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Journal of Pharmaceutical Sciences Sep 2016Orally administered drugs are categorized into 4 classes depending on the solubility and permeability in a Biopharmaceutics Classification System. Prodrug derivatization... (Review)
Review
Orally administered drugs are categorized into 4 classes depending on the solubility and permeability in a Biopharmaceutics Classification System. Prodrug derivatization is one of feasible approaches in modifying the physicochemical properties such as low solubility and low permeability without changing the in vivo pharmacological action of the parent drug. In this article, prodrug-targeted solute carrier (SLC) transporters were searched randomly by PubMed. Collected SLC transporters are amino acid transporter 1, bile acid transporter, carnitine transporter 2, glucose transporter 1, peptide transporter 1, vitamin C transporter 1, and multivitamin transporter. The usefulness of transporter-targeted prodrugs was evaluated in terms of membrane permeability, stability under acidic condition, and conversion to the parent drug. Among prodrugs collected, peptide transporter-targeted prodrugs exhibited the highest number, and some prodrugs such as valaciclovir and valganciclovir are clinically available. ATP-binding cassette efflux transporter, P-glycoprotein (P-gp), reduces the intestinal absorption of lipophilic P-gp substrate drugs, and SLC transporter-targeted prodrugs of P-gp substrate drugs circumvented the P-gp-mediated efflux transport. Thus, SLC transporter-targeted prodrug derivatization seems to be feasible approach to increase the oral bioavailability by overcoming various unwanted physicochemical properties of orally administered drugs, although the effect of food on prodrug absorption should be taken into consideration.
Topics: Cell Membrane Permeability; Drug Stability; Humans; Membrane Transport Proteins; Prodrugs; Substrate Specificity
PubMed: 27321236
DOI: 10.1016/j.xphs.2016.05.012 -
ACS Chemical Biology Jun 2016The intracellular delivery of peptide and protein therapeutics is a major challenge due to the plasma membrane, which acts as a barrier between the extracellular... (Review)
Review
The intracellular delivery of peptide and protein therapeutics is a major challenge due to the plasma membrane, which acts as a barrier between the extracellular environment and the intracellular milieu. Over the past two decades, a nontoxic PA/LFN delivery platform derived from anthrax lethal toxin has been developed for the transport of non-native cargo into the cytosol of cells in order to understand the translocation process through a protective antigen (PA) pore and to probe intracellular biological functions. Enzyme-mediated ligation using sortase A and native chemical ligation are two facile methods used to synthesize these non-native conjugates, inaccessible by recombinant technology. Cargo molecules that translocate efficiently include enzymes from protein toxins, antibody mimic proteins, and peptides of varying lengths and non-natural amino acid compositions. The PA pore has been found to effectively convey over 30 known cargos other than native lethal factor (LF; i.e., non-native) with diverse sequences and functionalities on the LFN transporter protein. All together these studies demonstrated that non-native cargos must adopt an unfolded or extended conformation and contain a suitable charge composition in order to efficiently pass through the PA pore. This review provides insight into design parameters for the efficient delivery of new cargos using PA and LFN.
Topics: Aminoacyltransferases; Animals; Antigens, Bacterial; Bacterial Proteins; Bacterial Toxins; Cell Line, Tumor; Cysteine Endopeptidases; Cytosol; Drug Carriers; Humans; Membrane Transport Proteins; Protein Transport; Proteins
PubMed: 27055654
DOI: 10.1021/acschembio.6b00169 -
FEBS Letters Oct 2018Proton-dependent oligopeptide transporters (POTs) are important for the uptake of di-/tripeptides in many organisms and for drug transport in humans. The binding mode of...
Proton-dependent oligopeptide transporters (POTs) are important for the uptake of di-/tripeptides in many organisms and for drug transport in humans. The binding mode of dipeptides has been well described. However, it is still debated how tripeptides are recognized. Here, we show that tripeptides of the sequence Phe-Ala-Xxx bind with similar affinities as dipeptides to the POT transporter from Streptococcus thermophilus (PepT ). We furthermore determined a 2.3-Å structure of PepT in complex with Phe-Ala-Gln. The phenylalanine and alanine residues of the peptide adopt the same positions as previously observed for the Phe-Ala dipeptide, while the glutamine side chain extends into a hitherto uncharacterized pocket. This pocket is adaptable in size and can likely accommodate a wide variety of peptide side chains.
Topics: Bacterial Proteins; Binding Sites; Biological Transport; Crystallography, X-Ray; Membrane Transport Proteins; Models, Molecular; Mutation; Oligopeptides; Protein Conformation; Protons
PubMed: 30194725
DOI: 10.1002/1873-3468.13246 -
Planta Mar 2022A critical investigation into arsenic uptake and transportation, its phytotoxic effects, and defense strategies including complex signaling cascades and regulatory... (Review)
Review
A critical investigation into arsenic uptake and transportation, its phytotoxic effects, and defense strategies including complex signaling cascades and regulatory networks in plants. The metalloid arsenic (As) is a leading pollutant of soil and water. It easily finds its way into the food chain through plants, more precisely crops, a common diet source for humans resulting in serious health risks. Prolonged As exposure causes detrimental effects in plants and is diaphanously observed through numerous physiological, biochemical, and molecular attributes. Different inorganic and organic As species enter into the plant system via a variety of transporters e.g., phosphate transporters, aquaporins, etc. Therefore, plants tend to accumulate elevated levels of As which leads to severe phytotoxic damages including anomalies in biomolecules like protein, lipid, and DNA. To combat this, plants employ quite a few mitigation strategies such as efficient As efflux from the cell, iron plaque formation, regulation of As transporters, and intracellular chelation with an array of thiol-rich molecules such as phytochelatin, glutathione, and metallothionein followed by vacuolar compartmentalization of As through various vacuolar transporters. Moreover, the antioxidant machinery is also implicated to nullify the perilous outcomes of the metalloid. The stress ascribed by the metalloid also marks the commencement of multiple signaling cascades. This whole complicated system is indeed controlled by several transcription factors and microRNAs. This review aims to understand, in general, the plant-soil-arsenic interaction, effects of As in plants, As uptake mechanisms and its dynamics, and multifarious As detoxification mechanisms in plants. A major portion of this article is also devoted to understanding and deciphering the nexus between As stress-responsive mechanisms and its underlying complex interconnected regulatory networks.
Topics: Arsenic; Biological Transport; Crops, Agricultural; Membrane Transport Proteins; Phytochelatins
PubMed: 35303194
DOI: 10.1007/s00425-022-03869-4 -
Science Signaling Sep 2019Intracellular calcium (Ca) signals are of prime importance for cellular function and behavior and are underpinned by a plethora of Ca channels, pumps, transporters, and...
Intracellular calcium (Ca) signals are of prime importance for cellular function and behavior and are underpinned by a plethora of Ca channels, pumps, transporters, and binding proteins that are regulated in complex ways. A series of biennial meetings, the International Meetings of the European Calcium Society (ECS), focuses on a better understanding of these complex mechanisms in the framework of cellular and organismal (patho)physiology.
Topics: Animals; Calcium; Calcium Channels; Calcium Signaling; Endoplasmic Reticulum; Humans; Intracellular Calcium-Sensing Proteins; Lysosomes; Membrane Proteins; Membrane Transport Proteins; Mitochondria; Models, Biological
PubMed: 31530730
DOI: 10.1126/scisignal.aaz0961 -
Microbiology (Reading, England) Nov 2023The controlled entry and expulsion of small molecules across the bacterial cytoplasmic membrane is essential for efficient cell growth and cellular homeostasis. While... (Review)
Review
The controlled entry and expulsion of small molecules across the bacterial cytoplasmic membrane is essential for efficient cell growth and cellular homeostasis. While much is known about the transcriptional regulation of genes encoding transporters, less is understood about how transporter activity is modulated once the protein is functional in the membrane, a potentially more rapid and dynamic level of control. In this review, we bring together literature from the bacterial transport community exemplifying the extensive and diverse mechanisms that have evolved to rapidly modulate transporter function, predominantly by switching activity off. This includes small molecule feedback, inhibition by interaction with small peptides, regulation through binding larger signal transduction proteins and, finally, the emerging area of controlled proteolysis. Many of these examples have been discovered in the context of metal transport, which has to finely balance active accumulation of elements that are essential for growth but can also quickly become toxic if intracellular homeostasis is not tightly controlled. Consistent with this, these transporters appear to be regulated at multiple levels. Finally, we find common regulatory themes, most often through the fusion of additional regulatory domains to transporters, which suggest the potential for even more widespread regulation of transporter activity in biology.
Topics: Membrane Transport Proteins; Cell Membrane; Bacteria
PubMed: 37948297
DOI: 10.1099/mic.0.001412 -
MBio Apr 2023The Gram-negative opportunistic pathogen Pseudomonas aeruginosa is a leading cause of infections and mortality in immunocompromised patients. This organism can overcome...
The Gram-negative opportunistic pathogen Pseudomonas aeruginosa is a leading cause of infections and mortality in immunocompromised patients. This organism can overcome iron deprivation during infection via the synthesis of two iron-chelating siderophores, pyoverdine and pyochelin, which scavenge iron from host proteins. P. aeruginosa can also uptake xenosiderophores produced by other bacteria or fungi using dedicated transporter systems. The precise substrate specificity of these siderophore transporters remains to be determined. The thiopeptide antibiotic thiostrepton exploits the pyoverdine transporters FpvA and FpvB to cross the outer membrane and reach intracellular targets. Using a series of intricate biochemical experiments, a recent study by Chan and Burrows capitalized on the specificity of thiostrepton to uncover that FpvB transports the xenosiderophores ferrichrome and ferrioxamine B with higher affinity than pyoverdine. This surprising result highlights an alternative uptake pathway for these siderophores and has significant implications for our understanding of iron acquisition in this organism.
Topics: Humans; Siderophores; Anti-Bacterial Agents; Thiostrepton; Bacterial Outer Membrane Proteins; Iron; Membrane Transport Proteins; Pseudomonas aeruginosa
PubMed: 36946760
DOI: 10.1128/mbio.03326-22 -
Journal of Bacteriology Apr 2018Pyruvate is an important intermediate of central carbon metabolism and connects a variety of metabolic pathways in Although the intracellular pyruvate concentration is...
Pyruvate is an important intermediate of central carbon metabolism and connects a variety of metabolic pathways in Although the intracellular pyruvate concentration is dynamically altered and tightly balanced during cell growth, the pyruvate transport system remains unclear. Here, we identified a pyruvate transporter in using high-throughput transposon sequencing. The transposon mutant library (a total of 5 × 10 mutants) was serially grown with a toxic pyruvate analog (3-fluoropyruvate [3FP]) to enrich for transposon mutants lacking pyruvate transport function. A total of 52 candidates were selected on the basis of a stringent enrichment level of transposon insertion frequency in response to 3FP treatment. Subsequently, their pyruvate transporter function was examined by conventional functional assays, such as those measuring growth inhibition by the toxic pyruvate analog and pyruvate uptake activity. The pyruvate transporter system comprises CstA and YbdD, which are known as a peptide transporter and a conserved protein, respectively, whose functions are associated with carbon starvation conditions. In addition to the presence of more than one endogenous pyruvate importer, it has been suggested that the genome encodes constitutive and inducible pyruvate transporters. Our results demonstrated that CstA and YbdD comprise the constitutive pyruvate transporter system in , which is consistent with the tentative genomic locus previously suggested and the functional relationship with the extracellular pyruvate sensing system. The identification of this pyruvate transporter system provides valuable genetic information for understanding the complex process of pyruvate metabolism in Pyruvate is an important metabolite as a central node in bacterial metabolism, and its intracellular levels are tightly regulated to maintain its functional roles in highly interconnected metabolic pathways. However, an understanding of the mechanism of how bacterial cells excrete and transport pyruvate remains elusive. Using high-throughput transposon sequencing followed by pyruvate uptake activity testing of the selected candidate genes, we found that a pyruvate transporter system comprising CstA and YbdD, currently annotated as a peptide transporter and a conserved protein, respectively, constitutively transports pyruvate. The identification of the physiological role of the pyruvate transporter system provides valuable genetic information for understanding the complex pyruvate metabolism in .
Topics: Biological Transport; DNA Transposable Elements; Escherichia coli; Escherichia coli Proteins; Gene Expression Regulation, Bacterial; Genes, Bacterial; High-Throughput Nucleotide Sequencing; Membrane Transport Proteins; Monocarboxylic Acid Transporters; Pyruvic Acid; Trans-Activators
PubMed: 29358499
DOI: 10.1128/JB.00771-17 -
SLAS Discovery : Advancing Life... Jul 2021Membrane proteins are involved in different physiological functions and are the target of pharmaceutical and abuse drugs. oocytes provide a powerful heterologous...
Membrane proteins are involved in different physiological functions and are the target of pharmaceutical and abuse drugs. oocytes provide a powerful heterologous expression system for functional studies of these proteins. Typical experiments investigate transport using electrophysiology and radiolabeled uptake. A two-electrode voltage clamp is suitable only for electrogenic proteins, and uptake measurements require the existence of radiolabeled substrates and adequate laboratory facilities.Recently, Nramp1 and NrampB were characterized using multidisciplinary approaches. NrampB showed no measurable electrogenic activity, and it was investigated in oocytes by acquiring confocal images of the quenching of injected fluorophore calcein.This method is adequate to measure the variation in emitted fluorescence, and thus transporter activity indirectly, but requires long experimental procedures to collect statistically consistent data. Considering that optimal expression of heterologous proteins lasts for 48-72 h, a slow acquiring process requires the use of more than one batch of oocytes to complete the experiments. Here, a novel approach to measure substrate uptake is reported. Upon injection of a fluorophore, oocytes were incubated with the substrate and the transport activity measured, evaluating fluorescence quenching in a microplate reader. The technique permits the testing of tens of oocytes in different experimental conditions simultaneously, and thus the collection of significant statistical data for each batch, saving time and animals.The method was tested with different metal transporters (SLC11), DMT1, Nramp1, and NrampB, and verified with the peptide transporter PepT1 (SLC15). Comparison with traditional methods (uptake, two-electrode voltage clamp) and with quenching images acquired by fluorescence microscopy confirmed its efficacy.
Topics: Animals; Biological Transport; Cation Transport Proteins; Dictyostelium; Electrophysiological Phenomena; Female; Fluoresceins; Fluorescent Dyes; Membrane Potentials; Membrane Transport Proteins; Microscopy, Fluorescence; Oocytes; Patch-Clamp Techniques; Xenopus laevis
PubMed: 33825579
DOI: 10.1177/24725552211004123 -
Proceedings of the National Academy of... Mar 2024The transporter associated with antigen processing (TAP) is a key player in the major histocompatibility class I-restricted antigen presentation and an attractive target...
The transporter associated with antigen processing (TAP) is a key player in the major histocompatibility class I-restricted antigen presentation and an attractive target for immune evasion by viruses. Bovine herpesvirus 1 impairs TAP-dependent antigenic peptide transport through a two-pronged mechanism in which binding of the UL49.5 gene product to TAP both inhibits peptide transport and triggers its proteasomal degradation. How UL49.5 promotes TAP degradation has, so far, remained unknown. Here, we use high-content siRNA and genome-wide CRISPR-Cas9 screening to identify CLR2 as the E3 ligase responsible for UL49.5-triggered TAP disposal. We propose that the C terminus of UL49.5 mimics a C-end rule degron that recruits the E3 to TAP and engages the cullin-RING E3 ligase in endoplasmic reticulum-associated degradation.
Topics: Antigen Presentation; ATP-Binding Cassette Transporters; Cytomegalovirus; Degrons; Endoplasmic Reticulum-Associated Degradation; Membrane Transport Proteins; Peptides; Ubiquitin-Protein Ligases; Herpesviridae
PubMed: 38442151
DOI: 10.1073/pnas.2309841121