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Infection and Immunity, April 2002, p. 1816-1823, Vol. 70, No. 4
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.4.1816-1823.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Entamoeba histolytica-Induced Dephosphorylation in Host Cells

José E. Teixeira1 and Barbara J. Mann1,2*

Departments of Internal Medicine,1 Microbiology, University of Virginia, School of Medicine, Charlottesville, Virginia 229082

Received 20 September 2001/ Returned for modification 31 October 2001/ Accepted 10 December 2001

Activation of host cell protein tyrosine phosphatases (PTPases) and protein dephosphorylation is an important mechanism used by various microorganisms to deactivate or kill host defense cells. To determine whether protein tyrosine dephosphorylation played a role in signaling pathways affecting Entamoeba histolytica-mediated host cell killing, we investigated the involvement of PTPases during the attachment of E. histolytica to target cells. We observed a rapid decrease in cellular protein tyrosine levels in Jurkat cells, as measured with an antiphosphotyrosine monoclonal antibody, following adherence to E. histolytica. Ameba-induced protein dephosphorylation was contact dependent and required intact parasite, since blocking amebic adherence with galactose inhibited tyrosine dephosphorylation and amebic lysates had no effect on phosphotyrosine levels. Moreover, disruption of amebic adherence with galactose promoted recovery of phosphorylation in Jurkat cells, indicating that dephosphorylation precedes target cell death. The evidence suggests that ameba-induced dephosphorylation is mediated by host cell phosphatases. Prior treatment of Jurkat cells with phenylarsine oxide, a PTPase inhibitor, inhibited ameba-induced dephosphorylation. We also found proteolytic cleavage of the PTPase 1B (PTP1B) in Jurkat cells after contact with amebae. The calcium-dependent protease calpain is responsible for PTP1B cleavage and enzymatic activation. Pretreatment of Jurkat cells with calpeptin, a calpain inhibitor, blocked PTP1B cleavage and inhibited ameba-induced dephosphorylation. In addition, inhibition of Jurkat cell PTPases with phenylarsine oxide blocked Jurkat cell apoptosis induced by E. histolytica. These results suggest that E. histolytica-mediated host cell death occurs by a mechanism that involves PTPase activation.

* Corresponding author. Mailing address: Room 2159 MR4 Building, University of Virginia Health System, P.O. Box 801340, Charlottesville, VA 22908-1340. Phone: (434) 924-9666. Fax: (434) 924-0075. E-mail: bjm2r{at}virginia.edu.

Infection and Immunity, April 2002, p. 1816-1823, Vol. 70, No. 4
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.4.1816-1823.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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