This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Barr, S. C. Articles by Gilmour, R. F. Search for Related Content PubMed PubMed Citation Articles by Barr, S. C. Articles by Gilmour, R. F., Jr

 Previous Article  |  Next Article 

Infect. Immun., May 1996, 1770-1777, Vol 64, No. 5
Copyright © 1996, American Society for Microbiology

A factor from Trypanosoma cruzi induces repetitive cytosolic free Ca2+ transients in isolated primary canine cardiac myocytes

SC Barr, W Han, NW Andrews, JW Lopez, BA Ball, TL Pannabecker and RF Gilmour Jr
College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA. scb6@cornell.edu

An unusual 120-kDa alkaline peptidase contained in a trypomastigote soluble fraction (TSF) of Trypanosoma cruzi is associated with the induction of repetitive Ca2+ transients and subsequent invasion by the parasite of a number of mammalian cell lines, including tissue culture L6E2 myoblasts (B. A. Burleigh and N. W. Andrews, J. Biol. Chem. 270:5172-5180, 1995; S. N. J. Moreno, J. Silva, A. E. Vercesi, and R. Docampo, J. Exp. Med. 180:1535-1540, 1994; A. Rodriguez, M. G. Rioult, A. Ora, and N. W. Andrews, J. Cell Biol. 129:1263-1273, 1995; I. Tardieux, M. H. Nathanson, and N. W. Andrews, J. Exp. Med. 179:1017- 1022, 1994). Using single cell spectrofluorometry and whole-cell patch clamping, we show that TSF produces rapid repetitive cytosolic Ca2+ transients (each associated with cell contraction) in primary cardiac myocytes isolated from dogs. The response of myocytes to TSF was dose dependent in that increasing numbers of cells responded to increasing concentrations of TSF. The TSF-induced Ca2+ transients could be obliterated when TSF was heated or treated with trypsin or the protease inhibitor leupeptin. Aprotinin, pepstatin A, and E-64 did not affect TSF activity. The TSF-induced Ca2+ transients and trypomastigote cell invasion could not be inhibited by alpha (prazosin)- or beta (propanolol)-adrenergic blockers or L-type Ca2+ channel blockers (verapamil, nisoldipine, or cadmium) or by removal of extracellular Ca2+. However, inhibition of pertussis toxin-sensitive G proteins and Ca2+ release from the sarcoplasmic reticulum (with thapsigargin or ryanodine) prevented the TSF-induced Ca2+ transients and cell invasion by trypomastigotes. These data suggested that cardiac myocyte pertussis toxin-sensitive G proteins are associated with the regulation of TSF- induced Ca2+ transients and myocyte invasion by trypomastigotes but are independent of Ca2+ entry into the cytosol via L-type Ca2+ channels. The Ca2+ transients are dependent on release of Ca2+ from sarcoplasmic reticulum Ca2+ stores, but this release is not dependent on extracellular Ca2+ or on the classic model of Ca2+ -induced Ca2+ release in cardiac myocytes. Further, subthreshold depolarizations, together with cell contraction as demonstrated by whole-cell patch clamping, occurred with each Ca2+ transient. However, the depolarizations were of magnitude insufficient to generate an action potential, providing further evidence for a lack of dependence on L- type Ca2+ channels and other voltage-dependent channels (Na+ and K+ channels) in the generation of TSF-induced Ca2+ transients. Our findings suggest that primary canine cardiac myocytes respond to TSF and parasite invasion in ways similar to those of the in vitro cell lines studied to date. Since cardiac myocytes are primary targets for T. cruzi in the vertebrate host, our study indicates that TSF may play a role in the pathogenesis of Chagas' disease in humans.

This article has been cited by other articles:

• Manque, P. M., Eichinger, D., Juliano, M. A., Juliano, L., Araya, J. E., Yoshida, N. (2000). Characterization of the Cell Adhesion Site of Trypanosoma cruzi Metacyclic Stage Surface Glycoprotein gp82. Infect. Immun. 68: 478-484 [Abstract] [Full Text]  
• Burleigh, B. A., Caler, E. V., Webster, P., Andrews, N. W. (1997). A Cytosolic Serine Endopeptidase from Trypanosoma cruzi Is Required for the Generation of Ca2+ Signaling in Mammalian Cells. J. Cell Biol. 136: 609-620 [Abstract] [Full Text]