Stimulation of Trypanosoma cruzi adenylyl cyclase by an alpha D-globin fragment from Triatoma hindgut: effect on differentiation of epimastigote to trypomastigote forms.

Abstract

A peptide from hindguts of the Triatoma hematophagous Chagas insect vector activates adenylyl cyclase activity in Trypanosoma cruzi epimastigote membranes and stimulates the in vitro differentiation of epimatigotes to metacyclic trypomastigotes. Hindguts were obtained from insects fed 2 days earlier with chicken blood. Purification was performed by gel fDtration and HPLC on Cis and C4 columns. SDS/PAGE of the purified peptide showed a single band of about 10 kDa. The foilowing sequence was determined for the 20 amino-terminal residues of this peptide: H2N-Met-Leu-Thr-Ala-Glu-Asp-LysLys-Leu-lle-Gln-Gln-Ala-Trp-Glu-Lys-Ala-Ala-Ser-His. This sequence is identical to the amino terminus ofchicken aD-globin. On a Western blot, the peptide immunoreacted with a polyclonal antibody against chicken globin D. A synthetic peptide corresponding to residues 1-40 of the aD-globin amino terminus also stimulated adenylyl cyclase activity and promoted differentiation. This 125I-labeled synthetic peptide bound specificaily to T. cyui epimastiote cells. Activation of epimastigote adenylyl cyclase by the hemoglobin-derived peptide may play an important role in T. cru differentiation and consequently in the transmission of Chagas disease.A major endemia in Latin America is Chagas disease. Its etiological agent is Trypanosoma cruzi, a flagellate protozoan that undergoes complex morphological changes throughout its life cycle in both the insect vector and the vertebrate host (1, 2). The hematophagous Triatoma vector ingests circulating trypomastigote forms while feeding on the blood of an infected vertebrate host. In the insect digestive tract, ingested trypomastigotes initially differentiate to epimastigotes; in a second stage, which occurs within the vector hindgut, epimastigotes that are proliferative but not infectious convert to metacyclic trypomastigotes. The latter are infectious and nonproliferative parasite forms (3)(4)(5). This differentiation process, known as metacyclogenesis, can be induced in epimastigote liquid cultures by mammalian serum components (6), the use of medium mimicking insect urine (7), metabolic stress (8, 9), Triatoma infestans hindgut extracts (10, 11), or cyclic AMP (12).In addition, metacyclic trypomastigotes exhibit higher intracellular cyclic AMP levels than epimastigotes (13), and evidence from this laboratory has shown that T. cruzi membranes possess an adenylyl cyclase associated with the a subunit of the stimulatory guanine nucleotide-binding regu-

A Novel Phosphatidylinositol-Phospholipase C of Trypanosoma cruzi That Is Lipid Modified and Activated during Trypomastigote to Amastigote Differentiation

“…A PI-PLC activity was also detected in epimastigote lysates using PI as substrate (15). A synthetic peptide corresponding to a chicken ␣ D -globin fragment was able to increase inositol monophosphate (IP) and IP 3 levels in epimastigotes (16) and stimulate transformation of epimastigotes into trypomastigotes (metacyclogenesis) (17). A protein kinase C was also characterized in T. cruzi epimastigotes (18).…”

Biological factors involving Trypanosoma cruzi life cycle in the invertebrate vector, Rhodnius prolixus

“…Several aspects on this subject are discussed by Azambuja et al (present Symposium). Fraidenraich et al (1993) isolated peptides from the hindgut of Triatoma infestans resulting from the digestion of a component of the α D -globin chain of chicken blood that are capable to induce the metacyclogenesis of T. cruzi in vitro. Later, Garcia et al (1995) demonstrated that differentiation of epimastigotes into metacyclic trypomastigotes in the insect's intestine is obtained if either hemoglobin or peptides corresponding to residues 30-49 and 35-73 of α D -globin chain are added to an infective plasma diet.…”

Intracellular Signaling Pathways Involved in Cell Differentiation in Trypanosomatids

“…Fraidenraich and co-workers [22] showed that intestinal extracts of Triatoma infestans, containing peptides derived from hemoglobin breakdown, stimulated adenylate cyclase and induced metacyclogenesis. In addition, peptides released from the proteolysis of fibronectin increased cAMP levels in trypomastigotes [23].…”