title: Optogenetic modulation of an adenylate cyclase in Toxoplasma gondii demonstrates a requirement of the parasite cAMP for host-cell invasion and stage differentiation.
abstract: BACKGROUND
  cAMP research in intracellular parasites remains underappreciated, and it requires a specific method for cyclic nucleotide regulation.
  
  
  RESULTS
  Optogenetic induction of cAMP in T. gondii affects host-cell invasion, stage-specific expression, and parasite differentiation. The underlying method allows a versatile control of parasite cAMP.
  
  
  CONCLUSIONS
  Optogenetic parasite strains offer valuable tools for dissecting cAMP-mediated processes.
  
  
  CONCLUSIONS
  The method is applicable to other gene-tractable intertwined systems. Successful infection and transmission of the obligate intracellular parasite Toxoplasma gondii depends on its ability to switch between fast-replicating tachyzoite (acute) and quiescent bradyzoite (chronic) stages. Induction of cAMP in the parasitized host cells has been proposed to influence parasite differentiation. It is not known whether the parasite or host cAMP is required to drive this phenomenon. Other putative roles of cAMP for the parasite biology also remain to be identified. Unequivocal research on cAMP-mediated signaling in such intertwined systems also requires a method for an efficient and spatial control of the cAMP pool in the pathogen or in the enclosing host cell. We have resolved these critical concerns by expressing a photoactivated adenylate cyclase that allows light-sensitive control of the parasite or host-cell cAMP. Using this method, we reveal multiple roles of the parasite-derived cAMP in host-cell invasion, stage-specific expression, and asexual differentiation. An optogenetic method provides many desired advantages such as: (i) rapid, transient, and efficient cAMP induction in extracellular/intracellular and acute/chronic stages; (ii) circumvention of the difficulties often faced in cultures, i.e. poor diffusion, premature degradation, steady activation, and/or pleiotropic effects of cAMP agonists and antagonists; (iii) genetically encoded enzyme expression, thus inheritable to the cell progeny; and (iv) conditional and spatiotemporal control of cAMP levels. Importantly, a successful optogenetic application in Toxoplasma also illustrates its wider utility to study cAMP-mediated signaling in other genetically amenable two-organism systems such as in symbiotic and pathogen-host models.
authors.affiliation: Departments of Molecular Parasitology, Humboldt University, 10115 Berlin, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Hartmann
authors.forename: Ruben Dario
authors.initials: RD
authors.lastname: Arroyo-Olarte
authors.forename: Katharina
authors.initials: K
authors.lastname: Imkeller
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
authors.forename: Richard
authors.initials: R
authors.lastname: Lucius
authors.forename: Nishith
authors.initials: N
authors.lastname: Gupta
mesh_terms: D000262:Adenylyl Cyclases / Q000096:biosynthesis* / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology*; D005347:Fibroblasts / Q000378:metabolism / Q000469:parasitology; D015971:Gene Expression Regulation, Enzymologic; D006790:Host-Parasite Interactions; D006801:Humans; D062308:Optogenetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D015290:Second Messenger Systems; D014122:Toxoplasma / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D000242:Cyclic AMP; D000262:Adenylyl Cyclases
keywords: Adenylate Cyclase (Adenylyl Cyclase); Cell Differentiation; Cyclic Nucleotides; Optogenetics; Parasitology