51
|
Seebacher F, Little AG. Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms. Front Physiol 2017; 8:575. [PMID: 28824463 PMCID: PMC5543086 DOI: 10.3389/fphys.2017.00575] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/25/2017] [Indexed: 12/25/2022] Open
Abstract
Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid) endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM) and the AMP-activated protein kinase (AMPK) both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits.
Collapse
Affiliation(s)
- Frank Seebacher
- School of Life and Environmental Sciences, University of SydneySydney, NSW, Australia
| | - Alexander G Little
- Rosenstiel School of Marine and Atmospheric Science, The University of MiamiMiami, FL, United States
| |
Collapse
|
52
|
Fujita T, Higashitsuji H, Higashitsuji H, Liu Y, Itoh K, Sakurai T, Kojima T, Kandori S, Nishiyama H, Fukumoto M, Fukumoto M, Shibasaki K, Fujita J. TRPV4-dependent induction of a novel mammalian cold-inducible protein SRSF5 as well as CIRP and RBM3. Sci Rep 2017; 7:2295. [PMID: 28536481 PMCID: PMC5442135 DOI: 10.1038/s41598-017-02473-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 04/11/2017] [Indexed: 02/06/2023] Open
Abstract
Cold-inducible RNA-binding protein (CIRP) and RNA-binding motif protein 3 (RBM3) are two evolutionarily conserved RNA-binding proteins that are structurally related to hnRNPs and upregulated in response to moderately low temperatures in mammalian cells. Although contributions of splicing efficiency, the gene promoters activated upon mild hypothermia and the transcription factor Sp1 to induction of CIRP have been reported, precise mechanisms by which hypothermia and other stresses induce the expression of mammalian cold-inducible proteins (CIPs) are poorly understood. By screening the serine/arginine-rich splicing factors (SRSFs), we report that the transcript and protein levels of SRSF5 were increased in mammalian cells cultured at 32 °C. Expression of SRSF5 as well as CIRP and RBM3 were also induced by DNA damage, hypoxia, cycloheximide and hypotonicity. Immunohistochemical studies demonstrated that SRSF5 was constitutively expressed in male germ cells and the level was decreased in human testicular germ cell tumors. SRSF5 facilitated production of p19 H-RAS, and increased sensitivity to doxorubicin in human U-2 OS cells. Induction of CIPs was dependent on transient receptor potential vanilloid 4 (TRPV4) channel protein, but seemed independent of its ion channel activity. These findings indicate a previously unappreciated role for the TRP protein in linking environmental stress to splicing.
Collapse
Affiliation(s)
- Takanori Fujita
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan.,School of Economics, Nagoya University, Nagoya, Nagoya, 464-8601, Japan
| | - Hiroaki Higashitsuji
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan
| | - Hisako Higashitsuji
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan
| | - Yu Liu
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan
| | - Katsuhiko Itoh
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan
| | - Toshiharu Sakurai
- Department of Gastroenterology and Hepatology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, 589-8511, Japan
| | - Takahiro Kojima
- Department of Urology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan
| | - Shuya Kandori
- Department of Urology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan
| | - Hiroyuki Nishiyama
- Department of Urology, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, 305-8575, Japan
| | - Motoi Fukumoto
- Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi, 980-8575, Japan
| | - Manabu Fukumoto
- Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi, 980-8575, Japan.,Department of Molecular Pathology, Tokyo Medical University, Shinjuku-ku, Tokyo, 160-8402, Japan
| | - Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Gunma, 371-8511, Japan
| | - Jun Fujita
- Department of Clinical Molecular Biology, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, 606-8507, Japan. .,Department of Rehabilitation Medicine, Biwako-Chuo Hospital, Otsu, Shiga, 520-0834, Japan.
| |
Collapse
|
53
|
White JPM, Cibelli M, Urban L, Nilius B, McGeown JG, Nagy I. TRPV4: Molecular Conductor of a Diverse Orchestra. Physiol Rev 2017; 96:911-73. [PMID: 27252279 DOI: 10.1152/physrev.00016.2015] [Citation(s) in RCA: 263] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Transient receptor potential vanilloid type 4 (TRPV4) is a calcium-permeable nonselective cation channel, originally described in 2000 by research teams led by Schultz (Nat Cell Biol 2: 695-702, 2000) and Liedtke (Cell 103: 525-535, 2000). TRPV4 is now recognized as being a polymodal ionotropic receptor that is activated by a disparate array of stimuli, ranging from hypotonicity to heat and acidic pH. Importantly, this ion channel is constitutively expressed and capable of spontaneous activity in the absence of agonist stimulation, which suggests that it serves important physiological functions, as does its widespread dissemination throughout the body and its capacity to interact with other proteins. Not surprisingly, therefore, it has emerged more recently that TRPV4 fulfills a great number of important physiological roles and that various disease states are attributable to the absence, or abnormal functioning, of this ion channel. Here, we review the known characteristics of this ion channel's structure, localization and function, including its activators, and examine its functional importance in health and disease.
Collapse
Affiliation(s)
- John P M White
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Mario Cibelli
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Laszlo Urban
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Bernd Nilius
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - J Graham McGeown
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| | - Istvan Nagy
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Anaesthetics, The Queen Elizabeth Hospital, Birmingham, United Kingdom; Academic Department of Anaesthesia and Intensive Care Medicine, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham, United Kingdom; Preclinical Secondary Pharmacology, Preclinical Safety, Novartis Institute for Biomedical Research, Cambridge, Massachusetts; Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg, Leuven, Belgium; and School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, United Kingdom
| |
Collapse
|
54
|
Shavit-Stein E, Artan-Furman A, Feingold E, Ben Shimon M, Itzekson-Hayosh Z, Chapman J, Vlachos A, Maggio N. Protease Activated Receptor 2 (PAR2) Induces Long-Term Depression in the Hippocampus through Transient Receptor Potential Vanilloid 4 (TRPV4). Front Mol Neurosci 2017; 10:42. [PMID: 28303089 PMCID: PMC5332813 DOI: 10.3389/fnmol.2017.00042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 02/07/2017] [Indexed: 11/25/2022] Open
Abstract
Protease activated receptors (PARs) are involved in regulating synaptic transmission and plasticity in the brain. While it is well-accepted that PAR1 mediates long-term potentiation (LTP) of excitatory synaptic strength, the role of PAR2 in synaptic plasticity remains not well-understood. In this study, we assessed the role of PAR2-signaling in plasticity at hippocampal Schaffer collateral-CA1 synapses. Using field potential recordings, we report that PAR2-activation leads to long-term depression (LTD) of synaptic transmission through a protein kinase A -dependent, Transient Receptor Potential Vanilloid 4 -mediated mechanism, which requires the activation of N-methyl-D-aspartate receptors. These results demonstrate that the effects of PAR2 on synaptic plasticity are distinct from what is observed upon PAR1-activation. Thus, we propose that the activation of different classes of PARs, i.e., PAR1 and PAR2, may set the threshold of synaptic plasticity in the hippocampal network by balancing LTP and LTD.
Collapse
Affiliation(s)
- Efrat Shavit-Stein
- Department of Neurology, The Chaim Sheba Medical Center Tel HaShomer, Israel
| | - Avital Artan-Furman
- Department of Neurology, The Chaim Sheba Medical Center Tel HaShomer, Israel
| | - Ekaterina Feingold
- Department of Neurology, The Chaim Sheba Medical Center Tel HaShomer, Israel
| | - Marina Ben Shimon
- Department of Neurology, The Chaim Sheba Medical CenterTel HaShomer, Israel; Department of Neurology and Neurosurgery, Sackler Faculty of Medicine, Tel Aviv UniversityTel Aviv, Israel
| | | | - Joab Chapman
- Department of Neurology, The Chaim Sheba Medical CenterTel HaShomer, Israel; Department of Neurology and Neurosurgery, Sackler Faculty of Medicine, Tel Aviv UniversityTel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv UniversityTel Aviv, Israel
| | - Andreas Vlachos
- Institute of Anatomy II, Faculty of Medicine, Heinrich-Heine-University Duesseldorf, Germany
| | - Nicola Maggio
- Department of Neurology, The Chaim Sheba Medical CenterTel HaShomer, Israel; Department of Neurology and Neurosurgery, Sackler Faculty of Medicine, Tel Aviv UniversityTel Aviv, Israel; Sagol School of Neuroscience, Tel Aviv UniversityTel Aviv, Israel; Talpiot Medical Leadership Program, The Chaim Sheba Medical CenterTel HaShomer, Israel
| |
Collapse
|
55
|
Sugio S, Nagasawa M, Kojima I, Ishizaki Y, Shibasaki K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility. FASEB J 2016; 31:1368-1381. [PMID: 28007781 DOI: 10.1096/fj.201600686rr] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 12/12/2016] [Indexed: 11/11/2022]
Abstract
We have previously reported that transient receptor potential vanilloid 2 (TRPV2) can be activated by mechanical stimulation, which enhances axonal outgrowth in developing neurons; however, the molecular mechanisms that govern the contribution of TRPV2 activation to axonal outgrowth remain unclear. In the present study, we examined this mechanism by using PC12 cells as a neuronal model. Overexpression of TRPV2 enhanced axonal outgrowth in a mechanical stimulus-dependent manner. Accumulation of TRPV2 at the cell surface was 4-fold greater in the growth cone compared with the soma. In the growth cone, TRPV2 is not static, but dynamically accumulates (within ∼100 ms) to the site of mechanical stimulation. The dynamic and acute clustering of TRPV2 can enhance very weak mechanical stimuli via focal accumulation of TRPV2. Focal application of mechanical stimuli dramatically increased growth cone motility and caused actin reorganization via activation of TRPV2. We also found that TRPV2 physically interacts with actin and that changes in the actin cytoskeleton are required for its activation. Here, we demonstrated for the first time to our knowledge that TRPV2 clustering is induced by mechanical stimulation generated by axonal outgrowth and that TRPV2 activation is triggered by actin rearrangements that result from mechanical stimulation. Moreover, TRPV2 activation enhances growth cone motility and actin accumulation to promote axonal outgrowth. Sugio, S., Nagasawa, M., Kojima, I., Ishizaki, Y., Shibasaki, K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility.
Collapse
Affiliation(s)
- Shouta Sugio
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masami Nagasawa
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Itaru Kojima
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yasuki Ishizaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan;
| |
Collapse
|
56
|
Kanju P, Liedtke W. Pleiotropic function of TRPV4 ion channels in the central nervous system. Exp Physiol 2016; 101:1472-1476. [PMID: 27701788 DOI: 10.1113/ep085790] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 09/30/2016] [Indexed: 12/28/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this concise review, we highlight insights into the role of transient receptor potential, vanilloid type 4 (TRPV4) ion channels in the CNS, results that have been contributed over the last 16 years since the initial discovery of the channel. What advances does it highlight? TRPV4 has been found to function in neurons, astroglia and microglia, both in physiological (e.g. astrocytic neurovascular coupling, neuronal membrane potential at physiological temperature) and in pathological conditions (e.g. mechanical trauma), so far recorded as exciting findings in need of more in-depth mechanistic clarification. Transient receptor potential, vanilloid type 4 (TRPV4) ion channels are osmo-mechano-TRP channels, with pleiotropic function and expression in many different types of tissues and cells. They have also been found to be involved in pain and inflammation. Studies have focused on the role of TRPV4 in peripheral sensory neurons, but its expression and function in central nervous glial cells and neurons has also been documented. In this overview, based on the senior author's (WL) lecture at the recent recent joint meeting of APS/The Physiological Society in Dublin, we concisely review evidence of TRPV4 expression and function in the CNS and how TRPV4 function can be modulated for therapeutic benefit of neuropsychiatric disorders. Novel TRPV4-inhibitory compounds developed recently in the authors' laboratory are also discussed.
Collapse
Affiliation(s)
- Patrick Kanju
- Department of Neurology, Duke University, Durham, NC, 27710, USA
| | - Wolfgang Liedtke
- Department of Neurology, Duke University, Durham, NC, 27710, USA
| |
Collapse
|
57
|
Shibasaki K. Physiological significance of TRPV2 as a mechanosensor, thermosensor and lipid sensor. J Physiol Sci 2016; 66:359-65. [PMID: 26841959 PMCID: PMC10717341 DOI: 10.1007/s12576-016-0434-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 01/21/2016] [Indexed: 11/28/2022]
Abstract
This review provides a summary of the physiological significance of the TRPV2 ion channel. While TRPV2 was initially characterized as a noxious heat sensor, we found that TRPV2 can also act as a mechanosensor in embryonic neurons or adult myenteric neurons. Here, we summarize the newly characterized functions of TRPV2, including the research progress that has been made toward our understanding of TRPV2 physiology, and discuss other recent data pertaining to TRPV2. It is thought that TRPV2 may be an important drug target based on its broad expression patterns and important physiological roles. The possible associations between diseases and TRPV2 are also discussed.
Collapse
Affiliation(s)
- Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan.
| |
Collapse
|
58
|
Shibasaki K, Hosoi N, Kaneko R, Tominaga M, Yamada K. Glycine release from astrocytes via functional reversal of GlyT1. J Neurochem 2016; 140:395-403. [PMID: 27419919 DOI: 10.1111/jnc.13741] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/14/2016] [Accepted: 07/07/2016] [Indexed: 11/30/2022]
Abstract
It was previously reported that functional glycine receptors were expressed in neonatal prefrontal cortex; however, the glycine-releasing cells were unknown. We hypothesized that astrocytes might be a major glycine source, and examined the glycine release properties of astrocytes. We also hypothesized that dopamine (DA) might be a trigger for the astrocytic glycine release, as numerous DA terminals localize in the cortex. We combined two different methods to confirm the glycine release from astrocytes. Firstly, we analyzed the supernatant of astrocytes by amino acid analyzer after DA stimulation, and detect significant glycine peak. Furthermore, we utilized a patch-clamp biosensor method to confirm the glycine release from astrocytes by using GlyRα1 and Glyβ-expressing HEK293T cells, and detected significant glycine-evoked current upon DA stimulation. Thus, we clearly demonstrated that DA induces glycine release from astrocytes. Surprisingly, DA caused a functional reversal of astrocytic glycine transporter 1, an astrocytic type of glycine transporter, causing astrocytes to release glycine. Hence, astrocytes transduce pre-synaptic DA signals to glycine signals through a reversal of astrocytic glycine transporter 1 to regulate neuronal excitability. Cover Image for this issue: doi: 10.1111/jnc.13785.
Collapse
Affiliation(s)
- Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan.,Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan.,Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Nobutake Hosoi
- Department of Neurophysiology and Neural Repair, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Ryosuke Kaneko
- Bioresource Center, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Makoto Tominaga
- Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki, Japan.,Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Katsuya Yamada
- Department of Physiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| |
Collapse
|
59
|
Abstract
This review provides a summary of the physiological significance of the TRPV4 ion channel. Although TRPV4 was initially characterized as an osmosensor, we found that TRPV4 can also act as a thermosensor or a mechanosensor in brain neurons or epithelial cells in the urinary bladder. Here, we summarize the newly characterized functions of TRPV4, including the research progress that has been made toward our understanding of TRPV4 physiology, and discuss other recent data pertaining to TRPV4. It is thought that TRPV4 may be an important drug target based on its broad expression patterns and important physiological functions. Possible associations between diseases and TRPV4 are also discussed.
Collapse
Affiliation(s)
- Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, 371-8511, Japan.
| |
Collapse
|
60
|
Belanger-Willoughby N, Linehan V, Hirasawa M. Thermosensing mechanisms and their impairment by high-fat diet in orexin neurons. Neuroscience 2016; 324:82-91. [PMID: 26964685 DOI: 10.1016/j.neuroscience.2016.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 03/01/2016] [Accepted: 03/02/2016] [Indexed: 01/12/2023]
Abstract
In homeotherms, the hypothalamus controls thermoregulatory and adaptive mechanisms in energy balance, sleep-wake and locomotor activity to maintain optimal body temperature. Orexin neurons may be involved in these functions as they promote thermogenesis, food intake and behavioral arousal, and are sensitive to temperature and metabolic status. How thermal and energy balance signals are integrated in these neurons is unknown. Thus, we investigated the cellular mechanisms of thermosensing in orexin neurons and their response to a change in energy status using whole-cell patch clamp on rat brain slices. We found that warming induced an increase in miniature excitatory postsynaptic current (EPSC) frequency, which was blocked by the transient receptor potential vanilloid-1 (TRPV1) receptor antagonist AMG9810 and mimicked by its agonist capsaicin, suggesting that the synaptic effect is mediated by heat-sensitive TRPV1 channels. Furthermore, warming inhibits orexin neurons by activating ATP-sensitive potassium (KATP) channels, an effect regulated by uncoupling protein 2 (UCP2), as the UCP2 inhibitor genipin abolished this response. These properties are unique to orexin neurons in the lateral hypothalamus, as neighboring melanin-concentrating hormone neurons showed no response to warming within the physiological temperature range. Interestingly, in rats fed with western diet for 1 or 11weeks, orexin neurons had impaired synaptic and KATP response to warming. In summary, this study reveals several mechanisms underlying thermosensing in orexin neurons and their attenuation by western diet. Overeating induced by western diet may in part be due to impaired orexin thermosensing, as post-prandial thermogenesis may promote satiety and lethargy by inhibiting orexin neurons.
Collapse
Affiliation(s)
- N Belanger-Willoughby
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, Newfoundland A1B 3V6, Canada
| | - V Linehan
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, Newfoundland A1B 3V6, Canada
| | - M Hirasawa
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, Newfoundland A1B 3V6, Canada.
| |
Collapse
|