Mechanism of 4-aminopyridine inhibition of the lysosomal channel TMEM175.

Transmembrane protein 175 (TMEM175) is an evolutionarily distinct lysosomal cation channel whose mutation is associated with the development of Parkinson's disease. Here, we present a cryoelectron microscopy structure and molecular simulations of TMEM175 bound to 4-aminopyridine (4-AP), the only known small-molecule inhibitor of TMEM175 and a broad K+ channel inhibitor, as well as a drug approved by the Food and Drug Administration against multiple sclerosis. The structure shows that 4-AP, whose mode of action had not been previously visualized, binds near the center of the ion conduction pathway, in the open state of the channel. Molecular dynamics simulations reveal that this binding site is near the middle of the transmembrane potential gradient, providing a rationale for the voltage-dependent dissociation of 4-AP from TMEM175. Interestingly, bound 4-AP rapidly switches between three predominant binding poses, stabilized by alternate interaction patterns dictated by the twofold symmetry of the channel. Despite this highly dynamic binding mode, bound 4-AP prevents not only ion permeation but also water flow. Together, these studies provide a framework for the rational design of novel small-molecule inhibitors of TMEM175 that might reveal the role of this channel in human lysosomal physiology both in health and disease.

Asymmetric drug binding in an ATP-loaded inward-facing state of an ABC transporter.

Substrate efflux by ATP-binding cassette (ABC) transporters, which play a major role in multidrug resistance, entails the ATP-powered interconversion between transporter intermediates. Despite recent progress in structure elucidation, a number of intermediates have yet to be visualized and mechanistically interpreted. Here, we combine cryogenic-electron microscopy (cryo-EM), double electron-electron resonance spectroscopy and molecular dynamics simulations to profile a previously unobserved intermediate of BmrCD, a heterodimeric multidrug ABC exporter from Bacillus subtilis. In our cryo-EM structure, ATP-bound BmrCD adopts an inward-facing architecture featuring two molecules of the substrate Hoechst-33342 in a striking asymmetric head-to-tail arrangement. Deletion of the extracellular domain capping the substrate-binding chamber or mutation of Hoechst-coordinating residues abrogates cooperative stimulation of ATP hydrolysis. Together, our findings support a mechanistic role for symmetry mismatch between the nucleotide binding and the transmembrane domains in the conformational cycle of ABC transporters and is of notable importance for rational design of molecules for targeted ABC transporter inhibition.

HSK3486 Inhibits Colorectal Cancer Growth by Promoting Oxidative Stress and ATPase Inhibitory Factor 1 Activation.

BACKGROUND: HSK3486 (ciprofol), a new candidate drug similar to propofol, exerts sedative and hypnotic effects through gamma-aminobutyric acid type A receptors; however, its potential role in colorectal cancer is currently unknown. AIMS: This study aimed to evaluate the effects of HSK3486 on colorectal cancer cell proliferation. METHODS: Imaging was performed to detect reactive oxygen species and mitochondrial membrane potential. Western blotting was used to determine the expression of target signals. The HSK3486 molecular mechanism was investigated through ATPase inhibitory factor 1 knockdown and xenograft model experiments to assess mitochondrial function in colorectal cancer cells. RESULTS: Cell Counting Kit-8 and Annexin V/propidium iodide double staining assays showed that HSK3486 inhibited colorectal cancer cell proliferation in a concentration-dependent manner. In addition, HSK3486 treatment increased the expression of B-cell lymphoma-2-associated X, cleaved caspase 3, and cleaved poly (ADP-ribose) polymerase, whereas myeloid cell leukemia-1 and B-cell lymphoma 2 expression decreased. HSK3486 promoted mitochondrial dysfunction by inducing ATPase inhibitor factor 1 expression. Furthermore, HSK3486 promoted oxidative stress, as shown by the increase in reactive oxygen species and lactate dehydrogenase levels, along with a decrease in mitochondrial membrane potential and ATP levels. ATPase inhibitor factor 1 small interfering RNA pretreatment dramatically increased the mitochondrial membrane potential and tumor size in a xenograft model following exposure to HSK3486. CONCLUSION: Collectively, our findings revealed that HSK3486 induces oxidative stress, resulting in colorectal cancer cell apoptosis, making it a potential candidate therapeutic strategy for colorectal cancer.

Conserved binding site in the N-lobe of prokaryotic MATE transporters suggests a role for Na+ in ion-coupled drug efflux.

In both prokaryotes and eukaryotes, multidrug and toxic-compound extrusion (MATE) transporters catalyze the efflux of a broad range of cytotoxic compounds, including human-made antibiotics and anticancer drugs. MATEs are secondary-active antiporters, i.e. their drug-efflux activity is coupled to, and powered by, the uptake of ions down a pre-existing transmembrane electrochemical gradient. Key aspects of this mechanism, however, remain to be delineated, such as its ion specificity and stoichiometry. We previously revealed the existence of a Na+-binding site in a MATE transporter from Pyroccocus furiosus (PfMATE) and hypothesized that this site might be broadly conserved among prokaryotic MATEs. Here, we evaluate this hypothesis by analyzing VcmN and ClbM, which along with PfMATE are the only three prokaryotic MATEs whose molecular structures have been determined at resolutions better than 3 Å. Analysis of available crystallographic data and molecular dynamics simulations indeed reveal an occupied Na+-binding site in the N-terminal lobe of both structures, analogous to that identified in PfMATE. We likewise find this site to be strongly selective against K+, suggesting it is mechanistically significant. Consistent with these computational results, DEER spectroscopy measurements for multiple doubly-spin-labeled VcmN constructs demonstrate Na+-dependent changes in protein conformation. The existence of this binding site in three MATE orthologs implicates Na+ in the ion-coupled drug-efflux mechanisms of this class of transporters. These results also imply that observations of H+-dependent activity stem either from a site elsewhere in the structure, or from H+ displacing Na+ under certain laboratory conditions, as has been noted for other Na+-driven transport systems.

Conserved binding site in the N-lobe of prokaryotic MATE transporters suggests a role for Na+ in ion-coupled drug efflux.

In both prokaryotes and eukaryotes, multidrug and toxic-compound extrusion (MATE) transporters catalyze the efflux of a broad range of cytotoxic compounds, including human-made antibiotics and anticancer drugs. MATEs are secondary-active antiporters, i.e., their drug-efflux activity is coupled to, and powered by, the uptake of ions down a preexisting transmembrane electrochemical gradient. Key aspects of this mechanism, however, remain to be delineated, such as its ion specificity and stoichiometry. We previously revealed the existence of a Na+-binding site in a MATE transporter from Pyroccocus furiosus (PfMATE) and hypothesized that this site might be broadly conserved among prokaryotic MATEs. Here, we evaluate this hypothesis by analyzing VcmN and ClbM, which along with PfMATE are the only three prokaryotic MATEs whose molecular structures have been determined at atomic resolution, i.e. better than 3 Å. Reinterpretation of existing crystallographic data and molecular dynamics simulations indeed reveal an occupied Na+-binding site in the N-terminal lobe of both structures, analogous to that identified in PfMATE. We likewise find this site to be strongly selective against K+, suggesting it is mechanistically significant. Consistent with these computational results, DEER spectroscopy measurements for multiple doubly-spin-labeled VcmN constructs demonstrate Na+-dependent changes in protein conformation. The existence of this binding site in three MATE orthologs implicates Na+ in the ion-coupled drug-efflux mechanisms of this class of transporters. These results also imply that observations of H+-dependent activity likely stem either from a site elsewhere in the structure, or from H+ displacing Na+ under certain laboratory conditions, as has been noted for other Na+-driven transport systems.

On the Role of a Conserved Methionine in the Na+-Coupling Mechanism of a Neurotransmitter Transporter Homolog.

Excitatory amino acid transporters (EAAT) play a key role in glutamatergic synaptic communication. Driven by transmembrane cation gradients, these transporters catalyze the reuptake of glutamate from the synaptic cleft once this neurotransmitter has been utilized for signaling. Two decades ago, pioneering studies in the Kanner lab identified a conserved methionine within the transmembrane domain as key for substrate turnover rate and specificity; later structural work, particularly for the prokaryotic homologs GltPh and GltTk, revealed that this methionine is involved in the coordination of one of the three Na+ ions that are co-transported with the substrate. Albeit extremely atypical, the existence of this interaction is consistent with biophysical analyses of GltPh showing that mutations of this methionine diminish the binding cooperativity between substrates and Na+. It has been unclear, however, whether this intriguing methionine influences the thermodynamics of the transport reaction, i.e., its substrate:ion stoichiometry, or whether it simply fosters a specific kinetics in the binding reaction, which, while influential for the turnover rate, do not fundamentally explain the ion-coupling mechanism of this class of transporters. Here, studies of GltTk using experimental and computational methods independently arrive at the conclusion that the latter hypothesis is the most plausible, and lay the groundwork for future efforts to uncover the underlying mechanism.

Broadly conserved Na+-binding site in the N-lobe of prokaryotic multidrug MATE transporters.

Multidrug and toxic-compound extrusion (MATE) proteins comprise an important but largely uncharacterized family of secondary-active transporters. In both eukaryotes and prokaryotes, these transporters protect the cell by catalyzing the efflux of a broad range of cytotoxic compounds, including human-made antibiotics and anticancer drugs. MATEs are thus potential pharmacological targets against drug-resistant pathogenic bacteria and tumor cells. The activity of MATEs is powered by transmembrane electrochemical ion gradients, but their molecular mechanism and ion specificity are not understood, in part because high-quality structural information is limited. Here, we use computational methods to study PfMATE, from Pyrococcus furiosus, whose structure is the best resolved to date. Analysis of available crystallographic data and additional molecular dynamics simulations unequivocally reveal an occupied Na+-binding site in the N-lobe of this transporter, which had not been previously recognized. We find this site to be selective against K+ and broadly conserved among prokaryotic MATEs, including homologs known to be Na+-dependent such as NorM-VC, VmrA, and ClbM, for which the location of the Na+ site had been debated. We note, however, that the chemical makeup of the proposed Na+ site indicates it is weakly specific against H+, explaining why MATEs featuring this Na+-binding motif may be solely driven by H+ in laboratory conditions. We further posit that the concurrent coupling to H+ and Na+ gradients observed for some Na+-driven MATEs owes to a second H+-binding site, within the C-lobe. In summary, our study provides insights into the structural basis for the complex ion dependency of MATE transporters.

TRPV1 pore turret dictates distinct DkTx and capsaicin gating.

Many neurotoxins inflict pain by targeting receptors expressed on nociceptors, such as the polymodal cationic channel TRPV1. The tarantula double-knot toxin (DkTx) is a peptide with an atypical bivalent structure, providing it with the unique capability to lock TRPV1 in its open state and evoke an irreversible channel activation. Here, we describe a distinct gating mechanism of DkTx-evoked TRPV1 activation. Interestingly, DkTx evokes significantly smaller TRPV1 macroscopic currents than capsaicin, with a significantly lower unitary conductance. Accordingly, while capsaicin evokes aversive behaviors in TRPV1-transgenic Caenorhabditis elegans, DkTx fails to evoke such response at physiological concentrations. To determine the structural feature(s) responsible for this phenomenon, we engineered and evaluated a series of mutated toxins and TRPV1 channels. We found that elongating the DkTx linker, which connects its two knots, increases channel conductance compared with currents elicited by the native toxin. Importantly, deletion of the TRPV1 pore turret, a stretch of amino acids protruding out of the channel's outer pore region, is sufficient to produce both full conductance and aversive behaviors in response to DkTx. Interestingly, this deletion decreases the capsaicin-evoked channel activation. Taken together with structure modeling analysis, our results demonstrate that the TRPV1 pore turret restricts DkTx-mediated pore opening, probably through steric hindrance, limiting the current size and mitigating the evoked downstream physiological response. Overall, our findings reveal that DkTx and capsaicin elicit distinct TRPV1 gating mechanisms and subsequent pain responses. Our results also indicate that the TRPV1 pore turret regulates the mechanisms of channel gating and permeation.

Characterization of essential domains in HSD17B13 for cellular localization and enzymatic activity.

Human genetic studies recently identified an association of SNPs in the 17-ß hydroxysteroid dehydrogenase 13 (HSD17B13) gene with alcoholic and nonalcoholic fatty liver disease development. Mutant HSD17B13 variants devoid of enzymatic function have been demonstrated to be protective from cirrhosis and liver cancer, supporting the development of HSD17B13 as a promising therapeutic target. Previous studies have demonstrated that HSD17B13 is a lipid droplet (LD)-associated protein. However, the critical domains that drive LD targeting or determine the enzymatic activity have yet to be defined. Here we used mutagenesis to generate multiple truncated and point-mutated proteins and were able to demonstrate in vitro that the N-terminal hydrophobic domain, PAT-like domain, and a putative α-helix/ß-sheet/α-helix domain in HSD17B13 are all critical for LD targeting. Similarly, we characterized the predicted catalytic, substrate-binding, and homodimer interaction sites and found them to be essential for the enzymatic activity of HSD17B13, in addition to our previous identification of amino acid P260 and cofactor binding site. In conclusion, we identified critical domains and amino acid sites that are essential for the LD localization and protein function of HSD17B13, which may facilitate understanding of its function and targeting of this protein to treat chronic liver diseases.

Membrane plasticity facilitates recognition of the inhibitor oligomycin by the mitochondrial ATP synthase rotor.

Enzymes in the respiratory chain are increasingly seen as potential targets against multi-drug resistance of human pathogens and cancerous cells. However, a detailed understanding of the mechanism and specificity determinants of known inhibitors is still lacking. Oligomycin, for example, has been known to be an inhibitor of the membrane motor of the mitochondrial ATP synthase for over five decades, and yet little is known about its mode of action at the molecular level. In a recent breakthrough, a crystal structure of the S. cerevisiae c-subunit ring with bound oligomycin revealed the inhibitor docked on the outer face of the proton-binding sites, deep into the transmembrane region. However, the structure of the complex was obtained in an organic solvent rather than detergent or a lipid bilayer, and therefore it has been unclear whether this mode of recognition is physiologically relevant. Here, we use molecular dynamics simulations to address this question and gain insights into the mechanism of oligomycin inhibition. Our findings lead us to propose that oligomycin naturally partitions into the lipid/water interface, and that in this environment the inhibitor can indeed bind to any of the c-ring proton-carrying sites that are exposed to the membrane, thereby becoming an integral component of the proton-coordinating network. As the c-ring rotates within the membrane, driven either by downhill proton permeation or ATP hydrolysis, one of the protonated, oligomycin-bound sites eventually reaches the subunit-a interface and halts the rotary mechanism of the enzyme.

Intermittent Bellerophon state in frequency-weighted Kuramoto model.

Recently, the Bellerophon state, which is a quantized, time dependent, clustering state, was revealed in globally coupled oscillators [Bi et al., Phys. Rev. Lett. 117, 204101 (2016)]. The most important characteristic is that in such a state, the oscillators split into multiple clusters. Within each cluster, the instantaneous frequencies of the oscillators are not the same, but their average frequencies lock to a constant. In this work, we further characterize an intermittent Bellerophon state in the frequency-weighted Kuramoto model with a biased Lorentzian frequency distribution. It is shown that the evolution of oscillators exhibits periodical intermittency, following a synchronous pattern of bursting in a short period and resting in a long period. This result suggests that the Bellerophon state might be generic in Kuramoto-like models regardless of different arrangements of natural frequencies.

Prospects of molecular hydrogen in cancer prevention and treatment.

Gas signaling molecules, including carbon monoxide (CO), nitric oxide (NO), and hydrogen sulfide (H2S), have been shown to have cancer therapeutic potential, pointing to a new direction for cancer treatment. In recent years, a series of studies have confirmed that hydrogen (H2), a weakly reductive gas, also has therapeutic effects on various cancers and can mitigate oxidative stress caused by radiation and chemotherapy, reducing tissue damage and immunosuppression to improve prognosis. Meanwhile, H2 also has immunomodulatory effects, inhibiting T cell exhaustion and enhancing T cell anti-tumor function. It is worth noting that human intestinal flora can produce large amounts of H2 daily, which becomes a natural barrier to maintaining the body's resistance to diseases such as tumors. Although the potential anti-tumor mechanisms of H2 are still to be investigated, previous studies have shown that H2 can selectively scavenge highly toxic reactive oxygen species (ROS) and inhibit various ROS-dependent signaling pathways in cancer cells, thus inhibiting cancer cell proliferation and metastasis. The ROS scavenging ability of H2 may also be the underlying mechanism of its immunomodulatory function. In this paper, we review the significance of H2 produced by intestinal flora on the immune homeostasis of the body, the role of H2 in cancer therapy and the underlying mechanisms, and the specific application of H2 to provide new ideas for the comprehensive treatment of cancer patients.

Identification of the critical structural determinants of the EF-hand domain arrangements in calcium binding proteins.

EF-hand calcium binding proteins (CaBPs) share strong sequence homology, but exhibit great diversity in structure and function. Thus although calmodulin (CaM) and calcineurin B (CNB) both consist of four EF hands, their domain arrangements are quite distinct. CaM and the CaM-like proteins are characterized by an extended architecture, whereas CNB and the CNB-like proteins have a more compact form. In this study, we performed structural alignments and molecular dynamics (MD) simulations on 3 CaM-like proteins and 6 CNB-like proteins, and quantified their distinct structural and dynamical features in an effort to establish how their sequences specify their structures and dynamics. Alignments of the EF2-EF3 region of these proteins revealed that several residues (not restricted to the linker between the EF2 and EF3 motifs) differed between the two groups of proteins. A customized inverse folding approach followed by structural assessments and MD simulations established the critical role of these residues in determining the structure of the proteins. Identification of the critical determinants of the two different EF-hand domain arrangements and the distinct dynamical features relevant to their respective functions provides insight into the relationships between sequence, structure, dynamics and function among these EF-hand CaBPs.

Ca2+ efflux facilitated by co-transport of inorganic phosphate anion in the H+/Ca2+ antiporter YfkE.

Ca2+ is an important signaling messenger. In microorganisms, fungi, and plants, H+/Ca2+ antiporters (CAX) are known to play key roles in the homeostasis of intracellular Ca2+ by catalyzing its efflux across the cell membrane. Here, we reveal that the bacterial CAX homolog YfkE transports Ca2+ in two distinct modes: a low-flux H+/Ca2+ exchange mode and a high-flux mode in which Ca2+ and phosphate ions are co-transported (1:1) in exchange for H+. Coupling with phosphate greatly accelerates the Ca2+ efflux activity of YfkE. Our studies reveal that Ca2+ and phosphate bind to adjacent sites in a central translocation pathway and lead to mechanistic insights that explain how this CAX alters its conserved alpha-repeat motifs to adopt phosphate as a specific "transport chaperon" for Ca2+ translocation. This finding uncovers a co-transport mechanism within the CAX family that indicates this class of proteins contributes to the cellular homeostasis of both Ca2+ and phosphate.

Fasting-Mimicking Diet Drives Antitumor Immunity against Colorectal Cancer by Reducing IgA-Producing Cells.

As a safe, feasible, and inexpensive dietary intervention, fasting-mimicking diet (FMD) exhibits excellent antitumor efficacy by regulating metabolism and boosting antitumor immunity. A better understanding of the specific mechanisms underlying the immunoregulatory functions of FMD could help improve and expand the clinical application of FMD-mediated immunotherapeutic strategies. In this study, we aimed to elucidate the role of metabolic reprogramming induced by FMD in activation of antitumor immunity against colorectal cancer. Single-cell RNA sequencing analysis of intratumoral immune cells revealed that tumor-infiltrating IgA+ B cells were significantly reduced by FMD treatment, leading to the activation of antitumor immunity and tumor regression in murine colorectal cancer models. Mechanistically, FMD delayed tumor growth by repressing B-cell class switching to IgA. Therefore, FMD-induced reduction of IgA+ B cells overcame the suppression of CD8+ T cells. The immunoregulatory and antitumor effects of FMD intervention were reversed by IgA+ B-cell transfer. Moreover, FMD boosted fatty acid oxidation (FAO) to trigger RUNX3 acetylation, thus inactivating Cα gene transcription and IgA class switching. IgA+ B-cell expansion was also impeded in patients placed on FMD, while B-cell expression of carnitine palmitoyl transferase 1A (CPT1A), the rate-limiting enzyme of FAO, was increased. Furthermore, CPT1A expression was negatively correlated with both IgA+ B cells and IgA secretion within colorectal cancer. Together, these results highlight that FMD holds great promise for treating colorectal cancer. Furthermore, the degree of IgA+ B cell infiltration and FAO-associated metabolic status are potential biomarkers for evaluating FMD efficacy. SIGNIFICANCE: Metabolic reprogramming of B cells induced by fasting-mimicking diet suppresses IgA class switching and production to activate antitumor immunity and inhibit tumor growth. See related commentary by Bush and Perry, p. 3493.

Development of a one-step immunocapture real-time RT-PCR assay for detection of tobacco mosaic virus in soil.

Tobacco mosaic virus (TMV) causes significant losses in many economically important crops. Contaminated soils may play roles as reservoirs and sources of transmission for TMV. In this study we report the development of an immunocapture real-time RT-PCR (IC-real-time RT-PCR) assay for direct detection of TMV in soils without RNA isolation. A series of TMV infected leaf sap dilutions of 1:101, 1:102, 1:103, 1:104, 1:105 and 1:106 (w/v, g/mL) were added to one gram of soil. The reactivity of DAS-ELISA and conventional RT-PCR was in the range of 1:102 and 1:103 dilution in TMV-infested soils, respectively. Meanwhile, the detection limit of IC-real-time RT-PCR sensitivity was up to 1:106 dilution. However, in plant sap infected by TMV, both IC-real-time RT-PCR and real-time RT-PCR were up to 1:106 dilution, DAS-ELISA could detect at least 1:103 dilution. IC-real-time RT-PCR method can use either plant sample extracts or cultivated soils, and show higher sensitivity than RT-PCR and DAS-ELISA for detection of TMV in soils. Therefore, the proposed IC-real-time RT-PCR assay provides an alternative for quick and very sensitive detection of TMV in soils, with the advantage of not requiring a concentration or RNA purification steps while still allowing detection of TMV for disease control.

Differential ion dehydration energetics explains selectivity in the non-canonical lysosomal K+ channel TMEM175.

Structures of the human lysosomal K+ channel transmembrane protein 175 (TMEM175) in open and closed states revealed a novel architecture lacking the canonical K+ selectivity filter motif present in previously known K+ channel structures. A hydrophobic constriction composed of four isoleucine residues was resolved in the pore and proposed to serve as the gate in the closed state, and to confer ion selectivity in the open state. Here, we achieve higher-resolution structures of the open and closed states and employ molecular dynamics simulations to analyze the conducting properties of the putative open state, demonstrating that it is permeable to K+ and, to a lesser degree, also Na+. Both cations must dehydrate significantly to penetrate the narrow hydrophobic constriction, but ion flow is assisted by a favorable electrostatic field generated by the protein that spans the length of the pore. The balance of these opposing energetic factors explains why permeation is feasible, and why TMEM175 is selective for K+ over Na+, despite the absence of the canonical selectivity filter. Accordingly, mutagenesis experiments reveal an exquisite sensitivity of the channel to perturbations that mitigate the constriction. Together, these data reveal a novel mechanism for selective permeation of ions by TMEM175 that is unlike that of other K+ channels.

Predicting the structural basis of targeted protein degradation by integrating molecular dynamics simulations with structural mass spectrometry.

Targeted protein degradation (TPD) is a promising approach in drug discovery for degrading proteins implicated in diseases. A key step in this process is the formation of a ternary complex where a heterobifunctional molecule induces proximity of an E3 ligase to a protein of interest (POI), thus facilitating ubiquitin transfer to the POI. In this work, we characterize 3 steps in the TPD process. (1) We simulate the ternary complex formation of SMARCA2 bromodomain and VHL E3 ligase by combining hydrogen-deuterium exchange mass spectrometry with weighted ensemble molecular dynamics (MD). (2) We characterize the conformational heterogeneity of the ternary complex using Hamiltonian replica exchange simulations and small-angle X-ray scattering. (3) We assess the ubiquitination of the POI in the context of the full Cullin-RING Ligase, confirming experimental ubiquitinomics results. Differences in degradation efficiency can be explained by the proximity of lysine residues on the POI relative to ubiquitin.

KMT5A downregulation participated in High Glucose-mediated EndMT via Upregulation of ENO1 Expression in Diabetic Nephropathy.

Diabetic nephropathy (DN) has become the common and principal microvascular complication of diabetes that could lead to end-stage renal disease. It was reported endothelial-to-mesenchymal transition (EndMT) in glomeruli plays an important role in DN. Enolase1 (ENO1) and Lysine Methyltransferase 5A (KMT5A) were found to modulate epithelial-to-mesenchymal transition in some situations. In the present study, we speculated KMT5A regulates ENO1 transcript, thus participating in hyperglycemia-induced EndMT in glomeruli of DN. Our study represented vimentin, αSMA and ENO1 expression elevated, and CD31 expression decreased in glomeruli of DN participants and rats. In vitro, high glucose induced EndMT by increase of ENO1 levels. Moreover, high glucose downregulated KMT5A levels and increased regulatory factor X1 (RFX1) levels. KMT5A upregulation or si-RFX1 decreased high glucose-induced ENO1 expression and EndMT. RFX1 overexpression- or sh-KMT5A-induced EndMT was attenuated by si-ENO1. Further, the association between KMT5A and RFX1 was verified. Furthermore, histone H4 lysine20 methylation (the direct target of KMT5A) and RFX1 positioned on ENO1 promoter region. sh-KMT5A enhanced positive action of RFX1 on ENO1 promoter activity. KMT5A reduction and RFX1 upregulation were verified in glomeruli of DN patients and rats. KMT5A associated with RFX1 to modulate ENO1, thus involved in hyperglycemia-mediated EndMT in glomeruli of DN.