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1 September 2002 Epidermal Growth Factor Binds to a Receptor on Trypanosoma cruzi Amastigotes Inducing Signal Transduction Events and Cell Proliferation
TOMAR J. GHANSAH, EDWARD C. AGER, PHYLLIS FREEMAN-JUNIOR, FERNANDO VILLALTA, MARIA F. LIMA
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Abstract

Host growth factors induce proliferation of Trypanosoma cruzi amastigotes by mechanisms that remain poorly defined. Here we examined human epidermal growth factor (EGF) for its ability to bind to the mammalian multiplicative forms of T. cruzi and to induce growth of the parasites. EGF stimulated incorporation of [3H] thymidine into DNA and growth of amastigotes both in a concentration-dependent manner. Radiolabeled EGF was found to bind to amastigotes in a concentration-dependent and saturable manner but it did not bind to trypomastigotes. Scatchard analysis showed a single class of receptors with a Kd of 0.8 nM and numbering 3.1 × 103 per amastigote. Results from internalization experiments provided evidence of receptor-mediated endocytosis of EGF. Northern analysis showed a 3.0-kb transcript for the putative EGF receptor (EGFR) homologue in amastigotes, but not trypomastigotes. Binding of EGF to amastigotes induced signal transduction events. EGF induced “in vitro” kinase activity as determined by γ;en[32P] ATP incorporation into amastigote proteins. EGF also increased protein kinase C activity in a concentration-dependent manner and Mitogen Activated Protein (MAP) kinase activity in a time- and concentration-dependent manner. A specific inhibitor (AG14782) of the EGFR and a MAP kinase inhibitor (PD98059) decreased EGF-dependent T. cruzi MAP kinase activity. These results describe a novel mechanism used by amastigotes to regulate their proliferation mediated by an EGF-dependent signal transduction pathway.

TOMAR J. GHANSAH, EDWARD C. AGER, PHYLLIS FREEMAN-JUNIOR, FERNANDO VILLALTA, and MARIA F. LIMA "Epidermal Growth Factor Binds to a Receptor on Trypanosoma cruzi Amastigotes Inducing Signal Transduction Events and Cell Proliferation," The Journal of Eukaryotic Microbiology 49(5), 383-390, (1 September 2002). https://doi.org/10.1111/j.1550-7408.2002.tb00216.x
Received: 1 April 2002; Accepted: 2 August 2002; Published: 1 September 2002
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KEYWORDS
Chagas' disease
EGF receptors
kinase activity
ligand-receptor binding
MAP kinase
Northern blot
protein kinase C
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