title: Expression of a major surface protein of Trypanosoma brucei insect forms is controlled by the activity of mitochondrial enzymes.
abstract: In cycling between the mammalian host and the tsetse fly vector, trypanosomes undergo major changes in energy metabolism and surface coat composition. Early procyclic (insect) forms in the tsetse fly midgut are coated by glycoproteins known as EP and GPEET procyclins. EP expression continues in late procyclic forms, whereas GPEET is down-regulated. In culture, expression of GPEET is modulated by glycerol or glucose. Here, we demonstrate that a glycerol-responsive element of 25 nucleotides within the 3' untranslated region of GPEET mRNA also controls expression by glucose and during development in the fly. In trypanosomes, mitochondrial ATP is produced mainly by the acetate: succinate-CoA transferase/succinyl-CoA synthetase (ASCT) cycle, the citric acid cycle, and the cytochromes. Silencing of the pyruvate dehydrogenase or succinyl-CoA synthetase from the ASCT cycle by RNA interference induces reexpression of GPEET in late procyclic forms, whereas inhibition of the citric acid cycle or the cytochromes has no effect. In contrast, inhibition of the alternative oxidase, the second branch of the electron transport chain, with salicylhydroxamic acid overrides the effect of glucose or glycerol and causes a reduction in the level of GPEET mRNA. Our results reveal a new mechanism by which expression of a surface glycoprotein is controlled by the activity of mitochondrial enzymes.
authors.affiliation: Institute of Cell Biology, University of Bern, CH-3012 Bern, Switzerland. erik.vassella@izb.unibe.ch
authors.forename: Erik
authors.initials: E
authors.lastname: Vassella
authors.forename: Matthias
authors.initials: M
authors.lastname: Probst
authors.forename: André
authors.initials: A
authors.lastname: Schneider
authors.forename: Erwin
authors.initials: E
authors.lastname: Studer
authors.forename: Christina Kunz
authors.initials: CK
authors.lastname: Renggli
authors.forename: Isabel
authors.initials: I
authors.lastname: Roditi
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000235:genetics; D004734:Energy Metabolism; D015870:Gene Expression / Q000187:drug effects; D017125:Genes, Protozoan; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D015800:Protozoan Proteins / Q000235:genetics*; D034622:RNA Interference; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016053:RNA, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D014370:Tsetse Flies / Q000469:parasitology
chemical_list: D020413:3' Untranslated Regions; D016054:DNA, Protozoan; C406750:EP procyclin protein, Trypanosoma brucei; C406751:GPEET protein, Trypanosoma brucei; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D005947:Glucose; D005990:Glycerol