Heledd Davies | University College London (original) (raw)

Papers by Heledd Davies

Antimicrobial Agents and Chemotherapy, Jul 10, 2023

Malaria parasites in the blood stage express a single transmembrane transport protein for the rel... more Malaria parasites in the blood stage express a single transmembrane transport protein for the release of the glycolytic end product l -lactate/H + from the cell. This transporter is a member of the strictly microbial formate-nitrite transporter (FNT) family and a novel putative drug target.

Proceedings of the National Academy of Sciences of the United States of America, Nov 24, 2021

Antimicrobial Agents and Chemotherapy

Plasmodium falciparum is a deadly protozoan parasite and the causative agent of malaria, which ac... more Plasmodium falciparum is a deadly protozoan parasite and the causative agent of malaria, which accounts for close to 200 million cases and 400,000 deaths every year. It has been identified to possess a tightly regulated gene expression profile that is integrally linked to its timely development during the intraerythrocytic stage. Epigenetic modifiers of the histone acetylation code have been identified as key regulators of the parasite’s transcriptome. In this study, we characterize the solitary class I histone deacetylase PfHDAC1 and demonstrate that phosphorylation is required for its catalytic activity. PfHDAC1 binds to and regulates parasite genes responsible for housekeeping and stress-responsive functions. We show that PfHDAC1 activity in parasites is crucial for normal intraerythrocytic development and that its cellular abundance is correlated with parasitemia progression. We further show that PfHDAC1 has differential abundance and genomic occupancy in artemisinin drug-resist...

Nature Biotechnology, 2020

Epilepsy & Behavior, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

FEMS Microbiology Reviews, 2017

Five species of parasite cause malaria in humans with the most severe disease caused by Plasmodiu... more Five species of parasite cause malaria in humans with the most severe disease caused by Plasmodium falciparum. Many of the proteins encoded in the P. falciparum genome are unusually enriched in repetitive low-complexity sequences containing a limited repertoire of amino acids. These repetitive sequences expand and contract dynamically and are among the most rapidly changing sequences in the genome. The simplest repetitive sequences consist of single amino acid repeats such as poly-asparagine tracts that are found in approximately 25% of P. falciparum proteins. More complex repeats of two or more amino acids are also common in diverse parasite protein families. There is no universal explanation for the occurrence of repetitive sequences and it is possible that many confer no function to the encoded protein and no selective advantage or disadvantage to the parasite. However, there are increasing numbers of examples where repetitive sequences are important for parasite protein function. We discuss the diverse roles of low-complexity repetitive sequences throughout the parasite life cycle, from mediating protein-protein interactions to enabling the parasite to evade the host immune system.

ABSTRACTReverse genetics is key to understanding protein function, but the mechanistic connection... more ABSTRACTReverse genetics is key to understanding protein function, but the mechanistic connection between a gene of interest and the observed phenotype is not always clear. Here we describe the use of proximity labeling using TurboID and site-specific quantification of biotinylated peptides to measure changes to the local protein environment of selected targets upon perturbation. We apply this technique, which we call PerTurboID, to understand how theP. falciparumexported kinase, FIKK4.1, regulates the function of the major virulence factor of the malaria causing parasite, PfEMP1. We generated independent TurboID fusions of 2 proteins that are predicted substrates of FIKK4.1 in a FIKK4.1 conditional KO parasite line. Comparing the abundance of site-specific biotinylated peptides between wildtype and kinase deletion lines reveals the differential accessibility of proteins to biotinylation, indicating changes to localization, protein-protein interactions, or protein structure which ar...

Nature Microbiology, 2020

The most severe form of human malaria is caused by Plasmodium falciparum . Its virulence is close... more The most severe form of human malaria is caused by Plasmodium falciparum . Its virulence is closely linked to the increase in rigidity of infected erythrocytes and their adhesion to endothelial receptors, obstructing blood flow to vital organs. Unlike other human-infecting Plasmodium species, P. falciparum exports a family of 18 FIKK serine/threonine kinases into the host cell, suggesting that phosphorylation may modulate erythrocyte modifications. We reveal substantial species-specific phosphorylation of erythrocyte proteins by P. falciparum but not by Plasmodium knowlesi , which does not export FIKK kinases. By conditionally deleting all FIKK kinases combined with large-scale quantitative phosphoproteomics we identified unique phosphorylation fingerprints for each kinase, including phosphosites on parasite virulence factors and host erythrocyte proteins. Despite their non-overlapping target sites, a network analysis revealed that some FIKKs may act in the same pathways. Only the deletion of the non-exported kinase FIKK8 resulted in reduced parasite growth, suggesting the exported FIKKs may instead support functions important for survival in the host. We show that one kinase, FIKK4.1, mediates both rigidification of the erythrocyte cytoskeleton and trafficking of the adhesin and key virulence factor PfEMP1 to the host cell surface. This establishes the FIKK family as important drivers of parasite evolution and malaria pathology. An analysis of Plasmodium falciparum FIKK serine/threonine kinases elucidates how phosphorylation regulates parasite infection of host red blood cells.

Plasmodium malaria parasites are obligate intracellular protozoans that use a unique form of loco... more Plasmodium malaria parasites are obligate intracellular protozoans that use a unique form of locomotion, termed gliding motility, to move through host tissues and invade cells. The process is substrate-dependent and powered by an actomyosin motor that drives the posterior translocation of extracellular adhesins which in turn propel the parasite forward. Gliding motility is essential for tissue translocation in the sporozoite and ookinete stages; however, the short-lived erythrocyte-invading merozoite stage has never been observed to undergo gliding movement. Here we show Plasmodium merozoites possess the ability to undergo gliding motility and that this mechanism is likely an important precursor step for successful parasite invasion. We demonstrate that two human infective species, P. falciparum and P. knowlesi, have distinct merozoite motility profiles which may reflect distinct invasion strategies. Additionally, we develop and validate a higher throughput assay to evaluate the eff...

The Journal of biological chemistry, Jan 9, 2016

Madriñan, was found to inhibit the growth of Mycobacterium tuberculosis H37Rv. A biomimetic appr... more Madriñan, was found to inhibit the growth of Mycobacterium tuberculosis H37Rv. A biomimetic approach for the chemical synthesis of a wide array of 1-substituted tetrahydroisoquinolines was undertaken with the aim of elucidating a common pharmacophore for these compounds with novel mode(s) of anti-TB action. Methods: Biomimetic Pictet–Spengler or Bischler–Napieralski synthetic routes were employed followed by an evaluation of the biological activity of the synthesized compounds.

Nature Biotechnology

In the version of this article initially published online, only the people now included in the ma... more In the version of this article initially published online, only the people now included in the main author list were listed as members of The Crick COVID-19 Consortium. The authorship has now been amended to also include the full list of consortium members and their affiliations; this has been corrected in the print and online versions of the article.

Malaria is a mosquito-borne disease caused by apicomplexan parasites of the genus Plasmodium. Com... more Malaria is a mosquito-borne disease caused by apicomplexan parasites of the genus Plasmodium. Completion of the parasite’s life cycle depends on the transmission of sexual stages, the gametocytes, from an infected human host to the mosquito vector. Sexual commitment occurs in only a small fraction of asexual blood stage parasites and is initiated by external cues. The gametocyte development protein 1 (GDV1) has been described as a key facilitator to trigger sexual commitment. GDV1 interacts with the silencing factor heterochromatin protein 1 (HP1), leading to its dissociation from heterochromatic DNA at the genomic locus encoding AP2-G, the master transcription factor of gametocytogenesis. How this process is regulated is not known. In this study we have addressed the role of protein kinases implicated in gametocyte development. From a pool of available protein kinase KO lines, we identified two kinase knockout lines which fail to produce gametocytes. However, independent genetic ve...

mSphere

Transmission of malaria-causing Plasmodium species by mosquitos requires the parasite to change f... more Transmission of malaria-causing Plasmodium species by mosquitos requires the parasite to change from a continuously growing asexual parasite form growing in the blood to a sexually differentiated form, the gametocyte. Only a small subset of asexual parasites differentiates into gametocytes that are taken up by the mosquito.

Repetitive low complexity sequences, mostly assumed to have no function, are common in proteins t... more Repetitive low complexity sequences, mostly assumed to have no function, are common in proteins that are exported by the malaria parasite into its host erythrocyte. We identify a group of exported proteins containing short lysine-rich tandemly repeated sequences that are sufficient to localize to the erythro-cyte periphery, where key virulence-related modifications to the plasma membrane and the underlying cytoskeleton are known to occur. Efficiency of targeting is dependent on repeat number, indicating that novel targeting modules could evolve by expansion of short lysine-rich sequences. Indeed, analysis of fragments of GARP from different species shows that two novel targeting sequences have arisen via the process of repeat expansion in this protein. In the protein Hyp12, the targeting function of a lysine-rich sequence is masked by a neighboring repetitive acidic sequence, further highlighting the importance of repetitive low complexity sequences. We show that sequences capable of targeting the erythrocyte periphery are present in at least nine proteins from Plasmodium falciparum and one from Plasmo-dium knowlesi. We find these sequences in proteins known to be involved in erythrocyte rigidification and cytoadhesion as well as in previously uncharacterized exported proteins. Together, these data suggest that expansion and contraction of lysine-rich repeats could generate targeting sequences de novo as well as modulate protein targeting efficiency and function in response to selective pressure.

The Journal of antimicrobial chemotherapy, Jan 4, 2015

Objectives: (S)-Leucoxine, isolated from the Colombian Lauraceae tree Rhodostemonodaphne crenatic... more Objectives: (S)-Leucoxine, isolated from the Colombian Lauraceae tree Rhodostemonodaphne crenaticupula Madriñ an, was found to inhibit the growth of Mycobacterium tuberculosis H 37 Rv. A biomimetic approach for the chemical synthesis of a wide array of 1-substituted tetrahydroisoquinolines was undertaken with the aim of elucidating a common pharmacophore for these compounds with novel mode(s) of anti-TB action.