Biology subjects

Flueck, C.

Publications and source records attributed to Flueck, C..

4 recordsLinked to original sources

bioRxiv2026

Dynamic phosphorylation of the Plasmodium falciparum Myosin A motor regulates motor speed and is important for asexual replication

Malaria parasite invasion of red blood cells is powered by Myosin A (MyoA), the actomyosin motor which is a core component of the glideosome. Our previous phosphoproteomic study identified a cyclic GMP-dependent phosphorylation site on MyoA at Ser19, suggesting that cyclic nucleotide signalling may directly regulate motor activity during invasion. However, the functional significance of this phosphorylation site remains unclear. Here, we show that Plasmodium falciparum MyoA phosphorylation at Ser19 is dynamically regulated during the intraerythrocytic cycle, peaking in extracellular merozoites and rapidly declining following invasion. Using conditional depletion of MyoA, we show that MyoA is essential for red blood cell invasion but dispensable for gametocyte development. Conditional complementation with mutant versions of MyoA that either mimic (S19D) or ablate phosphorylation (S19A) reveal markedly impaired asexual parasite proliferation, highlighting the importance of precise regulation of MyoA phosphorylation at Ser19. In vitro motility assays using parasite-derived MyoA showed that ablating phosphorylation either pharmacologically or by introducing an S19A mutation, reduces motor speed. Conversely, introducing a phosphomimetic S19D mutation restores motility levels comparable to phosphorylated wild type MyoA. Collectively, these results establish MyoA Ser19 phosphorylation as a regulatory switch for actomyosin motor activity.

cell biology↗

bioRxiv2020

Plasmodium falciparum guanylyl cyclase-alpha and the activity of its appended P4-ATPase domain are essential for cGMP synthesis and blood stage egress

In malaria parasites, guanylyl cyclases (GCs), which synthesise cyclic GMP (cGMP), are associated with a P4-ATPase-like domain in a unique bifunctional configuration. P4-ATPases generate membrane bilayer lipid asymmetry by translocating phospholipids from the outer to the inner leaflet. Here we investigate the role of Plasmodium falciparum guanylyl cyclase alpha (GC) and its associated P4-ATPase module, showing that asexual blood stage parasites lacking both the cyclase and P4-ATPase domains are unable to egress from host erythrocytes. GC-null parasites cannot synthesise cGMP, or mobilise calcium, a cGMP-dependent protein kinase (PKG)-driven requirement for egress. Using chemical complementation with a cGMP analogue and point mutagenesis of a crucial conserved residue within the P4-ATPase domain, we show that ATPase activity is up stream of and linked to cGMP synthesis. Collectively, our results demonstrate that GC is a critical regulator of PKG and that its associated P4-ATPase domain plays a primary role in generating cGMP for merozoite egress.

molecular biology↗

bioRxiv2020

Use of a highly specific kinase inhibitor for rapid, simple and precise synchronization of Plasmodium falciparum and Plasmodium knowlesi asexual stage parasites

During the course of the asexual erythrocytic stage of development, Plasmodium spp. parasites undergo a series of morphological changes and induce alterations in the host cell. At the end of this stage, the parasites exit the host cell, after which the progeny invade a new host cell. These processes are rapid and occur in a time-dependent manner. Of particular importance, egress and invasion of erythrocytes by the parasite are difficult to capture in an unsynchronized culture, or even a culture that has been synchronized to within hours. Therefore, precise synchronization of parasite cultures is of paramount importance for the investigation of these processes. Here we describe a method for synchronizing Plasmodium falciparum and Plasmodium knowlesi asexual blood stage parasites with ML10, a highly specific inhibitor of the cGMP-dependent protein kinase (PKG) that arrests parasite growth approximately 15 minutes prior to egress. This inhibitor allows parasite cultures to be synchronized to within minutes, with a simple wash step. Furthermore, we show that parasites remain viable for several hours after becoming arrested by the compound and that ML10 has advantages over the previously used PKG inhibitor Compound 2. Here, we demonstrate that ML10 is an invaluable tool for the study of Plasmodium spp. asexual blood stage biology and for the routine synchronization of P. falciparum and P. knowlesi cultures.

microbiology↗

bioRxiv2019

Modification of an atypical clathrin-independent AP-2 adaptin complex of Plasmodium falciparum reduces susceptibility to artemisinin

The efficacy of current antimalarial drugs is threatened by reduced susceptibility of Plasmodium falciparum to artemisinin. In the Mekong region this is associated with mutations in the kelch propeller-encoding domain of pfkelch13, but variants of other parasite proteins are also thought to modulate the response to drug. Evidence from human and rodent studies suggests that the -subunit of the AP-2 adaptin trafficking complex is one such protein of interest. We generated transgenic Plasmodium falciparum parasites encoding the I592T variant of pfap2, orthologous to the I568T mutation associated with in vivo artemisinin resistance in P. chabaudi. When exposed to a four-hour pulse of dihydroartemisin in the ring-stage survival assay, two P. falciparum clones expressing AP-2 I592T displayed significant and reproducible survival of 8.0% and 10.3%, respectively, compared to <2% for the 3D7 parental line (P = 0.0011 for each clone). In immunoprecipitation and localisation studies of HA-tagged AP-2, we identified interacting partners including AP-2, AP-1/2{beta}, AP-2{sigma} and a kelch-domain protein encoded on chromosome 10 of P. falciparum, K10. Conditional knockout indicates that the AP-2 trafficking complex in P. falciparum is essential for the fidelity of merozoite biogenesis and membrane organisation in the mature schizont. We also show that while other heterotetrameric AP-complexes and secretory factors interact with clathrin, AP-2 complex subunits do not. Thus, the AP-2 complex may be diverted from a clathrin-dependent endocytic role seen in most eukaryotes into a Plasmodium-specific function. These findings represent striking divergences from eukaryotic dogma and support a role for intracellular traffic in determining artemisinin sensitivity in vitro, confirming the existence of multiple functional routes to reduced ring-stage artemisinin susceptibility. Therefore, the utility of pfkelch13 variants as resistance markers is unlikely to be universal, and phenotypic surveillance of parasite susceptibility in vivo may be needed to identify threats to our current combination therapies.

microbiology↗