Download or read book ANALYSIS OF PLASMODIUM FALCIPARUM CHLOROQUINE RESISTANCE TRANSPORTER ISOFORMS written by Paul Samuel Callaghan and published by . This book was released on 2015 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Finally, I also carry out a large-scale chemogenetic screen of the Saccharomyces cerevisiae deletion mutant library to identify yeast genes relevant for resistance and sensitivity to CQ. This approach reveals overlapping gene pathways relevant to CQ toxicity, some of which have also been previously identified in related chemogenomic screens vs other quinoline drugs (e.g. quinine). Significantly enriched gene ontology (GO) terms persisted across increasingly stringent subsets of phenotypic grouping down to

Download or read book Analysis of Plasmodium Falciparum Chloroquine Resistance Transporters in Saccharomyces Cerevisiae written by Nicholas Kyle Baro and published by . This book was released on 2012 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study demonstrates the use of a model eukaryotic heterologous system to elucidate key features of a resistance protein from malaria parasites and highlights the potential of using this system to characterize its endogenous substrate.

Download or read book Structural Investigation of Plasmodium Falciparum Chloroquine Resistance Transporter in the Context of Anti Malarial Drug Resistance written by Jonathan Young Kim and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: All CQ resistance-conferring PfCRT isoforms share the K76T mutation, which is widely used as a molecular marker for CQ resistance. Despite the significance in the impact of drug-resistant malaria, a detailed understanding of PfCRT physiological function and the molecular basis of PfCRT-mediated drug resistance have been hampered by a lack of high-resolution structural information. This dissertation describes the first structure of PfCRT and reveals the interaction of drugs with the purified and reconstituted protein. We determined the structure of the 49-kDa PfCRT 7G8, a clinically relevant CQ-resistant isoform found in South America, to 3.2 Å resolution by single-particle cryo-electron microscopy (cryo-EM), in complex with a specific antigen-binding fragment (Fab) to overcome current size limitations in cryo-EM. Our PfCRT structure displays an inward-open conformation, consists of 10 transmembrane (TM) helices with an inverted topology, and has unique elements including two juxtamembrane helices and a highly conserved cysteine-rich loop between TM helix 7 and 8.

Download or read book Studies of Malarial Parasite Chloroquine Resistance Transporter and Kinase Proteins Key Targets for Evolving Drug Therapies written by Matthew Ryan Hassett and published by . This book was released on 2017 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: I have continued the use of an optimized CRT expression system in S. cerevisiae to elucidate drug transport ability. CQ resistance (CQR) is well understood in P. falciparum, but in Plasmodium vivax (another species of malaria), CQR remains a mystery. Multiple mutations in PfCRT are characteristic of drug resistant isolates, and contrary to PfCRT, the P. vivax orthologue (named PvCRT) primarily shows only single mutations in CRT. In this thesis, I measure the drug transport efficiencies of multiple Pf and PvCRT isoforms. My results show that there is a range of quinolone drug transport across the isoforms analyzed. Additionally, some CQR isolates expressing certain CRT isoforms likely have other genetic events that shape CQR.

Download or read book Analysis of Parasite Chloroquine Resistance Transporter Proteins and Their Roles in Drug Resistance Phenomena written by Bryce Riegel and published by . This book was released on 2020 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, I measure drug transport efficiencies of multiple PvCRT isoforms heterologously expressed in yeast. I also measure drug transport for novel PPQR-associated PfCRT isoforms, and test whether an orthologue of PfCRT found in the closely related apicomplexan parasite Toxoplasma gondii (TgCRT), is a functional transporter of CQ, as part of a broader investigation of the role of TgCRT in the endolysosomal system of T. gondii.

Download or read book Structure function Analysis of Plasmodium Falciparum Chloroquine Resistance Transporter in Chloroquine Resistance written by Kit Ying Choy and published by . This book was released on 2013 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Malaria Parasite s Chloroquine Resistance Transporter written by Robert Leon Summers and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The malaria parasite's chloroquine resistance transporter: An exploration of its interactions with drugs and of its evolution as a drug transporter Abstract: Initially identified as the primary determinant of chloroquine resistance in the malaria parasite Plasmodium falciparum, mutations in the 'chloroquine resistance transporter' (PfCRT) can influence the parasite's susceptibility to diverse molecules. The ability of PfCRT to affect the activity of so many compounds is likely to be a product of its location at the membrane of the parasite's digestive vacuole - an acidic compartment in which many types of drugs accumulate, act, and/or are activated. The Xenopus laevis oocyte system enables the functional expression of PfCRT and has been used to demonstrate that a mutant isoform of PfCRT mediates the efflux of chloroquine from the vacuole (i.e., away from its site of action), whereas the wild-type protein lacks this activity. However, the evolution of chloroquine transport activity by PfCRT has yet to be explored, and little is known of how PfCRT interacts with diverse compounds. The overarching aim of this study was to understand how mutations in PfCRT confer chloroquine transport activity and alter the parasite's susceptibility to diverse pharmacons. A kinetic analysis of the inhibition of PfCRT-mediated chloroquine transport by verapamil, a compound which partially restores the activity of chloroquine against drug-resistant parasites, was undertaken in the oocyte system. The findings of this work revealed verapamil to be a partial-mixed-type inhibitor of the transporter, and suggested that the mutations required for chloroquine transport introduce multiple substrate-binding sites into PfCRT. A series of complementary assays were then applied to examine the interactions of PfCRT with a range of compounds to identify, and distinguish between, PfCRT substrates and inhibitors. Using the oocyte system, two new classes of compounds were identified as potent inhibitors of the PfCRT-mediated transport of chloroquine. Transgenic parasite lines that are isogenic except for their pfcrt allele were employed, in conjunction with an assay that indirectly detects the transport of drugs out of the parasite's digestive vacuole, to further characterise these compounds. The resulting data revealed that most of these molecules are not substrates of the mutant transporter. Furthermore, parasite proliferation assays demonstrated that the compounds possessed enhanced activities against parasites harbouring mutant PfCRT. Structure-activity relationships were consistent with these compounds binding to multiple points of attachment within PfCRT via lipophilic and electrostatic interactions. Measurements of chloroquine transport via diverse isoforms of PfCRT (as well as by a series of chimeric proteins) were also undertaken in the oocyte system. These analyses revealed that multiple mutational pathways lead to saturable chloroquine transport via PfCRT. The finding that diverse PfCRT variants are all limited in their capacity to transport chloroquine suggests that resistance could be overcome by re-optimising the chloroquine dosage. Moreover, the results of this study indicated that the remodelling of PfCRT for chloroquine transport required a complex reorganisation of interacting residues. These studies support the idea that, in addition to being a mediator of multidrug resistance, PfCRT is itself a viable drug target. Antimalarial therapies could be formulated to exert opposing selection forces upon PfCRT, thereby exploiting a key resistance mechanism and prolonging drug efficacy against this important human pathogen.

Download or read book Biochemical and Biophysical Analysis of Recombinant Plasmodium Falciparum Chloroquine Resistance Transporter pfcrt written by Michelle Fortaleza Paguio and published by . This book was released on 2009 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two new methods were also developed: a high throughput fluorescence assay for antimalarial drug screening and a convenient scheme for the purification of recombinant PfCRT. The drug assay has contributed to the efficiency and ease of testing numerous compounds while the optimization of purifying recombinant PfCRT has produced a cleaner and more reliable system to investigate its function. These methods significantly aided in understanding the mechanism of chloroquine resistance.

Download or read book Molecular Characterisation of the Plasmodium Falciparum Pfcrt Gene Involved in Chloroquine Resistance written by and published by . This book was released on 2008 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chloroquine (CQ) resistant P. falciparum was first reported in the 1960s at the Thai-Cambodia border. Gradually CQ resistance has spread and is found in all regions where P. falciparum transmission occurs. The emergence of CQ resistance due to excessive CQ selection pressure on the parasite populations has become an important issue because of the higher mortality and morbidity associated with drug resistance. Currently CQ is no longer recommended to treat falciparum malaria. CQ resistance in P. falciparum has been attributed to a single amino acid substitution on the P. falciparum chloroquine resistant transporter (pfcrt) at position 76 where Iysine is substituted with threonine (K76T). Molecular studies showed that CQ resistance emerged independently at five different geographical locations namely: Southeast Asia, two sites in South America, Papua New Guinea and the Philippines. Further analysis of resistant isolates revealed 22 additional non-silent amino acid substitutions on the pfcrt gene with a new amino acid substitution detected in the study reported here.

Download or read book Mutational Analysis of Chloroquine Resistance Transporter crt Gene in Human Plasmodium Falciparum and Plasmodium Vivax Isolated from Sabah written by Lii Lian Tan and published by . This book was released on 2013 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of the Cellular and Molecular Mechanisms of Chloroquine Resistance in Plasmodium Falciparum written by and published by . This book was released on 2009 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CQR phenotype has traditionally been defined at low nanomolar cytostatic CQ concentrations but these do not correspond to medically relevant cytotoxic doseages. Thus, CQ accumulation was also measured using 3H-CQ and infected red blood cells at external CQ that corresponds to cytotoxic vs cytostatic concentrations. It was discovered that reduced CQ accumulation is not the underlying cause of cytotoxic CQR.

Download or read book Investigating the Plasmodium Falciparum Chloroquine Resistance Transporter in a Heterologous Expression System written by David A. Liebelt and published by . This book was released on 2007 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Plasmodium Falciparum Chloroquine Resistance Transporter PFCRT Mediates the Activity of Chloroquine resistance Reversal Agents in the Malaria Parasite written by Kristin Lane and published by . This book was released on 2007 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure and Functional Differentiation of PfCRT Mutation in Chloroquine Resistance CQR in Plasmodium Falciparum Malaria written by Pratap Parida and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately one million deaths are attributed to malaria every year. Latest reports of multi-drug treatment failure of falciparum malaria underscore the desideratum to understand the molecular substratum of drug resistance. The mutations in the digestive vacuole transmembrane protein Plasmodium falciparum chloroquine resistance transporter (PfCRT) are mainly responsible for chloroquine resistance (CQR) in Plasmodium falciparum. Multiple mutations in the PfCRT are concerned in chloroquine resistance, but the evolution of intricate haplotypes is not yet well understood. P. falciparum resistance to chloroquine is the standard antimalarial drug and is mediated primarily by mutant forms of the PfCRT. In this chapter, we present the mechanism of action of the chloroquine, the structural changes of the gene after the mutations as well as different haplotypes of the PfCRT.

Download or read book Antimicrobial Drug Resistance written by Douglas L. Mayers and published by Springer. This book was released on 2017-06-19 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt: The two volumes included in Antimicrobial Drug Resistance, Second Edition is an updated, comprehensive and multidisciplinary reference covering the area of antimicrobial drug resistance in bacteria, fungi, viruses, and parasites from basic science, clinical, and epidemiological perspectives. This newly revised compendium reviews the most current research and development on drug resistance while still providing the information in the accessible format of the first edition. The first volume, Antimicrobial Drug Resistance: Mechanisms of Drug Resistance, is dedicated to the biological basis of drug resistance and effective avenues for drug development. With the emergence of more drug-resistant organisms, the approach to dealing with the drug resistance problem must include the research of different aspects of the mechanisms of bacterial resistance and the dissemination of resistance genes as well as research utilizing new genomic information. These approaches will permit the design of novel strategies to develop new antibiotics and preserve the effectiveness of those currently available. The second volume, Antimicrobial Drug Resistance: Clinical and Epidemiological Aspects, is devoted to the clinical aspects of drug resistance. Although there is evidence that restricted use of a specific antibiotic can be followed by a decrease in drug resistance to that agent, drug resistance control is not easily achieved. Thus, the infectious diseases physician requires input from the clinical microbiologist, antimicrobial stewardship personnel, and infection control specialist to make informed choices for the effective management of various strains of drug-resistant pathogens in individual patients. This 2-volume set is an important reference for students in microbiology, infectious diseases physicians, medical students, basic scientists, drug development researchers, microbiologists, epidemiologists, and public health practitioners.

Download or read book Assessment of Long Term Health Effects of Antimalarial Drugs When Used for Prophylaxis written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2020-04-24 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the many who serve in the United States Armed Forces and who are deployed to distant locations around the world, myriad health threats are encountered. In addition to those associated with the disruption of their home life and potential for combat, they may face distinctive disease threats that are specific to the locations to which they are deployed. U.S. forces have been deployed many times over the years to areas in which malaria is endemic, including in parts of Afghanistan and Iraq. Department of Defense (DoD) policy requires that antimalarial drugs be issued and regimens adhered to for deployments to malaria-endemic areas. Policies directing which should be used as first and as second-line agents have evolved over time based on new data regarding adverse events or precautions for specific underlying health conditions, areas of deployment, and other operational factors At the request of the Veterans Administration, Assessment of Long-Term Health Effects of Antimalarial Drugs When Used for Prophylaxis assesses the scientific evidence regarding the potential for long-term health effects resulting from the use of antimalarial drugs that were approved by FDA or used by U.S. service members for malaria prophylaxis, with a focus on mefloquine, tafenoquine, and other antimalarial drugs that have been used by DoD in the past 25 years. This report offers conclusions based on available evidence regarding associations of persistent or latent adverse events.

Download or read book Handbook of Antimicrobial Resistance written by Matthias Gotte and published by Springer. This book was released on 2018-02-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: While many volumes have been written about various aspects of antimicrobial resistance, this book is a comprehensive reference work. All manifestations of resistance are addressed: viral; bacterial, parasitical and fungal are given dedicated sections. The underlining molecular mechanisms, which depend not only on the microbe but on the specific drug (target), are highly diverse. This work discusses and compares the biological, biochemical and structural aspects of resistance and its evolution.