1
|
Huang J, Korsunsky A, Yazdani M, Chen J. Targeting TRP channels: recent advances in structure, ligand binding, and molecular mechanisms. Front Mol Neurosci 2024; 16:1334370. [PMID: 38273937 PMCID: PMC10808746 DOI: 10.3389/fnmol.2023.1334370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/26/2023] [Indexed: 01/27/2024] Open
Abstract
Transient receptor potential (TRP) channels are a large and diverse family of transmembrane ion channels that are widely expressed, have important physiological roles, and are associated with many human diseases. These proteins are actively pursued as promising drug targets, benefitting greatly from advances in structural and mechanistic studies of TRP channels. At the same time, the complex, polymodal activation and regulation of TRP channels have presented formidable challenges. In this short review, we summarize recent progresses toward understanding the structural basis of TRP channel function, as well as potential ligand binding sites that could be targeted for therapeutics. A particular focus is on the current understanding of the molecular mechanisms of TRP channel activation and regulation, where many fundamental questions remain unanswered. We believe that a deeper understanding of the functional mechanisms of TRP channels will be critical and likely transformative toward developing successful therapeutic strategies targeting these exciting proteins. This endeavor will require concerted efforts from computation, structural biology, medicinal chemistry, electrophysiology, pharmacology, drug safety and clinical studies.
Collapse
Affiliation(s)
- Jian Huang
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | - Aron Korsunsky
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | - Mahdieh Yazdani
- Modeling and Informatics, Merck & Co., Inc., West Point, PA, United States
| | - Jianhan Chen
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| |
Collapse
|
2
|
Leong IL, Yu CM, Shiao LR, Chan P, Wu KC, Leung YM. Sensitivity of Ca 2+-sensing receptor-transient receptor potential-mediated Ca 2+ influx to extracellular acidity in bEND.3 endothelial cells. CHINESE J PHYSIOL 2022; 65:277-281. [PMID: 36588353 DOI: 10.4103/0304-4920.365460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Ca2+-sensing receptors (CaSRs) are G protein-coupled receptors activated by elevated concentrations of extracellular Ca2+. In our previous works, we showed protein and functional expression of CaSR in mouse cerebral endothelial cell (EC) (bEND.3); the CaSR response (high Ca2+-elicited cytosolic [Ca2+] elevation) was unaffected by suppression of phospholipase C but in part involved Ca2+ influx through transient receptor potential V1 (TRPV1) channels. In this work, we investigated if extracellular acidity affected CaSR-mediated Ca2+ influx triggered by high (3 mM) Ca2+ (CaSR agonist), 3 mM spermine (CaSR agonist), and 10 mM cinacalcet (positive allosteric modulator of CaSR). Extracellular acidosis (pH 6.8 and pH 6.0) strongly suppressed cytosolic [Ca2+] elevation triggered by high Ca2+, spermine, and cinacalcet; acidosis also inhibited Mn2+ influx stimulated by high Ca2+ and cinacalcet. Purinoceptor-triggered Ca2+ response, however, was not suppressed by acidosis. Extracellular acidity also did not affect membrane potential, suggesting suppressed CaSR-mediated Ca2+ influx in acidity did not result from the reduced electrical driving force for Ca2+. Our results suggest Ca2+ influx through a putative CaSR-TRP complex in bEND.3 EC was sensitive to extracellular pH.
Collapse
Affiliation(s)
- Iat-Lon Leong
- Division of Cardiology, Department of Internal Medicine, Kiang Wu Hospital, Macau, China
| | - Chung-Ming Yu
- Department of Anesthesiology, Chang Gung Memorial Hospital, Chiayi, Taiwan
| | - Lian-Ru Shiao
- Department of Physiology, China Medical University, Taichung, Taiwan
| | - Paul Chan
- Division of Cardiology, Department of Medicine, Taipei Medical University Wan Fang Hospital, Taipei, Taiwan
| | - King-Chuen Wu
- Department of Anesthesiology, Chang Gung Memorial Hospital, Chiayi; Department of Nursing, Chang Gung University of Science and Technology, Chiayi; Department of Information Management, Shu-Zen Junior College of Medicine and Management, Kaohsiung, Taiwan
| | - Yuk-Man Leung
- Department of Physiology, China Medical University, Taichung, Taiwan
| |
Collapse
|
3
|
Jeong S, Ko J, Kim M, Park KC, Park EYJ, Kim J, Baik Y, Wie J, Cho AE, Jeon JH, So I. Englerin A-sensing charged residues for transient receptor potential canonical 5 channel activation. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2019; 23:191-201. [PMID: 31080350 PMCID: PMC6488704 DOI: 10.4196/kjpp.2019.23.3.191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 03/25/2019] [Accepted: 03/26/2019] [Indexed: 11/17/2022]
Abstract
The transient receptor potential canonical (TRPC) 5 channel, known as a nonselective cation channel, has a crucial role in calcium influx. TRPC5 has been reported to be activated by muscarinic receptor activation and extracellular pH change and inhibited by the protein kinase C pathway. Recent studies have also suggested that TRPC5 is extracellularly activated by englerin A (EA), but the mechanism remains unclear. The purpose of this study is to identify the EA-interaction sites in TRPC5 and thereby clarify the mechanism of TRPC5 activation. TRPC5 channels are over-expressed in human embryonic kidney (HEK293) cells. TRPC5 mutants were generated by site-directed mutagenesis. The whole-cell patch-clamp configuration was used to record TRPC5 currents. Western analysis was also performed to observe the expression of TRPC5 mutants. To identify the EA-interaction site in TRPC5, we first generated pore mutants. When screening the mutants with EA, we observed the EA-induced current increases of TRPC5 abolished in K554N, H594N, and E598Q mutants. The current increases of other mutants were reduced in different levels. We also examined the functional intactness of the mutants that had no effect by EA with TRPC5 agonists, such as carbachol or GTPγS. Our results suggest that the three residues, Lys-554, His-594, and Glu-598, in TRPC5 might be responsible for direct interaction with EA, inducing the channel activation. We also suggest that although other pore residues are not critical, they could partly contribute to the EA-induced channel activation.
Collapse
Affiliation(s)
- SeungJoo Jeong
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Juyeon Ko
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Minji Kim
- College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Korea
| | - Ki Chul Park
- Department of Bioinformatics, Korea University, Sejong 30019, Korea
| | - Eunice Yon June Park
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Jinsung Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Youngjoo Baik
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Jinhong Wie
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Art E Cho
- Department of Bioinformatics, Korea University, Sejong 30019, Korea
| | - Ju-Hong Jeon
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea
| |
Collapse
|
4
|
Patrone LGA, Duarte JB, Bícego KC, Steiner AA, Romanovsky AA, Gargaglioni LH. TRPV1 Inhibits the Ventilatory Response to Hypoxia in Adult Rats, but Not the CO₂-Drive to Breathe. Pharmaceuticals (Basel) 2019; 12:ph12010019. [PMID: 30682830 PMCID: PMC6469189 DOI: 10.3390/ph12010019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 11/27/2018] [Accepted: 12/07/2018] [Indexed: 12/31/2022] Open
Abstract
Receptors of the transient receptor potential (TRP) channels superfamily are expressed in many tissues and have different physiological functions. However, there are few studies investigating the role of these channels in cardiorespiratory control in mammals. We assessed the role of central and peripheral TRPV1 receptors in the cardiorespiratory responses to hypoxia (10% O2) and hypercapnia (7% CO2) by measuring pulmonary ventilation (V˙E), heart rate (HR), mean arterial pressure (MAP) and body temperature (Tb) of male Wistar rats before and after intraperitoneal (AMG9810 [2.85 µg/kg, 1 mL/kg]) or intracebroventricular (AMG9810 [2.85 µg/kg, 1 µL] or AMG7905 [28.5 μg/kg, 1 µL]) injections of TRPV1 antagonists. Central or peripheral injection of TRPV1 antagonists did not change cardiorespiratory parameters or Tb during room air and hypercapnic conditions. However, the hypoxic ventilatory response was exaggerated by both central and peripheral injection of AMG9810. In addition, the peripheral antagonist blunted the drop in Tb induced by hypoxia. Therefore, the current data provide evidence that TRPV1 channels exert an inhibitory modulation on the hypoxic drive to breathe and stimulate the Tb reduction during hypoxia.
Collapse
Affiliation(s)
- Luis Gustavo A Patrone
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Jaime B Duarte
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Kênia Cardoso Bícego
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| | - Alexandre A Steiner
- Department of Immunology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-090, Brazil.
| | - Andrej A Romanovsky
- Thermoregulation and Systemic Inflammation Laboratory (FeverLab), Trauma Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ 85013, USA.
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, Faculty of Agricultural and Veterinarian Sciences, UNESP at Jaboticabal, Rod. Prof. Paulo Donato Castellane s/n, Jaboticabal SP 14870-000, Brazil.
| |
Collapse
|
5
|
Myeong J, Kwak M, Jeon JP, Hong C, Jeon JH, So I. Close spatio-association of the transient receptor potential canonical 4 (TRPC4) channel with Gαi in TRPC4 activation process. Am J Physiol Cell Physiol 2015; 308:C879-89. [PMID: 25788576 DOI: 10.1152/ajpcell.00374.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 03/12/2015] [Indexed: 01/03/2023]
Abstract
TPRC channels are Ca(2+)-permeable, nonselective cation channels that are activated by a wide variety of stimuli, including G protein-coupled receptors (GPCRs). TRPC4 is commonly assumed to be activated by Gq/phospholipase C-coupled receptors. However, the other molecular mechanisms by which Gα proteins regulate TRPC4 remain unclear. Here, we found that Gαi2 regulates TRPC4 activation by direct binding. To investigate this mechanism, we used whole patch clamp and fluorescence resonance energy transfer (FRET). We tagged an isoform of mTRPC4 and G protein with CFP and YFP, respectively, and transiently transfected cells with the FRET pair. The FRET efficiency between TRPC4β-CFP and the constitutively active mutant form of Gαi2 was nearly 15% and was greater than that observed with wild-type Gαi2 (nearly 5%). Gβγ and the TRPC4 channel showed a FRET efficiency lower than 6%. In HEK293 cells transfected with the M2 muscarinic receptor, the application of carbachol increased the FRET efficiency between TRPC4β-CFP and Gαi2(WT)-YFP from 4.7 ± 0.4% (n = 7) to 12.6 ± 1.4% (n = 7). We also found that the TRPC4 channel directly interacts with Gαi2, but not with Gαq, when the channel is open. We analyzed the calcium levels in HEK293 cells expressing the channels and Gαi2 or Gαq using the calcium indicator YC6.1 (Yellow Cameleon 6.1). In response to the muscarinic agonist carbachol, M2-, Gαi2-, and TRPC4-expressing cells showed a prolonged Ca(2+) influx compared with cells expressing only M2. Together, these data suggest that Gαi2 activates the TRPC4 channel by direct binding, which then induces Ca(2+) entry.
Collapse
Affiliation(s)
- JongYun Myeong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Misun Kwak
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Jae-Pyo Jeon
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas
| | - Chansik Hong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Ju-Hong Jeon
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea; and
| |
Collapse
|
6
|
Myeong J, Kwak M, Hong C, Jeon JH, So I. Identification of a membrane-targeting domain of the transient receptor potential canonical (TRPC)4 channel unrelated to its formation of a tetrameric structure. J Biol Chem 2014; 289:34990-5002. [PMID: 25349210 DOI: 10.1074/jbc.m114.584649] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Canonical transient receptor potential (TRPC) channels are Ca(2+)-permeable nonselective cation channels that are activated by a wide variety of stimuli, including G protein-coupled receptors (GPCRs). The TRPC4 channel is expressed in a punctate distribution in the membrane. To identify the regulating region of the channel trafficking to the membrane, we generated deletion mutants of the TRPC4 channel. We determined that when either region that was downstream of the 20 amino acids of the N terminus or the 700-730 amino acids was deleted, the mutants were retained in the endoplasmic reticulum. By coexpression of the wild-type TRPC4 with deletion mutants, we found that the 23-29 amino acids of the N terminus regulate a membrane trafficking. Additionally, by the fluorescence resonance energy transfer (FRET) method, we found that the regions downstream of the 99 amino acid region of the N terminus and upstream of the 730 amino acid region in the C terminus produce assembly of the TRPC4 tetramers. We inferred the candidate proteins that regulate or interact with the 23-29 domain of TRPC4.
Collapse
Affiliation(s)
- Jongyun Myeong
- From the Department of Physiology, Seoul National University College of Medicine
| | - Misun Kwak
- From the Department of Physiology, Seoul National University College of Medicine
| | - Chansik Hong
- From the Department of Physiology, Seoul National University College of Medicine
| | - Ju-Hong Jeon
- From the Department of Physiology, Seoul National University College of Medicine
| | - Insuk So
- From the Department of Physiology, Seoul National University College of Medicine
| |
Collapse
|
7
|
Hong C, Kwak M, Myeong J, Ha K, Wie J, Jeon JH, So I. Extracellular disulfide bridges stabilize TRPC5 dimerization, trafficking, and activity. Pflugers Arch 2014; 467:703-12. [PMID: 24859801 DOI: 10.1007/s00424-014-1540-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 05/04/2014] [Accepted: 05/16/2014] [Indexed: 12/01/2022]
Abstract
Crucial cysteine residues can be involved in the modulation of protein activity via the modification of thiol (-SH) groups. Among these reactions, disulfide bonds (S-S) play a key role in the folding, stability, and activity of membrane proteins. However, the regulation of extracellular cysteines in classical transient receptor potential (TRPC) channels remains controversial. Here, we examine the functional importance of the extracellular disulfide bond in TRPC5 in modulating channel gating and trafficking. Specifically, we investigated TRPC5 activity in transiently transfected HEK293 cells with wild-type (WT) or cysteine (C553 and C558) mutants in the pore loop. Using reducing agents, we determined that a disulfide linkage mediates the tetrameric formation of the TRPC5 channel. By measuring the TRPC5 current, we observed that C553S or C558S mutants completely lose channel activity induced by lanthanides or receptor stimulation. Co-expression of TRPC5 (WT) with mutants demonstrated a dominant-negative function in mutants, which inhibited the activity of TRPC5 (WT). We generated TRPC5-TRPC5 dimers and observed reduced activity of WT-mutant (C553S or C558S) dimers compared to WT-WT dimers. When pretreated with reducing agents for 12 h, the TRPC5 current decreased due to a reduction in membrane TRPC5 distribution. In addition, we identified a reduced expression of C553S mutant in plasma membrane. We analyzed a dimeric interaction of wild-type and mutant TRPC5 using co-immunoprecipitation and FRET method, indicating a weak interaction between dimeric partners. These results indicated that the disulfide bond between conserved extracellular cysteines, especially C553, is essential for functional TRPC5 activity by channel multimerization and trafficking.
Collapse
Affiliation(s)
- Chansik Hong
- Department of Physiology and Institute of Dermatological Science, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, 110-799, South Korea
| | | | | | | | | | | | | |
Collapse
|
8
|
Abstract
Transient receptor potential (TRP) channels are cellular sensors for a wide spectrum of physical and chemical stimuli. They are involved in the formation of sight, hearing, touch, smell, taste, temperature, and pain sensation. TRP channels also play fundamental roles in cell signaling and allow the host cell to respond to benign or harmful environmental changes. As TRP channel activation is controlled by very diverse processes and, in many cases, exhibits complex polymodal properties, understanding how each TRP channel responds to its unique forms of activation energy is both crucial and challenging. The past two decades witnessed significant advances in understanding the molecular mechanisms that underlie TRP channels activation. This review focuses on our current understanding of the molecular determinants for TRP channel activation.
Collapse
Affiliation(s)
- Jie Zheng
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, California, USA.
| |
Collapse
|
9
|
Kim H, Jeon JP, Hong C, Kim J, Myeong J, Jeon JH, So I. An essential role of PI(4,5)P₂ for maintaining the activity of the transient receptor potential canonical (TRPC)4β. Pflugers Arch 2013; 465:1011-21. [PMID: 23417604 DOI: 10.1007/s00424-013-1236-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 01/30/2013] [Accepted: 01/31/2013] [Indexed: 01/21/2023]
Abstract
The transient receptor potential canonical 4 (TRPC4) channel is a Ca(2+)-permeable nonselective cation channel in mammalian cells and mediates a number of cellular functions. Many studies show that TRPC channels are activated by stimulation of Gαq-phospholipase C (PLC)-coupled receptors. However, our previous study showed that the TRPC4 current was inhibited by co-expression of a constitutively active form of Gαq (Gαq (Q209L)). A shortage of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] in Gαq (Q209L) may be responsible for reduced TRPC4 activity. Here, we tested this hypothesis by using a rapamycin-inducible system that regulates PI(4,5)P2 acutely and specifically. Our results showed that the TRPC4β current was reduced by inducible Gαq (Q209L), but not by the mutants with impaired binding ability to PLCβ. Depletion of PI(4,5)P2 by inducing the inositol polyphosphate 5-phosphatase to HEK293 cells that express TRPC4β led to an irreversible inhibition of TRPC4β currents. In contrast, inducing phosphatidylinositol 4-phosphate 5-kinase or intracellular PI(4,5)P2 application did not activate the TRPC4β current. Finally, we revealed that PI(4,5)P2 is important in delaying the desensitization of TRPC4β. Taken together, we suggest that PI(4,5)P2 is not the activator of TRPC4β activation, but it is still necessary for regulating TRPC4β activation.
Collapse
Affiliation(s)
- Hana Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
10
|
TRPC5 channel is the mediator of neurotrophin-3 in regulating dendritic growth via CaMKIIα in rat hippocampal neurons. J Neurosci 2012; 32:9383-95. [PMID: 22764246 DOI: 10.1523/jneurosci.6363-11.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Neurotrophin-3 (NT-3) plays numerous important roles in the CNS and the elevation of intracellular Ca(2+) ([Ca(2+)](i)) is critical for these functions of NT-3. However, the mechanism by which NT-3 induces [Ca(2+)](i) elevation remains largely unknown. Here, we found that transient receptor potential canonical (TRPC) 5 protein and TrkC, the NT-3 receptor, exhibited a similar temporal expression in rat hippocampus and cellular colocalization in hippocampal neurons. Stimulation of the neurons by NT-3 induced a nonselective cation conductance and PLCγ-dependent [Ca(2+)](i) elevation, which were both blocked when TRPC5, but not TRPC6 channels, were inhibited. Moreover, the Ca(2+) influx through TRPC5 induced by NT-3 inhibited the neuronal dendritic growth through activation of calmodulin-dependent kinase (CaMK) IIα. In contrast, the Ca(2+) influx through TRPC6 induced by NT-4 promoted the dendritic growth. Thus, TRPC5 acts as a novel and specific mediator for NT-3 to regulate dendrite development through CaMKIIα.
Collapse
|
11
|
Kim H, Kim J, Jeon JP, Myeong J, Wie J, Hong C, Kim HJ, Jeon JH, So I. The roles of G proteins in the activation of TRPC4 and TRPC5 transient receptor potential channels. Channels (Austin) 2012; 6:333-43. [PMID: 22878724 PMCID: PMC3508772 DOI: 10.4161/chan.21198] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
TRPC4 and TRPC5 channels are important regulators of electrical excitability in both gastrointestinal myocytes and neurons. Much is known regarding the assembly and function of these channels including TRPC1 as a homotetramer or a heteromultimer and the roles that their interacting proteins play in controlling these events. Further, they are one of the best-studied targets of G protein-coupled receptors and growth factors in general and Gαq protein coupled receptor or epidermal growth factor in particular. However, our understanding of the roles of Gαi/o proteins on TRPC4/5 channels is still rudimentary. We discuss potential roles for Gαi/o proteins in channel activation in addition to their known role in cellular signaling.
Collapse
Affiliation(s)
- Hana Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Jeon JP, Hong C, Park EJ, Jeon JH, Cho NH, Kim IG, Choe H, Muallem S, Kim HJ, So I. Selective Gαi subunits as novel direct activators of transient receptor potential canonical (TRPC)4 and TRPC5 channels. J Biol Chem 2012; 287:17029-17039. [PMID: 22457348 DOI: 10.1074/jbc.m111.326553] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ubiquitous transient receptor potential canonical (TRPC) channels function as non-selective, Ca(2+)-permeable channels and mediate numerous cellular functions. It is commonly assumed that TRPC channels are activated by stimulation of Gα(q)-PLC-coupled receptors. However, whether the Gα(q)-PLC pathway is the main regulator of TRPC4/5 channels and how other Gα proteins may regulate these channels are poorly understood. We previously reported that TRPC4/TRPC5 can be activated by Gα(i). In the current work, we found that Gα(i) subunits, rather than Gα(q), are the primary and direct activators of TRPC4 and TRPC5. We report a novel molecular mechanism in which TRPC4 is activated by several Gα(i) subunits, most prominently by Gα(i2), and TRPC5 is activated primarily by Gα(i3). Activation of Gα(i) by the muscarinic M2 receptors or expression of the constitutively active Gα(i) mutants equally and fully activates the channels. Moreover, both TRPC4 and TRPC5 are activated by direct interaction of their conserved C-terminal SESTD (SEC14-like and spectrin-type domains) with the Gα(i) subunits. Two amino acids (lysine 715 and arginine 716) of the TRPC4 C terminus were identified by structural modeling as mediating the interaction with Gα(i2). These findings indicate an essential role of Gα(i) proteins as novel activators for TRPC4/5 and reveal the molecular mechanism by which G-proteins activate the channels.
Collapse
Affiliation(s)
- Jae-Pyo Jeon
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Chansik Hong
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Eun Jung Park
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Ju-Hong Jeon
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Nam-Hyuk Cho
- Department of Microbiology and Immunology, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - In-Gyu Kim
- Department of Biochemistry, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Han Choe
- Department of Physiology, University of Ulsan College of Medicine, Seoul 136-748, Korea
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892
| | - Hyun Jin Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Korea.
| |
Collapse
|
13
|
Cui N, Zhang X, Tadepalli JS, Yu L, Gai H, Petit J, Pamulapati RT, Jin X, Jiang C. Involvement of TRP channels in the CO₂ chemosensitivity of locus coeruleus neurons. J Neurophysiol 2011; 105:2791-801. [PMID: 21430274 DOI: 10.1152/jn.00759.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Catecholaminergic neurons in the locus coeruleus (LC) play a role in the ventilatory response to hypercapnia. Here, we show evidence for the involvement of transient receptor potential (TRP) channels. We found that the input resistance was reduced during an exposure to 8% CO(2) in ~35% LC neurons in mouse brain slices, accompanied by depolarization and higher firing activity. The neuronal responses suggest the opening of Na(+) or nonselective cationic channels instead of the closure of K(+) channels. As a major group of cationic channels, the TRP channels are expressed in the brain, some of which are activated by acidic pH. We therefore screened all representative TRP channels using the quantitative real-time PCR analysis. High levels of mRNA expression of TRPC5, TRPM2, and TRPM7 were found in the LC tissue. Of them, the TRPC5 transcript was the most abundant. The TRPC5 channel was activated by extracellular acidification when expressed in human embryonic kidney (HEK) cells. The TRPC5 currents started to be activated at pH 7.4 with pKa 6.9. The TRPC5 currents were also activated by isohydric hypercapnic and intracellular acidosis in a Ca(2+)-dependent manner. Consistently, the LC neurons were stimulated by both extra- and intracellular acidosis. The stimulatory effect of hypercapnia on LC neurons was eliminated by selective TRPC inhibitor SKF-96365 with and without the blockade of synaptic transmission. Single-cell PCR analysis indicated that TRPC5 mRNAs existed in the LC neurons. Thus these results strongly suggest that the TRP channels are likely to play a role in the CO(2) chemosensitivity of LC neurons, especially TRPC5.
Collapse
Affiliation(s)
- Ningren Cui
- Department of Biology, Georgia State University, Atlanta, GA 30302, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Sung TS, Kim MJ, Hong S, Jeon JP, Kim BJ, Jeon JH, Kim SJ, So I. Functional characteristics of TRPC4 channels expressed in HEK 293 cells. Mol Cells 2009; 27:167-73. [PMID: 19277498 DOI: 10.1007/s10059-009-0021-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Revised: 11/25/2008] [Accepted: 12/01/2008] [Indexed: 12/12/2022] Open
Abstract
The classical type of transient receptor potential (TRPC) channel is a molecular candidate for Ca(2+)-permeable cation channels in mammalian cells. Because TRPC4 and TRPC5 belong to the same subfamily of TRPC, they have been assumed to have the same physiological properties. However, we found that TRPC4 had its own functional characteristics different from those of TRPC5. TRPC4 channels had no constitutive activity and were activated by muscarinic stimulation only when a muscarinic receptor was co-expressed with TRPC4 in human embryonic kidney (HEK) cells. Endogenous muscarinic receptor appeared not to interact with TRPC4. TPRC4 activation by GTPgammaS was not desensitized. TPRC4 activation by GTPgammaS was not inhibited by either Rho kinase inhibitor or MLCK inhibitor. TRPC4 was sensitive to external pH with pK (a) of 7.3. Finally, TPRC4 activation by GTPgammaS was inhibited by the calmodulin inhibitor W-7. We conclude that TRPC4 and TRPC5 have different properties and their own physiological roles.
Collapse
Affiliation(s)
- Tae Sik Sung
- Center for Bio-Artificial Muscle and Department of Physiology, Seoul National University College of Medicine, Seoul, 110-799, Korea
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Jeon JP, Lee KP, Park EJ, Sung TS, Kim BJ, Jeon JH, So I. The specific activation of TRPC4 by Gi protein subtype. Biochem Biophys Res Commun 2008; 377:538-543. [PMID: 18854172 DOI: 10.1016/j.bbrc.2008.10.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 10/03/2008] [Indexed: 11/19/2022]
Abstract
The classical type of transient receptor potential channel (TRPC) is a molecular candidate for Ca(2+)-permeable cation channels in mammalian cells. Especially, TRPC4 has the similar properties to Ca(2+)-permeable nonselective cation channels (NSCCs) activated by muscarinic stimulation in visceral smooth muscles. In visceral smooth muscles, NSCCs activated by muscarinic stimulation were blocked by anti-Galphai/o antibodies. However, there is still no report which Galpha proteins are involved in the activation process of TRPC4. Among Galpha proteins, only Galphai protein can activate TRPC4 channel. The activation effect of Galphai was specific for TRPC4 because Galphai has no activation effect on TRPC5, TRPC6 and TRPV6. Coexpression with muscarinic receptor M2 induced TRPC4 current activation by muscarinic stimulation with carbachol, which was inhibited by pertussis toxin. These results suggest that Galphai is involved specifically in the activation of TRPC4.
Collapse
Affiliation(s)
- Jae-Pyo Jeon
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Kyu Pil Lee
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Eun Jung Park
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Tae Sik Sung
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Byung Joo Kim
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Ju-Hong Jeon
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea.
| |
Collapse
|
16
|
Kim BJ, Kim MT, Jeon JH, Kim SJ, So I. Involvement of phosphatidylinositol 4,5-bisphosphate in the desensitization of canonical transient receptor potential 5. Biol Pharm Bull 2008; 31:1733-1738. [PMID: 18758068 DOI: 10.1248/bpb.31.1733] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
The classic transient receptor potential channel (TRPC) is a candidate for Ca(2+)-permeable cation channel in mammalian cells. TRPC5 is desensitized rapidly after activation by G protein-coupled receptor. Here we investigate the mechanisms of desensitization of TRPC5 using patch-clamp recording. TRPC5 was initially activated by muscarinic stimulation using 50 microM carbachol (CCh) and decayed rapidly in the presence of CCh (desensitization). Intracellularly-applied phosphatidylinositol 4,5-bisphosphate (PIP(2)) slowed the rate of desensitization. In contrast, several other phosphoinositides, including PI(3,4)P(2), PI(3,5)P(2), PI(3,4,5)P(3) and PI(4)P, had no effect on the desensitization of the TRPC5 current. This indicates that PIP(2) attenuates the desensitization of the TRPC5 current in a highly selective manner. Neither wortmannin, an inhibitor of phosphatidylinositol 4-kinase, or poly-L-lysine (PLL), a scavenger of PIP(2), had any effect on desensitization of the TRPC5 current. PIP(2) breakdown appears to be a required step in the desensitization of TRPC5 current, but PIP(2) depletion alone was insufficient for channel desensitization. TRPC5 was inhibited by cytochalasin D treatment. In mouse ileal myocytes, the desensitization of CCh-activated inward current (I(CCh)) also slowed in the presence of PIP(2) in recording pipettes. These results indicate that PIP(2) is involved in the desensitization of TRPC5 currents.
Collapse
Affiliation(s)
- Byung Joo Kim
- Center for Bio-Artificial Muscle and Department of Physiology, Seoul National University College of Medicine, Seoul, Korea
| | | | | | | | | |
Collapse
|