A positive feedback loop mediates crosstalk between calcium, cyclic nucleotide and lipid signaling in Toxoplasma gondii.

ABSTRACT: Fundamental processes of obligate intracellular parasites, such as Plasmodium falciparum and Toxoplasma gondii are controlled by a set of plant-like calcium dependent kinases (CDPKs), the conserved cAMP- and cGMP-dependent protein kinases (PKA and PKG), second messengers and lipid signalling. While some major components of the signalling networks have been identified, how these are connected is largely not known. Here, we compare the phospho-signalling networks during Toxoplasma egress from its host cell by artificially raising cGMP or calcium levels to activate PKG or CDPKs, respectively. We show that both these inducers trigger near identical signalling pathways and provide evidence for a feedback loop involving CDPK3. We measure phospho- and lipid signalling in parasites treated with the Ca2+ ionophore A23187 in a sub-minute timecourse and show CDPK3-dependent regulation of diacylglycerol levels and increased phosphorylation of four phosphodiesterases (PDEs), suggesting their function in the feedback loop. Disruption of CDPK3 leads to elevated cAMP levels and inhibition of PKA signalling rescues the egress defect of ΔCDPK3 parasites treated with A23187. Biochemical analysis of the four PDEs identifies PDE2 as the only cAMP-specific PDE among these candidates while the other PDEs are cGMP specific; two of which are inhibited by the predicted PDE inhibitor BIPPO. Conditional deletion of the 4 PDEs supports an important, but non-essential role of PDE1 and PDE2 for growth, while only the latter plays a role in controlling A23187-mediated egress. In summary, we uncover a positive feedback loop that potentiates signalling during egress and links several signalling pathways together.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human) Toxoplasma Gondii Rh

TISSUE(S): Epithelial Cell, Foreskin Fibroblast Cell Line, Cell Culture

DISEASE(S): Toxoplasmosis

SUBMITTER: Malgorzata Broncel  

LAB HEAD: Moritz Treeck

PROVIDER: PXD030057 | Pride | 2022-10-17

REPOSITORIES: Pride