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Microbiology (Reading, England) Oct 2023Multidrug efflux pumps are molecular machines that sit in the bacterial cell membrane and pump molecules out from either the periplasm or cytoplasm to outside the cell....
Multidrug efflux pumps are molecular machines that sit in the bacterial cell membrane and pump molecules out from either the periplasm or cytoplasm to outside the cell. While involved in a variety of biological roles, they are primarily known for their contribution to antibiotic resistance by limiting the intracellular accumulation of antimicrobial compounds within bacteria. These transporters are often overexpressed in clinical isolates, leading to multidrug-resistant phenotypes. Efflux pumps are classified into several families based on their structure and understanding the characteristics of each family is important for the development of novel therapies to restore antibiotic potency.
Topics: Humans; Cytoplasm; Periplasm; Cell Membrane; Anti-Bacterial Agents; Membrane Transport Proteins
PubMed: 37787650
DOI: 10.1099/mic.0.001370 -
International Journal of Molecular... Aug 2023ABC transporters are ubiquitous in the human body and are responsible for the efflux of drugs. They are present in the placenta, intestine, liver and kidney, which are... (Review)
Review
ABC transporters are ubiquitous in the human body and are responsible for the efflux of drugs. They are present in the placenta, intestine, liver and kidney, which are the major organs that can affect the pharmacokinetic and pharmacologic properties of drugs. P-gp and BCRP transporters are the best-characterized transporters in the ABC superfamily, and they have a pivotal role in the barrier tissues due to their efflux mechanism. Moreover, during pregnancy, drug efflux is even more important because of the developing fetus. Recent studies have shown that placental and intestinal ABC transporters have great importance in drug absorption and distribution. Placental and intestinal P-gp and BCRP show gestational-age-dependent expression changes, which determine the drug concentration both in the mother and the fetus during pregnancy. They may have an impact on the efficacy of antibiotic, antiviral, antihistamine, antiemetic and oral antidiabetic therapies. In this review, we would like to provide an overview of the pharmacokinetically relevant expression alterations of placental and intestinal ABC transporters during pregnancy.
Topics: Female; Humans; Pregnancy; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Intestines; Membrane Transport Proteins; Neoplasm Proteins; Placenta
PubMed: 37685897
DOI: 10.3390/ijms241713089 -
Nature Structural & Molecular Biology Dec 2023Over half of mitochondrial proteins are imported from the cytosol via the pre-sequence pathway, controlled by the TOM complex in the outer membrane and the TIM23 complex...
Over half of mitochondrial proteins are imported from the cytosol via the pre-sequence pathway, controlled by the TOM complex in the outer membrane and the TIM23 complex in the inner membrane. The mechanisms through which proteins are translocated via the TOM and TIM23 complexes remain unclear. Here we report the assembly of the active TOM-TIM23 supercomplex of Saccharomyces cerevisiae with translocating polypeptide substrates. Electron cryo-microscopy analyses reveal that the polypeptide substrates pass the TOM complex through the center of a Tom40 subunit, interacting with a glutamine-rich region. Structural and biochemical analyses show that the TIM23 complex contains a heterotrimer of the subunits Tim23, Tim17 and Mgr2. The polypeptide substrates are shielded from lipids by Mgr2 and Tim17, which creates a translocation pathway characterized by a negatively charged entrance and a central hydrophobic region. These findings reveal an unexpected pre-sequence pathway through the TOM-TIM23 supercomplex spanning the double membranes of mitochondria.
Topics: Membrane Transport Proteins; Mitochondrial Precursor Protein Import Complex Proteins; Carrier Proteins; Mitochondrial Membrane Transport Proteins; Saccharomyces cerevisiae Proteins; Protein Transport; Mitochondria; Saccharomyces cerevisiae; Mitochondrial Proteins; Peptides; Membrane Proteins
PubMed: 37696957
DOI: 10.1038/s41594-023-01103-7 -
PloS One 2023Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies...
Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.
Topics: Humans; Mice; Animals; Blood-Brain Barrier; Amisulpride; Alzheimer Disease; Glucose Transporter Type 1; Molecular Docking Simulation; Brain; Membrane Transport Proteins; Antipsychotic Agents; Glucose; Glucose Transport Proteins, Facilitative; ATP Binding Cassette Transporter, Subfamily B
PubMed: 37874822
DOI: 10.1371/journal.pone.0286278 -
Cellular and Molecular Life Sciences :... Aug 2023Neutropenia and neutrophil dysfunction in glycogen storage disease type 1b (GSD1b) and severe congenital neutropenia type 4 (SCN4), associated with deficiencies of the...
Neutropenia and neutrophil dysfunction in glycogen storage disease type 1b (GSD1b) and severe congenital neutropenia type 4 (SCN4), associated with deficiencies of the glucose-6-phosphate transporter (G6PT/SLC37A4) and the phosphatase G6PC3, respectively, are the result of the accumulation of 1,5-anhydroglucitol-6-phosphate in neutrophils. This is an inhibitor of hexokinase made from 1,5-anhydroglucitol (1,5-AG), an abundant polyol in blood. 1,5-AG is presumed to be reabsorbed in the kidney by a sodium-dependent-transporter of uncertain identity, possibly SGLT4/SLC5A9 or SGLT5/SLC5A10. Lowering blood 1,5-AG with an SGLT2-inhibitor greatly improved neutrophil counts and function in G6PC3-deficient and GSD1b patients. Yet, this effect is most likely mediated indirectly, through the inhibition of the renal 1,5-AG transporter by glucose, when its concentration rises in the renal tubule following inhibition of SGLT2. To identify the 1,5-AG transporter, both human and mouse SGLT4 and SGLT5 were expressed in HEK293T cells and transport measurements were performed with radiolabelled compounds. We found that SGLT5 is a better carrier for 1,5-AG than for mannose, while the opposite is true for human SGLT4. Heterozygous variants in SGLT5, associated with a low level of blood 1,5-AG in humans cause a 50-100% reduction in 1,5-AG transport activity tested in model cell lines, indicating that SGLT5 is the predominant kidney 1,5-AG transporter. These and other findings led to the conclusion that (1) SGLT5 is the main renal transporter of 1,5-AG; (2) frequent heterozygous mutations (allelic frequency > 1%) in SGLT5 lower blood 1,5-AG, favourably influencing neutropenia in G6PC3 or G6PT deficiency; (3) the effect of SGLT2-inhibitors on blood 1,5-AG level is largely indirect; (4) specific SGLT5-inhibitors would be more efficient to treat these neutropenias than SGLT2-inhibitors.
Topics: Animals; Humans; Mice; Antiporters; HEK293 Cells; Kidney; Membrane Transport Proteins; Monosaccharide Transport Proteins; Neutropenia; Sodium-Glucose Transporter 2
PubMed: 37594549
DOI: 10.1007/s00018-023-04884-8 -
Nature Structural & Molecular Biology Nov 2023Organic anion transporters (OATs) of the SLC22 family have crucial roles in the transport of organic anions, including metabolites and therapeutic drugs, and in...
Organic anion transporters (OATs) of the SLC22 family have crucial roles in the transport of organic anions, including metabolites and therapeutic drugs, and in transporter-mediated drug-drug interactions. In the kidneys, OATs facilitate the elimination of metabolic waste products and xenobiotics. However, their transport activities can lead to the accumulation of certain toxic compounds within cells, causing kidney damage. Moreover, OATs are important drug targets, because their inhibition modulates the elimination or retention of substrates linked to diseases. Despite extensive research on OATs, the molecular basis of their substrate and inhibitor binding remains poorly understood. Here we report the cryo-EM structures of rat OAT1 (also known as SLC22A6) and its complexes with para-aminohippuric acid and probenecid at 2.1, 2.8 and 2.9 Å resolution, respectively. Our findings reveal a highly conserved substrate binding mechanism for SLC22 transporters, wherein four aromatic residues form a cage to accommodate the polyspecific binding of diverse compounds.
Topics: Rats; Animals; Organic Anion Transport Protein 1; Cryoelectron Microscopy; Membrane Transport Proteins; Organic Anion Transporters; Kidney
PubMed: 37845412
DOI: 10.1038/s41594-023-01123-3 -
Pharmacological Reviews Dec 2023The neutral amino acid transporter subfamily that consists of six members, consecutively SLC6A15-SLC620, also called orphan transporters, represents membrane,... (Review)
Review
The neutral amino acid transporter subfamily that consists of six members, consecutively SLC6A15-SLC620, also called orphan transporters, represents membrane, sodium-dependent symporter proteins that belong to the family of solute carrier 6 (SLC6). Primarily, they mediate the transport of neutral amino acids from the extracellular milieu toward cell or storage vesicles utilizing an electric membrane potential as the driving force. Orphan transporters are widely distributed throughout the body, covering many systems; for instance, the central nervous, renal, or intestinal system, supplying cells into molecules used in biochemical, signaling, and building pathways afterward. They are responsible for intestinal absorption and renal reabsorption of amino acids. In the central nervous system, orphan transporters constitute a significant medium for the provision of neurotransmitter precursors. Diseases related with aforementioned transporters highlight their significance; SLC6A19 mutations are associated with metabolic Hartnup disorder, whereas altered expression of SLC6A15 has been associated with a depression/stress-related disorders. Mutations of SLC6A18-SLCA20 cause iminoglycinuria and/or hyperglycinuria. SLC6A18-SLC6A20 to reach the cellular membrane require an ancillary unit ACE2 that is a molecular target for the spike protein of the SARS-CoV-2 virus. SLC6A19 has been proposed as a molecular target for the treatment of metabolic disorders resembling gastric surgery bypass. Inhibition of SLC6A15 appears to have a promising outcome in the treatment of psychiatric disorders. SLC6A19 and SLC6A20 have been suggested as potential targets in the treatment of COVID-19. In this review, we gathered recent advances on orphan transporters, their structure, functions, related disorders, and diseases, and in particular their relevance as therapeutic targets. SIGNIFICANCE STATEMENT: The following review systematizes current knowledge about the SLC6A15-SLCA20 neutral amino acid transporter subfamily and their therapeutic relevance in the treatment of different diseases.
Topics: Humans; Amino Acid Transport Systems, Neutral; Kidney; Amino Acids; Amino Acids, Neutral; COVID-19; Membrane Transport Proteins; Nerve Tissue Proteins
PubMed: 37940347
DOI: 10.1124/pharmrev.123.000886 -
Clinical Laboratory Oct 2023Acinetobacter baumannii produce biofilm and efflux pumps. This systematic review study aimed to provide new strategies to inhibit the efflux pumps and biofilm in A.... (Review)
Review
BACKGROUND
Acinetobacter baumannii produce biofilm and efflux pumps. This systematic review study aimed to provide new strategies to inhibit the efflux pumps and biofilm in A. baumannii using nanoparticles.
METHODS
In this research, analyses from 2000 to February 24, 2022, were performed by the Statement of Preferred Reporting Items for Systematic Reviews (PRISMA). Keywords include Acinetobacter baumannii (A. baumannii) AND (biofilm) AND (anti-biofilm activity) AND (nanoparticles) AND (solid lipid NPS) AND (lipid nanocarriers), and in other searches include Acinetobacter baumannii (A. baumanni) AND (efflux pumps) AND (nanoparticles) AND (solid lipid NPS) AND (lipid nanocarriers). Searches were conducted in English databases, including Science Direct, PubMed, Scopus, Ovid, and Cochrane.
RESULTS
At first, 136 studies were extracted, but after removing duplicates, 116 cases remained for further analysis. After evaluating the title and abstract of each study, 95 unrelated studies were excluded. The remaining 25 studies were reviewed based on full texts. Considering the inclusion/exclusion criteria, 19 studies were selected. In this study, metal nanoparticles were the most used nanoparticles for anti-biofilm and efflux pump purposes, and among these nanoparticles, silver nanoparticles (AgNPs) contributed the most.
CONCLUSIONS
The present study shows that nanoparticles have potential and significant effects in inhibiting biofilm and efflux pumps in A. baumannii isolates, which researchers can consider in light of the increasing prevalence of antibiotic resistance.
Topics: Humans; Anti-Bacterial Agents; Membrane Transport Proteins; Acinetobacter baumannii; Metal Nanoparticles; Silver; Biofilms; Lipids; Microbial Sensitivity Tests; Drug Resistance, Multiple, Bacterial; Bacterial Proteins
PubMed: 37844038
DOI: 10.7754/Clin.Lab.2023.230227 -
Journal of Global Antimicrobial... Sep 2023Mycobacterium avium (M. avium) complex bacteria cause opportunistic infections in humans. Treatment yields cure rates of 60% and consists of a macrolide, a rifamycin,...
OBJECTIVES
Mycobacterium avium (M. avium) complex bacteria cause opportunistic infections in humans. Treatment yields cure rates of 60% and consists of a macrolide, a rifamycin, and ethambutol, and in severe cases, amikacin. Mechanisms of antibiotic tolerance remain mostly unknown. Therefore, we studied the contribution of efflux and amikacin modification to antibiotic susceptibility.
METHODS
We characterised M. avium ABC transporters and studied their expression together with other transporters following exposure to clarithromycin, amikacin, ethambutol, and rifampicin. We determined the effect of combining the efflux pump inhibitors berberine, verapamil and CCCP (carbonyl cyanide m-chlorophenyl hydrazone), to study the role of efflux on susceptibility. Finally, we studied the modification of amikacin by M. avium using metabolomic analysis.
RESULTS
Clustering shows conservation between M. avium and M. tuberculosis and transporters from most bacterial subfamilies (2-6, 7a/b, 10-12) were found. The largest number of transporter encoding genes was up-regulated after clarithromycin exposure, and the least following amikacin exposure. Only berberine increased the susceptibility to clarithromycin. Finally, because of the limited effect of amikacin on transporter expression, we studied amikacin modification and showed that M. avium, in contrast to M. abscessus, is not able to modify amikacin.
CONCLUSION
We show that M. avium carries ABC transporters from all major families important for antibiotic efflux, including homologues shown to have affinity for drugs included in treatment. Efflux inhibition in M. avium can increase susceptibility, but this effect is efflux pump inhibitor- and antibiotic-specific. Finally, the lack of amikacin modifying activity in M. avium is important for its activity.
Topics: Humans; Amikacin; Mycobacterium avium; Clarithromycin; Ethambutol; Berberine; Anti-Bacterial Agents; Mycobacterium avium Complex; Membrane Transport Proteins; Mycobacterium tuberculosis; ATP-Binding Cassette Transporters
PubMed: 37453496
DOI: 10.1016/j.jgar.2023.07.007 -
Circulation Research Jun 2024Calcium (Ca) uptake by mitochondria occurs via the mitochondrial Ca uniporter. Mitochondrial Ca uniporter exists as a complex, regulated by 3 MICU (mitochondrial Ca...
BACKGROUND
Calcium (Ca) uptake by mitochondria occurs via the mitochondrial Ca uniporter. Mitochondrial Ca uniporter exists as a complex, regulated by 3 MICU (mitochondrial Ca uptake) proteins localized in the intermembrane space: MICU1, MICU2, and MICU3. Although MICU3 is present in the heart, its role is largely unknown.
METHODS
We used CRISPR-Cas9 to generate a mouse with global deletion of MICU3 and an adeno-associated virus (AAV9) to overexpress MICU3 in wild-type mice. We examined the role of MICU3 in regulating mitochondrial calcium ([Ca]) in ex vivo hearts using an optical method following adrenergic stimulation in perfused hearts loaded with a Ca-sensitive fluorophore. Additionally, we studied how deletion and overexpression of MICU3, respectively, impact cardiac function in vivo by echocardiography and the molecular composition of the mitochondrial Ca uniporter complex via Western blot, immunoprecipitation, and Blue native-PAGE analysis. Finally, we measured MICU3 expression in failing human hearts.
RESULTS
MICU3 knock out hearts and cardiomyocytes exhibited a significantly smaller increase in [Ca] than wild-type hearts following acute isoproterenol infusion. In contrast, heart with overexpression of MICU3 exhibited an enhanced increase in [Ca] compared with control hearts. Echocardiography analysis showed no significant difference in cardiac function in knock out MICU3 mice relative to wild-type mice at baseline. However, mice with overexpression of MICU3 exhibited significantly reduced ejection fraction and fractional shortening compared with control mice. We observed a significant increase in the ratio of heart weight to tibia length in hearts with overexpression of MICU3 compared with controls, consistent with hypertrophy. We also found a significant decrease in MICU3 protein and expression in failing human hearts.
CONCLUSIONS
Our results indicate that increased and decreased expression of MICU3 enhances and reduces, respectively, the uptake of [Ca] in the heart. We conclude that MICU3 plays an important role in regulating [Ca] physiologically, and overexpression of MICU3 is sufficient to induce cardiac hypertrophy, making MICU3 a possible therapeutic target.
Topics: Animals; Humans; Calcium-Binding Proteins; Mitochondria, Heart; Mice; Myocytes, Cardiac; Mice, Knockout; Male; Mitochondrial Membrane Transport Proteins; Calcium; Cardiomegaly; Mice, Inbred C57BL; Calcium Channels; Calcium Signaling; Heart Failure; Cation Transport Proteins; Female
PubMed: 38747181
DOI: 10.1161/CIRCRESAHA.123.324026