title: Invitro effect of Canavalia ensiformis urease and the derived peptide Jaburetox-2Ec on Rhodnius prolixus Malpighian tubules.
abstract: Ureases are metalloenzymes that are widespread among plants, fungi and bacteria. Urease isoforms (jack bean urease-JBU and canatoxin) from Canavalia ensiformis seeds are toxic to insects and fungi, suggesting a role in plant defense. The entomotoxic effect is due to the release of a 10-kDa peptide by cathepsin-like enzymes in the insect's midgut. Urease causes a decrease in post-feeding weight loss in Rhodnius prolixus, suggesting an effect on water balance. To investigate how this impairment occurs, we have evaluated the action of JBU and the urease-derivated peptide Jaburetox-2Ec on R. prolixus Malpighian tubules and also investigated the involvement of second messengers. JBU and Jaburetox-2Ec affect serotonin-induced secretion from Malpighian tubules. This effect is not cAMP-dependent, but the Jaburetox-2Ec effect is cGMP-dependent. Eicosanoid metabolites and calcium ions appear to be involved in JBU effect on diuresis, but are not involved in the action of Jaburetox-2Ec. Jaburetox-2Ec, but not JBU, causes a change in the transepithelial potential of the tubules. Canatoxin has a similar effect on tubules secretion, decreasing the secretion rate, but the urease from Helicobacter pylori has no significant effect. These data are helpful in our understanding of the actions of ureases and derived peptides on insects, and also reinforces the potential use of these proteins as biopesticides.
authors.affiliation: Department of Biophysics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91501-970, Brazil. fernanda.staniscuaski@ufrgs.br
authors.forename: Fernanda
authors.initials: F
authors.lastname: Stanisçuaski
authors.forename: Victoria
authors.initials: V
authors.lastname: Te Brugge
authors.forename: Célia R
authors.initials: CR
authors.lastname: Carlini
authors.forename: Ian
authors.initials: I
authors.lastname: Orchard
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D007814:Larva / Q000187:drug effects; D008317:Malpighian Tubules / Q000187:drug effects* / Q000378:metabolism; D010940:Plant Proteins; D011863:Radioimmunoassay; D012239:Rhodnius / Q000187:drug effects*; D015290:Second Messenger Systems / Q000187:drug effects*; D012701:Serotonin / Q000378:metabolism; D014510:Urease / Q000633:toxicity*
chemical_list: D010940:Plant Proteins; D012701:Serotonin; D014510:Urease; C525847:jaburetox-2Ec, Canavalia ensiformis