and highlights potential opportunities for therapeutic intervention.
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Affiliation(s)
- Magdalene M Moran
- Hydra Biosciences, 790 Memorial Drive, Cambridge, Massachusetts 02139, USA
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131
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Vanoevelen J, Janssens A, Huitema LFA, Hammond CL, Metz JR, Flik G, Voets T, Schulte-Merker S. Trpv5/6 is vital for epithelial calcium uptake and bone formation. FASEB J 2011; 25:3197-207. [PMID: 21670068 DOI: 10.1096/fj.11-183145] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calcium is an essential ion serving a multitude of physiological roles. Aside from its role as a second messenger, it is an essential component of the vertebrate bone matrix. Efficient uptake and storage of calcium are therefore indispensable for all vertebrates. Transient receptor potential family, vanilloid type (TRPV)5 and TRPV6 channels are known players in transcellular calcium uptake, but the exact contribution of this pathway is unclear. We used forward genetic screening in zebrafish (Danio rerio) to identify genes essential in bone formation and identified a lethal zebrafish mutant (matt-und-schlapp) with severe defects in bone formation, including lack of ossification of the vertebral column and craniofacial structures. Mutant embryos show a 68% reduction in calcium content, and systemic calcium homeostasis is disturbed when compared with siblings. The phenotype can be partially rescued by increasing ambient calcium levels to 25 mM. We identified the mutation as a loss-of-function mutation in the single orthologue of TRPV5 and 6, trpv5/6. Expression in HEK293 cells showed that Trpv5/6 is a calcium-selective channel capable of inward calcium transport at physiological concentrations whereas the mutant channel is not. Taken together, this study provides both genetic and functional evidence that transcellular epithelial calcium uptake is vital to sustain life and enable bone formation.
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Affiliation(s)
- Jo Vanoevelen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Centre, Utrecht, The Netherlands.
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132
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Andreucci E, Aftimos S, Alcausin M, Haan E, Hunter W, Kannu P, Kerr B, McGillivray G, McKinlay Gardner RJ, Patricelli MG, Sillence D, Thompson E, Zacharin M, Zankl A, Lamandé SR, Savarirayan R. TRPV4 related skeletal dysplasias: a phenotypic spectrum highlighted byclinical, radiographic, and molecular studies in 21 new families. Orphanet J Rare Dis 2011; 6:37. [PMID: 21658220 PMCID: PMC3135501 DOI: 10.1186/1750-1172-6-37] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 06/09/2011] [Indexed: 08/30/2023] Open
Abstract
Background The TRPV4 gene encodes a calcium-permeable ion-channel that is widely expressed, responds to many different stimuli and participates in an extraordinarily wide range of physiologic processes. Autosomal dominant brachyolmia, spondylometaphyseal dysplasia Kozlowski type (SMDK) and metatropic dysplasia (MD) are currently considered three distinct skeletal dysplasias with some shared clinical features, including short stature, platyspondyly, and progressive scoliosis. Recently, TRPV4 mutations have been found in patients diagnosed with these skeletal phenotypes. Methods and Results We critically analysed the clinical and radiographic data on 26 subjects from 21 families, all of whom had a clinical diagnosis of one of the conditions described above: 15 with MD; 9 with SMDK; and 2 with brachyolmia. We sequenced TRPV4 and identified 9 different mutations in 22 patients, 4 previously described, and 5 novel. There were 4 mutation-negative cases: one with MD and one with SMDK, both displaying atypical clinical and radiographic features for these diagnoses; and two with brachyolmia, who had isolated spine changes and no metaphyseal involvement. Conclusions Our data suggest the TRPV4 skeletal dysplasias represent a continuum of severity with areas of phenotypic overlap, even within the same family. We propose that AD brachyolmia lies at the mildest end of this spectrum and, since all cases described with this diagnosis and TRPV4 mutations display metaphyseal changes, we suggest that it is not a distinct entity but represents the mildest phenotypic expression of SMDK.
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Affiliation(s)
- Elena Andreucci
- Genetic Health Services Victoria and Murdoch Childrens Research Institute, Parkville, Victoria, Australia.
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Loukin S, Su Z, Kung C. Increased basal activity is a key determinant in the severity of human skeletal dysplasia caused by TRPV4 mutations. PLoS One 2011; 6:e19533. [PMID: 21573172 PMCID: PMC3088684 DOI: 10.1371/journal.pone.0019533] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 04/04/2011] [Indexed: 02/01/2023] Open
Abstract
TRPV4 is a mechanically activated Ca2+-passing channel implicated in the sensing of forces, including those acting on bones. To date, 33 mutations are known to affect human bone development to different extents. The spectrum of these skeletal dysplasias (SD) ranges from dominantly inherited mild brachylomia (BO) to neonatal lethal forms of metatropic dysplasia (MD). Complexities of the results from fluorescence and electrophysiological studies have led to questions on whether channel activity is a good predictor of disease severity. Here we report on a systematic examination of 14 TRPV4 mutant alleles covering the entire SD spectrum. Expressed in Xenopus oocyte and without any stimulation, the wild-type channel had a ∼1% open probability (Po) while those of most of the lethal MD channels approached 100%. All mutant channels had higher basal open probabilities, which limited their further increase by agonist or hypotonicity. The magnitude of this limitation revealed a clear correlation between the degree of over-activity (the molecular phenotype) and the severity of the disease over the entire spectrum (the biological phenotype). Thus, while other factors are at play, our results are consistent with the increased TRPV4 basal activity being a critical determinant of the severity of skeletal dysplasia. We discuss how the channel over-activity may lead to the “gain-of-function” phenotype and speculate that the function of wild-type TRPV4 may be secondary in normal bone development but crucial in an acute process such as fracture repair in the adult.
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Affiliation(s)
- Stephen Loukin
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail:
| | - Zhenwei Su
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- Department of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
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134
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Abstract
The transient receptor potential (TRP) multigene superfamily encodes integral membrane proteins that function as ion channels. Members of this family are conserved in yeast, invertebrates and vertebrates. The TRP family is subdivided into seven subfamilies: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), TRPA (ankyrin) and TRPN (NOMPC-like); the latter is found only in invertebrates and fish. TRP ion channels are widely expressed in many different tissues and cell types, where they are involved in diverse physiological processes, such as sensation of different stimuli or ion homeostasis. Most TRPs are non-selective cation channels, only few are highly Ca2+ selective, some are even permeable for highly hydrated Mg2+ ions. This channel family shows a variety of gating mechanisms, with modes of activation ranging from ligand binding, voltage and changes in temperature to covalent modifications of nucleophilic residues. Activated TRP channels cause depolarization of the cellular membrane, which in turn activates voltage-dependent ion channels, resulting in a change of intracellular Ca2+ concentration; they serve as gatekeeper for transcellular transport of several cations (such as Ca2+ and Mg2+), and are required for the function of intracellular organelles (such as endosomes and lysosomes). Because of their function as intracellular Ca2+ release channels, they have an important regulatory role in cellular organelles. Mutations in several TRP genes have been implicated in diverse pathological states, including neurodegenerative disorders, skeletal dysplasia, kidney disorders and pain, and ongoing research may help find new therapies for treatments of related diseases.
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Affiliation(s)
- Bernd Nilius
- Department of Molecular Cell Biology, Laboratory of Ion Channel Research, Campus Gasthuisberg, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
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135
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Recent Advances in the Genetics of Hereditary Axonal Sensory-Motor Neuropathies Type 2. Curr Neurol Neurosci Rep 2011; 11:262-73. [DOI: 10.1007/s11910-011-0185-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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136
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Montell C. The history of TRP channels, a commentary and reflection. Pflugers Arch 2011; 461:499-506. [PMID: 21287198 DOI: 10.1007/s00424-010-0920-3] [Citation(s) in RCA: 322] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 12/23/2010] [Indexed: 11/30/2022]
Abstract
The transient receptor potential (TRP) family of cation channels has redefined our understanding of sensory physiology. In one animal or another, all senses depend on TRP channels. These include vision, taste, smell, hearing, and various forms of touch, including the ability to sense changes in temperature. The first trp gene was identified because it was disrupted in a Drosophila mutant with defective vision. However, there was no clue as to its biochemical function until the cloning, and analysis of the deduced amino acid sequence suggested that trp encoded a cation channel. This concept was further supported by subsequent electrophysiological studies, including alteration of its ion selectivity by an amino acid substitution within the pore loop. The study of TRP channels emerged as a field with the identification of mammalian homologs, some of which are direct sensors of environmental temperature. At least one TRP channel is activated downstream of a thermosensory signaling cascade, demonstrating that there exist two modes of activation, direct and indirect, through which TRP channels respond to changes in temperature. Mutations in many TRP channels result in disease, including a variety of sensory impairments.
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Affiliation(s)
- Craig Montell
- Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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137
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Klein CJ, Shi Y, Fecto F, Donaghy M, Nicholson G, McEntagart ME, Crosby AH, Wu Y, Lou H, McEvoy KM, Siddique T, Deng HX, Dyck PJ. TRPV4 mutations and cytotoxic hypercalcemia in axonal Charcot-Marie-Tooth neuropathies. Neurology 2011; 76:887-94. [PMID: 21288981 DOI: 10.1212/wnl.0b013e31820f2de3] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To improve understanding of TRPV4-associated axonal Charcot-Marie-Tooth (CMT) neuropathy phenotypes and their debated pathologic mechanism. METHODS A total of 17 CMT2C phenotypic families with vocal cord and diaphragmatic involvement and 36 clinically undifferentiated CMT2 subjects underwent sequencing analysis of the coding region of TRPV4. Functional studies of mutant proteins were performed using transiently transfected cells for TRPV4 subcellular localization, basal and stimulated Ca(2+) channel analysis, and cell viability assay with or without channel blockade. RESULTS Two TRPV4 mutations R232C and R316H from 17 CMT2C families were identified in the ankyrin repeat domains. The R316H is a novel de novo mutation found in a patient with CMT2C phenotype. The family with R232C mutation had individuals with and without vocal cord and diaphragm involvement. Both mutant TRPV4 proteins had normal subcellular localization in HEK293 and HeLa cells. Cells transfected with R232C and R316H displayed increased intracellular Ca(2+) levels and reversible cell death by the TRPV channel antagonist, ruthenium red. CONCLUSION TRPV4 ankyrin domain alterations including a novel de novo mutation cause axonal CMT2. Individuals with the same mutation may have nondistinct CMT2 or have phenotypic CMT2C with vocal cord paresis. Reversible hypercalcemic gain-of-function of mutant TRPV4 instead of loss-of-function appears to be pathologically important. The reversibility of cell death by channel blockade provides an attractive area of investigation in consideration of treatable axonal degeneration.
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Affiliation(s)
- C J Klein
- Department of Neurology and Division of Peripheral Nerve Diseases, Mayo Clinic Foundation, Rochester, MN 55905, USA.
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Zaninetti R, Fornarelli A, Ciarletta M, Lim D, Caldarelli A, Pirali T, Cariboni A, Owsianik G, Nilius B, Canonico PL, Distasi C, Genazzani AA. Activation of TRPV4 channels reduces migration of immortalized neuroendocrine cells. J Neurochem 2011; 116:606-15. [PMID: 21166676 DOI: 10.1111/j.1471-4159.2010.07144.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Calcium is a universal signal, and its capacity to encode intracellular messages via spatial, temporal and amplitude characteristics allows it to participate in most cellular events. In a specific context, calcium plays a pivotal role in migration, although its role has not been elucidated fully. By using immortalized gonadotropin-releasing hormone-secreting neurons (GN11), we have now investigated the role of TRPV4, a member of the vanilloid family of Ca(2+) channels, in neuronal migration. Our results show that TRPV4 channels are present and functional in GN11 cells and their localization is polarized and enriched in lamellipodial structures. TRPV4 activation leads to a retraction of the lamellipodia and to a decrease in migratory behaviour; moreover cells migrate slower and in a more random manner. We therefore provide evidence for a new regulation of gonadotropin-releasing hormone neurons and a new role for calcium at the leading edge of migratory cells.
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Affiliation(s)
- Roberta Zaninetti
- Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, Università degli Studi del Piemonte Orientale A. Avogadro, Novara, Italy
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139
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The Role of Transient Receptor Potential Channels in Respiratory Symptoms and Pathophysiology. TRANSIENT RECEPTOR POTENTIAL CHANNELS 2011; 704:969-86. [DOI: 10.1007/978-94-007-0265-3_50] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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140
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141
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Transient Receptor Potential Genes and Human Inherited Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:1011-32. [DOI: 10.1007/978-94-007-0265-3_52] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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142
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Chen DH, Sul Y, Weiss M, Hillel A, Lipe H, Wolff J, Matsushita M, Raskind W, Bird T. CMT2C with vocal cord paresis associated with short stature and mutations in the TRPV4 gene. Neurology 2010; 75:1968-75. [PMID: 21115951 DOI: 10.1212/wnl.0b013e3181ffe4bb] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Recently, mutations in the transient receptor potential cation channel, subfamily V, member 4 gene (TRPV4) have been reported in Charcot-Marie-Tooth Type 2C (CMT2C) with vocal cord paresis. Other mutations in this same gene have been described in separate families with various skeletal dysplasias. Further clarification is needed of the different phenotypes associated with this gene. METHODS We performed clinical evaluation, electrophysiology, and genetic analysis of the TRPV4 gene in 2 families with CMT2C. RESULTS Two multigenerational families had a motor greater than sensory axonal neuropathy associated with variable vocal cord paresis. The vocal cord paresis varied from absent to severe, requiring permanent tracheotomy in 2 subjects. One family with mild neuropathy also manifested pronounced short stature, more than 2 SD below the average height for white Americans. There was one instance of dolichocephaly. A novel S542Y mutation in the TRPV4 gene was identified in this family. The other family had a more severe, progressive, motor neuropathy with sensory loss, but less remarkable short stature and an R315W mutation in TRPV4. Third cranial nerve involvement and sleep apnea occurred in one subject in each family. CONCLUSION CMT2C with axonal neuropathy, vocal cord paresis, and short stature is a unique syndrome associated with mutations in the TRPV4 gene. Mutations in TRPV4 can cause abnormalities in bone, peripheral nerve, or both and may result in highly variable orthopedic and neurologic phenotypes.
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Affiliation(s)
- D-H Chen
- Department of Neurology, University of Washington Medical School, Seattle, WA, USA
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143
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Wu LJ, Sweet TB, Clapham DE. International Union of Basic and Clinical Pharmacology. LXXVI. Current progress in the mammalian TRP ion channel family. Pharmacol Rev 2010; 62:381-404. [PMID: 20716668 DOI: 10.1124/pr.110.002725] [Citation(s) in RCA: 426] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential (TRP) channels are a large family of ion channel proteins, surpassed in number in mammals only by voltage-gated potassium channels. TRP channels are activated and regulated through strikingly diverse mechanisms, making them suitable candidates for cellular sensors. They respond to environmental stimuli such as temperature, pH, osmolarity, pheromones, taste, and plant compounds, and intracellular stimuli such as Ca(2+) and phosphatidylinositol signal transduction pathways. However, it is still largely unknown how TRP channels are activated in vivo. Despite the uncertainties, emerging evidence using TRP channel knockout mice indicates that these channels have broad function in physiology. Here we review the recent progress on the physiology, pharmacology and pathophysiological function of mammalian TRP channels.
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Affiliation(s)
- Long-Jun Wu
- Howard Hughes Medical Institute, Department of Cardiology, Children's Hospital Boston, 320 Longwood Avenue, Boston, MA 02115, USA
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144
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Clark AL, Votta BJ, Kumar S, Liedtke W, Guilak F. Chondroprotective role of the osmotically sensitive ion channel transient receptor potential vanilloid 4: age- and sex-dependent progression of osteoarthritis in Trpv4-deficient mice. ACTA ACUST UNITED AC 2010; 62:2973-83. [PMID: 20583100 DOI: 10.1002/art.27624] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Mechanical loading significantly influences the physiology and pathology of articular cartilage, although the mechanisms of mechanical signal transduction are not fully understood. Transient receptor potential vanilloid 4 (TRPV4) is a Ca(++)-permeable ion channel that is highly expressed by articular chondrocytes and can be gated by osmotic and mechanical stimuli. The goal of this study was to determine the role of Trpv4 in the structure of the mouse knee joint and to determine whether Trpv4(-/-) mice exhibit altered Ca(++) signaling in response to osmotic challenge. METHODS Knee joints of Trpv4(-/-) mice were examined histologically and by microfocal computed tomography for osteoarthritic changes and bone structure at ages 4, 6, 9, and 12 months. Fluorescence imaging was used to quantify chondrocytic Ca(++) signaling within intact femoral cartilage in response to osmotic stimuli. RESULTS Deletion of Trpv4 resulted in severe osteoarthritic changes, including cartilage fibrillation, eburnation, and loss of proteoglycans, that were dependent on age and male sex. Subchondral bone volume and calcified meniscal volume were greatly increased, again in male mice. Chondrocytes from Trpv4(+/+) mice demonstrated significant Ca(++) responses to hypo-osmotic stress but not to hyperosmotic stress. The response to hypo-osmotic stress or to the TRPV4 agonist 4α-phorbol 12,13-didecanoate was eliminated in Trpv4(-/-) mice. CONCLUSION Deletion of Trpv4 leads to a lack of osmotically induced Ca(++) signaling in articular chondrocytes, accompanied by progressive, sex-dependent increases in bone density and osteoarthritic joint degeneration. These findings suggest a critical role for TRPV4-mediated Ca(++) signaling in the maintenance of joint health and normal skeletal structure.
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145
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Hung CT. Transient receptor potential vanilloid 4 channel as an important modulator of chondrocyte mechanotransduction of osmotic loading. ACTA ACUST UNITED AC 2010; 62:2850-1. [PMID: 20583111 DOI: 10.1002/art.27617] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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146
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Inhibition of the cation channel TRPV4 improves bladder function in mice and rats with cyclophosphamide-induced cystitis. Proc Natl Acad Sci U S A 2010; 107:19084-9. [PMID: 20956320 DOI: 10.1073/pnas.1005333107] [Citation(s) in RCA: 312] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Reduced functional bladder capacity and concomitant increased micturition frequency (pollakisuria) are common lower urinary tract symptoms associated with conditions such as cystitis, prostatic hyperplasia, neurological disease, and overactive bladder syndrome. These symptoms can profoundly affect the quality of life of afflicted individuals, but available pharmacological treatments are often unsatisfactory. Recent work has demonstrated that the cation channel TRPV4 is highly expressed in urothelial cells and plays a role in sensing the normal filling state of the bladder. In this article, we show that the development of cystitis-induced bladder dysfunction is strongly impaired in Trpv4(-/-) mice. Moreover, we describe HC-067047, a previously uncharacterized, potent, and selective TRPV4 antagonist that increases functional bladder capacity and reduces micturition frequency in WT mice and rats with cystitis. HC-067047 did not affect bladder function in Trpv4(-/-) mice, demonstrating that its in vivo effects are on target. These results indicate that TRPV4 antagonists may provide a promising means of treating bladder dysfunction.
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147
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Abstract
The skeletal dysplasias (osteochondrodysplasias) are a heterogeneous group of more than 350 disorders frequently associated with orthopedic complications and varying degrees of dwarfism or short stature. These disorders are diagnosed based on radiographic, clinical, and molecular criteria. The molecular mechanisms have been elucidated in many of these disorders providing for improved clinical diagnosis and reproductive choices for affected individuals and their families. An increasing variety of medical and surgical treatment options can be offered to affected individuals to try to improve their quality of life and lifespan.
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148
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Nishimura G, Dai J, Lausch E, Unger S, Megarbané A, Kitoh H, Kim OH, Cho TJ, Bedeschi F, Benedicenti F, Mendoza-Londono R, Silengo M, Schmidt-Rimpler M, Spranger J, Zabel B, Ikegawa S, Superti-Furga A. Spondylo-epiphyseal dysplasia, Maroteaux type (pseudo-Morquio syndrome type 2), and parastremmatic dysplasia are caused by TRPV4 mutations. Am J Med Genet A 2010; 152A:1443-9. [PMID: 20503319 DOI: 10.1002/ajmg.a.33414] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Recent discoveries have established the existence of a family of skeletal dysplasias caused by dominant mutations in TRPV4. This family comprises, in order of increasing severity, dominant brachyolmia, spondylo-metaphyseal dysplasia Kozlowski type, and metatropic dysplasia. We tested the hypothesis that a further condition, Spondylo-epiphyseal dysplasia (SED), Maroteaux type (MIM 184095; also known as pseudo-Morquio syndrome type 2), could be caused by TRPV4 mutations. We analyzed six individuals with Maroteaux type SED, including three who had previously been reported. All six patients were found to have heterozygous TRPV4 mutations; three patients had unreported mutations, while three patients had mutations previously described in association with metatropic dysplasia. In addition, we tested one individual with a distinct rare disorder, parastremmatic dysplasia (MIM 168400). This patient had a common, recurrent mutation seen in several patients with Kozlowski type spondylo-metaphyseal dysplasia. We conclude that SED Maroteaux type and parastremmatic dysplasia are part of the TRPV4 dysplasia family and that TRPV4 mutations show considerable variability in phenotypic expression resulting in distinct clinical-radiographic phenotypes.
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Affiliation(s)
- Gen Nishimura
- Department of Radiology, Tokyo Metropolitan Kiyose Children's Hospital, Kiyose, Japan
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149
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Loukin S, Zhou X, Su Z, Saimi Y, Kung C. Wild-type and brachyolmia-causing mutant TRPV4 channels respond directly to stretch force. J Biol Chem 2010; 285:27176-27181. [PMID: 20605796 PMCID: PMC2930716 DOI: 10.1074/jbc.m110.143370] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/24/2010] [Indexed: 11/06/2022] Open
Abstract
Whether animal ion channels functioning as mechanosensors are directly activated by stretch force or indirectly by ligands produced by the stretch is a crucial question. TRPV4, a key molecular model, can be activated by hypotonicity, but the mechanism of activation is unclear. One model has this channel being activated by a downstream product of phospholipase A(2), relegating mechanosensitivity to the enzymes or their regulators. We expressed rat TRPV4 in Xenopus oocytes and repeatedly examined >200 excised patches bathed in a simple buffer. We found that TRPV4 can be activated by tens of mm Hg pipette suctions with open probability rising with suction even in the presence of relevant enzyme inhibitors. Mechanosensitivity of TRPV4 provides the simplest explanation of its various force-related physiological roles, one of which is in the sensing of weight load during bone development. Gain-of-function mutants cause heritable skeletal dysplasias in human. We therefore examined the brachyolmia-causing R616Q gain-of-function channel and found increased whole-cell current densities compared with wild-type channels. Single-channel analysis revealed that R616Q channels maintain mechanosensitivity but have greater constitutive activity and no change in unitary conductance or rectification.
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MESH Headings
- Animals
- Bone Diseases, Developmental/genetics
- Bone Diseases, Developmental/metabolism
- Bone Diseases, Developmental/pathology
- Bone Diseases, Developmental/physiopathology
- Disease Models, Animal
- Genetic Diseases, Inborn/genetics
- Genetic Diseases, Inborn/metabolism
- Genetic Diseases, Inborn/pathology
- Genetic Diseases, Inborn/physiopathology
- Humans
- Mutation, Missense
- Oocytes
- Phospholipases A2/genetics
- Phospholipases A2/metabolism
- Rats
- TRPV Cation Channels/genetics
- TRPV Cation Channels/metabolism
- Weight-Bearing
- Xenopus
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Affiliation(s)
- Stephen Loukin
- Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706.
| | - Xinliang Zhou
- Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706
| | - Zhenwei Su
- Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706
| | - Yoshiro Saimi
- Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706
| | - Ching Kung
- Laboratory of Molecular Biology, University of Wisconsin, Madison, Wisconsin 53706; Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706
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150
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Camacho N, Krakow D, Johnykutty S, Katzman PJ, Pepkowitz S, Vriens J, Nilius B, Boyce BF, Cohn DH. Dominant TRPV4 mutations in nonlethal and lethal metatropic dysplasia. Am J Med Genet A 2010; 152A:1169-77. [PMID: 20425821 DOI: 10.1002/ajmg.a.33392] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Metatropic dysplasia is a clinical heterogeneous skeletal dysplasia characterized by short extremities, a short trunk with progressive kyphoscoliosis, and craniofacial abnormalities that include a prominent forehead, midface hypoplasia, and a squared-off jaw. Dominant mutations in the gene encoding TRPV4, a calcium permeable ion channel, were identified all 10 of a series of metatropic dysplasia cases, ranging in severity from mild to perinatal lethal. These data demonstrate that the lethal form of the disorder is dominantly inherited and suggest locus homogeneity in the disease. Electrophysiological studies demonstrated that the mutations activate the channel, indicating that the mechanism of disease may result from increased calcium in chondrocytes. Histological studies in two cases of lethal metatropic dysplasia revealed markedly disrupted endochondral ossification, with reduced numbers of hypertrophic chondrocytes and presence of islands of cartilage within the zone of primary mineralization. These data suggest that altered chondrocyte differentiation in the growth plate leads to the clinical findings in metatropic dysplasia.
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Affiliation(s)
- Natalia Camacho
- Department of Orthopedic Surgery, University of California at Los Angeles, Los Angeles, CA 90048, USA
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