Bacterial effector binds host cell adenylyl cyclase to potentiate Gαs-dependent cAMP production.
Subversion of host organism cAMP signaling is an efficient and widespread mechanism of microbial pathogenesis. Bartonella effector protein A (BepA) of vasculotumorigenic Bartonella henselae protects the infected human endothelial cells against apoptotic stimuli by elevation of cellular cAMP levels by an as yet unknown mechanism. Here, adenylyl cyclase (AC) and the α-subunit of the AC-stimulating G protein (Gαs) were identified as potential cellular target proteins for BepA by gel-free proteomics. Results of the proteomics screen were evaluated for physical and functional interaction by: (i) a heterologous in vivo coexpression system, where human AC activity was reconstituted under the regulation of Gαs and BepA in Escherichia coli; (ii) in vitro AC assays with membrane-anchored full-length human AC and recombinant BepA and Gαs; (iii) surface plasmon resonance experiments; and (iv) an in vivo fluorescence bimolecular complementation-analysis. The data demonstrate that BepA directly binds host cell AC to potentiate the Gαs-dependent cAMP production. As opposed to the known microbial mechanisms, such as ADP ribosylation of G protein α-subunits by cholera and pertussis toxins, the fundamentally different BepA-mediated elevation of host cell cAMP concentration appears subtle and is dependent on the stimulus of a G protein-coupled receptor-released Gαs. We propose that this mechanism contributes to the persistence of Bartonella henselae in the chronically infected vascular endothelium.
Biozentrum,  University of Basel, CH-4056 Basel,  Switzerland.
Arto T
AT
Pulliainen
Kathrin
K
Pieles
Cameron S
CS
Brand
Barbara
B
Hauert
Alex
A
Böhm
Maxime
M
Quebatte
Alexander
A
Wepf
Matthias
M
Gstaiger
Ruedi
R
Aebersold
Carmen W
CW
Dessauer
Christoph
C
Dehio
D000262:Adenylyl Cyclases / Q000378:metabolism*; D001473:Bartonella / Q000378:metabolism*; D020134:Catalytic Domain; D000242:Cyclic AMP / Q000096:biosynthesis*; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism*
D000242:Cyclic AMP; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases