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J. Biol. Chem., Vol. 280, Issue 44, 36841-36847, November 4, 2005

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A Malaria Parasite-encoded Vacuolar H⁺-ATPase Is Targeted to the Host Erythrocyte^*

Norma Marchesini1, Mauricio Vieira1, Shuhong Luo1, Silvia N. J. Moreno, and Roberto Docampo2

From the Department of Pathobiology and Center for Zoonoses Research, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802 and the Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, Georgia 30602

The asexual development of malaria parasites inside the erythrocyte is accompanied by changes in the composition, structure, and function of the host cell membrane and cytoplasm. The parasite exports a membrane network into the host cytoplasm and several proteins that are inserted into the erythrocyte membrane, although none of these proteins has been shown to have enzymatic activity. We report here that a functional malaria parasite-encoded vacuolar (V)-H⁺-ATPase is exported to the erythrocyte and localized in membranous structures and in the plasma membrane of the infected erythrocyte. This localization was determined by separation of parasite and erythrocyte membranes and determination of enzyme marker activities and by immunofluorescence microscopy assays using antibodies against the B subunit of the malarial V-H⁺-ATPase and erythrocyte (spectrins) and parasite (merozoite surface protein 1) markers. Our results suggest that this pump has a role in the maintenance of the intracellular pH (pH_i) of the infected erythrocyte. Our results also indicate that although the pH_i maintained by the V-H⁺-ATPase is important for maximum uptake of small metabolites at equilibrium, it does not appear to affect transport across the erythrocyte membrane and is, therefore, not involved in the previously described phenomenon of increased permeability of infected erythrocytes that is sensitive to chloride channel inhibitors (new permeation pathway). This constitutes the first report of the presence of a functional enzyme of parasite origin in the plasma membrane of its host.

Received for publication, July 15, 2005 , and in revised form, August 25, 2005.

^* This work was supported in part by a Burroughs Wellcome New Initiatives in Malaria Research Award (to R. D.) and a Burroughs Wellcome New Investigator Research Award (to S. N. J. M.) This investigation was conducted in part in a facility constructed with support from Research Facility Improvement Grant C06 RR16515-01 from the National Center for Research Resources, National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ These authors contributed equally to this study.

² To whom correspondence should be addressed. Tel.: 706-542-8104; Fax: 706-542-4271; E-mail: rdocampo{at}uga.edu.

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