Electron cryo-microscopy structure of a human TRPM4 channel

Magneto-structural correlations of cyclo-tetravanadates functionalized with mixed-ligand copper(ii) complexes

Bimetallic materials based on tetravanadate anions and mixed ligand copper(ii) complexes were readily synthesized under non-hydrothermal conditions. The compounds show interesting structural and magnetic diversity mediated by copper symmetry.

Inherited Cardiac Arrhythmia Syndromes: Focus on Molecular Mechanisms Underlying TRPM4 Channelopathies

The Transient Receptor Potential Melastatin 4 (TRPM4) is a transmembrane N-glycosylated ion channel that belongs to the large family of TRP proteins. It has an equal permeability to Na⁺ and K⁺ and is activated via an increase of the intracellular calcium concentration and membrane depolarization. Due to its wide distribution, TRPM4 dysfunction has been linked with several pathophysiological processes, including inherited cardiac arrhythmias. Many pathogenic variants of the TRPM4 gene have been identified in patients with different forms of cardiac disorders such as conduction defects, Brugada syndrome, and congenital long QT syndrome. At the cellular level, these variants induce either gain- or loss-of-function of TRPM4 channels for similar clinical phenotypes. However, the molecular mechanisms associating these functional alterations to the clinical phenotypes remain poorly understood. The main objective of this article is to review the major cardiac TRPM4 channelopathies and recent advances regarding their genetic background and the underlying molecular mechanisms.

TRPM Channels in Human Diseases

The transient receptor potential melastatin (TRPM) subfamily belongs to the TRP cation channels family. Since the first cloning of TRPM1 in 1989, tremendous progress has been made in identifying novel members of the TRPM subfamily and their functions. The TRPM subfamily is composed of eight members consisting of four six-transmembrane domain subunits, resulting in homomeric or heteromeric channels. From a structural point of view, based on the homology sequence of the coiled-coil in the C-terminus, the eight TRPM members are clustered into four groups: TRPM1/M3, M2/M8, M4/M5 and M6/M7. TRPM subfamily members have been involved in several physiological functions. However, they are also linked to diverse pathophysiological human processes. Alterations in the expression and function of TRPM subfamily ion channels might generate several human diseases including cardiovascular and neurodegenerative alterations, organ dysfunction, cancer and many other channelopathies. These effects position them as remarkable putative targets for novel diagnostic strategies, drug design and therapeutic approaches. Here, we review the current knowledge about the main characteristics of all members of the TRPM family, focusing on their actions in human diseases.

The structural basis for an on-off switch controlling Gβγ-mediated inhibition of TRPM3 channels

TRPM3 channels play important roles in the detection of noxious heat and in inflammatory thermal hyperalgesia. The activity of these ion channels in somatosensory neurons is tightly regulated by µ-opioid receptors through the signaling of Gβγ proteins, thereby reducing TRPM3-mediated pain. We show here that Gβγ directly binds to a domain of 10 amino acids in TRPM3 and solve a cocrystal structure of this domain together with Gβγ. Using these data and mutational analysis of full-length proteins, we pinpoint three amino acids in TRPM3 and their interacting partners in Gβ1 that are individually necessary for TRPM3 inhibition by Gβγ. The 10-amino-acid Gβγ-interacting domain in TRPM3 is subject to alternative splicing. Its inclusion in or exclusion from TRPM3 channel proteins therefore provides a mechanism for switching on or off the inhibitory action that Gβγ proteins exert on TRPM3 channels.

Coupling of NMDA receptors and TRPM4 guides discovery of unconventional neuroprotectants

Excitotoxicity induced by NMDA receptors (NMDARs) is thought to be intimately linked to high intracellular calcium load. Unexpectedly, NMDAR-mediated toxicity can be eliminated without affecting NMDAR-induced calcium signals. Instead, excitotoxicity requires physical coupling of NMDARs to TRPM4. This interaction is mediated by intracellular domains located in the near-membrane portions of the receptors. Structure-based computational drug screening using the interaction interface of TRPM4 in complex with NMDARs identified small molecules that spare NMDAR-induced calcium signaling but disrupt the NMDAR/TRPM4 complex. These interaction interface inhibitors strongly reduce NMDA-triggered toxicity and mitochondrial dysfunction, abolish cyclic adenosine monophosphate-responsive element-binding protein (CREB) shutoff, boost gene induction, and reduce neuronal loss in mouse models of stroke and retinal degeneration. Recombinant or small-molecule NMDAR/TRPM4 interface inhibitors may mitigate currently untreatable human neurodegenerative diseases.

Association Analysis Between Common Variants of the TRPM1 Gene and Three Mental Disorders in the Han Chinese Population

Objective: Our study was designed to determine if the TRPM1 gene is associated with any of three mental disorders. The project included a cross disorder meta-analysis and association analysis including 141701 cases and 175248 controls. Materials and Methods: We genotyped eight tag single nucleotide polymorphisms (SNPs) in 1248 unrelated schizophrenia (SCZ) patients, 1056 major depressive disorder patients, 1344 bipolar disorder patients, and 1248 normal controls. We then performed a meta-analysis of 10 GWASs to identify common genetic factors among these three mental disorders. Finally, we performed a meta-analysis of six GWASs to explore the role of rs10162727 in SCZ. Result: Although two haplotypes of the TRPM1 gene, rs1035706-rs10162727 and rs10162727-rs3784599, were identified in the control group, as well as all three disease groups, none of the eight tag SNP associations remained significant after correction for multiple tests. In this cross-disorder meta-analysis of the three diseases, none of the tag SNPs were confirmed to be common among the diseases. In addition, in the meta-analysis conducted for the rs10162727 locus in SCZ, there was no significant association (p-value = 0.84, odds ratio = 1.02 [95% CI = 0.87-1.19]). Conclusion: In the Han Chinese population, no significant evidence was found linking variants of the TRPM1 gene with any of the mental disorders examined.

Structure-Function Relationship of TRPM2: Recent Advances, Contradictions, and Open Questions

When in a particular scientific field, major progress is rapidly reached after a long period of relative stand-still, this is often achieved by the development or exploitation of new techniques and methods. A striking example is the new insights brought into the understanding of the gating mechanism of the transient receptor potential melastatin type 2 cation channel (TRPM2) by cryogenic electron microscopy structure analysis. When conventional methods are complemented by new ones, it is quite natural that established researchers are not fully familiar with the possibilities and limitations of the new method. On the other hand, newcomers may need some assistance in perceiving the previous knowledge in detail; they may not realize that some of their interpretations are at odds with previous results and need refinement. This may in turn trigger further studies with new and promising perspectives, combining the promises of several methodological approaches. With this review, I aim to give a comprehensive overview on functional data of several orthologous of TRPM2 that are nicely explained by structural studies. Moreover, I wish to point out some functional contradictions raised by the structural data. Finally, some open questions and some lines of possible future experimental approaches shall be discussed.

Global alignment and assessment of TRP channel transmembrane domain structures to explore functional mechanisms

The recent proliferation of published TRP channel structures provides a foundation for understanding the diverse functional properties of this important family of ion channel proteins. To facilitate mechanistic investigations, we constructed a structure-based alignment of the transmembrane domains of 120 TRP channel structures. Comparison of structures determined in the absence or presence of activating stimuli reveals similar constrictions in the central ion permeation pathway near the intracellular end of the S6 helices, pointing to a conserved cytoplasmic gate and suggesting that most available structures represent non-conducting states. Comparison of the ion selectivity filters toward the extracellular end of the pore supports existing hypotheses for mechanisms of ion selectivity. Also conserved to varying extents are hot spots for interactions with hydrophobic ligands, lipids and ions, as well as discrete alterations in helix conformations. This analysis therefore provides a framework for investigating the structural basis of TRP channel gating mechanisms and pharmacology, and, despite the large number of structures included, reveals the need for additional structural data and for more functional studies to establish the mechanistic basis of TRP channel function.

Domain zipping and unzipping modulates TRPM4's properties in human cardiac conduction disease

The transient receptor potential melastatin 4 (TRPM4) is a Ca²⁺ -activated nonselective cation channel linked to human cardiac diseases. The human mutation K914R within TRPM4's S4-S5 linker was identified in patients with atrioventricular block. During UV-flash-mediated Ca²⁺ transients, TRPM4^K914R  generated a threefold augmented membrane current concomitant with 2 to 3-fold slowed down activation and deactivation kinetics resulting in excessive membrane currents during human cardiac action potentials. Mutagenesis of K914 paired with molecular modeling suggested the importance of the nanoscopic interface between the S4-S5 linker, the MHR4-, and TRP-domain as a major determinant for TRPM4's behavior. Rational mutagenesis of an interacting amino acid (R1062Q) in the TRP domain was able to offset K914R`s gain-of-function by zipping and unzipping of this nanoscopic interface. In conclusion, repulsion and attraction between the amino acids at positions 914 and 1062 alters the flexibility of the nanoscopic interface suggesting a zipping and unzipping mechanism that modulates TRPM4's functions. Pharmacological modulation of this intramolecular mechanism might represent a novel therapeutic strategy for the management of TRPM4-mediated cardiac diseases.

Mapping of CaM, S100A1 and PIP2-Binding Epitopes in the Intracellular N- and C-Termini of TRPM4

Molecular determinants of the binding of various endogenous modulators to transient receptor potential (TRP) channels are crucial for the understanding of necessary cellular pathways, as well as new paths for rational drug designs. The aim of this study was to characterise interactions between the TRP cation channel subfamily melastatin member 4 (TRPM4) and endogenous intracellular modulators-calcium-binding proteins (calmodulin (CaM) and S100A1) and phosphatidylinositol 4, 5-bisphosphate (PIP2). We have found binding epitopes at the N- and C-termini of TRPM4 shared by CaM, S100A1 and PIP2. The binding affinities of short peptides representing the binding epitopes of N- and C-termini were measured by means of fluorescence anisotropy (FA). The importance of representative basic amino acids and their combinations from both peptides for the binding of endogenous TRPM4 modulators was proved using point alanine-scanning mutagenesis. In silico protein-protein docking of both peptides to CaM and S100A1 and extensive molecular dynamics (MD) simulations enabled the description of key stabilising interactions at the atomic level. Recently solved cryo-Electron Microscopy (EM) structures made it possible to put our findings into the context of the entire TRPM4 channel and to deduce how the binding of these endogenous modulators could allosterically affect the gating of TRPM4. Moreover, both identified binding epitopes seem to be ideally positioned to mediate the involvement of TRPM4 in higher-order hetero-multimeric complexes with important physiological functions.

Current View of Ligand and Lipid Recognition by the Menthol Receptor TRPM8

Transient receptor potential (TRP) melastatin member 8 (TRPM8), which is a calcium-permeable ion channel, functions as the primary molecular sensor of cold and menthol in humans. Recent cryoelectron microscopy (cryo-EM) studies of TRPM8 have shown distinct structural features in its architecture and domain assembly compared with the capsaicin receptor TRP vanilloid member 1 (TRPV1). Moreover, ligand-bound TRPM8 structures have uncovered unforeseen binding sites for both cooling agonists and membrane lipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P₂]. These complex structures unveil the molecular basis of cooling agonist sensing by TRPM8 and the allosteric role of PI(4,5)P₂ in agonist binding for TRPM8 activation. Here, we review the recent advances in TRPM8 structural biology and investigate the molecular principles governing the distinguishing role of TRPM8 as the evolutionarily conserved menthol receptor.

TRPM4 is overexpressed in breast cancer associated with estrogen response and epithelial-mesenchymal transition gene sets

Ion channels form an important class of drug targets in malignancies. Transient receptor potential cation channel subfamily M member 4 (TRPM4) plays oncological roles in various solid tumors. Herein, we examined TRPM4 protein expression profile by immunohistochemistry (IHC) in breast cancer cases compared with normal breast ducts, its association with clinico-demographical parameters, and its potential function in breast cancers by Gene Set Enrichment Analysis (GSEA). Data-mining demonstrated that TRPM4 transcript levels were significantly higher in The Cancer Genome Atlas series of breast cancer cases (n = 1,085) compared with normal breast tissues (n = 112) (p = 1.03 x 10⁻¹¹). Our IHC findings in tissue microarrays showed that TRPM4 protein was overexpressed in breast cancers (n = 83/99 TRPM4⁺; 83.8%) compared with normal breast ducts (n = 5/10 TRPM4⁺; 50%) (p = 0.022). Higher TRPM4 expression (median frequency cut-off) was significantly associated with higher lymph node status (N1-N2 vs N0; p = 0.024) and higher stage (IIb-IIIb vs I-IIa; p = 0.005). GSEA evaluation in three independent gene expression profiling (GEP) datasets of breast cancer cases (GSE54002, n = 417; GSE20685, n = 327; GSE23720, n = 197) demonstrated significant association of TRPM4 transcript expression with estrogen response and epithelial-mesenchymal transition (EMT) gene sets (p<0.01 and false discovery rate<0.05). These gene sets were not enriched in GEP datasets of normal breast epithelium cases (GSE10797, n = 5; GSE9574, n = 15; GSE20437, n = 18). In conclusion, TRPM4 protein expression is upregulated in breast cancers associated with worse clinico-demographical parameters, and TRPM4 potentially regulates estrogen receptor signaling and EMT progression in breast cancer.

Cyclo-tetravanadate bridged copper complexes as potential double bullet pro-metallodrugs for cancer treatment

Over the last decade, copper and vanadium complexes have shown promising properties for the treatment of several types of cancer. In particular, Casiopeinas®, a group of copper-based complexes, has received specific attention, and their mechanism of action has been extensively studied since their structure is simple and their synthesis may be affordable. Similarly, vanadium-containing compounds in the form of complexes and simple polyoxovanadates have also been studied as antitumor agents. Here, potential prodrugs that would release the two metals, V and Cu, in usable form to act in conjunction against cancer cells are reported. The new series of Casiopeinas-like compounds are bridged by a cyclotetravanadate ion with the generic formula [Cu(N,N')(AA)]₂•(V₄O₁₂), where (N,N') represent 1,10-phenanthroline and 2,2'-bipyridine, and (AA) are aminoacidate ions (Lysine and Ornithine). The compounds were characterized by elemental analysis, single-crystal X-ray diffraction and Visible, FTIR, and Raman spectroscopies, as well as ⁵¹V NMR, EPR, and Thermogravimetric Analysis. Additionally, theoretical calculations based on the Density Functional Theory (DFT) were carried out to model the compounds. Optimized structures, theoretical IR, and Raman spectra were also obtained, as well as docking analysis to test DNA interactions with the casiopeina-like complexes. The compounds may act as prodrugs by providing acting molecules that have showed potential pharmacological properties for the treatment of several types of cancer.

TRP ion channels: Proteins with conformational flexibility

Ion channels display conformational changes in response to binding of their agonists and antagonists. The study of the relationships between the structure and the function of these proteins has witnessed considerable advances in the last two decades using a combination of techniques, which include electrophysiology, optical approaches (i.e. patch clamp fluorometry, incorporation of non-canonic amino acids, etc.), molecular biology (mutations in different regions of ion channels to determine their role in function) and those that have permitted the resolution of their structures in detail (X-ray crystallography and cryo-electron microscopy). The possibility of making correlations among structural components and functional traits in ion channels has allowed for more refined conclusions on how these proteins work at the molecular level. With the cloning and description of the family of Transient Receptor Potential (TRP) channels, our understanding of several sensory-related processes has also greatly moved forward. The response of these proteins to several agonists, their regulation by signaling pathways as well as by protein-protein and lipid-protein interactions and, in some cases, their biophysical characteristics have been studied thoroughly and, recently, with the resolution of their structures, the field has experienced a new boom. This review article focuses on the conformational changes in the pores, concentrating on some members of the TRP family of ion channels (TRPV and TRPA subfamilies) that result in changes in their single-channel conductances, a phenomenon that may lead to fine-tuning the electrical response to a given agonist in a cell.

Structure and function of the calcium-selective TRP channel TRPV6

Epithelial calcium channel TRPV6 is a member of the vanilloid subfamily of TRP channels that is permeable to cations and highly selective to Ca²⁺ ; it shows constitutive activity regulated negatively by Ca²⁺ and positively by phosphoinositol and cholesterol lipids. In this review, we describe the molecular structure of TRPV6 and discuss how its structural elements define its unique functional properties. High Ca²⁺ selectivity of TRPV6 originates from the narrow selectivity filter, where Ca²⁺ ions are directly coordinated by a ring of anionic aspartate side chains. Divalent cations Ca²⁺ and Ba²⁺ permeate TRPV6 pore according to the knock-off mechanism, while tight binding of Gd³⁺ to the aspartate ring blocks the channel and prevents Na⁺ from permeating the pore. The iris-like channel opening is accompanied by an α-to-π helical transition in the pore-lining transmembrane helix S6. As a result of this transition, the intracellular halves of the S6 helices bend and rotate by about 100 deg, exposing different residues to the channel pore in the open and closed states. Channel opening is also associated with changes in occupancy of the transmembrane domain lipid binding sites. The inhibitor 2-aminoethoxydiphenyl borate (2-APB) binds to TRPV6 in a pocket formed by the cytoplasmic half of the S1-S4 transmembrane helical bundle and shifts open-closed channel equilibrium towards the closed state by outcompeting lipids critical for activation. Ca²⁺ inhibits TRPV6 via binding to calmodulin (CaM), which mediates Ca²⁺ -dependent inactivation. The TRPV6-CaM complex exhibits 1:1 stoichiometry; one TRPV6 tetramer binds both CaM lobes, which adopt a distinct head-to-tail arrangement. The CaM C-terminal lobe plugs the channel through a unique cation-π interaction by inserting the side chain of lysine K115 into a tetra-tryptophan cage at the ion channel pore intracellular entrance. Recent studies of TRPV6 structure and function described in this review advance our understanding of the role of this channel in physiology and pathophysiology and inform new therapeutic design.

Case Report: Investigation and molecular genetic diagnosis of familial hypomagnesaemia

Genetic mutations causing familial hypomagnesaemia syndromes are well-recognised.  Affected patients can present with severe symptoms of hypomagnesaemia, such as seizures or cardiac arrhythmia.  We report an affected child, from a consanguineous family, who presented in the first weeks of life with seizures secondary to hypomagnesaemia, without other associated clinical features.  We performed whole exome sequencing in the affected child and segregation analysis within the family, which revealed a novel homozygous missense mutation in TRPM6, which was confirmed as a heterozygous allele in both parents and two younger siblings who had transient hypomagnesaemia. Using in silico modelling, we provide evidence that the missense variant p.(K1098E) in TRPM6 is pathogenic, as it disrupts stabilising TRP domain interactions. Management of familial hypomagnesaemia relies on prompt recognition, early magnesium replacement and lifelong monitoring.

Aberrant Deactivation-Induced Gain of Function in TRPM4 Mutant Is Associated with Human Cardiac Conduction Block

A gain-of-function mutation in the Ca²⁺-activated transient receptor potential melastatin member 4 (TRPM4^A432T) is linked to life-threatening cardiac conduction disturbance, but the underlying mechanism is unclear. For deeper insights, we used photolysis of caged Ca²⁺, quantitative Ca²⁺, and electrophysiological measurements. TRPM4^A432T's 2-fold larger membrane current was associated with 50% decreased plasma membrane expression. Kinetic analysis unveiled 4-fold slower deactivation that was responsible for the augmented membrane current progressively rising during repetitive human cardiac action potentials. Rational mutagenesis of TRPM4 at position 432 revealed that the bulkiness of the amino acid was key to TRPM4^A432T's aberrant gating. Charged amino acids rendered the channel non-functional. The slow deactivation caused by an amino acid substitution at position 432 from alanine to the bulkier threonine represents a key contributor to the gain of function in TRPM4^A432T. Thus, our results add a mechanism in the etiology of TRP channel-linked human cardiac channelopathies.

The structures and gating mechanism of human calcium homeostasis modulator 2

Calcium homeostasis modulators (CALHMs) are voltage-gated, Ca²⁺-inhibited nonselective ion channels that act as major ATP release channels, and have important roles in gustatory signalling and neuronal toxicity^1-3. Dysfunction of CALHMs has previously been linked to neurological disorders¹. Here we present cryo-electron microscopy structures of the human CALHM2 channel in the Ca²⁺-free active or open state and in the ruthenium red (RUR)-bound inhibited state, at resolutions up to 2.7 Å. Our work shows that purified CALHM2 channels form both gap junctions and undecameric hemichannels. The protomer shows a mirrored arrangement of the transmembrane domains (helices S1-S4) relative to other channels with a similar topology, such as connexins, innexins and volume-regulated anion channels^4-8. Upon binding to RUR, we observed a contracted pore with notable conformational changes of the pore-lining helix S1, which swings nearly 60° towards the pore axis from a vertical to a lifted position. We propose a two-section gating mechanism in which the S1 helix coarsely adjusts, and the N-terminal helix fine-tunes, the pore size. We identified a RUR-binding site near helix S1 that may stabilize this helix in the lifted conformation, giving rise to channel inhibition. Our work elaborates on the principles of CALHM2 channel architecture and symmetry, and the mechanism that underlies channel inhibition.

A structural overview of the ion channels of the TRPM family

The TRPM (transient receptor potential melastatin) family belongs to the superfamily of TRP cation channels. The TRPM subfamily is composed of eight members that are involved in diverse biological functions such as temperature sensing, inflammation, insulin secretion, and redox sensing. Since the first cloning of TRPM1 in 1998, tremendous progress has been made uncovering the function, structure, and pharmacology of this family. Complete structures of TRPM2, TRPM4, and TRPM8, as well as a partial structure of TRPM7, have been determined by cryo-EM, providing insights into their channel assembly, ion permeation, gating mechanisms, and structural pharmacology. Here we summarize the current knowledge about channel structure, emphasizing general features and principles of the structure of TRPM channels discovered since 2017. We also discuss some of the key unresolved issues in the field, including the molecular mechanisms underlying voltage and temperature dependence, as well as the functions of the TRPM channels' C-terminal domains.

Structure of the thermo-sensitive TRP channel TRP1 from the alga Chlamydomonas reinhardtii

Algae produce the largest amount of oxygen on earth and are invaluable for human nutrition and biomedicine, as well as for the chemical industry, energy production and agriculture. The mechanisms by which algae can detect and respond to changes in their environments can rely on membrane receptors, including TRP ion channels. Here we present a 3.5-Å resolution cryo-EM structure of the transient receptor potential (TRP) channel crTRP1 from the alga Chlamydomonas reinhardtii that opens in response to increased temperature and is positively regulated by the membrane lipid PIP₂. The structure of crTRP1 significantly deviates from the structures of other TRP channels and has a unique 2-fold symmetrical rose-shape architecture with elbow domains and ankyrin repeat domains submerged and dipping into the membrane, respectively. Our study provides a structure of a TRP channel from a micro-organism and a structural framework for better understanding algae biology and TRP channel evolution.

TRPM6 N-Terminal CaM- and S100A1-Binding Domains

Transient receptor potential (TRPs) channels are crucial downstream targets of calcium signalling cascades. They can be modulated either by calcium itself and/or by calcium-binding proteins (CBPs). Intracellular messengers usually interact with binding domains present at the most variable TRP regions-N- and C-cytoplasmic termini. Calmodulin (CaM) is a calcium-dependent cytosolic protein serving as a modulator of most transmembrane receptors. Although CaM-binding domains are widespread within intracellular parts of TRPs, no such binding domain has been characterised at the TRP melastatin member-the transient receptor potential melastatin 6 (TRPM6) channel. Another CBP, the S100 calcium-binding protein A1 (S100A1), is also known for its modulatory activities towards receptors. S100A1 commonly shares a CaM-binding domain. Here, we present the first identified CaM and S100A1 binding sites at the N-terminal of TRPM6. We have confirmed the L520-R535 N-terminal TRPM6 domain as a shared binding site for CaM and S100A1 using biophysical and molecular modelling methods. A specific domain of basic amino acid residues (R526/R531/K532/R535) present at this TRPM6 domain has been identified as crucial to maintain non-covalent interactions with the ligands. Our data unambiguously confirm that CaM and S100A1 share the same binding domain at the TRPM6 N-terminus although the ligand-binding mechanism is different.

The oncogenic roles of TRPM ion channels in cancer

Transient receptor potential (TRP) proteins are a diverse family of ion channels present in multiple types of tissues. They function as gatekeepers for responses to sensory stimuli including temperature, vision, taste, and pain through their activities in conducting ion fluxes. The TRPM (melastatin) subfamily consists of eight members (i.e., TRPM1-8), which collectively regulate fluxes of various types of cations such as K⁺ , Na⁺ , Ca²⁺ , and Mg²⁺ . Growing evidence in the past two decades indicates that TRPM ion channels, their isoforms, or long noncoding RNAs encoded within the locus may be oncogenes involved in the regulation of cancer cell growth, proliferation, autophagy, invasion, and epithelial-mesenchymal transition, and their significant association with poor clinical outcomes of cancer patients. In this review, we describe and discuss recent findings implicating TRPM channels in different malignancies, their functions, mechanisms, and signaling pathways involved in cancers, as well as summarizing their normal physiological functions and the availability of ion channel pharmacological inhibitors.

Visualizing structural transitions of ligand-dependent gating of the TRPM2 channel

The transient receptor potential melastatin 2 (TRPM2) channel plays a key role in redox sensation in many cell types. Channel activation requires binding of both ADP-ribose (ADPR) and Ca²⁺. The recently published TRPM2 structures from Danio rerio in the ligand-free and the ADPR/Ca²⁺-bound conditions represent the channel in closed and open states, which uncovered substantial tertiary and quaternary conformational rearrangements. However, it is unclear how these rearrangements are achieved within the tetrameric channel during channel gating. Here we report the cryo-electron microscopy structures of Danio rerio TRPM2 in the absence of ligands, in complex with Ca²⁺ alone, and with both ADPR and Ca²⁺, resolved to ~4.3 Å, ~3.8 Å, and ~4.2 Å, respectively. In contrast to the published results, our studies capture ligand-bound TRPM2 structures in two-fold symmetric intermediate states, offering a glimpse of the structural transitions that bridge the closed and open conformations.

The transient receptor potential channel member 2 (TRPM2) ion channel has a function in redox-dependent signaling. Here the authors present the cryo-EM structures of zebrafish TRPM2 in the ligand-free form, with Ca²⁺ and both ADP-ribose/Ca²⁺ and observe two-fold symmetric quaternary structure rearrangements in the ligand-bound structures that likely represent intermediate gating states.

The role of π-helices in TRP channel gating

Transient Receptor Potential (TRP) channels are a large superfamily of polymodal ion channels, which perform important roles in numerous physiological processes. The architecture of their transmembrane (TM) domains closely resembles that of voltage-gated potassium channels (K_V). However, recent cryoEM and crystallographic studies of TRP channels have identified π-helices in functionally important regions, and it is increasingly recognized that they utilize a distinct mechanism of gating that relies on α-to-π secondary structure transitions. Here we review our current understanding of the role of π-helices in TRP channel function and their broader impact on different classes of ion channels.

Exploring Wells-Dawson Clusters Associated With the Small Ribosomal Subunit

The polyoxometalate P₂W₁₈O626-, the Wells-Dawson cluster, stabilized the ribosome sufficiently for the crystallographers to solve the phase problem and improve the structural resolution. In the following we characterize the interaction of the Wells-Dawson cluster with the ribosome small subunit. There are 14 different P₂W₁₈O626- clusters interacting with the ribosome, and the types of interactions range from one simple residue interaction to complex association of multiple sites including backbone interactions with a Wells-Dawson cluster. Although well-documented that bridging oxygen atoms are the main basic sites on other polyoxometalate interaction with most proteins reported, the W=O groups are the main sites of the Wells-Dawson cluster interacting with the ribosome. Furthermore, the peptide chain backbone on the ribosome host constitutes the main sites that associate with the Wells-Dawson cluster. In this work we investigate the potential of one representative pair of closely-located Wells-Dawson clusters being a genuine Double Wells-Dawson cluster. We found that the Double Wells-Dawson structure on the ribosome is geometrically sound and in line with other Double Wells-Dawson clusters previously observed in the solid state and solution. This information suggests that the Double Wells-Dawson structure on the ribosome is real and contribute to characterization of this particular structure of the ribosome.

Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling

The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca²⁺ concentration and localized Ca²⁺ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca²⁺ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca²⁺ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.

Mechanism of TRPM2 channel gating revealed by cryo-EM

Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that allows Ca²⁺ influx across the plasma membrane and efflux from lysosomes upon opening. TRPM2 is best known as a biosensor of reactive oxygen species (ROS), which mediates some of the body's responses to oxidative stress. As such, TRPM2 is involved in a plethora of biological processes including immune response, insulin secretion, body temperature control and neuronal cell death, and represents an emerging therapeutic target for many human diseases, from diabetes to inflammatory and neurodegenerative diseases. A direct ligand of TRPM2 is ADP-ribose (ADPR), which accumulates in cells at high levels of ROS, and activates TRPM2 synergistically with intracellular calcium (Ca²⁺ ). Here, we describe recent cryo-electron microscopy (cryo-EM) structures of TRPM2 and summarize the insights they provided into the gating mechanism of the channel.

Transient Receptor Potential Channels and Calcium Signaling

Transient receptor potential (TRP) cation channels play diverse roles in cellular Ca²⁺ signaling. First, as Ca²⁺-permeable channels that respond to a variety of stimuli, TRP channels can directly initiate cellular Ca²⁺ signals. Second, as nonselective cation channels, TRP channel activation leads to membrane depolarization, influencing Ca²⁺ influx via voltage-gated and store-operated Ca²⁺ channels. Finally, Ca²⁺ modulates the activity of most TRP channels, allowing them to function as molecular effectors downstream of intracellular Ca²⁺ signals. Whereas the TRP channel field has long been devoid of detailed channel structures, recent advances, particularly in cryo-electron microscopy-based structural approaches, have yielded a flurry of TRP channel structures, including members from all seven subfamilies. These structures, in conjunction with mutagenesis-based functional approaches, provided important new insights into the mechanisms whereby TRP channels permeate and sense Ca²⁺ These insights will be highly instrumental in the rational design of novel treatments for the multitude of TRP channel-related diseases.

Transcriptome profiles revealed the mechanisms underlying the adaptation of yak to high-altitude environments

The yak is a valuable species in the Qinghai-Tibet Plateau of China. Nevertheless, the molecular mechanisms underlying its adaptation to high-altitude environments remain largely unknown. In the present study, comparative transcriptome sequencing was performed for lung and gluteus tissues from two species of low-altitude cattle (Sanjiang and Holstein cattle), Tibetan cattle (living at a moderate altitude), and yak (living at a high altitude) and the differentially expressed genes were validated using real-time quantitative PCR. The results showed that CD36 antigen was up-regulated and CD59 antigen was down-regulated in yak in comparison to the other animals, which might promote the development of red blood cells and inhibit the development of lymphocytes in yak. In addition, thrombospondin type 1, coagulation factor 5/8, and fibronectin were all down-regulated, but serpin and alpha 2-macroglobulin (A2M) were up-regulated. These differences would inhibit blood coagulation, thus reducing the risk of pulmonary edema. The expression levels of the calcium-release, potassium, and transient receptor potential channels decreased in yak, minimizing membrane depolarization and the harmful effects of pulmonary edema. Eleven KEGG pathways associated with innate immunity were more activated in yak and Tibetan cattle than in other cattle strains, which should reduce their risk of infection and disease. These changes together might facilitate the adaptation of yak and Tibetan cattle to live in high-altitude habitats.

Nanodiscs for Structural Biology in a Membranous Environment

The structures of many membrane proteins have been analyzed in detergent micelles. However, the environment of detergent micelles differs somewhat from that of the lipid bilayer, where membrane proteins exhibit physiological functions. Therefore, a more membrane-like environment has been awaited for structural analysis of membrane proteins. Nanodiscs are "hockey-puck"-shaped lipid bilayer particles that distribute in a monodispersed manner in aqueous solution. We review how nanodiscs or protein-reconstituted nanodiscs are prepared and how they are utilized to analyze protein structure, dynamics, and interactions with lipid molecules using solution NMR and cryo-electron microscopy.

Human mutations highlight an intersubunit cation-π bond that stabilizes the closed but not open or inactivated states of TRPV channels

An adequate response of a living cell to the ever-changing environment requires integration of numerous sensory inputs. In many cases, it can be achieved even at the level of a single receptor molecule. Polymodal transient receptor potential (TRP) channels have been shown to integrate mechanical, chemical, electric, and thermal stimuli. Inappropriate gating can lead to pathologies. Among the >60 known TRP vanilloid subfamily (V) 4 mutations that interfere with bone development are Y602C or R616Q at the S4-S5 linker. A cation-π bond between the conservative residues Y602 and R616 of neighboring subunits appears likely in many homologous channel structures in a closed state. Our experiments with TRPV4 mutants indicate that the resting-closed state remains stable while the bond is substituted by a salt bridge or disulfide bond, whereas disruption of the contact by mutations like Y602C or R616Q produces gain-of-function phenotypes when TRPV4 is heterologously expressed in the Xenopus oocyte or yeast. Our data indicate that the Y602-R616 cation-π interactions link the four S4-S5 linker helices together, forming a girdle backing the closed gate. Analogous cation-π bonds and the girdle are seen in many closed TRP channel structures. This girdle is not observed in the cryo-EM structure of amphibian TRPV4 (Protein Data Bank ID code 6BBJ), which appears to be in a different impermeable state-we hypothesize this is the inactivated state.

TRPM4 and TRPM5 Channels Share Crucial Amino Acid Residues for Ca2+ Sensitivity but Not Significance of PI(4,5)P2

Transient receptor potential melastatin member 4 (TRPM4) and 5 (TRPM5) channels are Ca²⁺-activated nonselective cation channels. Intracellular Ca²⁺ is the most important regulator for them to open, though PI(4,5)P₂, a membrane phosphoinositide, has been reported to regulate their Ca²⁺-sensitivities. We previously reported that negatively-charged amino acid residues near and in the TRP domain are necessary for the normal Ca²⁺ sensitivity of TRPM4. More recently, a cryo-electron microscopy structure of Ca²⁺-bound (but closed) TRPM4 was reported, proposing a Ca²⁺-binding site within an intracellular cavity formed by S2 and S3. Here, we examined the functional effects of mutations of the amino acid residues related to the proposed Ca²⁺-binding site on TRPM4 and also TRPM5 using mutagenesis and patch clamp techniques. The mutations of the amino acid residues of TRPM4 and TRPM5 reduced their Ca²⁺-sensitivities in a similar way. On the other hand, intracellular applications of PI(4,5)P₂ recovered Ca²⁺-sensitivity of desensitized TRPM4, but its effect on TRPM5 was negligible. From these results, the Ca²⁺-binding sites of TRPM4 and TRPM5 were shown to be formed by the same amino acid residues by functional analyses, but the impact of PI(4,5)P₂ on the regulation of TRPM5 seemed to be smaller than that on the regulation of TRPM4.

Enzyme activity and selectivity filter stability of ancient TRPM2 channels were simultaneously lost in early vertebrates

Transient Receptor Potential Melastatin 2 (TRPM2) is a cation channel important for the immune response, insulin secretion, and body temperature regulation. It is activated by cytosolic ADP ribose (ADPR) and contains a nudix-type motif 9 (NUDT9)-homology (NUDT9-H) domain homologous to ADPR phosphohydrolases (ADPRases). Human TRPM2 (hsTRPM2) is catalytically inactive due to mutations in the conserved Nudix box sequence. Here, we show that TRPM2 Nudix motifs are canonical in all invertebrates but vestigial in vertebrates. Correspondingly, TRPM2 of the cnidarian Nematostella vectensis (nvTRPM2) and the choanoflagellate Salpingoeca rosetta (srTRPM2) are active ADPRases. Disruption of ADPRase activity fails to affect nvTRPM2 channel currents, reporting a catalytic cycle uncoupled from gating. Furthermore, pore sequence substitutions responsible for inactivation of hsTRPM2 also appeared in vertebrates. Correspondingly, zebrafish (Danio rerio) TRPM2 (drTRPM2) and hsTRPM2 channels inactivate, but srTRPM2 and nvTRPM2 currents are stable. Thus, catalysis and pore stability were lost simultaneously in vertebrate TRPM2 channels.

The structure of TRPC ion channels

Briefly review the recent structural work of transient receptor potential canonical (TRPC) ion channels by using electron cryo-microscopy (cryo-EM). The high resolution structures of TRPC3, TRPC4, TRPC5 and TRPC6 are discussed.

Recent innovations in membrane-protein structural biology

Innovations are expanding the capabilities of experimental investigations of the structural properties of membrane proteins. Traditionally, three-dimensional structures have been determined by measuring x-ray diffraction using protein crystals with a size of least 100 μm. For membrane proteins, achieving crystals suitable for these measurements has been a significant challenge. The availabilities of micro-focus x-ray beams and the new instrumentation of x-ray free-electron lasers have opened up the possibility of using submicrometer-sized crystals. In addition, advances in cryo-electron microscopy have expanded the use of this technique for studies of protein crystals as well as studies of individual proteins as single particles. Together, these approaches provide unprecedented opportunities for the exploration of structural properties of membrane proteins, including dynamical changes during protein function.

Multimerization of Homo sapiens TRPA1 ion channel cytoplasmic domains

The transient receptor potential Ankyrin-1 (TRPA1) ion channel is modulated by myriad noxious stimuli that interact with multiple regions of the channel, including cysteine-reactive natural extracts from onion and garlic which modify residues in the cytoplasmic domains. The way in which TRPA1 cytoplasmic domain modification is coupled to opening of the ion-conducting pore has yet to be elucidated. The cryo-EM structure of TRPA1 revealed a tetrameric C-terminal coiled-coil surrounded by N-terminal ankyrin repeat domains (ARDs), an architecture shared with the canonical transient receptor potential (TRPC) ion channel family. Similarly, structures of the TRP melastatin (TRPM) ion channel family also showed a C-terminal coiled-coil surrounded by N-terminal cytoplasmic domains. This conserved architecture may indicate a common gating mechanism by which modification of cytoplasmic domains can transduce conformational changes to open the ion-conducting pore. We developed an in vitro system in which N-terminal ARDs and C-terminal coiled-coil domains can be expressed in bacteria and maintain the ability to interact. We tested three gating regulators: temperature; the polyphosphate compound IP6; and the covalent modifier allyl isothiocyanate to determine whether they alter N- and C-terminal interactions. We found that none of the modifiers tested abolished ARD-coiled-coil interactions, though there was a significant reduction at 37˚C. We found that coiled-coils tetramerize in a concentration dependent manner, with monomers and trimers observed at lower concentrations. Our system provides a method for examining the mechanism of oligomerization of TRPA1 cytoplasmic domains as well as a system to study the transmission of conformational changes resulting from covalent modification.

Trpm4 ion channels in pre-Bötzinger complex interneurons are essential for breathing motor pattern but not rhythm

Inspiratory breathing movements depend on pre-Bötzinger complex (preBötC) interneurons that express calcium (Ca2+)-activated nonselective cationic current (ICAN) to generate robust neural bursts. Hypothesized to be rhythmogenic, reducing ICAN is predicted to slow down or stop breathing; its contributions to motor pattern would be reflected in the magnitude of movements (output). We tested the role(s) of ICAN using reverse genetic techniques to diminish its putative ion channels Trpm4 or Trpc3 in preBötC neurons in vivo. Adult mice transduced with Trpm4-targeted short hairpin RNA (shRNA) progressively decreased the tidal volume of breaths yet surprisingly increased breathing frequency, often followed by gasping and fatal respiratory failure. Mice transduced with Trpc3-targeted shRNA survived with no changes in breathing. Patch-clamp and field recordings from the preBötC in mouse slices also showed an increase in the frequency and a decrease in the magnitude of preBötC neural bursts in the presence of Trpm4 antagonist 9-phenanthrol, whereas the Trpc3 antagonist pyrazole-3 (pyr-3) showed inconsistent effects on magnitude and no effect on frequency. These data suggest that Trpm4 mediates ICAN, whose influence on frequency contradicts a direct role in rhythm generation. We conclude that Trpm4-mediated ICAN is indispensable for motor output but not the rhythmogenic core mechanism of the breathing central pattern generator.

New Structures and Gating of Voltage-Dependent Potassium (Kv) Channels and Their Relatives: A Multi-Domain and Dynamic Question

Voltage-dependent potassium channels (Kv channels) are crucial regulators of cell excitability that participate in a range of physiological and pathophysiological processes. These channels are molecular machines that display a mechanism (known as gating) for opening and closing a gate located in a pore domain (PD). In Kv channels, this mechanism is triggered and controlled by changes in the magnitude of the transmembrane voltage sensed by a voltage-sensing domain (VSD). In this review, we consider several aspects of the VSD–PD coupling in Kv channels, and in some relatives, that share a common general structure characterized by a single square-shaped ion conduction pore in the center, surrounded by four VSDs located at the periphery. We compile some recent advances in the knowledge of their architecture, based in cryo-electron microscopy (cryo-EM) data for high-resolution determination of their structure, plus some new functional data obtained with channel variants in which the covalent continuity between the VSD and PD modules has been interrupted. These advances and new data bring about some reconsiderations about the use of exclusively a classical electromechanical lever model of VSD–PD coupling by some Kv channels, and open a view of the Kv-type channels as allosteric machines in which gating may be dynamically influenced by some long-range interactional/allosteric mechanisms.

Tuning the interactions of decavanadate with thaumatin, lysozyme, proteinase K and human serum proteins by its coordination to a pentaaquacobalt(ii) complex cation

Inorganic functionalization of the decavanadate anion promotes a different type of interaction with model proteins thaumatin, lysozyme, proteinase K, human serum albumin and transferrin.

Combining Structural Data with Computational Methodologies to Investigate Structure-Function Relationships in TRP Channels

Since the emergence of high-resolution three-dimensional structures of membrane proteins, and the increasing availability of state-of-the-art algorithms and high-performance-computing facilities, classical molecular dynamics (MD) simulations have become a routine device to explore the molecular behavior of these proteins. The rise of cryo-electron microscopy (cryo-EM) as a credible experimental tool to resolve structures at an atomic level has revolutionized structural biology in recent years, culminating in the disclosure of the first high-resolution three-dimensional structure of a transient receptor potential (TRP) channel, the vanilloid receptor 1 (TRPV1). As a result, the number of research articles investigating the molecular behavior of TRP channels using macromolecular simulation techniques has proliferated. This review provides an overview of the current state of this field, including our understanding of TRP channel structure, the framework of classical MD simulations, and how to perform such simulations to investigate structure-function relationships in TRP channels.

Structural biology and structure–function relationships of membrane proteins

The study of structure–function relationships of membrane proteins (MPs) has been one of the major goals in the field of structural biology. Many Noble Prizes regarding remarkable accomplishments in MP structure determination and biochemistry have been awarded over the last few decades. Mutations or improper folding of these proteins are associated with numerous serious illnesses. Therefore, as important drug targets, the study of their primary sequence and three-dimensional fold, combined with cell-based assays, provides vital information about their structure–function relationships. Today, this information is vital to drug discovery and medicine. In the last two decades, many have been the technical advances and breakthroughs in the field of MP structural biology that have contributed to an exponential growth in the number of unique MP structures in the Protein Data Bank. Nevertheless, given the medical importance and many unanswered questions, it will never be an excess of MP structures, regardless of the method used. Owing to the extension of the field, in this brief review, we will only focus on structure–function relationships of the three most significant pharmaceutical classes: G protein-coupled receptors, ion channels and transporters.

Gain-of-Function Mutations in TRPM4 Activation Gate Cause Progressive Symmetric Erythrokeratodermia

Transient receptor potential (TRP) channels respond to various chemical and physical stimuli by mediating cation influx. The skin expresses abundant TRP channels of different subtypes, which play an essential role in the maintenance of skin functionality. Here, we report cases of mutations in TRPM4, which encodes TRPM4, a Ca²⁺-activated monovalent cation channel, as a cause of an autosomal dominant form of progressive symmetric erythrokeratodermia. In three separate families with progressive symmetric erythrokeratodermia, we identified two missense mutations (c.3099C>G and c.3119T>C) that produce p.Ile1033Met and p.Ile1040Thr, both of which are located in the S6 transmembrane domain of the TRPM4 protein. The substitutions are expected to directly affect activation gating of TRPM4 according to the cryo-EM structures. Electrophysiological studies of the mutants showed substantial hyperactivity, as evidenced by pronounced baseline activity, enhanced sensitivity to intracellular Ca²⁺, and an elevated resting membrane potential. In vitro studies showed enhanced proliferation in keratinocytes overexpressing either of the mutants. We also detected an up-regulation of markers for proliferation and differentiation of keratinocytes in the affected skin tissues. Our study identified TRPM4 as an important player in the pathogenesis of skin TRP channelopathies and a potential target for treatment of skin hyperkeratotic disorders.

Structures and gating mechanism of human TRPM2

Transient receptor potential (TRP) melastatin 2 (TRPM2) is a cation channel associated with numerous diseases. It has a C-terminal NUDT9 homology (NUDT9H) domain responsible for binding adenosine diphosphate (ADP)-ribose (ADPR), and both ADPR and calcium (Ca²⁺) are required for TRPM2 activation. Here we report cryo-electron microscopy structures of human TRPM2 alone, with ADPR, and with ADPR and Ca²⁺ NUDT9H forms both intra- and intersubunit interactions with the N-terminal TRPM homology region (MHR1/2/3) in the apo state but undergoes conformational changes upon ADPR binding, resulting in rotation of MHR1/2 and disruption of the intersubunit interaction. The binding of Ca²⁺ further engages transmembrane helices and the conserved TRP helix to cause conformational changes at the MHR arm and the lower gating pore to potentiate channel opening. These findings explain the molecular mechanism of concerted TRPM2 gating by ADPR and Ca²⁺ and provide insights into the gating mechanism of other TRP channels.

Decavanadate Inhibits Mycobacterial Growth More Potently Than Other Oxovanadates

51V NMR spectroscopy is used to document, using speciation analysis, that one oxometalate is a more potent growth inhibitor of two Mycobacterial strains than other oxovanadates, thus demonstrating selectivity in its interaction with cells. Historically, oxometalates have had many applications in biological and medical studies, including study of the phase-problem in X-ray crystallography of the ribosome. The effect of different vanadate salts on the growth of Mycobacterium smegmatis (M. smeg) and Mycobacterium tuberculosis (M. tb) was investigated, and speciation was found to be critical for the observed growth inhibition. Specifically, the large orange-colored sodium decavanadate (V10O 28 6 - ) anion was found to be a stronger inhibitor of growth of two mycobacterial species than the colorless oxovanadate prepared from sodium metavanadate. The vanadium(V) speciation in the growth media and conversion among species under growth conditions was monitored using 51V NMR spectroscopy and speciation calculations. The findings presented in this work is particularly important in considering the many applications of polyoxometalates in biological and medical studies, such as the investigation of the phase-problem in X-ray crystallography for the ribosome. The findings presented in this work investigate the interactions of oxometalates with other biological systems.

A Versatile Polyoxovanadate in Diverse Cation Matrices: A Supramolecular Perspective

A series of decavanadate based compounds, formulated as [Co(H₂O)₆][{Na₄(H₂O)₁₄}{V₁₀O₂₈}]·4H₂O (1), [Zn(H₂O)₆][Na₃(H₂O)₁₄] [HV₁₀O₂₈]·4H₂O (2), [HMTAH]₂ [{Zn(H₂O)₄}₂{V₁₀O₂₈}]·2H₂O (3), [{Co(3-amp)(H₂O)₅}]₂ [3-ampH]₂ [V₁₀O₂₈] · 6H₂O (4), [4-ampH]₁₀[{Na(H₂O)₆}{HV₁₀O₂₈}][V₁₀O₂₈]·15H₂O (5), [{4-ampH}₆ {Co(H₂O)₆}₃][V₁₀O₂₈]₂·14H₂O (6), and [{4-ampH}₁₀{Zn(H₂O)₆}][V₁₀O₂₈]₂·10H₂O (7), have been synthesized (where HMTAH = mono-protonated hexamethylenetetramine, 3-ampH = protonated 3-amino pyridine and 4-ampH= protonated 4-aminopyridine) from the relevant aqueous sodium-vanadate solution, by varying the pH of the solution and amino pyridine/hexamine derivatives as well as transition metal salts (Co(II)- and Zn(II)-salts). In this series of compounds 1-7, the polyoxovanadate (POV) cluster [V₁₀O₂₈]^6- is the common cluster anion, stabilized by diverse cations. The diverse supramolecular patterns around the decavanadate cluster anion in different cationic matrices have been described to understand the microenvironment in the decavanadate-based minerals. All of these compounds have solvent water molecules in their respective crystal lattices. Since water can interact directly with cations and anions, providing an additional stability and structural diversity, we have analyzed supramolecular water structures in all these compounds to comprehend the role of the lattice water in the formation of natural decavanadate containing minerals. Compounds 1-7, that are isolated at an ambient condition from aqueous solution, are characterized by routine spectral analysis, elemental analyses and finally unambiguously by single crystal X-ray crystallography.