Anthrax edema toxin modulates PKA- and CREB-dependent signaling in two phases.
BACKGROUND
Anthrax edema toxin (EdTx) is an adenylate cyclase which operates in the perinuclear region of host cells. However, the action of EdTx is poorly understood, especially at molecular level. The ability of EdTx to modulate cAMP-dependent signaling was studied in Jurkat T cells and was compared with that of other cAMP-rising agents: Bordetella pertussis adenylate cyclase toxin, cholera toxin and forskolin.


RESULTS
EdTx caused a prolonged increase of the intracellular cAMP concentration. This led to nuclear translocation of the cAMP-dependent protein kinase (PKA) catalytic subunit, phosphorylation of cAMP response element binding protein (CREB) and expression of a reporter gene under control of the cAMP response element. Neither p90 ribosomal S6 kinase nor mitogen- and stress-activated kinase, which mediate CREB phosphorylation during T cell activation, were involved. The duration of phospho-CREB binding to chromatin correlated with the spatio-temporal rise of cAMP levels. Strikingly, EdTx pre-treated T cells were unresponsive to other stimuli involving CREB phosphorylation such as addition of forskolin or T cell receptor cross-linking.


CONCLUSIONS
We concluded that, in a first intoxication phase, EdTx induces PKA-dependent signaling, which culminates in CREB phosphorylation and activation of gene transcription. Subsequently CREB phosphorylation is impaired and therefore T cells are not able to respond to cues involving CREB. The present data functionally link the perinuclear localization of EdTx to its intoxication mechanism, indicating that this is a specific feature of its intoxication mechanism.
Puhar
Andrea
A
Dipartimento di Scienze Biomediche Sperimentali, Università di Padova, Padova, Italy. andrea.puhar@pasteur.fr
Dal Molin
Federica
F
Horvath
Stéphanie
S
Ladant
Daniel
D
Ladants
Daniel
D
Montecucco
Cesare
C
D000262:Adenylyl Cyclases / Q000494:pharmacology*; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D020218:Response Elements / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects*; D013379:Substrate Specificity; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C030325:anthrax toxin; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases