Entamoeba invadens contains the components of a classical adrenergic signaling system.
Epinephrine (Epi) was previously found to bypass the need for galactose ligands during early steps in the initiation of Entamoeba encystment. Epinephrine is presumed to act on amoebae through a classical adrenergic signaling pathway that results in the increased production of cyclic adenosine monophosphate (cAMP). The object of this study was to verify the existence of an adrenergic like pathway and its response to Epi in both whole Entamoeba trophozoites and purified plasma membrane preparations. Whole trophozoite and purified membrane preparations from Entamoeba invadens responded to the presence of Epi by increasing the production of cAMP. The modulators of heterotrimeric G protein signaling, forskolin (FK), pertussis toxin (PTX) and cholera toxin (CTX), also increased cAMP levels in whole cells and membrane fragments. All of these increases in cAMP were inhibited by specific inhibitors of adenylyl cyclase (AC). Treatment of membrane fragments with epinephrine caused an increased binding of non-hydrolysable GTP analogs. Entamoeba trophozoites therefore appear to contain G-protein-regulated adenylyl cyclase that functions downstream of an adrenergic ligand receptor.
Frederick
Jesse
J
Medical and Molecular Parasitology, New York University School of Medicine, 341 East 25th Street, New York, NY 10010, USA. jf468@med.nyu.edu
Eichinger
Dan
D
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004747:Entamoeba / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D008024:Ligands; D037342:Pertussis Toxin / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
D008024:Ligands; D011941:Receptors, Adrenergic; D005576:Colforsin; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases; D004837:Epinephrine