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Review
. 2024 Dec;18(1):2313323.
doi: 10.1080/19336950.2024.2313323. Epub 2024 Feb 14.

Recent advances on the structure and the function relationships of the TRPV4 ion channel

Raúl Sánchez-Hernández  1 , Miguel Benítez-Angeles  1 , Ana M Hernández-Vega  1 , Tamara Rosenbaum  1
Affiliations
Review

Recent advances on the structure and the function relationships of the TRPV4 ion channel

Raúl Sánchez-Hernández et al. Channels (Austin). 2024 Dec.

Abstract

The members of the superfamily of Transient Receptor Potential (TRP) ion channels are physiologically important molecules that have been studied for many years and are still being intensively researched. Among the vanilloid TRP subfamily, the TRPV4 ion channel is an interesting protein due to its involvement in several essential physiological processes and in the development of various diseases. As in other proteins, changes in its function that lead to the development of pathological states, have been closely associated with modification of its regulation by different molecules, but also by the appearance of mutations which affect the structure and gating of the channel. In the last few years, some structures for the TRPV4 channel have been solved. Due to the importance of this protein in physiology, here we discuss the recent progress in determining the structure of the TRPV4 channel, which has been achieved in three species of animals (Xenopus tropicalis, Mus musculus, and Homo sapiens), highlighting conserved features as well as key differences among them and emphasizing the binding sites for some ligands that play crucial roles in its regulation.

Keywords: 4α-PDD; Cryo-EM; HC-067047; Ion channel; TRPV4; structure.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

TRPV4 modulation and expression. a, endogenous (top), synthetic (middle) and plant-derived (bottom) molecules, as well as other activators of the TRPV4 channel (tetramer shown on left). b, Examples of some types of cells that express TRPV4 and roles of the ion channel in their function [52]. Created with PyMOL and BioRender.com.
Figure 1.
TRPV4 modulation and expression. a, the TRPV4 channel can respond to several stimuli, such as changes in temperature (27–35°C) or pH (4.5–7.5), shear stress, and endogenously produced molecules like LPC (lysophosphatidylcholine), AA (arachidonic acid), and PIP2 (phosphatidylinositol 4,5-bisphosphate). Some synthetic ligands of TRPV4 function as agonists (i.e. 4-αPDD (4-alpha-phorbol 12, 13-didecanoate) and GSK1016790A ((N-((1S)-1-([4-((2S)-2-([(2,4-Dichlorophenyl)sulfonyl]amino)-3hydroxypropanoyl)-1-piperazinyl]carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide)) or antagonists (i.e. GSK2798745 (3-[[(5S,7S)-3-[5-(2-hydroxypropan-2-yl)pyrazin-2-yl]-7-methyl-2-oxo-1-oxa-3-azaspiro[4.5]decan-7-yl]methyl]benzimidazole-5-carbonitrile) and HC-067047 (2-methyl-1-[3-(4-morpholinyl)propyl]-5-phenyl-N-[3-(trifluoromethyl)phenyl]-1 H-pyrrole-3-carboxamide)) of the channel. Extracts from plants include BAA (bisandrographolide A), apigenin, and eugenol. b, examples of some types of cells that express TRPV4, along with their corresponding functions are depicted. PDB: 8T1B (3.0-Å resolution) [52]. Created with PyMOL and BioRender.com.
Domain organization of the TRPV4 channel. a, schematic representation of a subunit of TRPV4 and of important functional domains. b, side (left) view of a human TRPV4 tetramer and zoom (right) view of PIP2 (PBD) and PACSIN3 binding domains and the proline rich domain (PRD). c, Superimposition of ankyrin repeat domains (ARD) of several TRPV channels. d, Conformational changes in the ARD with or without bound ATP. Created with PyMOL and BioRender.com based on references [43, 52, 99, 101-103].
Figure 2.
Domain organization of the TRPV4 channel. a, representation of a subunit of the hTRPV4 channel. From left to right: N-terminal region, which consists of the PIP2 binding domain (PBD); proline-rich domain (PRD); Ankyrin repeat domain (ARD); and coupling domain (CD); the transmembrane region where the voltage sensor-like domain (VSLD, S1–S4 α-helices) and the pore domain (S5-S6 α-helices) are located; and the C-terminal region, which includes the TRP box and the calmodulin interaction site (CAM) and the PDZ-like domain. Capital and bold letters are amino acid residues that are part of the domains described or interaction sites with other proteins (numbers represent the positions of these amino acids). b, human TRPV4 in the apo state is shown and its interaction with PIP2 and PACSIN3 is represented; a zoom-in into the PRD shows that P142 and P143 are involved in these interactions with PACSIN3; other proline residues among the PRD are shown in purple sticks. c, comparison of the ARD between several members of the vanilloid subfamily, where the alignment shows mostly conserved structure among species. Only the human TRPV4 complete subunit is represented in a side view parallel to the membrane. d, zoomed-in view of the ARD of the human TRPV4 is shown, where finger 3 acquires a different conformation when it is unbound to ATP (yellow sticks). PDB 8T1B, 6L93, 2PNN, 2F37, 4N5Q, and 6F55 (resolutions were 3.0 Å, 4.47 Å, 2.70 Å, 1.70 Å, 1.9 Å and nuclear magnetic resonance structure, respectively) [43,52,92–95]. Created with PyMOL and BioRender.com.
hTRPV4 interactions with RhoA GTPase. a, GDP (green sticks) bound to RhoA. b, Human TRPV4 tetramer (top view) in complex with RhoA. c, Side view of two TRPV4 subunits bound to RhoA (top) and detail of the interface between the ARD of hTRPV4 (yellow sticks) and the β sheets of RhoA (blue sticks) [52, 53]. Created with PyMOL and BioRender.com.
Figure 3.
hTRPV4 interactions with RhoA GTPase. a, cartoon representation of the RhoA structure. The RhoA protein is bound to GDP (green sticks). b, the homotetramer of the human TRPV4 in complex with RhoA is shown; each subunit of TRPV4 is identified with a different color, RhoA (wheat) is shown interacting with the TRPV4 bottom layer; the stoichiometry is 1:1. c, lateral view of two subunits of TRPV4 in complex with RhoA and a close-up view of the interaction zone between the ARD of hTRPV4 (yellow sticks) and the β sheets of RhoA (blue sticks). PDB: 8FC9 (resolution 3.75 Å) [52,53]. Created with PyMOL and BioRender.com.
The S4-S5 linker/TRP box interface. a, Superimposition of the S4-S6 and the TRP box of TRPV4 from several species (lateral view) b, Detail of the interaction zone between the S4-S5 linker and the TRP box, same species as in (a) [52, 53, 131]. Created with PyMOL and BioRender.com.
Figure 4.
The S4–S5 linker/TRP box interface. a, alignment of the TRPV4 interface of different species as described in the text is shown in a lateral view, only the S4–S6 and the TRP box are represented. b, zoomed-in view of the interaction zone between the S4–S5 linker and the TRP box, where the amino acid residues L596 (human and mouse) or L592/L594 (frog) form a hydrogen bond with the conserved residue W733. The frog TRPV4 linker has the most flexible interface. The amino acid residues are shown in orange sticks and the hydrogen bridges are shown in dotted lines. PDB: 8J1D, 8T1B, and 6BBJ (resolutions of 3.59 Å, 3.00 Å and 3.80 Å, respectively) [52,53,127]. Created with PyMOL and BioRender.com.
Pore domain of TRPV4. Apo state of the pore regions of the TRPV4 channel from a, frog, b, mouse, and c, human. Distances between residues in the selectivity filter (upper region) and the gate (bottom region) [45, 52, 131]. Created with PyMOL and BioRender.com.
Figure 5.
Pore domain of TRPV4. the pore regions of the TRPV4 channel from a, frog, b, mouse, and c, human are shown in the apo state; all of them have a selectivity filter in the upper region which differs in their cross-pore distances. The lower region of the pore domain contains the intracellular gate, where the distance between the side chains of the nearest amino acids is less than 6 Å, preventing the passage of ions. Mammalian ion TRPV4 channels show similarity in structure in contrast to the frog TRPV4, which displays a “tighter” conformation. The amino acids in the selectivity filter and the intracellular gate are shown as sticks. PDB: 6BBJ, 8J1D, and 8T1B (resolutions of 3.80Å, 3.59 Å and 3.00 Å, respectively) [45,52,127]. Created with PyMOL and BioRender.com.
Contact domain of TRPV4. a, Alignment of the mouse and human TRPV4 channel cytoplasmic domains and of helices S1 and. S6. b, Details of the interactions between the coupling domain (CD) and the C-terminal regions, which allow for the movement of the TRP box towards the plasma membrane [52, 131]. Created with PyMOL and BioRender.com.
Figure 6.
Contact domain of TRPV4. a, the cytoplasmic domains and helices S1 and S6 of the mouse and human TRPV4 channel are represented. b, zoomed-in views of the coupling domain (CD), where the β1 and β2 strands of the N-terminal regions interact with the β3 strand of the C-terminal region, which brings these two regions closer to each other. The arrangement of the tertiary structure allows certain domains such as the TRP box to come into contact with key areas of the protein for its regulation. The black arrows represent the movement of the TRP box toward the plasma membrane facilitated by the HLH motif. PDB: 8J1D and 8T1B (resolutions of 3.59 Å and 3.00 Å, respectively) [52,127]. Created with PyMOL and BioRender.com.
Human TRPV4 ligand binding site. a, TRPV4 in the apo conformation with ligand binding sites (light purple). b, Amino acid residues that bind ligands shown in c and d. c, TRPV4 channel in the open-state in complex with agonist 4α-PDD (orange ribbon) or d, with agonist GSK1016790A (pink ribbon). e, TRPV4 in the closed-state in complex with antagonist HC-067047 (blue ribbon) or f, with antagonist GSK2798745 (cyan ribbon) [52, 53]. Created with PyMOL and BioRender.com.
Figure 7.
Human TRPV4 ligand binding site. a, schematic representation of the apo structure of TRPV4 channel (white ribbon) with the identified ligand binding site highlighted in light purple. b, zoomed-in view of the ligand binding pocket shown in a, (purple ribbon). c, zoomed-in view of the structure of TRPV4 in the open-state in complex with agonists 4α-PDD (orange ribbon) and d, GSK1016790A (pink ribbon). Closed-state structures in complex with antagonists are shown in e, HC-067047 (blue ribbon) and f, GSK2798745 (cyan ribbon). The side chains of the polar and aromatic residues essential for binding agonists and antagonists (shown in gray) are represented as sticks. Hydrogen bonds are represented as dashed lines. Both agonists and antagonists are stably positioned within the ligand binding pocket and share some residues with which they interact, such as S470, N474, F524, N528, Y553, Y591, D743, and S747. However, they are also closely surrounded by particular residues: 4α-PDD (F478); GSK1016790A (Q550, D531, F549, L523); HC-067047 (Y478, F592) and GSK2798745 (Y478, F524). PDB: 8T1B, 8FCA, 8FC7, and 8FC8 (resolutions of 3.00 Å, 3.41 Å, 3.30 Å and 3.47 Å, respectively) [52,53]. Created with PyMOL and BioRender.com.
Comparison between hTRPV4 and mTRPV4 channels. a, Human TRPV4 (hTRPV4; pink ribbons) and mouse (mTRPV4, cyan ribbons) in the apo state (left and middle) and detail of the pore domain (right; gate residues at I715 (human, green sticks) or M718 (mouse, orange sticks). Cross-pore distances are shown with dotted lines. b, TRPV4 channel structure in the open state in complex with the agonist GSK1016790A (left). Detail of GSK1016790A in the ligand binding pocket between the S1-S4 and the TRP box (human, pink ribbons; mouse, cyan ribbons) [53, 131]. Created with PyMOL and BioRender.com.
Figure 8.
Comparison between hTRPV4 and mTRPV4 channels. a, schematic representation of the apo structure of human (pink ribbons) and mouse (cyan ribbons) TRPV4 channels along with a close-up of the pore domain with the identified intracellular gate residues at I715 (human, green sticks) or M718 (mouse, orange sticks) and its cross-pore distances. b, TRPV4 channel structure in the open state in complex with the agonist GSK1016790A. A zoom-in of the ligand binding pocket between the S1–S4 and the TRP box (human, pink ribbons; mouse, cyan ribbons) is shown. The key amino acid residues and the agonist structure are shown in purple sticks. PDB: 8J1D, 8FC9, 8J1F, and 8FC8 (resolutions are 3.59 Å, 3.75 Å, 3.62 Å and 3.47 Å, respectively) [53,127]. Created with PyMOL and BioRender.com.
Structural changes in the closed and open states of hTRPV4. Detail of the key residues in the ligand binding pocket located at the coupling interface between the S1-S4, CD, and TRP domains in the a, closed and b, open states with hydrogen-bonds and salt bridges (dashed lines). Conformational changes in the selectivity filter and the intracellular gate of the pore region due to binding of the agonists c, 4α-PDD (yellow structure) and GSK1016790A (pink structure), or antagonists d, HC-067047 (blue structure) and GSK2798745 (cyan structure). Dashed lines are the distances between gating residues in opposite subunits. Opening of the channel is accompanied by a transition from α to π in the S6 helix [52]. Created with PyMOL and BioRender.com.
Figure 9.
Structural changes in the closed and open states of hTRPV4. Close-up view of the ligand binding pocket showing the key residues that form the coupling interface between the S1–S4, CD, and TRP domains in the a, closed and b, open states. Dashed lines indicate hydrogen-bonds and salt bridges. Representation of the structural changes in the selectivity filter and the intracellular gate of the pore region caused by the binding of the agonists c, 4α-PDD (yellow structure) and GSK1016790A (pink structure), or antagonists d, HC-067047 (blue structure) and GSK2798745 (cyan structure). Dashed lines indicate the distances between gating (I715 in the open state and M718 in the closed state) and selectivity filter (G679, M680) residues in opposite subunits. Upon activation by the agonist, a transition from α to π secondary structure occurs in the S6 helix, inducing a helical bend (π-hinge). The binding of the antagonist promotes a transition from π to α secondary structure, inducing the formation of an α-helix. The position of residue F707 is highlighted since it putatively stabilizes the π-helices structure through H-C···π interactions. PDB: 8FCA, 8FC8, 8T1F, and 8FC7 (resolutions are 3.41 Å, 3.47 Å, 3.49 Å and 3.30 Å, respectively) [52]. Created with PyMOL and BioRender.com.
The “vanilloid pocket” in TRPV4. a, Human TRPV4 tetramer in the apo state. Detailed view of the ligand binding pocket between the S1-S4 and the TRP box with key amino acid residues. for b, endogenous (pink ribbons, orange sticks) or c, synthetic (cyan ribbons, orange sticks) ligands [52]. Created with PyMOL and BioRender.com.
Figure 10.
The “vanilloid pocket” in TRPV4. a, schematic representation of the apo structure of human TRPV4 channel in a parallel view with the membrane. Each subunit of the homotetramer is shown by a different color. A zoom-in of the ligand binding pocket between the S1–S4 and the TRP box where key amino acid residues for the binding of b, endogenous (pink ribbons, orange sticks) or c, synthetic (cyan ribbons, orange sticks) ligands are represented. The chemical structures of the modulators of the TRPV4 channel discussed in this review are shown as well. PDB: 8T1B (resolution 3.00 Å) [52]. Created with PyMOL and BioRender.com.
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T.R. received funding from Consejo Nacional de Humanidades, Ciencias y Tecnologías (#A1-S-8760) and from Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México, (PAPIIT #IN200423).