Cation Transport Research Articles

Prognostic significance of CNNM4 in ovarian cancer: a comprehensive bioinformatics analysis.

Ovarian cancer (OV) is a common malignancy in the female reproductive system, characterized by poor prognosis and high recurrence rates. The discovery of dependable molecular markers is crucial for improving the timeliness of detection, diagnosis, and treatment, ultimately aiming to lower fatality rates. CNNM4 (cyclin and CBS domain divalent metal cation transport mediator 4), a member of the CNNM (Cyclin M) family, binds to PRL (prolactin) to regulate magnesium homeostasis and influence tumor cell proliferation. Although CNNM4 is implicated in various cancers, its role in OV remains unclear. In vitro experiments assessed CNNM4 expression and its impact on the proliferation and migration of OV cells. Comparisons of TCGA and GTEx data were used to identify correlations between clinical features and outcomes. The role of CNNM4 in OV was further explored through comprehensive bioinformatics analyses. Elevated levels of CNNM4 expression were observed in OV cells and tissues, and were linked to a poor prognosis. CNNM4 could modulate the proliferation and migration of various OV cell lines, including IOSE-80, SKOV-3, and A2780. Through involvement in multiple signaling pathways, evidenced by GSVA and GSEA, CNNM4 was implicated in OV progression. CNNM4 positively regulated the infiltration level of Macrophages M2, T cells CD4 memory resting and NK cells resting, and had a negative regulation effect on NK cells activated and T cells gamma delta. Moreover, CNNM4 is related to drug sensitivity of OV. A prediction model based on CNNM4 expression and clinical symptoms was constructed to predict OV prognosis. CNNM4 may affect the progression of OV and is associated with a poor prognosis. It has potential as a biomarker for predicting survival and as a target for therapeutic interventions in OV patients.

Effects of genetic variants of organic cation transporters on metformin response in newly diagnosed patients with type 2 diabetes.

Type 2 diabetes mellitus (T2DM) is a chronic disease that affects millions of people worldwide. Metformin is the optimal initial therapy for patients with T2DM. Genetic factors play a vital role in metformin response, including variations in drug efficacy and potential side effects. To determine the effects of genetic variants of multidrug and toxin extrusion protein 2 (MATE2), ataxia telangiectasia mutated (ATM), and serine/threonine kinase 11 (STK11) genes on metformin response in a cohort of Saudi patients. This prospective observational study included 76 T2DM newly diagnosed Saudi patients treated with metformin monotherapy and 80 control individuals. Demographic data, lipid profiles, creatinine levels, and hemoglobin A1c (HbA1c) levels were collected before and after treatment. All participants were genotyped for 5 single-nucleotide polymorphisms (SNPs), including rs4621031, rs34399035, rs2301759, rs1800058, and rs11212617, using TaqMan R genotyping assays. This study included 156 subjects. The subjects' mean ± SD age was 50.4 ± 10.14 years. The difference in HbA1c levels in T2DM after treatment ranged from -1.20% to 8.8%, with a mean value of 0.927 ± 1.73%. In general, 73.7% of the patients with T2DM showed an adequate response to metformin (HbA1c < 7%). STK11 (rs2301759) significantly affects the response to metformin in T2DM patients. In the rs2301759 single-nucleotide polymorphisms, the prevalence of an adequate response to metformin was significantly higher among patients with C/C and T/C genotypes than among non-responders (P = .021). However, no statistically significant associations were observed for the other tested SNPs. Our study provides evidence of an association between STK11 (rs2301759) and response to metformin in Saudi patients with T2DM. The need for targeted studies on specific gene-drug associations is emphasized, and further studies with a larger population should be conducted.

Comparative genomics reveals putative copper tolerance genes in a Fusarium oxysporum strain.

Copper has been widely used as a main component in fungicides due to its versatility and effectivity. However, copper contamination from the environment creates selective pressure for the emergence of copper-tolerant pathogenic fungal strains that may proliferate and further cause damage to important agricultural crops. Although some studies focused on specific cellular mechanisms of copper tolerance, comprehensive genomic data is lacking. Here, we examined the genes potentially involved in copper tolerance by conducting a comparative analysis of newly sequenced genomes of two Fusarium oxysporum strains, IB-SN1W (copper-tolerant) and Foc-3429 (copper-sensitive), with other Fusarium species. Whole genome assembly and annotation identified ten core chromosomes shared between the two strains. Protein prediction revealed 16,894 and 15,420 protein coding genes for IB-SN1W and Foc-3429, respectively. There are 388 unique genes in IB-SN1W not found in Foc-3429, potentially contributing to copper tolerance. Furthermore, the identification of synteny between the two strains, including the analysis of orthologous genes within the Fusarium genus, confirmed the presence of accessory chromosomes that are specific to IB-SN1W, accounting for 13% of the genome. These accessory chromosomes consist of genes associated with cation transporter activity, vacuole, copper oxidases, and copper transporters which shed light on the potential mechanism of copper tolerance in this strain. Additionally, a region within an accessory chromosome contains a high density of copper-related genes, raising the possibility that horizontal transfer of these chromosomes may contribute to copper tolerance.

Examining Erythrocytes as Potential Blood Biomarkers for Autism Spectrum Disorder: Their Relationship to Symptom Severity and Adaptive Behavior.

Multiple research teams have documented various abnormalities in erythrocyte properties in children with autism spectrum disorder (ASD) compared with neurotypical individuals. Reduced erythrocyte deformability, a crucial factor for microcirculation and oxygen delivery, may affect brain function. Other key factors like nitric oxide (NO) and Na,K-ATPase-regulated cation transport also play roles in both erythrocyte deformability and ASD, suggesting a possible relationship between erythrocyte parameters and autism severity. Thus, this study aims to describe these associations, exploring erythrocyte properties as potential biomarkers in ASD. A total of 179 ASD children were enrolled in this study. Diagnosis was confirmed by the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) and Autism Diagnostic Interview-Revised. The Vineland Adaptive Behavior Scales, Third Edition (VABS-3), was used to assess adaptive behavior. RBC deformability was measured using a filtration technique, while NO production by RBCs was assessed via DAF-2DA fluorescence. Na,K-ATPase kinetics and RBC osmotic resistance were evaluated spectrophotometrically. Children with more severe ASD symptoms had more impaired deformability and osmotic resistance than children with mild symptoms. Higher RBC NO production was linked to better scores in some VABS-3 subdomains, and in the social affect domain of ADOS-2. Higher affinity of Na,K-ATPase for sodium negatively correlated with the occurrence of repetitive and restricted behavior-one of the core ASD symptoms. This study identified potential links between ASD severity and RBC properties. While erythrocyte quality can influence ASD symptomatology, the observed relationships-such as those involving RBC deformability, NO production, Na,K-ATPase kinetics, and osmotic resistance-were not strong or consistent enough to be considered reliable diagnostic or prognostic biomarkers.

Underneath the Gut-Brain Axis in IBD-Evidence of the Non-Obvious.

The gut-brain axis (GBA) plays a pivotal role in human health and wellness by orchestrating complex bidirectional regulation and influencing numerous critical processes within the body. Over the past decade, research has increasingly focused on the GBA in the context of inflammatory bowel disease (IBD). Beyond its well-documented effects on the GBA-enteric nervous system and vagus nerve dysregulation, and gut microbiota misbalance-IBD also leads to impairments in the metabolic and cellular functions: metabolic dysregulation, mitochondrial dysfunction, cationic transport, and cytoskeleton dysregulation. These systemic effects are currently underexplored in relation to the GBA; however, they are crucial for the nervous system cells' functioning. This review summarizes the studies on the particular mechanisms of metabolic dysregulation, mitochondrial dysfunction, cationic transport, and cytoskeleton impairments in IBD. Understanding the involvement of these processes in the GBA may help find new therapeutic targets and develop systemic approaches to improve the quality of life in IBD patients.

Three-chamber electrochemical reactor for selective lithium extraction from brine

Efficient lithium recovery from geothermal brines is crucial for the battery industry. Current electrochemical separation methods struggle with the simultaneous presence of Na+, K+, Mg2+, and Ca2+ because these cations are similar to Li+, making it challenging to separate effectively. We address these challenges with a three-chamber reactor featuring a polymer porous solid electrolyte in the middle layer. This design improves the transference number of Li+ (tLi+) by 2.1 times compared to the two-chamber reactor and also reduces the chlorine evolution reaction, a common side reaction in electrochemical lithium extraction, to only 6.4% in Faradaic Efficiency. Employing a lithium-ion conductive glass ceramic (LICGC) membrane, the reactor achieved high tLi+ of 97.5% in LiOH production from simulated brine, while the concentrations of Na+ K+, Mg2+, and Ca2+ are below the detection limit. Electrochemical experiments and surface analysis elucidated the cation transport mechanism, highlighting the impact of Na+ on Li+ migration at the LICGC interface.

Study of red vine phenotypic plasticity across central-southern Italy sites: an integrated analysis of the transcriptome and weather indices through WGCNA.

The grapevine (Vitis spp., family Vitaceae) is characterized by marked phenotypic plasticity. Its ability to withstand specific environmental conditions depends on the activation of highly coordinated responses resulting from interactions among genotypes (G) and environmental factors (E). In this study, the transcriptomes of commercially ripe berries of the Cabernet Sauvignon and Aglianico genotypes grown in open fields at three different sites in central-southern Italy (Campania, Molise and Sicily) were analyzed with RNA sequencing. These transcriptomic data were integrated with a comprehensive set of weather course indices through weighted gene co-expression network analysis (WGCNA). A total of 11,887 differentially expressed genes (DEGs) were retrieved, most of which were associated with the Aglianico genotype. The plants from the Sicilian site presented the greatest number of DEGs for both genotypes. Most of the weather course data (daily maximum air temperature, relative humidity, air pressure, dew point, and hours of sun radiation) were significantly correlated with the "lightcyan1" module, confirming WGCNA as a powerful method for identifying genes of high biological interest. Within this module, the gene encoding the ACA10 cation transporter was highly expressed in plants of both genotypes from Campania, where the lowest anthocyanin content was recorded. The transcriptome was also correlated with quality traits, such as total soluble solids and polyphenol content. This approach could lead to the identification of a transcriptomic profile that may specifically identify a genotype and its growing site and to the discovery of hub genes that might function as markers of wine quality.

Hypertensive Nephropathy Changes the Expression of Drug-Metabolizing Enzymes and Transporters in Spontaneously Hypertensive Rat Liver and Kidney.

Hypertensive nephropathy (HN) has become one of the main causes of end-stage renal disease. Drug combination therapy is a common clinical treatment for HN. However, the impact of HN on drug-metabolizing enzymes and transporters, which may lead to drug-drug interactions (DDIs) and even trigger toxic side effects, remains unclear. The aim of this study was to investigate changes in major drug-metabolizing enzymes and transporters in the liver and kidney of HN rats to improve the scientific foundations for the clinical treatment of HN. Spontaneously hypertensive rats (SHRs) were used as an animal HN model because their hypertension is similar to that of humans. Wistar-Kyoto rats (WKYs) were used as the control group. Body weight, blood pressure, hematoxylin-eosin (HE) staining and biochemical analysis were performed to evaluate whether the HN model was successfully constructed. Quantitative real-time polymerase chain reaction (PCR) and western blotting were used to evaluate the mRNA and protein expression of drug-metabolizing enzymes, transporters and related nuclear transcription factors. In HN rats, the mRNA expression of the drug-metabolizing enzymes cytochrome P450 (Cyp) 2b1, Cyp2c11, Cyp3a1 and Cyp7a1 was significantly upregulated. The protein level of CYP3A1 was consistent with its mRNA expression. Interestingly, the mRNA expression of the hepatic transporters organic cation transporter (Oct) 1, Oct2, organic anion transporter (Oat) 1, Oat2, multidrug resistant protein (Mrp) 2, multidrug resistance (Mdr) 1, organic anion transporting polypeptide (Oatp) 1b2 and na+/taurocholate cotransporting polypeptide (Ntcp) was also markedly upregulated. This may be directly influenced by the upregulation of the expression of the nuclear receptors farnesoid X receptor (Fxr), pregnane X receptor (Pxr), liver X-activated receptor (Lxr) and constitutive androstane receptor (Car). In the kidney of HN rats, the mRNA level of the drug-metabolizing enzyme Cyp2b1 significantly increased, while levels of Cyp1a1, Cyp2c11, Cyp3a1 and Cyp3a2 did not significantly change. The mRNA expression of the transporters multidrug and toxin extrusion (Mate) 1 and Mrp2 was obviously increased but was markedly depressed for peptide transporters (Pept) 1 and Pept2. These changes may be related to the cross effects of Pxr, Fxr and Car in kidney. HN pathological status can alter the expression of drug-metabolizing enzymes and transporters in the liver and kidney to varying degrees, thus affecting the disposition of substrate drugs in vivo. This suggests that to avoid potential risks, caution should be exercised when administering combination therapy for HN treatment.

Thermogenic Adipocytes Promote M2 Macrophage Polarization through CNNM4-Mediated Mg Secretion.

M2 macrophages promote adipose tissue thermogenesis which dissipates energy in the form of heat to combat obesity. However, the regulation of M2 macrophages by thermogenic adipocytes is unclear. Here, it is identified magnesium (Mg) as a thermogenic adipocyte-secreted factor to promote M2 macrophage polarization. Mg transporter Cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) induced by ADRB3-PKA-CREB signaling in thermogenic adipocytes during cold exposure mediates Mg efflux and Mg in turn binds to the DFG motif in mTOR to facilitate mTORC2 activation and M2 polarization in macrophages. In obesity, downregulation of CNNM4 expression inhibits Mg secretion from thermogenic adipocytes, which leads to decreased M2 macrophage polarization and thermogenesis. As a result, CNNM4 overexpression in adipocytes or Mg supplementation in adipose tissue ameliorates obesity by promoting thermogenesis. Importantly, an Mg wire implantation (AMI) approach is introduced to achieve adipose tissue-specific long-term Mg supplement. AMI promotes M2 macrophage polarization and thermogenesis and ameliorates obesity in mice. Taken together, a reciprocal regulation of thermogenic adipocytes and M2 macrophages important for thermogenesis is identified, and AMI is offered as a promising strategy against obesity.

Effects of Cimetidine and Dolutegravir on the Endogenous Drug-Drug Interaction Biomarkers for Organic Cation Transporter 2 and Multidrug and Toxin Extrusion Protein 1 in Healthy Volunteers.

This study was designed to assess the quantitative performance of endogenous drug-drug interaction (DDI) biomarkers (N1-methylnicotinamide (1-NMN), N1-methyladenosine (m1A), and creatinine) for the organic cation transporters, OCT2 and MATE1/2K in the kidney. Ten healthy volunteers received cimetidine (400 and 800 mg, single dose) or dolutegravir (50 mg, twice a day) together with metformin (500 mg). Cimetidine and dolutegravir were considered to act mainly as MATE1/2K and OCT2 inhibitors, respectively. The renal clearance (CLr) of metformin was decreased by 15.5% and 42.5% by cimetidine 400 and 800 mg, and by 26.8% and 56.9% by dolutegravir first and fifth doses, respectively. CLr ratio (CLrR) of 1-NMN were 0.93 and 0.64 for cimetidine 400 and 800 mg, and 0.87 and 0.47 for dolutegravir first and fifth doses, respectively. CLrR of m1A was less than that of 1-NMN: 1.0 and 0.80 for cimetidine 400 and 800 mg, and 0.77 and 0.71 for dolutegravir first and fifth doses, respectively. CLr of creatinine was significantly decreased only by cimetidine 800 mg. Individual CLrR of 1-NMN and m1A showed a positive correlation with the corresponding CLrR of metformin with r2 of 0.58 and 0.55, respectively. When evaluated individually, m1A showed a better correlation during cimetidine periods (r2 0.64) than 1-NMN (r2 0.36), but vice versa during dolutegravir periods (r2 1-NMN, 0.80; m1A, 0.32). These results suggest that 1-NMN and m1A might be more promising than creatinine as endogenous biomarkers for quantitatively assessing the DDI potential of investigational drugs for OCT2 and MATE1/2K based on their CLrR change.

Marked microcytosis and increased transferrin saturation: Think about variants in SLC11A2 (DMT1)

Congenital microcytic anemias are rare diseases associated with decreased hemoglobin synthesis and red blood cells of low corpuscular volume. DMT1/NRAMP2 is a highly conserved divalent cation transporter encoded by the SLC11A2 gene, expressed at the membrane of various cells. It ensures ferrous iron absorption from the apical membrane of enterocytes, iron recovery from urine by renal tubules, and acidified endosome uptake after transferrin internalization. Pathogenic DMT1 variants have been described in 10 individuals to date, associated with recessive hypochromic anemia and iron overload. Herein, we report a new variant of SLC11A2 (c.469A>G, p.Ile157Val) compound with known p.Arg416Cys associated with a frankly microcytic anemia and increased transferrin saturation. The clinical picture observed in the patient was exceptionally mild, extending the field of the DMT1 phenotypes to borderline anemias.

Boosting lithium/magnesium separation performance of selective electrodialysis membranes regulated by enamine reaction

Monovalent cation exchange membranes (MCEMs) have progressively played an important role in the field of ion separation. However, according to transition state theory (TST), synchronously tuning the enthalpy barrier (△H) and entropy barrier (△S) for cation transport to improve ion separation performance is challenging. Here, the enamine reaction between the -NH- and -CHO groups is applied to regulate the subsequent Schiff-base reaction between the -CHO and -NH2 groups, which reduces the positive charges of the selective layer but increases the steric hindrance. The increased -T△S (△S term) for cation transport plays an important role in improving Li+/Mg2+ separation performance. The optimal positively-charged glutaraldehyde@piperazine/polyethyleneimine assembled membrane (M-Glu@PIP/PEI) has a perm-selectivity (Li+/Mg2+) of 31.83 with a Li+ flux of 1.87 mol·m-2·h-1, surpassing the Li+/Mg2+ separation performance of state-of-the-art monovalent ion selective membranes (MISMs). Most importantly, the selective electrodialysis (S-ED) process with M-Glu@PIP/PEI can be directly applied to treat simulated salt-lake brines (SLBs), and its superior Li+/Mg2+ separation performance and operational stability enables 74.44 % of the lithium resources with a Li+ purity of 34.02 % to be recovered. This study presents new insights into the design of high-performance MCEMs for energy-efficient resource recovery.

Experimental investigation of an integrated electro-cation exchange reactor for better carbon dioxide extraction and environmental management

The research focuses on a uniquely designed three-compartment type integrated electrochemical reactor developed in a laboratory setting. This innovative reactor uses an electrolytic cation exchange technique to extract substantial quantities of carbon dioxide from ocean water as bicarbonate and carbonate while simultaneously producing hydrogen gas for potential hydrocarbon production. The study employs the Design Expert software package to evaluate and optimize the implementation of electrochemical carbon dioxide extraction from ocean water. The reactor is divided into three compartments by two cation-exchange membranes: a middle part and two electrode parts for the cathode and anode sides. The membranes possess acidic properties that facilitate cation transport while inhibiting anion transport. The laboratory studies, including 35-minute long experimental runs, are conducted to determine the system's feasibility by assessing carbon dioxide extraction under different conditions, such as electrolyte concentration, applied voltage, and pH levels. The reactor achieves a maximum CO₂ extraction rate of 1479.73 mg/min, with optimal conditions yielding 1514.6 mg/min. The ideal operating parameters are found to be a voltage of 14.8 V, an electrolyte concentration of 0.557 M, and a pH of 2.26. The results of the optimization study further reveal that carbon dioxide extraction increases with decreasing pH levels.

A Highly Sensitive UPLC-MS/MS Method for the Quantification of the Organic Cation Transporters' Mediated Metformin Uptake and Its Inhibition in Cells.

Metformin is the gold standard substrate for evaluating potential inhibitors of the organic cation transporters (OCTs). Here, we established a UPLC-MS/MS assay to quantify metformin in cell pellets with a range of 0.05-50 ng/mL using 6-deuterated metformin as an internal standard. We used an ion-pairing chromatographic approach with heptafluorobutyric acid, making use of a reverse-phase column, and overcame the associated ion-suppression via previously established post-column injection of aqueous ammonia. The assay was validated according to the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) recommendations for bioanalytical methods. The established extraction procedure was simple, very fast and ensured almost 100% recovery of the analyte. The exceptionally sharp peak form and retention of the ion-pairing chromatography are superior to other methods and allow us to measure as sensitively as 0.05 ng/mL. We used the herein established and validated method to develop a cellular OCT inhibition assay by using metformin as a substrate and human embryonic kidney cells (HEK) overexpressing the OCTs 1-3. The method presented may be useful for identifying new OCT inhibitors, but also for drug-drug interactions and other pharmacokinetic studies, where accurate quantification of low metformin amounts in relevant tissues is mandatory.

Metformin: Diverse molecular mechanisms, gastrointestinal effects and overcoming intolerance in type 2 Diabetes Mellitus: A review.

Metformin, the first line treatment for patients with type 2 diabetes mellitus, has alternative novel roles, including cancer and diabetes prevention. This narrative review aims to explore its diverse mechanisms, effects and intolerance, using sources obtained by searching Scopus, PubMed and Web of Science databases, and following Scale for the Assessment of Narrative Review Articles reporting guidelines. Metformin exerts it actions through duration influenced, and organ specific, diverse mechanisms. Its use is associated with inhibition of hepatic gluconeogenesis targeted by mitochondria and lysosomes, reduction of cholesterol levels involving brown adipose tissue, weight reduction influenced by growth differentiation factor 15 and novel commensal bacteria, in addition to counteraction of meta-inflammation alongside immuno-modulation. Interactions with the gastrointestinal tract include alteration of gut microbiota, enhancement of glucose uptake and glucagon like peptide 1 and reduction of bile acid absorption. Though beneficial, they may be linked to intolerance. Metformin related gastrointestinal adverse effects are associated with dose escalation, immediate release formulations, gut microbiota alteration, epigenetic predisposition, inhibition of organic cation transporters in addition to interactions with serotonin, histamine and the enterohepatic circulation. Potentially effective measures to overcome intolerance encompasses carefully objective targeted dose escalation, prescription of fixed dose combination, microbiome modulators and prebiotics, in addition to use of extended release formulations.

Efficient Li+/Mg2+ separation by two-dimensional montmorillonite membrane with stable channel structure through ion exchange and metal–organic coordination strategy

Two-dimensional (2D) nanochannel membranes stacked by nanosheets are promising membrane separation materials. However, intrinsic swelling properties of 2D membrane have emerged as a significant challenge to establish stable nanochannels and achieve high separation performance. Inspired by the natural ion exchange property of montmorillonite (MMT), we constructed a two-dimensional MMT membrane with robust nanochannels by exchanging Fe3+ into interlayer of the membrane, and further achieved efficient separation of Li+/Mg2+ through coordination manipulation of tannic acid (TA) and Fe3+. Swelling was dramatically prevented by strong interlayer interaction between exchanged Fe3+ and nanosheets resulting in a 32-fold increase in anti-swelling properties. Furthermore, experiments and simulations revealed that TA could rapidly chelate with Fe3+ to form a dense hydrophilic functional layer on the membrane interface, which endowed MMT membranes with enhanced mechanical strength, cation transport and recognition, as well as anti-fouling properties. Consequently, the resulting MMT membranes showed the Li+/Mg2+ selectivity as high as 9.98 with a fast Li+ permeation rate (0.108 mol m-2 h-1), which exceeded most of the previously reported membranes. This study proposed a novel strategy to diminish the trade-off effect among stability, ion flux, and selectivity of membranes, and inspired the development of next-generation ion selective separation membranes.

Facile design of a crown ether-functionalized polymeric membrane for highly efficient lithium and magnesium separation during electrodialysis

Efficient separation of magnesium and lithium is essential for the extraction of lithium resources from salt-lake brines. However, the current membrane separation technologies are challenged by the membrane permeability-selectivity trade-off. Herein, we demonstrated a facile and practical approach to fabricate crown ether-functionalized polymeric membranes with excellent Li+/Mg2+ separation performance by incorporating 12-crown-4 rings into the cellulose triacetate polymer network. The tightly and regularly arranged polymer chains anchored the crown ether rings firmly in the membrane structure, thereby facilitating the formation of stable and highly selective cation transport channels inside the membrane. As a result, the prepared membrane achieved an ultrahigh Li+/Mg2+ separation factor of ∼872 and Li+ flux of 22.6 μmol m−2 s−1, which was much superior to that of commercial CIMS and reported membrane separation technologies. The good long-term stability of the fabricated membrane is promising for achieving efficient magnesium-lithium separation in large-scale industrial applications.

Targeted Degradation of SOS1 Exhibits Potent Anticancer Activity and Overcomes Resistance in KRAS-Mutant Tumors and BCR-ABL-Positive Leukemia.

SOS1 is an essential guanine nucleotide exchange factor for RAS that also plays a critical role in the activation of the small GTPase RAC mediated by BCR-ABL in leukemogenesis. Despite this, small molecule inhibitors targeting SOS1 have shown limited efficacy in clinical trials for KRAS mutant cancers, and their potential as a therapeutic approach for chronic myeloid leukemia (CML) remains largely unexplored. In this study, we developed a potent SOS1 PROTAC SIAIS562055, which was designed by connecting a CRBN ligand to an analogue of the SOS1 inhibitor BI-3406. SIAIS562055 exhibited sustained degradation of SOS1 and inhibition of downstream ERK pathways, resulting in superior anti-proliferative activity compared to small molecule inhibitors. SIAIS562055 also potentiated the activity of both KRAS inhibitors in KRAS-mutant cancers and ABL inhibitors in BCR-ABL+ CML. In KRAS-mutant xenografts, SIAIS562055 displayed promising antitumor potency as a monotherapy and enhanced ERK inhibition and tumor regression when combined with KRAS inhibitors, overcoming acquired resistance. In CML cells, SIAIS562055 promoted the active uptake of BCR-ABL inhibitors by upregulating the carnitine/organic cation transporter SLC22A4. SIAIS562055 and BCR-ABL inhibitors synergistically enhanced inhibition of ABL phosphorylation and downstream signaling, demonstrating robust antitumor activities in both mouse xenografts and primary CML patient samples. In summary, this study suggests that PROTAC-mediated SOS1 degradation represents an effective therapeutic strategy for treating not only KRAS-mutant cancers but also BCR-ABL-harboring leukemia.

An extended substrate spectrum of the proton organic cation antiporter and relation to other cation transporters.

Most central nervous system (CNS) active drugs are organic cations, which need carrier proteins for efficient transfer through the blood-brain barrier (BBB). A genetically still unidentified proton organic cation (H+/OC) antiporter is found in several tissues, including endothelial cells of the BBB. We characterized the substrate spectrum of the H+/OC antiporter and the overlap in substrate spectrum with OCTN1, OCTN2 or OCT3 by screening 87 potential substrates for transport activity. Based on high antiport rates, 45 of the tested substances were substrates of the H+/OC antiporter. They included antidepressants (like tranylcypromine or nortriptyline), antipsychotics (like levomepromazine) and local anaesthetics. Concentration-dependent transport was confirmed for 38 of the substrates. Transport uptake depending on a pH gradient across the cell membrane confirmed that 43 drugs were indeed substrates of the H+/OC antiporter. However, the patterns of pH dependence differed between the substrates, possibly indicating different modes of transport or the existence of multiple antiporter proteins. The substrate overlap between the H+/OC antiporter and OCTN1, OCTN2 or OCT3 was minimal, indicating that the latter three are not the proteins underlying the H+/OC antiporter activity. Overall, about 50% of positively charged drugs may be substrates of the antiporter, which may be the most important membrane transport protein for many drugs.

Interruption of glucagon signaling augments islet non-alpha cell proliferation in SLC7A2- and mTOR-dependent manners

ObjectiveDysregulated glucagon secretion and inadequate functional beta cell mass are hallmark features of diabetes. While glucagon receptor (GCGR) antagonism ameliorates hyperglycemia and elicits beta cell regeneration in pre-clinical models of diabetes, it also promotes alpha and delta cell hyperplasia. We sought to investigate the mechanism by which loss of glucagon action impacts pancreatic islet non-alpha cells, and the relevance of these observations in a human islet context. MethodsWe used zebrafish, rodents, and transplanted human islets comprising six different models of interrupted glucagon signaling to examine their impact on delta and beta cell proliferation and mass. We also used models with global deficiency of the cationic amino acid transporter, SLC7A2, and mTORC1 inhibition via rapamycin, to determine whether amino acid-dependent nutrient sensing was required for islet non-alpha cell growth. ResultsInhibition of glucagon signaling stimulated delta cell proliferation in mouse and transplanted human islets, and in mouse islets. This was rapamycin-sensitive and required SLC7A2. Likewise, gcgr deficiency augmented beta cell proliferation via SLC7A2- and mTORC1-dependent mechanisms in zebrafish and promoted cell cycle engagement in rodent beta cells but was insufficient to drive a significant increase in beta cell mass in mice. ConclusionsOur findings demonstrate that interruption of glucagon signaling augments islet non-alpha cell proliferation in zebrafish, rodents, and transplanted human islets in a manner requiring SLC7A2 and mTORC1 activation. An increase in delta cell mass may be leveraged for future beta cell regeneration therapies relying upon delta cell reprogramming.