Functional allele of a MATE gene selected during domestication modulates seed color in chickpea

Seed color is one of the key target traits of domestication and artificial selection in chickpeas due to its implications on consumer preference and market value. The complex seed color trait has been well dissected in several crop species; however, the genetic mechanism underlying seed color variation in chickpea remains poorly understood. Here, we employed an integrated genomics strategy involving QTL mapping, high-density mapping, map-based cloning, association analysis, and molecular haplotyping in an inter-specific RIL mapping population, association panel, wild accessions, and introgression lines (ILs) of Cicer gene pool. This delineated a MATE gene, CaMATE23, encoding a Transparent Testa (TT) and its natural allele (8-bp insertion) and haplotype underlying a major QTL governing seed color on chickpea chromosome 4. Signatures of selective sweep and a strong purifying selection reflected that CaMATE23, especially its 8-bp insertion natural allelic variant, underwent selection during chickpea domestication. Functional investigations revealed that the 8-bp insertion containing the third cis-regulatory RY-motif element in the CaMATE23 promoter is critical for enhanced binding of CaFUSCA3 transcription factor, a key regulator of seed development and flavonoid biosynthesis, thereby affecting CaMATE23 expression and proanthocyanidin (PA) accumulation in the seed coat to impart varied seed color in chickpea. Consequently, overexpression of CaMATE23 in Arabidopsis tt12 mutant partially restored the seed color phenotype to brown pigmentation, ascertaining its functional role in PA accumulation in the seed coat. These findings shed new light on the seed color regulation and evolutionary history, and highlight the transcriptional regulation of CaMATE23 by CaFUSCA3 in modulating seed color in chickpea. The functionally relevant InDel variation, natural allele, and haplotype from CaMATE23 are vital for translational genomic research, including marker-assisted breeding, for developing chickpea cultivars with desirable seed color that appeal to consumers and meet global market demand.

The transcription factor SbHY5 mediates light to promote aluminum tolerance by activating SbMATE and SbSTOP1s expression

Aluminum (Al) toxicity is a major factor limiting crop yields in acid soils. Sweet sorghum (Sorghum bicolor L.) is a high-efficient energy crop widely grown in tropical and subtropical regions of the world, where acid soil is common and Al toxicity is widespread. Here, we characterized a transcription factor SbHY5 in sweet sorghum, which mediated light to promote plant Al stress adaptation. The expression of SbHY5 was induced by Al stress and increasing light intensity. The overexpression of SbHY5 improved Al tolerance in transgenic plants, which was associated with increased citrate secretion and reduced Al content in roots. Meanwhile, SbHY5 was found to localize to the nucleus and displayed transcriptional activity. SbHY5 directly activated the expression of SbMATE, indicating that a HY5-MATE-dependent citrate secretion pathway is involved in Al tolerance in plants. SbSTOP1 was reported as a key transcription factor, regulating several Al tolerance genes. Here, inspiringly, we found that SbHY5 directly promoted the transcription of SbSTOP1, implying the existence of HY5-STOP1-Al tolerance genes-mediated regulatory pathways. Besides, SbHY5 positively regulated its own transcription. Our findings revealed a novel regulatory network in which a light signaling factor, SbHY5, confers Al tolerance in plants by modulating the expression of Al stress response genes.

When Cannabis sativa L. Turns Purple: Biosynthesis and Accumulation of Anthocyanins

Environmental cues elicit anthocyanin synthesis in plant vegetative and reproductive tissues. Their accumulation in different organs accounts for their diverse biological functions, mainly related to their antioxidant properties, and it depends on a temporally and spatially regulated mechanism controlled by the action of a well-known multi-transcription factor complex. Despite the highly recognizable value of Cannabis sativa L. as a natural biorefinery of phytochemicals, very little information is known on anthocyanin pigmentation in this species. In this work, a targeted quantification of anthocyanins via HPLC-MS/MS, combined with the transcriptional profile via RT-qPCR of genes encoding for structural and decorating enzymes and regulatory transcription factors in different C. sativa tissues, help gain insights into the anthocyanin pathway in this species. To the best of our knowledge, this is the first report on the identification of cyanidin-3-rutinoside (keracyanin) as the major anthocyanin in C. sativa vegetative and floral tissues. Keracyanin amounts were higher than in small berries, suggesting that Cannabis biomass is a valuable source of colored antioxidants to be exploited in diverse applications. Furthermore, a gene putatively encoding for an anthocyanin DTX35 type transporter and CsTTG1 were identified in silico and their transcriptional levels were assessed via RT-qPCR. The results allow us to provide the first model of anthocyanin regulation in C. sativa, opening a new research scenario in this species for both breeding purposes and phytochemical exploitation.

Flavonoids: a review on biosynthesis and transportation mechanism in plants

In recent years, significant progress has been made in understanding the biosynthetic pathway and regulation of flavonoids through forward genetic approaches. However, there remains a notable gap in knowledge regarding the functional characterization and underlying processes of the transport framework responsible for flavonoid transport. This aspect requires further investigation and clarification to achieve a comprehensive understanding. Presently, there are a total of four proposed transport models associated with flavonoids, namely glutathione S-transferase (GST), multidrug and toxic compound extrusion (MATE), multidrug resistance-associated protein (MRPs), and bilitranslocase-homolog (BTL). Extensive research has been conducted on the proteins and genes related to these transport models. However, despite these efforts, numerous challenges still exist, leaving much to be explored in the future. Gaining a deeper understanding of the mechanisms underlying these transport models holds immense potential for various fields such as metabolic engineering, biotechnological approaches, plant protection, and human health. Therefore, this review aims to provide a comprehensive overview of recent advancements in the understanding of flavonoid transport mechanisms. By doing so, we aim to paint a clear and coherent picture of the dynamic trafficking of flavonoids.

Vacuolar MATE/DTX protein-mediated cucurbitacin C transport is co-regulated with bitterness biosynthesis in cucumber

Membrane-localized transporters constitute important components for specialized metabolism in plants. However, due to the vast array of specialized metabolites produced by plants, and the large families of transporter genes, knowledge about the intracellular and intercellular transport of plant metabolites is still in its infancy. Cucurbitacins are bitter and defensive triterpenoids produced mainly in the cucurbits. Using a comparative genomics and multi-omics approach, a MATE gene (CsMATE1), physically clustered with cucurbitacin C (CuC) biosynthetic genes, was identified and functionally shown to sequester CuC in cucumber leaf mesophyll cells. Notably, the CuC transport process is strictly co-regulated with CuC biosynthesis. CsMATE1 clustering with bitterness biosynthesis genes may provide benefits and a basis for this feedback regulation on CuC sequestration and biosynthesis. Identification of transport systems for plant-specialized metabolites can accelerate the metabolic engineering of high-value-added compounds by simplifying their purification process.

MATE1 expression in the cochlea and its potential involvement in cisplatin cellular uptake and ototoxicity

BACKGROUND

Cisplatin appears to enter the cochlear cells through the organic cation transporter 2 (OCT2). There is recent evidence that multidrug and toxin extrusion protein 1 (MATE1) is involved in cisplatin-induced nephrotoxicity. Its presence and role in the ear are unknown.

AIMS/OBJECTIVES

Evaluate the presence and localization of MATE1, and determine the localization of OCT2, in the cochlea. Evaluate cisplatin uptake with regard to MATE1 and OCT2 expression.

MATERIAL AND METHODS

Murine cochlear explants and paraffin-embedded cochleae were evaluated with immunohistochemistry for OCT2 and MATE1. Explant cultures were also treated with Texas Red cisplatin to determine their cellular uptake.

RESULTS

MATE1 is present in the cochlea. Most intense labeling of MATE1 and OCT2 was seen in the outer hair cells (OHCs) and pillar cells, respectively. Both transporters were observed in the spiral ganglion neurons and stria vascularis. Expression levels of OCT2 and MATE1 decreased following cisplatin exposure. Texas Red cisplatin staining was strong in OHCs and pillar cells.

CONCLUSIONS AND SIGNIFICANCE

To the best of our knowledge, this is the first study demonstrating the presence and localization of MATE1 in the cochlea. OCT2 labeling was seen in pillar cells. Consistently, OHCs and pillar cells uptake Texas Red cisplatin.

Genome-Wide Analysis of Multidrug and Toxic Compound Extruction Transporters in Grape

Grape (Vitis vinifera L.) is an important fruit crop in the world. It is used as a table grape and is also used for raisin and wine production. Grape berries accumulate secondary metabolites, such as anthocyanins, tannins, and resveratrol, which are known as functional compounds for human health. Multidrug and toxic compound extrusion transporter (MATEs) transport secondary metabolites. MATEs also transport other solutes, including organic acids, and toxic xenobiotics, depending on cation gradient and play various roles in plants. MATE comprises 300-500 amino acid residues and possesses a MATE domain and 8-12 transmembrane domains. In the present study, 59 MATE genes were identified in the grape genome, and phylogenetic analysis revealed the presence of four groups of grape MATEs (Group 1-4). Their information, such as gene structures, protein motifs, predicted subcellular localizations, and gene IDs of four genome annotations, that is, CRIBI v1, CRIBI v2, Genoscope, and Vcost v3, were annotated. The transport substrates and physiological functions of grape MATEs were estimated based on their homology with the analyzed MATEs in other plant species. Group 1 may transport toxic compounds and alkaloids, Group 2 may transport polyphenolic compounds, Group 3 may transport organic acids, and Group 4 may transport plant hormones related to signal transduction. In addition to the known anthocyanin transporters, VvMATE37 and VvMATE39, a novel anthocyanin transporter, VvMATE38 in Group 2, was suggested as a key transporter for anthocyanin accumulation in grape berry skin. VvMATE46, VvMATE47, and VvMATE49 in Group 3 may contribute to Al³⁺ detoxification and Fe²⁺/Fe³⁺ translocation via organic acid transport. This study provides helpful and fundamental information for grape MATE studies and resolves the confusion of gene IDs in different genome annotations.

Biochemistry and Molecular Basis of Intracellular Flavonoid Transport in Plants

Flavonoids are a biochemically diverse group of specialized metabolites in plants that are derived from phenylalanine. While the biosynthesis of the flavonoid aglycone is highly conserved across species and well characterized, numerous species-specific decoration steps and their relevance remained largely unexplored. The flavonoid biosynthesis takes place at the cytosolic side of the endoplasmatic reticulum (ER), but accumulation of various flavonoids was observed in the central vacuole. A universal explanation for the subcellular transport of flavonoids has eluded researchers for decades. Current knowledge suggests that a glutathione S-transferase-like protein (ligandin) protects anthocyanins and potentially proanthocyanidin precursors during the transport to the central vacuole. ABCC transporters and to a lower extend MATE transporters sequester anthocyanins into the vacuole. Glycosides of specific proanthocyanidin precursors are sequestered through MATE transporters. A P-ATPase in the tonoplast and potentially other proteins generate the proton gradient that is required for the MATE-mediated antiport. Vesicle-mediated transport of flavonoids from the ER to the vacuole is considered as an alternative or additional route.

Pseudomonas aeruginosa efflux pump superfamily (review of literature)

The significant increase in the number of antibiotic-resistant microorganisms observed in recent years is a public health problem worldwide. One of the molecular mechanisms for the formation of antimicrobial resistance in bacteria is the presence of efflux pumps. The review presents an analysis of experimental studies related to the study of efflux pumps in clinical strains of Pseudomonas aeruginosa, one of the representatives of hospital pathogens of the ESKAPE group. This review is intended for specialists developing new types of drugs against antibiotic-resistant strains, as well as researchers studying the mechanisms of bacterial resistance to antibiotics, heavy metals, biocides and other antimicrobial factors.

Plant Secondary Metabolite Transporters: Diversity, Functionality, and Their Modulation

Secondary metabolites (SMs) play crucial roles in the vital functioning of plants such as growth, development, defense, and survival via their transportation and accumulation at the required site. However, unlike primary metabolites, the transport mechanisms of SMs are not yet well explored. There exists a huge gap between the abundant presence of SM transporters, their identification, and functional characterization. A better understanding of plant SM transporters will surely be a step forward to fulfill the steeply increasing demand for bioactive compounds for the formulation of herbal medicines. Thus, the engineering of transporters by modulating their expression is emerging as the most viable option to achieve the long-term goal of systemic metabolic engineering for enhanced metabolite production at minimum cost. In this review article, we are updating the understanding of recent advancements in the field of plant SM transporters, particularly those discovered in the past two decades. Herein, we provide notable insights about various types of fully or partially characterized transporters from the ABC, MATE, PUP, and NPF families including their diverse functionalities, structural information, potential approaches for their identification and characterization, several regulatory parameters, and their modulation. A novel perspective to the concept of "Transporter Engineering" has also been unveiled by highlighting its potential applications particularly in plant stress (biotic and abiotic) tolerance, SM accumulation, and removal of anti-nutritional compounds, which will be of great value for the crop improvement program. The present study creates a roadmap for easy identification and a better understanding of various transporters, which can be utilized as suitable targets for transporter engineering in future research.

Genome-wide identification, characterization and expression analysis of MATE family genes in apple (Malus × domestica Borkh)

BACKGROUND

As an important group of the multidrug efflux transporter family, the multidrug and toxic compound extrusion (MATE) family has a wide range of functions and is distributed in all kingdoms of living organisms. However, only two MATE genes in apple have been analyzed and genome-wide comprehensive analysis of MATE family is needed.

RESULTS

In this study, a total of 66 MATE (MdMATE) candidates encoding putative MATE transporters were identified in the apple genome. These MdMATE genes were classified into four groups by phylogenetic analysis with MATE genes in Arabidopsis. Synteny analysis reveals that whole genome duplication (WGD) and segmental duplication events played a major role in the expansion of MATE gene family in apple. MdMATE genes show diverse expression patterns in different tissues/organs and developmental stages. Analysis of cis-regulatory elements in MdMATE promoter regions indicates that the function of MdMATE genes is mainly related to stress response. Besides, the changes of gene expression levels upon different pathogen infections reveal that MdMATE genes are involved in biotic stress response.

CONCLUSIONS

In this work, we systematically identified MdMATE genes in apple genome using a set of bioinformatics approaches. Our comprehensive analysis provided valuable resources for improving disease resistance in apple and further functional characterization of MATE genes in other species.

Genome-wide characterization of MATE gene family and expression profiles in response to abiotic stresses in rice (Oryza sativa)

Multidrug and toxic compound extrusion (MATE) proteins are involved in many physiological functions of plant growth and development. Although an increasing number of MATE proteins have been identified, the understanding of MATE proteins is still very limited in rice. In this study, 46 MATE proteins were identified from the rice (Oryza sativa) genome by homology searches and domain prediction. The rice MATE family was divided into four subfamilies based on the phylogenetic tree. Tandem repeats and fragment replication contribute to the expansion of the rice MATE gene family. Gene structure and cis-regulatory elements reveal the potential functions of MATE genes. Analysis of gene expression showed that most of MATE genes were constitutively expressed and the expression patterns of genes in different tissues were analyzed using RNA-seq. Furthermore, qRT-PCR-based analysis showed differential expression patterns in response to salt and drought stress. The analysis results of this study provide comprehensive information on the MATE gene family in rice and will aid in understanding the functional divergence of MATE genes.

Enhanced aluminum tolerance in sugarcane: evaluation of SbMATE overexpression and genome-wide identification of ALMTs in Saccharum spp

BACKGROUND

A major limiting factor for plant growth is the aluminum (Al) toxicity in acidic soils, especially in tropical regions. The exclusion of Al from the root apex through root exudation of organic acids such as malate and citrate is one of the most ubiquitous tolerance mechanisms in the plant kingdom. Two families of anion channels that confer Al tolerance are well described in the literature, ALMT and MATE family.

RESULTS

In this study, sugarcane plants constitutively overexpressing the Sorghum bicolor MATE gene (SbMATE) showed improved tolerance to Al when compared to non-transgenic (NT) plants, characterized by sustained root growth and exclusion of aluminum from the root apex based on the result obtained with hematoxylin staining. In addition, genome-wide analysis of the recently released sugarcane genome identified 11 ALMT genes and molecular studies showed potential new targets for aluminum tolerance.

CONCLUSIONS

Our results indicate that the transgenic plants overexpressing the Sorghum bicolor MATE has an improved tolerance to Al. The expression profile of ALMT genes revels potential candidate genes to be used has an alternative for agricultural expansion in Brazil and other areas with aluminum toxicity in poor and acid soils.

Update on Multidrug Resistance Efflux Pumps in Acinetobacter spp

Acinetobacter spp. have become of increased clinical importance as studies have shown the antimicrobial resistant potential of these species. Efflux pumps can lead to reduced susceptibility to a variety of antibiotics and are present in large number across Acinetobacter spp. There are six families of efflux pumps that have been shown to be of clinical relevance: the major facilitator superfamily (MFS), small multidrug resistance (SMR) family, ATP-binding cassette (ABC) family, multidrug and toxic compound extrusion (MATE) family, proteobacterial antimicrobial compound efflux (PACE) family, and the resistance-nodulation-division (RND) family. Much work has been done for understanding and characterizing the roles these efflux pumps play in relation to antimicrobial resistance and the physiology of these bacteria. RND efflux pumps, with their expansive substrate profiles, are a major component of Acinetobacter spp. antimicrobial resistance. New discoveries over the last decade have shed light on the complex regulation of these efflux pumps, leading to greater understanding and the potential of slowing the reduced susceptibility seen in these bacterial species.

Pharmacogenetic Evaluation of Metformin and Sulphonylurea Response in Mexican Mestizos with Type 2 Diabetes

BACKGROUND

In Mexico, approximately 25% of patients with type 2 diabetes (T2D) have adequate glycemic control. Polymorphisms in pharmacogenetic genes have been shown to have clinical consequences resulting in drug toxicity or therapeutic inefficacy.

OBJECTIVE

The study aimed to evaluate the impact of variants in genes known to be involved in response to oral hypoglycemic drugs, such as CYP2C9, OCT, MATE, ABCA1 and C11orf65, in the Mexican Mestizo population of T2D patients.

METHODS

In this study, 265 patients with T2D were enrolled from the Hospital Juárez de México, Mexico City. Genotyping was performed by TaqMan® assays. SNP-SNP interactions were analyzed using the multifactor dimensionality reduction (MDR) method.

RESULTS

Carriers of the del allele of rs72552763 could achieve better glycemic control than noncarriers. There was a significant difference in plasma glucose and HbA1c levels among rs622342 genotypes. The results suggested an SNP-SNP interaction between rs72552763 and rs622342 OCT1 and rs12943590 MATE2.

CONCLUSION

The interaction between rs72552763 and rs622342 in OCT1, and rs12943590 in MATE2 suggested an important role of these polymorphisms in metformin response in T2D Mexican Mestizo population.

Principles of Alternating Access in Multidrug and Toxin Extrusion (MATE) Transporters

The multidrug and toxin extrusion (MATE) transporters catalyze active efflux of a broad range of chemically- and structurally-diverse compounds including antimicrobials and chemotherapeutics, thus contributing to multidrug resistance in pathogenic bacteria and cancers. Multiple methodological approaches have been taken to investigate the structural basis of energy transduction and substrate translocation in MATE transporters. Crystal structures representing members from all three MATE subfamilies have been interpreted within the context of an alternating access mechanism that postulates occupation of distinct structural intermediates in a conformational cycle powered by electrochemical ion gradients. Here we review the structural biology of MATE transporters, integrating the crystallographic models with biophysical and computational studies to define the molecular determinants that shape the transport energy landscape. This holistic analysis highlights both shared and disparate structural and functional features within the MATE family, which underpin an emerging theme of mechanistic diversity within the framework of a conserved structural scaffold.

Differential in vitro interactions of the Janus kinase inhibitor ruxolitinib with human SLC drug transporters

Interactions of the Janus kinase (JAK) inhibitor ruxolitinib with solute carriers (SLCs) remain incompletely characterised. The present study was therefore designed to investigate this issue.The interactions of ruxolitinib with SLCs were analysed using transporter-overexpressing human embryonic kidney HEK293 cells. Substrate accumulation was detected by spectrofluorimetry, liquid chromatography coupled to tandem mass spectrometry or scintillation counting.Ruxolitinib was found to potently inhibit the activities of organic anion transporter 3 (OAT3), organic cation transporter 2 (OCT2), multidrug and toxin extrusion 1 (MATE1) and MATE2-K (half maximal inhibitory concentration (IC₅₀) < 10 µM). It blocked OAT1, OAT4, OATP1B1, OATP1B3, OATP2B1 and OCT3, but in a weaker manner (IC₅₀ > 10 µM), whereas OCT1 was not impacted. No time-dependent inhibition was highlighted. When applying the US Food and Drug Administration (FDA) criteria for transporters-related drug-drug interaction risk, OCT2 and MATE2-K, unlike MATE1 and OAT3, were predicted to be in vivo inhibited by ruxolitinib. Cellular uptake studies additionally indicated that ruxolitinib is a substrate for MATE1 and MATE2-K, but not for OAT3 and OCT2.Ruxolitinib in vitro blocked activities of most of SLC transporters. Only OCT2 and MATE-2K may be however clinically inhibited by the JAK inhibitor, with the caution for OCT2 that in vitro inhibition data were generated with an FDA-non recommended fluorescent substrate. Ruxolitinib MATEs-mediated transport may additionally deserve attention for its possible pharmacological consequences in MATE-positive cells.

Principles and Experimental Considerations for In Vitro Transporter Interaction Assays

Drug transporters are universally acknowledged as important determinants of the absorption, distribution, metabolism, and excretion of both endogenous and exogenous compounds. Altered transporter function, whether due to genetic polymorphism, DDIs, disease, or environmental factors such as dietary constituents, can result in changes in drug efficacy and/or toxicity due to changes in circulating or tissue levels of either drugs or endogenous substrates.Prediction of whether and to what extent the biological fate of a drug is influenced by drug transporters, therefore, requires in vitro test systems that can accurately predict the risk and magnitude of clinical DDIs. While these in vitro assessments appear simple in theory, practitioners recognize that there are multiple factors that can influence experimental outcomes. A better understanding of these variables, including test compound characteristics, test systems, assay formats, and experimental design, will enable clear, actionable steps and translatable outcomes that may avoid unnecessary downstream clinical engagement. This chapter will delineate the role of these variables in improving in vitro assay outcomes.

Trospium Chloride Transport by Mouse Drug Carriers of the Slc22 and Slc47 Families

Background: The muscarinic receptor antagonist trospium chloride (TCl) is used for pharmacotherapy of the overactive bladder syndrome. TCl is a hydrophilic positively charged drug. Therefore, it has low permeability through biomembranes and requires drug transporters for distribution and excretion. In humans, the organic cation transporters OCT1 and OCT2 and the multidrug and toxin extrusion MATE1 and MATE2-K carriers showed TCl transport. However, their individual role for distribution and excretion of TCl is unclear. Knockout mouse models lacking mOct1/mOct2 or mMate1 might help to clarify their role for the overall pharmacokinetics of TCl. Method: In preparation of such experiments, TCl transport was analyzed in HEK293 cells stably transfected with the mouse carriers mOct1, mOct2, mMate1, and mMate2, respectively. Results: Mouse mOct1, mOct2, and mMate1 showed significant TCl transport with Km values of 58.7, 78.5, and 29.3 µM, respectively. In contrast, mMate2 did not transport TCl but showed MPP⁺ transport with Km of 60.0 µM that was inhibited by the drugs topotecan, acyclovir, and levofloxacin. Conclusion: TCl transport behavior as well as expression pattern were quite similar for the mouse carriers mOct1, mOct2, and mMate1 compared to their human counterparts.

Identification and Expression of the Multidrug and Toxic Compound Extrusion (MATE) Gene Family in Capsicum annuum and Solanum tuberosum

Multidrug and Toxic Compound Extrusion (MATE) proteins are essential transporters that extrude metabolites and participate in plant development and the detoxification of toxins. Little is known about the MATE gene family in the Solanaceae, which includes species that produce a broad range of specialized metabolites. Here, we identified and analyzed the complement of MATE genes in pepper (Capsicum annuum) and potato (Solanum tuberosum). We classified all MATE genes into five groups based on their phylogenetic relationships and their gene and protein structures. Moreover, we discovered that tandem duplication contributed significantly to the expansion of the pepper MATE family, while both tandem and segmental duplications contributed to the expansion of the potato MATE family, indicating that MATEs took distinct evolutionary paths in these two Solanaceous species. Analysis of ω values showed that all potato and pepper MATE genes experienced purifying selection during evolution. In addition, collinearity analysis showed that MATE genes were highly conserved between pepper and potato. Analysis of cis-elements in MATE promoters and MATE expression patterns revealed that MATE proteins likely function in many stages of plant development, especially during fruit ripening, and when exposed to multiple stresses, consistent with the existence of functional differentiation between duplicated MATE genes. Together, our results lay the foundation for further characterization of pepper and potato MATE gene family members.

Tucatinib Inhibits Renal Transporters OCT2 and MATE Without Impacting Renal Function in Healthy Subjects

Tucatinib is a potent tyrosine kinase inhibitor selective for human epidermal growth factor receptor 2 (HER2) approved by the US Food and Drug Administration for the treatment of HER2‐positive metastatic breast cancer and in development for other HER2‐positive solid tumors. Modest, reversible serum creatinine (SCr) elevations have been observed in tucatinib clinical trials. SCr is conveyed by the renal drug transporters organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) and 2‐K (MATE2‐K) and can increase in the presence of inhibitors of these transporters. In vitro, tucatinib inhibited OCT2‐, MATE1‐, and MATE2‐K‐mediated transport of metformin, with IC₅₀ values of 14.7, 0.340, and 0.135 µM, respectively. Tucatinib also inhibited OCT2‐ and MATE1‐mediated transport of creatinine, with IC₅₀ values of 0.107 and 0.0855 µM, respectively. A phase 1 study with metformin administered orally in the absence and presence of tucatinib was conducted in 18 healthy subjects. Renal function was assessed by measuring glomerular filtration rate (GFR; based on iohexol plasma clearance) and endogenous markers (SCr, cystatin C‐based estimated glomerular filtration rate [eGFR]) with and without tucatinib. Metformin exposure increased (1.4‐fold) and renal clearance decreased (29.99‐17.64 L/h) with tucatinib, with no effect on metformin maximum concentration. Creatinine clearance transiently decreased 23% with tucatinib. GFR and eGFR, which are unaffected by OCT2 and/or MATE1/2‐K transport, were unchanged with tucatinib. These data demonstrate that tucatinib inhibits OCT2‐ and MATE1/2‐K‐mediated tubular secretion of creatinine, which may manifest as mild SCr elevations that are not indicative of renal impairment.

A single-population GWAS identified AtMATE expression level polymorphism caused by promoter variants is associated with variation in aluminum tolerance in a local Arabidopsis population

Organic acids (OA) are released from roots in response to aluminum (Al), conferring an Al tolerance to plants that is regulated by OA transporters such as ALMT (Al-activated malate transporter) and multi-drug and toxic compound extrusion (MATE). We have previously reported that the expression level polymorphism (ELP) of AtALMT1 is strongly associated with variation in Al tolerance among natural accessions of Arabidopsis. However, although AtMATE is also expressed following Al exposure and contributes to Al tolerance, whether AtMATE contributes to the variation of Al tolerance and the molecular mechanisms of ELP remains unclear. Here, we dissected the natural variation in AtMATE expression level in response to Al at the root using diverse natural accessions of Arabidopsis. Phylogenetic analysis revealed that more than half of accessions belonging to the Central Asia (CA) population show markedly low AtMATE expression levels, while the majority of European populations show high expression levels. The accessions of the CA population with low AtMATE expression also show significantly weakened Al tolerance. A single-population genome-wide association study (GWAS) of AtMATE expression in the CA population identified a retrotransposon insertion in the AtMATE promoter region associated with low gene expression levels. This may affect the transcriptional regulation of AtMATE by disrupting the effect of a cis-regulatory element located upstream of the insertion site, which includes AtSTOP1 (sensitive to proton rhizotoxicity 1) transcription factor-binding sites revealed by chromatin immunoprecipitation-qPCR analysis. Furthermore, the GWAS performed without the accessions expressing low levels of AtMATE, excluding the effect of AtMATE promoter polymorphism, identified several candidate genes potentially associated with AtMATE expression.

Cloning and Functional Characterization of a Flavonoid Transport-Related MATE Gene in Asiatic Hybrid Lilies (Lilium spp.)

Previous studies have suggested that multidrug and toxic compound extrusion (MATE) proteins might be involved in flavonoid transportation. However, whether MATE proteins are involved in anthocyanin accumulation in Lilium is unclear. Here, a flavonoid transport-related MATE candidate gene, LhDTX35, was cloned from the Asiatic hybrid lily cultivar ‘Tiny Padhye’ by rapid amplification of 5’ and 3’ cDNA ends (RACE) and found to encode 507 amino acids. BLASTx results indicated that LhDTX35 showed high homology to the DTX35 genes of other species. Bioinformatics analysis predicted that the protein encoded by LhDTX35 possessed 12 typical transmembrane segments and had functional domains typical of the MATE-like superfamily. Phylogenetic analysis grouped LhDTX35 in the same clade as the DTX35 of other species. Notably, the expression pattern of LhDTX35 was positively correlated with floral anthocyanin accumulation in ‘Tiny Padhye’. A subcellular localization assay showed that the protein encoded by LhDTX35 was plasmalemma localized but not nuclear, indicating that the LhDTX35 gene may function as a carrier protein to transport anthocyanins in Lilium. Functional complementation of the ArabidopsisDTX35 gene demonstrated that LhDTX35 could restore silique-infertility and the anthocyaninless phenotype of an ArabidopsisDTX35 mutant. These results indicated that LhDTX35 might be involved in anthocyanin accumulation in Lilium.

Identification and fine-mapping of a genetic locus underlying soybean tolerance to SMV infections

Soybean mosaic virus (SMV) is a major pathogen causing yield loss. Developing soybean plants tolerant or resistant to SMV is important for mitigating the adverse effects of the viral infection. However, most studies have focused on the resistance to normal SMV strains. Thus, investigations of the resistance or tolerance to the novel recombinant SMV strain have been limited. To address the threat of the recombinant SMV, two soybean parent genotypes with contrasting reactions to the recombinant SMV and 211 F9:11 recombinant inbred lines were evaluated under artificial inoculation conditions. The JD12 plants are resistant to the recombinant SMV, whereas HT is highly tolerant, but still susceptible. Genetic analyses suggested that the resistance of JD12 is controlled by a single dominant gene and the tolerance is a quantitative trait. The QTL mapping results revealed one QTL (qTsmv-13) for resistance and two QTLs (qTsmv-2 and qTsmv-3) for tolerance. A comparison between known resistance genes and the QTLs identified in this study suggested that qTsmv-13 and qTsmv-2 may correspond to Rsv1 and Rsv4, respectively, whereas qTsmv-3 represents a newly identified QTL for SMV tolerance. We further delimited qTsmv-3 to an interval of approximately 86 kb with a map-based cloning strategy. Only two of five candidate genes, Glyma.03G00550 and Glyma.03G00570, varied between the parents. Additionally, Glyma.03G00550, which is a multidrug and toxic compound extrusion transporter gene, is the likely candidate gene for qTsmv-3. In summary, our research opens a new avenue for formulating strategies to breed soybean varieties tolerant to SMV.

Sequence and structural determinants of ligand-dependent alternating access of a MATE transporter

Multidrug and toxic compound extrusion (MATE) transporters are ubiquitous ion-coupled antiporters that extrude structurally and chemically dissimilar cytotoxic compounds and have been implicated in conferring multidrug resistance. Here, we integrate double electron-electron resonance (DEER) with functional assays and site-directed mutagenesis of conserved residues to illuminate principles of ligand-dependent alternating access of PfMATE, a proton-coupled MATE from the hyperthermophilic archaeon Pyrococcus furiosus Pairs of spin labels monitoring the two sides of the transporter reconstituted into nanodiscs reveal large-amplitude movement of helices that alter the orientation of a putative substrate binding cavity. We found that acidic pH favors formation of an inward-facing (IF) conformation, whereas elevated pH (>7) and the substrate rhodamine 6G stabilizes an outward-facing (OF) conformation. The lipid-dependent PfMATE isomerization between OF and IF conformation is driven by protonation of a previously unidentified intracellular glutamate residue that is critical for drug resistance. Our results can be framed in a mechanistic model of transport that addresses central aspects of ligand coupling and alternating access.

An in vitro study on interaction of anisodine and monocrotaline with organic cation transporters of the SLC22 and SLC47 families

Current study systematically investigated the interaction of two alkaloids, anisodine and monocrotaline, with organic cation transporter OCT1, 2, 3, MATE1 and MATE2-K by using in vitro stably transfected HEK293 cells. Both anisodine and monocrotaline inhibited the OCTs and MATE transporters. The lowest IC₅₀ was 12.9 µmol·L^-1 of anisodine on OCT1 and the highest was 1.8 mmol·L^-1 of monocrotaline on OCT2. Anisodine was a substrate of OCT2 (K_m = 13.3 ± 2.6 µmol·L^-1 and V_max = 286.8 ± 53.6 pmol/mg protein/min). Monocrotaline was determined to be a substrate of both OCT1 (K_m = 109.1 ± 17.8 µmol·L^-1, V_max = 576.5 ± 87.5 pmol/mg protein/min) and OCT2 (K_m = 64.7 ± 14.8 µmol·L^-1, V_max = 180.7 ± 22.0 pmol/mg protein/min), other than OCT3 and MATE transporters. The results indicated that OCT2 may be important for renal elimination of anisodine and OCT1 was responsible for monocrotaline uptake into liver. However neither MATE1 nor MATE2-K could facilitate transcellular transport of anisodine and monocrotaline. Accumulation of these drugs in the organs with high OCT1 expression (liver) and OCT2 expression (kidney) may be expected.

nerii

During the last years, many evidences have been accumulating about the phytohormone indole-3-acetic acid (IAA) as a multifaceted compound in the microbial world, with IAA playing a role as a bacterial intra and intercellular signaling molecule or as an effector during pathogenic or beneficial plant–bacteria interactions. However, pretty much nothing is known on the mechanisms that bacteria use to modulate IAA homeostasis, in particular on IAA active transport systems. Here, by an approach combining in silico three-dimensional (3D) structural modeling and docking, mutagenesis, quantitative gene expression analysis, and HPLC FLD auxin quantitative detection, for the first time a bacterial multidrug and toxic compound extrusion (MATE) transporter was demonstrated to be involved in the efflux of IAA, as well as of its conjugate IAA–Lysine, in the plant pathogenic hyperplastic bacterium Pseudomonas savastanoi pv. nerii strain Psn23. Furthermore, according to the role proved to be played by Psn23 MatE in the development of plant disease, and to the presence of Psn23 MatE homologs in all the genomospecies of the P. syringae complex, this membrane transporter could likely represent a promising target for the design of novel and selective anti-infective molecules for plant disease control.

The Genome Structure of Ciprofloxacin-Resistant Mycoplasma Hominis Clinical Isolates

The genome structure of three ciprofloxacin-resistant Mycoplasma hominis clinical isolates was studied using next-generation sequencing on the Illumina platform. The protein sequences of the studied Mycoplasma strains were found to have a high degree of homology. Mycoplasma hominis (M45, M57, MH1866) was shown to have limited biosynthetic capabilities, associated with the predominance of the genes encoding the proteins involved in catabolic processes. Multiple single-nucleotide substitutions causing intraspecific polymorphism of Mycoplasma hominis were found. The genes encoding the efflux systems - ABC transporters (the ATP-binding cassette superfamily) and proteins of the MATE (multidrug and toxic compound extrusion) family - were identified. The molecular mechanism of ciprofloxacin resistance of the Mycoplasma hominis M45 and M57 isolates was found to be associated with the Ser83Leu substitution in DNA gyrase subunit A. In the Mycoplasma hominis MH1866 isolate it was related to the Lys144Arg substitution in topoisomerase IV subunit A.

A Self-Reported Version of the Measurements in the Addictions for Triage and Evaluation-Q: Concurrent Validity with the MATE 2.1

INTRODUCTION

Substance abuse treatment centers require reliable and valid instruments to monitor treatment progress, to evaluate treatment effectiveness, and to initiate clinical trials. Currently the Measurements in the Addictions for Triage and Evaluation (MATE) 2.1, an instrument that serves these purposes, is considered quite lengthy and intensive, especially in the case of allocation to milder treatment intensity. Therefore, a self-reported version of the MATE-Q was designed for patients with mild to moderate substance-abuse and co-occurring problems. The aim of the present study was to assess concurrent validity with the interviewer version of the MATE (version 2.1).

MATERIALS AND METHODS

Data were collected at 2 locations of a Dutch substance abuse treatment center, one location in a large city and one in a suburban area. A correlational design was employed, where each included participant completed a MATE-Q and a MATE 2.1 within 3 days or less (administered at intake, before treatment initiation). A total of 98 treatment-seeking patients were included (51.0% alcohol as a primary problem, 19.4% cannabis, 14.3% gambling and 6.1% cocaine). Measurements included the MATE-Q and the MATE 2.1. Intraclass correlation coefficients (ICCs) for single measures were calculated, deploying the 2-way mixed procedure with absolute agreement. Descriptives of scores comprise means and Cronbach's alpha for internal consistency.

RESULTS

For the majority (15 out of 24) of the scores ICCs were equal or above 0.7. For 93 patients (95%), the primary problem substance or problem behavior was reported correspondingly. Nine MATE-Q mean scores differed significantly from their MATE 2.1 counterparts.

DISCUSSION/CONCLUSION

For the majority of scores, the MATE-Q has acceptable concurrent validity for the assessment of patients with mild to moderate substance abuse and co-occurring problems.

Identification of genes encoding ALMT and MATE transporters as candidate aluminum tolerance genes from a typical acid soil plant, Psychotria rubra (Rubiaceae)

To understand how tropical plants have adapted to acid soils, we analyzed the transcriptome of seedlings of Psychotria rubra, a typical species found on acid soils. Using RNA-seq, we identified 22,798 genes, including several encoding proteins of the Al³⁺-activated malate transporter (ALMT) and multidrug and toxic compound extrusion (MATE) families. Molecular phylogenetic analysis of ALMTs and MATEs revealed the grouping of those from P. rubra, which may be useful to select targets for elucidating the molecular basis of P. rubra adaptation to acid soils in the future. The transcriptome datasets obtained in this study would help us to further understand the physiological and ecological aspects of soil adaptation of Psychotria species.

Lonicera japonica extract increases metformin distribution in the liver without change of systemic exposed metformin in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Flower and flower bud of Lonicera japonica, Lonicerae Flos, have been popularly used as medicinal plant for the treatment of clearing heat and thirst, thereby improving diabetic or diabetic associated symptoms (thirst and poor eyesight).

AIM OF THE STUDY

Organic cation transporters (OCTs) and multi-drug and toxin extrusion proteins (MATEs) are known to play important roles in metformin transport in the liver and kidneys. Thus, there might be interactions between Lonicerae Flos and metformin via OCTs and MATEs. Also treatment period has been issued in transporter-mediated drug interactions. The objective of this study was to determine the effect of Lonicerae Flos ethanol extract (LJ) on metformin pharmacokinetics and its glucose lowering activity in different treatment periods.

MATERIALS AND METHODS

Effect of LJ on metformin uptake was evaluated in vitro HEK-293 cells expressing human OCTs or MATEs. Treatment period-dependent impact of LJ on systemic exposure and hepatic distribution of metformin as well as its glucose tolerance activity were assessed in in vivo rats.

RESULTS

LJ substantially inhibited MATE1-mediated metformin uptake in vitro. In evaluating treatment period effects of LJ and metformin, 1-, 7-, and 28-day co-treatments of LJ with metformin did not change systemic exposure of metformin compared to those in metformin alone. Whereas, 28-day co-treatment of LJ with metformin increased metformin concentration in liver as a pharmacological target site of metformin. It could be due to the reduced MATE1-mediated metformin efflux from hepatocytes to bile by MATE1 inhibition in liver. Glucose tolerance activity was also enhanced by 28-day co-treatment of LJ and metformin compared to metformin alone.

CONCLUSIONS

In 28-day co-treatment of LJ and metformin, LJ increased metformin concentration in liver and improved glucose tolerance activity without systemic exposure change of metformin, suggesting the importance to consider treatment period effect and both systemic exposure and tissue distribution in drug interactions.

Investigating Aspects of Renal Physiology and Pharmacology in Organ and Organoid Culture

Some aspects of renal physiology, in particular transport across tubular epithelia, are highly relevant to pharmacokinetics and to drug toxicity. The use of animals to model human renal physiology is limited, but human-derived renal organoids offer an alternative, relevant system in culture. Here, we explain how the activity of specific transport systems can be assessed in renal organoid and organ culture, using a system illustrated mainly for mouse but that can be extended to human organoids.

Mechanisms of organic acids and boron induced tolerance of aluminum toxicity: A review

Aluminum is a major limiting abiotic factor for plant growth and productivity on acidic soils. The primary disorder of aluminum toxicity is the rapid cessation of root elongation. The root apex is the most sensitive part of this organ. Although significant literature evidence and hypothesis exist on aluminum toxicity, the explicit mechanism through which aluminum ceases root growth is still indefinable. The mechanisms of tolerance in plants have been the focus of intense research. Some plant species growing on acidic soils have developed tolerance mechanisms to overcome and mitigate aluminum toxicity, either by avoiding entry of Al³⁺ into roots (exclusion mechanism) or by being able to counterbalance toxic Al³⁺ engrossed by the root system (internal tolerance mechanism). Genes belonging to ALMT (Aluminum-activated malate transporter) and MATE (Multidrug and toxin compounds extrusion) have been identified that are involved in the aluminum-activated secretion of organic acids from roots. However, different plant species show different gene expression pattern. On the other hand, boron (B) (indispensable micronutrient) is a promising nutrient in the tolerance to aluminum toxicity. It not only hinders the adsorption of aluminum to the cell wall but also improves plant growth. This review mainly explains the critical roles of organic acid and B-induced tolerance to aluminum by summarizing the mechanisms of ALMT, MATE, internal detoxification, molecular traits and genetic engineering of crops.

Phylogenetic analysis of upland cotton MATE gene family reveals a conserved subfamily involved in transport of proanthocyanidins

The multidrug and toxic compound extrusion (MATE) protein belongs to a secondary transporter family, which plays a role in transporting different kinds of substrates like phytohormones and secondary metabolites. In plant, MATE transporters related to the endogenous and exogenous mechanisms of detoxification for secondary metabolites such as alkaloids, flavonoids, anthocyanins and other secondary metabolites have been studied. However, a genome-wide analysis of the MATE family is rarely reported in upland cotton (Gossypium hirsutum L.). In the study, a total of 72 GhMATEs were identified from the genome of upland cotton, which were classified into four subfamilies with possible diverse functions such as transport of proanthocyanidins (PAs), accumulation of alkaloids, extrusion of xenobiotic compounds, regulation of disease resistance and response to abiotic stresses. Meanwhile, the gene structure, evolutionary relationship, physical location, conservative motifs, subcellular localization and gene expression pattern of GhMATEs have been further analysed. Three of these MATE genes (GhMATE12, GhMATE16 and GhMATE38) were identified as candidate genes due to their functions in transport of PA similar to GhTT12. These results provide a new perspective on upland cotton MATE gene family for their potential roles in transport of PA and a theoretical basis for further analyzing the function of MATE genes and improving the fiber quality of brown cotton.

Sodium and proton coupling in the conformational cycle of a MATE antiporter from Vibrio cholerae

Secondary active transporters belonging to the multidrug and toxic compound extrusion (MATE) family harness the potential energy of electrochemical ion gradients to export a broad spectrum of cytotoxic compounds, thus contributing to multidrug resistance. The current mechanistic understanding of ion-coupled substrate transport has been informed by a limited set of MATE transporter crystal structures from multiple organisms that capture a 12-transmembrane helix topology adopting similar outward-facing conformations. Although these structures mapped conserved residues important for function, the mechanistic role of these residues in shaping the conformational cycle has not been investigated. Here, we use double-electron electron resonance (DEER) spectroscopy to explore ligand-dependent conformational changes of NorM from Vibrio cholerae (NorM-Vc), a MATE transporter proposed to be coupled to both Na⁺ and H⁺ gradients. Distance measurements between spin labels on the periplasmic side of NorM-Vc identified unique structural intermediates induced by binding of Na⁺, H⁺, or the substrate doxorubicin. The Na⁺- and H⁺-dependent intermediates were associated with distinct conformations of TM1. Site-directed mutagenesis of conserved residues revealed that Na⁺- and H⁺-driven conformational changes are facilitated by a network of polar residues in the N-terminal domain cavity, whereas conserved carboxylates buried in the C-terminal domain are critical for stabilizing the drug-bound state. Interpreted in conjunction with doxorubicin binding of mutant NorM-Vc and cell toxicity assays, these results establish the role of ion-coupled conformational dynamics in the functional cycle and implicate H⁺ in the doxorubicin release mechanism.

Aluminum-activated root malate and citrate exudation is independent of NIP1;2-facilitated root-cell-wall aluminum removal in Arabidopsis

In Arabidopsis, aluminum (Al) exclusion from the root is mainly facilitated by Al-activated root malate and citrate exudation through the ALMT1 malate transporter and the MATE citrate transporter, respectively. However, the nature of an internal Al tolerance mechanism remains largely unknown. In a recent study, we showed that NIP1;2 facilitates Al-malate transport from the root cell wall into the root symplasm and subsequent root-to-shoot translocation and thus NIP1;2 plays key roles in Al detoxification and internal tolerance in Arabidopsis. We discovered that the NIP1;2-mediated Al removal from the root cell wall requires a functional ALMT1-mediated malate exudation system, which allows the formation of an Al-malate complex in the root cell wall. Thus, a coordinated function between the exclusion and the internal resistance mechanisms, linked by the ALMT1-mediated root malate exudation and the NIP1;2-mediated Al uptake system, is critical for Al resistance in Arabidopsis.

Characterization of CcSTOP1; a C2H2-type transcription factor regulates Al tolerance gene in pigeonpea

MAIN CONCLUSION

Al-responsive citrate-transporting CcMATE1 function and its regulation by CcSTOP1 were analyzed using NtSTOP1 -KD tobacco- and pigeonpea hairy roots, respectively, CcSTOP1 binding sequence of CcMATE1 showed similarity with AtALMT1 promoter. The molecular mechanisms of Aluminum (Al) tolerance in pigeonpea (Cajanus cajan) were characterized to provide information for molecular breeding. Al-inducible citrate excretion was associated with the expression of MULTIDRUGS AND TOXIC COMPOUNDS EXCLUSION (CcMATE1), which encodes a citrate transporter. Ectopic expression of CcMATE1-conferred Al tolerance to hairy roots of transgenic tobacco with the STOP1 regulation system knocked down. This gain-of-function approach clearly showed CcMATE1 was involved in Al detoxification. The expression of CcMATE1 and another Al-tolerance gene, ALUMINUM SENSITIVE 3 (CcALS3), was regulated by SENSITIVE TO PROTON RHIZOTOXICITY1 (CcSTOP1) according to loss-of-function analysis of pigeonpea hairy roots in which CcSTOP1 was suppressed. An in vitro binding assay showed that the Al-responsive CcMATE1 promoter contained the GGNVS consensus bound by CcSTOP1. Mutation of GGNVS inactivated the Al-inducible expression of CcMATE1 in pigeonpea hairy roots. This indicated that CcSTOP1 binding to the promoter is critical for CcMATE1 expression. The STOP1 binding sites of both the CcMATE1 and AtALMT1 promoters contained GGNVS and a flanking 3' sequence. The GGNVS region was identical in both CcMATE1 and AtALMT1. By contrast, the 3' flanking sequence with binding affinity to STOP1 did not show similarity. Putative STOP1 binding sites with similar structures were also found in Al-inducible MATE and ALMT1 promoters in other plant species. The characterized Al-responsive CcSTOP1 and CcMATE1 genes will help in pigeonpea breeding in acid soil tolerance.

Two MATE Transporters with Different Subcellular Localization are Involved in Al Tolerance in Buckwheat

Buckwheat (Fagopyrum esculentum) shows high tolerance to aluminum (Al) toxicity, but the molecular mechanisms responsible for this high Al tolerance are still poorly understood. Here, we investigated the involvement of two MATE (multi-drug and toxic compound extrusion) genes in Al tolerance. Both FeMATE1 and FeMATE2 showed efflux transport activity for citrate, but not for oxalate when expressed in Xenopus oocytes. A transient assay with buckwheat leaf protoplasts using green fluorescent protein (GFP) fusion showed that FeMATE1 was mainly localized to the plasma membrane, whereas FeMATE2 was localized to the trans-Golgi and Golgi. The expression of FeMATE1 was induced by Al only in the roots, but that of FeMATE2 was up-regulated in both the roots and leaves. Furthermore, the expression of both genes only responded to Al toxicity, but not to other stresses including low pH, cadmium (Cd) and lanthanum (La). Heterologous expression of FeMATE1 or FeMATE2 in the Arabidopsis mutant atmate partially rescued its Al tolerance. Expression of FeMATE1 also partially recovered the Al-induced secretion of citrate in the transgenic lines, whereas expression of FeMATE2 did not complement the citrate secretion. Further physiological analysis showed that buckwheat roots also secreted citrate in addition to oxalate in response to Al in a dose-responsive manner. Taken together, our results indicate that FeMATE1 is involved in the Al-activated citrate secretion in the roots, while FeMATE2 is probably responsible for transporting citrate into the Golgi system for the internal detoxification of Al in the roots and leaves of buckwheat.

Renal Transporter-Mediated Drug-Drug Interactions: Are They Clinically Relevant?

The kidney, through the distinct processes of passive glomerular filtration and active tubular secretion, plays an important role in the elimination of numerous endobiotics (eg, hormones, metabolites), toxins, nutrients, and drugs. Renal transport pathways mediating active tubular secretion and reabsorption in the proximal tubule are complex, involving apical and basolateral transporters acting in concert. Detailed studies of the molecular mechanisms of net active tubular secretion have established the involvement of multiple transporters with overlapping substrate specificity mediating competing secretion and reabsorption pathways. Although drug interactions arising from inhibition of renal transporters are rare relative to other mechanisms, they can involve commonly administered drugs (eg, cimetidine, metformin), may be underappreciated due to muted effects on plasma pharmacokinetics relative to tissue levels, can affect narrow-therapeutic-index medications (eg, antiarrhythmic, oncology medications), and may disproportionately affect sensitive populations where polypharmacy is common (eg, the elderly, diabetics). In particular, there is the potential for larger-magnitude interactions in subjects with reduced glomerular filtration rates due to the increased relative contribution of tubular secretion. The assessment of additional endpoints in drug-drug interaction studies including pharmacodynamics, positron emission tomography imaging, and metabolomics promises to expand our understanding of the clinical relevance of renal drug interactions.

The R2R3-MYB TT2b and the bHLH TT8 genes are the major regulators of proanthocyanidin biosynthesis in the leaves of Lotus species

By exploiting interspecific hybrids and their progeny, we identified key regulatory and transporter genes intimately related to proanthocyanidin biosynthesis in leaves of Lotus spp. Proanthocyanidins (PAs), known as condensed tannins, are polymeric flavonoids enriching forage legumes of key nutritional value to prevent bloating in ruminant animals. Unfortunately, major forage legumes such as alfalfa and clovers lack PAs in edible tissues. Therefore, engineering the PA trait in herbage of forage legumes is paramount to improve both ecological and economical sustainability of cattle production system. Progresses on the understanding of genetic determinants controlling PA biosynthesis and accumulation have been mainly made studying mutants of Arabidopsis, Medicago truncatula and Lotus japonicus, model species unable to synthesize PAs in the leaves. Here, we exploited interspecific hybrids between Lotus corniculatus, with high levels of PAs in the leaves, and Lotus tenuis, with no PAs in these organs, and relative F₂ progeny, to identify among candidate PA regulators and transporters the genes mainly affecting this trait. We found that the levels of leaf PAs significantly correlate with the expression of MATE1, the putative transporter of glycosylated PA monomers, and, among the candidate regulatory genes, with the expression of the MYB genes TT2a, TT2b and MYB14 and the bHLH gene TT8. The expression levels of TT2b and TT8 also correlated with those of all key structural genes of the PA pathways investigated, MATE1 included. Our study unveils a different involvement of the three Lotus TT2 paralogs to the PA trait and highlights differences in the regulation of this trait in our Lotus genotypes with respect to model species. This information opens new avenues for breeding bloat safe forage legumes.

Identification and characterization of suppressor mutants of stop1

BACKGROUND

Proton stress and aluminum (Al) toxicity are major constraints limiting crop growth and yields on acid soils (pH < 5). In Arabidopsis, STOP1 is a master transcription factor that controls the expression of a set of well-characterized Al tolerance genes and unknown processes involved in low pH resistance. As a result, loss-of-function stop1 mutants are extremely sensitive to low pH and Al stresses.

RESULTS

Here, we report on screens of an ethyl-methane sulphonate (EMS)-mutagenized stop1 population and isolation of nine strong stop1 suppressor mutants, i.e., the tolerant to proton stress (tps) mutants, with significantly enhanced root growth at low pH (4.3). Genetic analyses indicated these dominant and partial gain-of-function mutants are caused by mutations in single nuclear genes outside the STOP1 locus. Physiological characterization of the responses of these tps mutants to excess levels of Al and other metal ions further classified them into five groups. Three tps mutants also displayed enhanced resistance to Al stress, indicating that these tps mutations partially rescue the hypersensitive phenotypes of stop1 to both low pH stress and Al stress. The other six tps mutants showed enhanced resistance only to low pH stress but not to Al stress. We carried out further physiologic and mapping-by-sequencing analyses for two tps mutants with enhanced resistance to both low pH and Al stresses and identified the genomic regions and candidate loci in chromosomes 1 and 2 that harbor these two TPS genes.

CONCLUSION

We have identified and characterized nine strong stop1 suppressor mutants. Candidate loci for two tps mutations that partially rescue the hypersensitive phenotypes of stop1 to low pH and Al stresses were identified by mapping-by-sequencing approaches. Further studies could provide insights into the structure and function of TPSs and the regulatory networks underlying the STOP1-mediated processes that lead to resistance to low pH and Al stresses in Arabidopsis.

Overexpression of BdMATE Gene Improves Aluminum Tolerance in Setaria viridis

Acidic soils are distributed worldwide, predominantly in tropical and subtropical areas, reaching around 50% of the arable soil. This type of soil strongly reduces crop production, mainly because of the presence of aluminum, which has its solubility increased at low pH levels. A well-known physiological mechanism used by plants to cope with Al stress involves activation of membrane transporters responsible for organic acid anions secretion from the root apex to the rhizosphere, which chelate Al, preventing its absorption by roots. In sorghum, a membrane transporter gene belonging to multidrug and toxic compound extrusion (MATE) family was identified and characterized as an aluminum-activated citrate transporter gene responsible for Al tolerance in this crop. Setaria viridis is an emerging model for C4 species and it is an important model to validate some genes for further C4 crops transformation, such as sugarcane, maize, and wheat. In the present work, Setaria viridis was used as a model plant to overexpress a newly identified MATE gene from Brachypodium distachyon (BdMATE), closely related to SbMATE, for aluminum tolerance assays. Transgenic S. viridis plants overexpressing a BdMATE presented an improved Al tolerance phenotype, characterized by sustained root growth and exclusion of aluminum from the root apex in transgenic plants, as confirmed by hematoxylin assay. In addition, transgenic plants showed higher root citrate exudation into the rhizosphere, suggesting that Al tolerance improvement in these plants could be related to the chelation of the metal by the organic acid anion. These results suggest that BdMATE gene can be used to transform C4 crops of economic importance with improved aluminum tolerance.

Transport properties of valsartan, sacubitril and its active metabolite (LBQ657) as determinants of disposition

1. The potential for drug-drug interactions of LCZ696 (a novel, crystalline complex comprising sacubitril and valsartan) was investigated in vitro. 2. Sacubitril was shown to be a highly permeable P-glycoprotein (P-gp) substrate and was hydrolyzed to the active anionic metabolite LBQ657 by human carboxylesterase 1 (CES1b and 1c). The multidrug resistance-associated protein 2 (MRP2) was shown to be capable of LBQ657 and valsartan transport that contributes to the elimination of either compound. 3. LBQ657 and valsartan were transported by OAT1, OAT3, OATP1B1 and OATP1B3, whereas no OAT- or OATP-mediated sacubitril transport was observed. 4. The contribution of OATP1B3 to valsartan transport (73%) was appreciably higher than that by OATP1B1 (27%), Alternatively, OATP1B1 contribution to the hepatic uptake of LBQ657 (∼70%) was higher than that by OATP1B3 (∼30%). 5. None of the compounds inhibited OCT1/OCT2, MATE1/MATE2-K, P-gp, or BCRP. Sacubitril and LBQ657 inhibited OAT3 but not OAT1, and valsartan inhibited the activity of both OAT1 and OAT3. Sacubitril and valsartan inhibited OATP1B1 and OATP1B3, whereas LBQ657 weakly inhibited OATP1B1 but not OATP1B3. 6. Drug interactions due to the inhibition of transporters are unlikely due to the redundancy of the available transport pathways (LBQ657: OATP1B1/OAT1/3 and valsartan: OATP1B3/OAT1/3) and the low therapeutic concentration of the LCZ696 analytes.

Molecular cloning and functional characterization of DkMATE1 involved in proanthocyanidin precursor transport in persimmon (Diospyros kaki Thunb.) fruit

Persimmon fruits accumulate a large amount of proanthocyanidins (PAs) in "tannin cells" during development that cause the sensation of astringency due to coagulation of oral proteins. Pollination-constant non-astringent (PCNA) is a spontaneous mutant persimmon phenotype that loses its astringency naturally on the tree at maturity; while the more common non-PCNA fruits remain rich in PAs until they are fully ripened. Here, we isolated a DkMATE1 gene encoding a Multidrug And Toxic Compound Extrusion (MATE) family protein from the Chinese PCNA (C-PCNA) 'Eshi 1'. Expression patterns of DkMATE1 were positively correlated with the accumulation of PAs in different types of persimmons fruits during fruit development. An analysis of the inferred amino acid sequences and phylogenetic relationships indicated that DkMATE1 is a putative PA precursor transporter, and subcellular localization assays revealed that DkMATE1 is localized in the vacuolar membrane. Ectopic expression of the DkMATE1 in Arabidopsis tt12 mutant supported that DkMATE1 could complement its biological function in transporting epicatechin 3'-O-glucoside as a PAs precursor from the cytoplasm to vacuole. Furthermore, the transient over-expression and silencing of DkMATE1 in 'Mopanshi' persimmon leaves resulted in a significant increase and a decrease in PA content, respectively. The analysis of cis-elements in DkMATE1 promoter regions indicated that DkMATE1 might be regulated by DkMYB4, another well-known structural gene in persimmon. Overall, our results show that DkMATE1 may be an essential PA precursor membrane transporter that plays an important role in PA biosynthesis in persimmon.

In vitro assessment of the roles of drug transporters in the disposition and drug-drug interaction potential of olaparib

1. In vitro assessments were conducted to examine interactions between olaparib (a potent oral inhibitor of poly[ADP-ribose] polymerase) and drug transporters. 2. Olaparib showed inhibition of the hepatic drug uptake transporters OATP1B1 (IC₅₀ values of 20.3 μM and 27.1 μM) and OCT1 (IC₅₀ 37.9 μM), but limited inhibition of OATP1B3 (25% at 100 μM); inhibition of the renal uptake transporters OCT2 (IC₅₀ 19.9 μM) and OAT3 (IC₅₀ 18.4 μM), but limited inhibition of OAT1 (13.5% at 100 μM); inhibition of the renal efflux transporters MATE1 and MATE2K (IC₅₀s 5.50 μM and 47.1 μM, respectively); inhibition of the efflux transporter MDR1 (IC₅₀ 76.0 μM), but limited inhibition of BCRP (47% at 100 μM) and no inhibition of MRP2. At clinically relevant exposures, olaparib has the potential to cause pharmacokinetic interactions via inhibition of OCT1, OCT2, OATP1B1, OAT3, MATE1 and MATE2K in the liver and kidney, as well as MDR1 in the liver and GI tract. Olaparib was found to be a substrate of MDR1 but not of several other transporters. 3. Our assessments indicate that olaparib is a substrate of MDR1 and may cause clinically meaningful inhibition of MDR1, OCT1, OCT2, OATP1B1, OAT3, MATE1 and MATE2K.

Urinary Dopamine as a Potential Index of the Transport Activity of Multidrug and Toxin Extrusion in the Kidney

Dopamine is a cationic natriuretic catecholamine synthesized in proximal tubular cells (PTCs) of the kidney before secretion into the lumen, a key site of its action. However, the molecular mechanisms underlying dopamine secretion into the lumen remain unclear. Multidrug and toxin extrusion (MATE) is a H⁺/organic cation antiporter that is highly expressed in the brush border membrane of PTCs and mediates the efflux of organic cations, including metformin and cisplatin, from the epithelial cells into the urine. Therefore, we hypothesized that MATE mediates dopamine secretion, a cationic catecholamine, into the tubule lumen, thereby regulating natriuresis. Here, we show that [³H]dopamine uptake in human (h) MATE1-, hMATE-2K- and mouse (m) MATE-expressing cells exhibited saturable kinetics. Fluid retention and decreased urinary excretion of dopamine and Na⁺ were observed in Mate1-knockout mice compared to that in wild-type mice. Imatinib, a MATE inhibitor, inhibited [³H]dopamine uptake by hMATE1-, hMATE2-K- and mMATE1-expressing cells in a concentration-dependent manner. At clinically-relevant concentrations, imatinib inhibited [³H]dopamine uptake by hMATE1- and hMATE2-K-expressing cells. The urinary excretion of dopamine and Na⁺ decreased and fluid retention occurred in imatinib-treated mice. In conclusion, MATE transporters secrete renally-synthesized dopamine, and therefore, urinary dopamine has the potential to be an index of the MATE transporter activity.

Polyspecific organic cation transporters and their impact on drug intracellular levels and pharmacodynamics

Most drugs are intended to act on molecular targets residing within a specific tissue or cell type. Therefore, the drug concentration within the target tissue or cells is most relevant to its pharmacological effect. Increasing evidences suggest that drug transporters not only play a significant role in governing systemic drug levels, but are also an important gate keeper for intra-tissue and intracellular drug concentrations. This review focuses on polyspecific organic cation transporters, which include the organic cation transporters 1-3 (OCT1-3), the multidrug and toxin extrusion proteins 1-2 (MATE1-2) and the plasma membrane monoamine transporter (PMAT). Following an overview of the tissue distribution, transport mechanisms, and functional characteristics of these transporters, we highlight the studies demonstrating the ability of locally expressed OCTs to impact intracellular drug concentrations and directly influence their pharmacological and toxicological activities. Specifically, OCT1-mediated metformin access to its site of action in the liver is impacted by genetic polymorphisms and chemical inhibition of OCT1. The impact of renal OCT2 and MATE1/2-K in cisplatin intrarenal accumulation and nephrotoxicity is reviewed. New data demonstrating the role of OCT3 in salivary drug accumulation and secretion is discussed. Whenever possible, the pharmacodynamic response and toxicological effects is presented and discussed in light of intra-tissue and intracellular drug exposure. Current challenges, knowledge gaps, and future research directions are discussed. Understanding the impact of transporters on intra-tissue and intracellular drug concentrations has important implications for rational-based optimization of drug efficacy and safety.

Identification of novel natural inhibitor for NorM - a multidrug and toxic compound extrusion transporter - an insilico molecular modeling and simulation studies

The emergence of bacterial multidrug resistance is an increasing problem in treatment of infectious diseases. An important cause for the multidrug resistance of bacteria is the expression of multidrug efflux transporters. The multidrug and toxic compound extrusion (MATE) transporters are most recently recognized as unique efflux system for extrusion of antimicrobials and therapeutic drugs due to energy stored in either Na⁺ or H⁺ electrochemical gradient. In the present study, high throughput virtual screening of natural compound collections against NorM - a MATE transporter from Neisseria gonorrhea (NorM-NG) has been carried out followed by flexible docking. The molecular simulation in membrane environment has been performed for understanding the stability and binding energetic of top lead compounds. Results identified a compound from the Indian medicinal plant "Terminalia chebula" which has good binding free energy compared to substrates (rhodamine 6 g, ethidium) and more favorable interactions with the central cavity forming active site residues. The compound has restricted movement in TM7, TM8, and TM1, thus blocking the disruption of Na+ - coordination along with equilibrium state bias towards occlude state of NorM transporter. Thus, this compound blocks the effluxing pathway of antimicrobial drugs and provides as a natural bioactive lead inhibitor against NorM transporter in drug-resistant gonorrhea.

Structure and function of multidrug and toxin extrusion proteins (MATEs) and their relevance to drug therapy and personalized medicine

Multidrug and toxin extrusion (MATE; SLC47A) proteins are membrane transporters mediating the excretion of organic cations and zwitterions into bile and urine and thereby contributing to the hepatic and renal elimination of many xenobiotics. Transported substrates include creatinine as endogenous substrate, the vitamin thiamine and a number of drug agents with in part chemically different structures such as the antidiabetic metformin, the antiviral agents acyclovir and ganciclovir as well as the antibiotics cephalexin and cephradine. This review summarizes current knowledge on the structural and molecular features of human MATE transporters including data on expression and localization in different tissues, important aspects on regulation and their functional role in drug transport. The role of genetic variation of MATE proteins for drug pharmacokinetics and drug response will be discussed with consequences for personalized medicine.

Genome-wide analysis of MATE transporters and expression patterns of a subgroup of MATE genes in response to aluminum toxicity in soybean

BACKGROUND

Multidrug and toxic compound extrusion (MATE) family is an important group of the multidrug efflux transporters that extrude organic compounds, transporting a broad range of substrates such as organic acids, plant hormones and secondary metabolites. However, genome-wide analysis of MATE family in plant species is limited and no such studies have been reported in soybean.

RESULTS

A total of 117 genes encoding MATE transporters were identified from the whole genome sequence of soybean (Glycine max), which were denominated as GmMATE1 - GmMATE117. These 117 GmMATE genes were unevenly localized on soybean chromosomes 1 to 20, with both tandem and segmental duplication events detected, and most genes showed tissue-specific expression patterns. Soybean MATE family could be classified into four subfamilies comprising ten smaller subgroups, with diverse potential functions such as transport and accumulation of flavonoids or alkaloids, extrusion of plant-derived or xenobiotic compounds, regulation of disease resistance, and response to abiotic stresses. Eight soybean MATE transporters clustered together with the previously reported MATE proteins related to aluminum (Al) detoxification and iron translocation were further analyzed. Seven stress-responsive cis-elements such as ABRE, ARE, HSE, LTR, MBS, as well as a cis-element of ART1 (Al resistance transcription factor 1), GGNVS, were identified in the upstream region of these eight GmMATE genes. Differential gene expression analysis of these eight GmMATE genes in response to Al stress helps us identify GmMATE75 as the candidate gene for Al tolerance in soybean, whose relative transcript abundance increased at 6, 12 and 24 h after Al treatment, with more fold changes in Al-tolerant than Al-sensitive cultivar, which is consistent with previously reported Al-tolerance related MATE genes.

CONCLUSIONS

A total of 117 MATE transporters were identified in soybean and their potential functions were proposed by phylogenetic analysis with known plant MATE transporters. The cis-elements and expression patterns of eight soybean MATE genes related to Al detoxification/iron translocation were analyzed, and GmMATE75 was identified as a candidate gene for Al tolerance in soybean. This study provides a first insight on soybean MATE family and their potential roles in soybean response to abiotic stresses especially Al toxicity.