单位:[1]Department of Microbiology and Molecular Medicine, CMU, University of Geneva, Geneva 4, Switzerland[2]Proteomic Mass-spectrometry Team, Wellcome Trust Sanger Institute, Hinxton, UK[3]Beijing Institute of Tropical Medicine, Beijing Friendship Hospital, Capital Medical University, Beijing, China首都医科大学附属北京友谊医院[4]Beijing Key Laboratory for Research on Prevention and Treatment of Tropical Diseases, Beijing, China[5]Biotech Research and Innovation Center, University of Copenhagen, Copenhagen N, Denmark
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 acylated PKAr1 Either a conditional knockdown of PKAr or the overexpression of PKAc1 blocks parasite division. Conversely, down-regulation of PKAc1 or stabilisation of a dominant-negative PKAr isoform that does not bind cAMP triggers premature parasite egress from infected cells followed by serial invasion attempts leading to host cell lysis. This untimely egress depends on host cell acidification. A phosphoproteome analysis suggested the interplay between cAMP and cGMP signalling as PKAc1 inactivation changes the phosphorylation profile of a putative cGMP-phosphodiesterase. Concordantly, inhibition of the cGMP-dependent protein kinase G (PKG) blocks egress induced by PKAc1 inactivation or environmental acidification, while a cGMP-phosphodiesterase inhibitor circumvents egress repression by PKAc1 or pH neutralisation. This indicates that pH and PKAc1 act as balancing regulators of cGMP metabolism to control egress. These results reveal a crosstalk between PKA and PKG pathways to govern egress in T. gondii.
基金:
Swiss National FoundationSwiss National Science Foundation (SNSF) [FN310030B_166678, BSSGI0_155852]; Swiss Government Excellence Scholarship