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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the studies reported here, we examined the role of calcium in the maturation of the human malaria parasite Plasmodium falciparum, and in the loss of red cell deformability associated with parasite maturation. P. falciparum alters the permeability of its host red cell, which normally maintains submicromolar cytoplasmic concentrations of calcium. Infection of the red cell and parasite maturation produce a 30-fold increase in calcium uptake. Both parasite maturation and the loss of red cell deformability are blocked by EGTA (by extracellular-free calcium concentrations less than or equal to 35 microM) and by other calcium antagonists. The loss of red cell deformability that occurs with parasite maturation is accompanied by alterations in the cytoskeletal proteins of parasitized red cells similar to those produced by the calcium ionophore A23187 (reductions in bands 2.1 [ankyrin], 4.1, and 5 [actin]). These results establish that parasite development and the loss of red cell deformability are calcium-dependent. They suggest that parasite-induced changes in the calcium permeability of the red cell activate endogenous transglutaminase activity by raising the free calcium concentration of the red cell cytoplasm.
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PMID:Calcium and the malaria parasite: parasite maturation and the loss of red cell deformability. 190 27

Transglutaminase was identified in malaria parasites by immunofluorescence microscopy using alpha-transglutaminase antiserum. Functional enzyme was demonstrated in vivo and in vitro using labeled polyamines that become incorporated into protein substrates through TGase activity. In Plasmodium falciparum intraerythrocytic parasites, transglutaminase activity was stage-dependent: it was weak in ring-forms but much stronger in trophozoites and schizonts. High levels of activity were detected in P. gallinaceum zygotes and ookinetes and in capsules of oocysts developing on mosquito midguts. Unlike most known transglutaminases, the enzymatic activity in Plasmodium was Ca(2+)-independent. Furthermore, levels of activity were similar at 37 and 26 degrees C. Parasite transglutaminase may be responsible for the modification of erythrocytic cytoskeleton in infected cells and it may facilitate the construction of oocyst capsules by cross-linking mosquito-derived basement membrane components with Plasmodium-derived proteins.
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PMID:Transglutaminase in Plasmodium parasites: activity and putative role in oocysts and blood stages. 1160 26

Insect seminal fluid proteins are powerful modulators of many aspects of female physiology and behaviour including longevity, egg production, sperm storage, and remating. The crucial role of these proteins in reproduction makes them promising targets for developing tools aimed at reducing the population sizes of vectors of disease. In the malaria mosquito Anopheles gambiae, seminal secretions produced by the male accessory glands (MAGs) are transferred to females in the form of a coagulated mass called the mating plug. The potential of seminal fluid proteins as tools for mosquito control demands that we improve our limited understanding of the composition and function of the plug. Here, we show that the plug is a key determinant of An. gambiae reproductive success. We uncover the composition of the plug and demonstrate it is formed through the cross-linking of seminal proteins mediated by a MAG-specific transglutaminase (TGase), a mechanism remarkably similar to mammalian semen coagulation. Interfering with TGase expression in males inhibits plug formation and transfer, and prevents females from storing sperm with obvious consequences for fertility. Moreover, we show that the MAG-specific TGase is restricted to the anopheline lineage, where it functions to promote sperm storage rather than as a mechanical barrier to re-insemination. Taken together, these data represent a major advance in our understanding of the factors shaping Anopheles reproductive biology.
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PMID:Transglutaminase-mediated semen coagulation controls sperm storage in the malaria mosquito. 2002 6

Unmethylated CpG dinucleotide motifs in bacterial DNA or in synthetic oligodeoxynucleotides (ODN) are potent stimulators of the vertebrate innate immune system. However, the potential of these DNA species to modulate mosquito immunity have not been explored. In the present study, we investigated the effects of CpG-ODN on the outcome of Plasmodium infection in insects and on the modulation of mosquito immunity to Plasmodium. Anopheles stephensi and Anopheles gambiae mosquitoes inoculated with CpG-ODN showed significant reductions in the prevalence of Plasmodium infection, intensity of Plasmodium infection, and number of eggs produced. Microarrays were used to elucidate the transcriptional profiles of the fat bodies of CpG-ODN-treated mosquitoes. In total, 172 genes were differentially expressed, of which 136 were up-regulated and 36 were down-regulated. The major functional class of CpG-ODN-regulated genes encoded immune response-related proteins (31%). Within this group, genes associated with coagulation/wound healing were the most frequently represented (23%). Knockdown of a transglutaminase gene that was up-regulated by the CpG-ODN and chemical inhibition of the enzyme resulted in a significant increase in Plasmodium infection. Mosquitoes that were treated with CpG-ODNs were found to be less susceptible to Plasmodium infection. Transcriptional profiling of the fat body suggests that protection is associated with coagulation/wound healing. We show for the first time that transglutaminase activity plays a role in the control of Plasmodium infection.
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PMID:CpG-containing oligodeoxynucleotides increases resistance of Anopheles mosquitoes to Plasmodium infection. 2288 18