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Activation loop phosphorylation and cGMP saturation of PKG regulate egress of malaria parasites

ABSTRACT: The cGMP-dependent protein kinase (PKG) is the sole cGMP sensor in malaria parasites, acting as an essential signalling hub to govern key developmental processes throughout the parasite life cycle. Despite the importance of PKG in the clinically relevant asexual blood stages, many aspects of malarial PKG regulation remain poorly understood. Here we use genetic and biochemical approaches to show that reduced cGMP binding to cyclic nucleotide binding domain B does not affect in vitro kinase activity but prevents parasite egress. Similarly, we show that phosphorylation of a key threonine residue (T695) in the activation loop is dispensable for kinase activity in vitro but is essential for in vivo PKG function, with loss of T695 phosphorylation leading to aberrant phosphorylation events across the parasite proteome and changes to the substrate specificity of PKG. Our findings indicate that Plasmodium PKG is uniquely regulated to transduce signals necessary for malaria parasite development.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Plasmodium Falciparum (isolate 3d7)

DISEASE(S): Plasmodium Falciparum Malaria

SUBMITTER: Helen Flynn

LAB HEAD: Mark Skehel

PROVIDER: PXD049083 | Pride | 2024-06-24

REPOSITORIES: Pride

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Activation loop phosphorylation and cGMP saturation of PKG regulate egress of malaria parasites

Project description:The cGMP-dependent protein kinase (PKG) is the sole cGMP sensor in malaria parasites, acting as an essential signalling hub to govern key developmental processes throughout the parasite life cycle. Despite the importance of PKG in the clinically relevant asexual blood stages, many aspects of malarial PKG regulation remain poorly understood. Here we use genetic and biochemical approaches to show that reduced cGMP binding to cyclic nucleotide binding domain B does not affect in vitro kinase activity but prevents parasite egress. Similarly, we show that phosphorylation of a key threonine residue (T695) in the activation loop is dispensable for kinase activity in vitro but is essential for in vivo PKG function, with loss of T695 phosphorylation leading to aberrant phosphorylation events across the parasite proteome and changes to the substrate specificity of PKG. Our findings indicate that Plasmodium PKG is uniquely regulated to transduce signals necessary for malaria parasite development

2024-06-24 | PXD048979 | Pride

Activation loop phosphorylation and cGMP saturation of PKG regulate egress of malaria parasites

2024-06-24 | PXD049017 | Pride

Plasmodium PKG interacts with ICM1, a multi-pass membrane protein, in both asexual and sexual stages

2021-02-10 | PXD020447 | Pride

A G-protein-coupled receptor modulates gametogenesis via PKG-mediated signaling cascade in Plasmodium berghei

Project description:Gametogenesis is essential for malaria parasite transmission, but the molecular mechanism of this process remains to be refined. Here, we identified a G-protein-coupled receptor 180 (GPR180) that plays a critical role in signal transduction during gametogenesis in Plasmodium. In the rodent parasite P. berghei, PbGPR180 was expressed during asexual and sexual development, with more prominent expression in gametocytes and ookinetes. While PbGPR180 was predominantly localized to cytoplasmic puncta in asexual stages and gametocytes, it became associated with the plasma membrane in female gametes and ookinetes. Knockout of pbgpr180 (Δpbgpr180) had no noticeable effect on asexual development or gametocytogenesis but impaired gamete formation and reduced transmission of the parasites to mosquitoes. Transcriptome analysis of the Δpbgpr180 gametocytes revealed a large proportion of the dysregulated genes with assigned functions in cyclic nucleotide signaling transduction, especially the cGMP-PKG-Ca2+ signaling cascade. Deletion of pbgpr180 resulted in a delay and reduction in cytosolic Ca2+ mobilization during the induction of gametogenesis. In addition, the intracellular cGMP level was significantly reduced in the Δpbgpr180 gametocytes, suggesting that PbGPR180 functions upstream of the cGMP-PKG-Ca2+ signaling pathway. In line with this function, PbGPR180 protein was found to interact with several transmembrane transporter proteins and a small GTPase, Rab6, in activated gametocytes. Allele replacement of pbgpr180 with the P. vivax ortholog pvgpr180 showed equal competence of the transgenic parasite in sexual development, suggesting functional conservation of this gene in Plasmodium spp . These results indicate that GPR180 is involved in cGMP-PKG-Ca2+ signal transduction to regulate gametogenesis in malaria parasites.

2022-04-01 | PXD030837 | Pride

A Protein Kinase G -interacting protein regulates critical calcium signals in malaria parasites (Co-IP)

Project description:In malaria parasites, cGMP signalling is mediated by a single cGMP-dependent protein kinase (PKG) . One of the major functions of PKG is to control calcium signals essential for the parasite to exit red blood cells or for the transmission of the gametocyte stages to the mosquito . However, how PKG controls these signals in the absence of known second messenger-dependent calcium channels or scaffolding proteins remains a mystery. Here we use pull-down approaches to identify a PKG partner protein in both Plasmodium falciparum schizonts and P. berghei gametocytes. This partner, named ICM1, is a polytopic membrane protein with homologies to transporters and calcium channels, raising the possibility of a direct functional link between PKG and calcium homeostasis. Phosphoproteomic analyses in both Plasmodium species highlight a densely phosphorylated region of ICM1 with multiple phosphorylation events dependent on PKG activity. Conditional disruption of the P. falciparum ICM1 gene results in reduced cGMP-dependent calcium mobilisation associated with defective egress and invasion. Stage-specific depletion of ICM1 in P. berghei gametocytes blocks gametogenesis due to the inability of mutant parasites to mobilise intracellular calcium upon PKG activation. These results provide us with new insights into the atypical calcium homeostasis in malaria parasites.

2021-01-25 | PXD020210 | Pride

Cross-talk between PKA and PKG controls pH-dependent host cell egress of Toxoplasma gondii

Project description:Toxoplasma gondii encodes three Protein Kinase A catalytic (PKAc1-3) and one regulatory (PKAr) subunits to integrate cAMP-dependent signals. Here, we show that inactive PKAc1 is maintained at the parasite pellicle by interacting with dually acylated PKAr. Either a conditional knockdown of PKAr or the overexpression of PKAc1 results in a block in parasite division. In contrast, conditional expression of a dominant negative PKAr isoform unable to bind cAMP, triggers premature egress of parasites from infected cells. This untimely egress critically depends on parasite density and host cell acidification. A comparative phosphoproteome analysis reveals that PKA genetic inhibition significantly changed the phosphorylation profile of a putative cGMP-phosphodiesterase, PDE2. Consistently, the phenotype of PKA genetic inhibition is alleviated by chemical inhibition of the cGMP-dependent protein kinase G (PKG). A phosphodiesterase inhibitor is able to circumvent egress repression by PKA or pH neutralisation, indicating that environmental acidification and PKA signalling act as balancing regulators of cGMP degradation to control PKG-mediated egress. Collectively, these results reveal a cross-talk between PKA and PKG pathways to govern egress in T. gondii.

2017-10-12 | PXD006045 | Pride

A Protein Kinase G-interacting protein regulates critical calcium signals in malaria parasites (phosphoproteomic)

Project description:In malaria parasites, cGMP signalling is mediated by a single cGMP-dependent protein kinase (PKG). One of the major functions of PKG is to control calcium signals essential for the parasite to exit red blood cells or for the transmission of the gametocyte stages to the mosquito. However, how PKG controls these signals in the absence of known second messenger-dependent calcium channels or scaffolding proteins remains a mystery. Here we use pull-down approaches to identify a PKG partner protein in both Plasmodium falciparum schizonts and P. berghei gametocytes. This partner, named ICM1, is a polytopic membrane protein with homologies to transporters and calcium channels, raising the possibility of a direct functional link between PKG and calcium homeostasis. Phosphoproteomic analyses in both Plasmodium species highlight a densely phosphorylated region of ICM1 with multiple phosphorylation events dependent on PKG activity. Conditional disruption of the P. falciparum ICM1 gene results in reduced cGMP-dependent calcium mobilisation associated with defective egress and invasion. Stage-specific depletion of ICM1 in P. berghei gametocytes blocks gametogenesis due to the inability of mutant parasites to mobilise intracellular calcium upon PKG activation. These results provide us with new insights into the atypical calcium homeostasis in malaria parasites

2021-01-25 | PXD020189 | Pride

Identification of plant PKG in GA signaling via fine-tuning GAMYB nuclear localization

Project description:Through transcriptomic profiling, we compared differentially expressed genes between WT and pkg mutant treated with Br-cGMP, we found that PKG as primary receptor mediated cGMP signaling in rice.

2020-08-24 | GSE119028 | GEO

PKG-dependent phosphoproteome of T. gondii treated with the phosphodiesterase inhibitor zaprinast

Project description:Apicomplexans are ubiquitous parasites of humans and cause diseases including toxoplasmosis, malaria, and cryptosporidiosis. Protein kinase G (PKG) possesses unique features in this phylum of parasites and is a demonstrated drug target. Phosphodiesterase inhibitors increase the concentration of cGMP in cells, thereby activating PKG. Here, we generate a phosphoproteome from parasites treated with the phosphodiesterase inhibitor zaprinast. We additionally use an auxin-inducible degron system to deplete parasites of PKG during this treatment.

2024-07-12 | PXD044361 | Pride

A multipass membrane protein interacts with the cGMP-dependent protein kinase to regulate critical calcium signals in malaria parasites

Project description:In malaria parasites, all cGMP-dependent signalling is mediated through a single cGMP-dependent protein kinase (PKG). A major function of PKG is to control calcium signals essential for the parasite to exit red blood cells or for transmission to the mosquito vector. However, how PKG controls these signals in the absence of known second messenger-dependent calcium channels or scaffolding proteins remains a mystery. Here we identify a tightly-associated PKG partner protein in both Plasmodium falciparum asexual blood stages and P. berghei gametocytes. Named ICM1, the partner is a polytopic membrane protein with homology to transporters and calcium channels, raising the possibility of a direct functional link between PKG and calcium homeostasis. Phosphoproteomic analyses in both Plasmodium species highlight a densely phosphorylated region of ICM1 with multiple phosphorylation events dependent upon PKG activity. Stage-specific depletion of ICM1 in P. berghei blocks gametogenesis due to the inability of mutant parasites to mobilise intracellular calcium upon PKG activation, whilst conditional disruption of P. falciparum ICM1 results in reduced cGMP-dependent calcium mobilisation associated with defective egress and invasion. Our findings provide new insights into the atypical calcium homeostasis in malaria parasites essential for pathology and disease transmission.

2021-02-10 | PXD020381 | Pride

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