A positive feedback loop mediates crosstalk between calcium, cyclic nucleotide and lipid signalling in calcium-induced Toxoplasma gondii egress
Fundamental processes that govern the lytic cycle of the intracellular parasite Toxoplasma gondii are regulated by several signalling pathways. However, how these pathways are connected remains largely unknown. Here, we compare the phospho-signalling networks during Toxoplasma egress from its host c...
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Published in | PLoS pathogens Vol. 18; no. 10; p. e1010901 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Public Library of Science
01.10.2022
Public Library of Science (PLoS) |
Subjects | |
Online Access | Get full text |
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Summary: | Fundamental processes that govern the lytic cycle of the intracellular parasite Toxoplasma gondii are regulated by several signalling pathways. However, how these pathways are connected remains largely unknown. Here, we compare the phospho-signalling networks during Toxoplasma egress from its host cell by artificially raising cGMP or calcium levels. We show that both egress inducers trigger indistinguishable signalling responses and provide evidence for a positive feedback loop linking calcium and cyclic nucleotide signalling. Using WT and conditional knockout parasites of the non-essential calcium-dependent protein kinase 3 (CDPK3), which display a delay in calcium inonophore-mediated egress, we explore changes in phosphorylation and lipid signalling in sub-minute timecourses after inducing Ca2+ release. These studies indicate that cAMP and lipid metabolism are central to the feedback loop, which is partly dependent on CDPK3 and allows the parasite to respond faster to inducers of egress. Biochemical analysis of 4 phosphodiesterases (PDEs) identified in our phosphoproteomes establishes PDE2 as a cAMP-specific PDE which regulates Ca2+ induced egress in a CDPK3-independent manner. The other PDEs display dual hydrolytic activity and play no role in Ca2+ induced egress. In summary, we uncover a positive feedback loop that enhances signalling during egress, thereby linking several signalling pathways. |
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Bibliography: | new_version ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 The authors have declared that no competing interests exist. |
ISSN: | 1553-7374 1553-7366 1553-7374 |
DOI: | 10.1371/journal.ppat.1010901 |