Plasmodium falciparum: Cloning by single-erythrocyte micromanipulation and heterogeneity in vitro

Oduola, A. M. J.; Weatherly, Norman F.; Bowdre, Jean H.; Desjardins, Robert E.

doi:10.1016/0014-4894(88)90053-7

Cited by 129 publications

(78 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1A, lanes 1-5). At least four radiolabeled proteins (38,43,46, and 56 kDa, some not well resolved on the gel) appear to be synthesized only at the trophozoite and schizont stages (Fig. 1A, compare lanes 2-7 with lane 1).…”

Section: Analysis Of Gpi Glycans By High Ph Anion Exchange Chromatogrmentioning

confidence: 99%

Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate Modification in Proteins of Intraerythrocytic Stage Plasmodium falciparum

Gowda

Gupta

Davidson

1997

Journal of Biological Chemistry

135

View full text Add to dashboard Cite

The nature and extent of carbohydrate modification in intraerythrocytic stage Plasmodium falciparum proteins have been controversial. This study describes the characterization of the carbohydrates in intraerythrocytic P. falciparum proteins and provides an overall picture of the nature of carbohydrate modification in the parasite proteins. P. falciparum strains were metabolically labeled with radioactive sugar precursors and ethanolamine at different developmental stages. The individual parasite proteins separated on SDS-polyacrylamide gels and whole parasite cell lysates were analyzed for the carbohydrate moieties. The results established the following: 1) glycosylphosphatidylinositol (GPI) anchors represent the major carbohydrate modification in the intraerythrocytic stage P. falciparum proteins; 2) in contrast to previous reports, O-linked carbohydrates are either absent or present only at very low levels in the parasite; and 3) P. falciparum contains low levels of N-glycosylation capability. The amount of N-linked carbohydrates in whole parasite proteins is ϳ6% compared with the GPI anchors attached to proteins based on radioactive GlcN incorporated into the proteins.The glycan cores of multiple parasite protein GPI anchors are all similar, consisting of protein-ethanolamine-phosphate-(Man␣1-2)6Man␣1-2Man␣1-6Man␣1-4GlcN. The fourth Man residues distal to GlcN of the GPI anchor glycan cores contain unidentified substituents that are susceptible to conditions of nitrous acid deamination. This unusual structural feature may contribute to the reported pathogenic properties of the P. falciparum GPI anchors.Malaria, a life-threatening disease caused by parasitic protozoa of the genus Plasmodium, is a major health problem throughout the tropical and subtropical regions of the world. Among the four species that infect humans, Plasmodium falciparum is the most virulent. New approaches such as vaccine development and novel therapeutic agents are urgently needed due to the emergence of parasite strains resistant to chloroquine and other commonly used drugs (1).Vaccines based on antigens of the blood stage parasite are under intensive study. A major focus has been on synthetic peptides or recombinant proteins of cell surface antigens (2-6). However, this approach has not been highly effective, although immunization with native cell surface proteins purified from the erythrocytic stage parasite is known to confer significant protective immunity (7-10). It is plausible that post-translational modifications play an important role in antigenicity. Accordingly, a basic understanding of such modifications may assist in the development of effective vaccines.Glycosylation is an often extensive post-translational modification of eukaryotic proteins. Carbohydrate moieties of glycoproteins perform a variety of functions including modulation of immunological properties, receptor-ligand interactions, sorting and localization of proteins, cell adhesion, and cell-cell communication (11). In addition, they contribute to protein conform...

show abstract

Section: Analysis Of Gpi Glycans By High Ph Anion Exchange Chromatogrmentioning

confidence: 99%

Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate Modification in Proteins of Intraerythrocytic Stage Plasmodium falciparum

Gowda

Gupta

Davidson

1997

Journal of Biological Chemistry

135

View full text Add to dashboard Cite

show abstract

“…For the PKA inhibition studies, two reference P. falciparum clones were used, D6 and W2. which are chloroquine sensitive and chloroquine resistant, respectively [14].…”

Section: A T E R I a L S A N D M E T H O D Smentioning

confidence: 99%

The H89 cAMP‐dependent protein kinase inhibitor blocks Plasmodium falciparum development in infected erythrocytes

Syin

Parzy

Traincard

et al. 2001

European Journal of Biochemistry

View full text Add to dashboard Cite

In Plasmodium falciparum, the causative agent of human malaria, the catalytic subunit gene of cAMP-dependent protein kinase (Pfpka-c ) exists as a single copy. Interestingly, its expression appears developmentally regulated, being at higher levels in the pathogenic asexual stages than in the sexual forms of parasite that are responsible for transmission to the mosquito vector. Within asexual parasites, PfPKA activity can be readily detected in schizonts. Similar to endogenous PKA activity of noninfected red blood cells, the parasite enzyme can be stimulated by cAMP and inhibited by protein kinase inhibitor. Importantly, ex vivo treatment of infected erythrocytes with the classical PKA-C inhibitor H89 leads to a block in parasite growth. This suggests that the PKA activities of infected red blood cells are essential for parasite multiplication. Finally, structural considerations suggest that drugs targeting the parasite, rather than the erythrocyte enzyme, might be developed that could help in the fight against malaria.Keywords: parasite; PKA; inhibition; H89.The emergence and dissemination of drug-resistant malaria parasites represents one of the most important public health problems in many parts of the world today. New antimalarials are urgently required, whose rational design and development requires the identification of potential therapeutic targets. This in turns rests on a better understanding of the molecular mechanisms controlling the progression of the complex life cycle of malaria parasites, especially Plasmodium falciparum, the species responsible for the lethal form of the disease. All Plasmodium species are intracellular parasites during infection of their vertebrate hosts. Sporozoites inoculated into a host during a bite by an infected Anopheles mosquito soon invade hepatocytes, within which intense asexual division takes place (exoerythrocytic schizogony), yielding up to 40 000 merozoites in the case of P. falciparum (http:// www.malaria.org). Upon schizont rupture, these merozoites invade red blood cells, where additional rounds of asexual replication occur (erythrocytic schizogony, the phase responsible for the pathogenesis of the disease). Some merozoites, instead of undergoing a further asexual cycle, arrest their cell cycle and differentiate into male or female gametocytes. Unlike asexual forms, these sexual forms are infective to the Anopheles vector.cAMP is involved in the regulation of development of several microorganisms, and cAMP-dependent pathways exist in most eukaryotic cells. For example, in the slime mold Dictyostelium discoideum, cAMP acts as a signal for the aggregation and differentiation of cells into a multicellular organism (reviewed in [1]). In most instances, cAMP exerts its action by binding to the regulatory subunit complexed to the catalytic subunit in an inactive holoenzyme of the protein kinase A (PKA or cAMPdependent protein kinase), thereby releasing the active catalytic subunit (PKA-C), whose substrates can include other protein kinases and transcription factors. P...

show abstract

“…Four P. falciparum malaria parasite clones from the CDC (Indochina III, W-2; Sierra Leone I, D-6), Southeast Asia (TM91C235), and Brazil (RCS) were utilized in susceptibility testing. They were derived by direct visualization and micromanipulation from patient isolates (20). The W-2 clone is susceptible to mefloquine but resistant to chloroquine, sulfadoxine, pyrimethamine, and quinine, whereas the D-6 clone is naturally resistant to mefloquine but susceptible to chloroquine, sulfadoxine, pyrimethamine, and quinine.…”

Section: Methodsmentioning

confidence: 99%

Antimalarial Activities of New Pyrrolo[3,2-f]Quinazoline-1,3-Diamine Derivatives

Guan

Zhang

O’Neil

et al. 2005

Antimicrob Agents Chemother

View full text Add to dashboard Cite

WR227825 is an antimalarial pyrroloquinazolinediamine derivative with a high potency but a low therapeutic index. A series of carbamate, carboxamide, succinimide, and alkylamine derivatives of WR227825 were prepared to search for compounds with an improved therapeutic index. The new acetamides and imide showed potent cell growth inhibition against four clones of Plasmodium falciparum (D-6, RCS, W-2, and TM91C235), with a 50% inhibitory concentration of ϳ0.01 ng/ml, and were highly active against Plasmodium berghei, with 100% cure at doses from <0.1 mg/kg of body weight to 220 mg/kg. The carbamates and alkyl derivatives, however, showed weak activity against Plasmodium falciparum cell growth but were highly efficacious in tests against P. berghei by the Thompson test. The best compounds, bis-ethylcarbamate (compound 2a) and tetraacetamide (3a) derivatives, further demonstrated high potency against the sporozoite Plasmodium yoelii in mice and P. falciparum and Plasmodium vivax in aotus monkeys. Against the AMRU-1 strain of P. vivax, which has four dihydrofolate reductase mutations and is highly resistant to antifolates, tetra-acetamide 3a cured the monkeys at doses of 1 and 3 mg/kg. Compound 2a cured only one out of two monkeys at 3 mg/kg. The results indicated that the new derivatives 2a and 3a not only have retained/improved the antimalarial efficacy of the parent compound WR227825 but also were less toxic to the animals used in the tests.Malaria is one of the most common diseases in countries of Africa, Southeast Asia, and South America (12,27,28,31,32). The increasing prevalence of multiple-drug-resistant strains of Plasmodium falciparum in most areas where malaria is endemic has significantly reduced the efficacy of current antimalarial drugs for the prophylaxis and treatment of this disease (17,19). Furthermore, the usefulness of many newer antimalarial drugs was impaired by their side effects. Lethal hemolysis side effects were observed in glucose-6-phosphate dehydrogenase-deficient recipients of 8-aminoquinoline drugs (2, 3), namely, primaquine and tafenoquine. Central nervous system toxicity was a problematic side effect in the patients treated with mefloquine (22, 24). Therefore, there is an eminent need for new and safe antimalarial drugs to combat this disease in areas of malaria endemicity.Pyrroloquinazolinediamine (PQZ) derivatives were reported to possess anticancer, antimicrobial, and antimalarial activities (13). Among the PQZ derivatives, WR227825 (compound 1) is one of the most potent antimalarial agents ever reported (26). This compound not only displayed high in vitro efficacy against P. falciparum, with a 50% inhibitory concentration (IC 50 ) of ϳ0.01 ng/ml, but was also highly active against Plasmodium berghei in a rodent model, with a 100% curative oral dose of Ͻ1 to 20 mg/kg of body weight. However, WR227825 also exhibited high host toxicity, with a subcutaneous 50% lethal dose in mice at less than 20 mg/kg, and produced deaths in aotus monkeys at doses less than 2 mg/kg (33). The PQZ was ...

show abstract

Plasmodium falciparum: Cloning by single-erythrocyte micromanipulation and heterogeneity in vitro

Cited by 129 publications

References 11 publications

Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate Modification in Proteins of Intraerythrocytic Stage Plasmodium falciparum

Glycosylphosphatidylinositol Anchors Represent the Major Carbohydrate Modification in Proteins of Intraerythrocytic Stage Plasmodium falciparum

The H89 cAMP‐dependent protein kinase inhibitor blocks Plasmodium falciparum development in infected erythrocytes

Antimalarial Activities of New Pyrrolo[3,2-f]Quinazoline-1,3-Diamine Derivatives

Contact Info

Product

Resources

About