RESUMO
As a first step towards developing a set of compartment-specific probes for studying protein trafficking in the malaria-infected erythrocyte, we describe here a family of Plasmodium falciparum Rab proteins. We characterise in detail P. falciparum Rab6 (PfRab6) a marker which in other cells is specific for the Golgi/trans Golgi network. Although PfRab6 mRNA is expressed throughout the intraerythrocytic cycle, maximal expression occurs at the trophozoite stage. Immunofluorescence microscopy shows that the distribution of PfRab6 changes during the final stages of parasite maturation, coalescing into multiple foci, each of which is associated with the nucleus of a forming daughter parasite.
Assuntos
Proteínas de Transporte/análise , Proteínas de Transporte/genética , Genes de Protozoários , Plasmodium falciparum/genética , Proteínas rab de Ligação ao GTP , Proteínas ras/análise , Proteínas ras/genética , Sequência de Aminoácidos , Animais , Proteínas de Transporte/química , Núcleo Celular/química , Clonagem Molecular , DNA Complementar/genética , Eritrócitos/parasitologia , Expressão Gênica , Microscopia de Fluorescência , Dados de Sequência Molecular , Plasmodium falciparum/química , Plasmodium falciparum/crescimento & desenvolvimento , Reação em Cadeia da Polimerase , Proteínas de Protozoários/análise , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas ras/químicaAssuntos
Proteínas de Ligação ao GTP/genética , Genes de Protozoários , Inibidores de Dissociação do Nucleotídeo Guanina , Plasmodium falciparum/genética , Sequência de Aminoácidos , Animais , Clonagem Molecular , DNA Complementar/genética , Dados de Sequência Molecular , Família Multigênica , Análise de Sequência de DNA , Homologia de Sequência de AminoácidosRESUMO
We report here the nucleotide sequence of hsp90 (heat shock protein 90) of Plasmodium falciparum. Computer analysis of the deduced protein sequence revealed an unusually large region of charged amino acids when compared to hsp90 from other species. This region shows striking homology to the calcium binding domain of calreticulin, the major calcium binding protein of endoplasmic reticulum. Phylogenetic tree analysis indicates that P. falciparum hsp90 is more closely related to hsp90 from plants than to hsp90 from vertebrates or other parasites. The malaria hsp90 is an ATP binding protein encoded by a single gene constitutively expressed in both asexual (trophozoite) and sexual (gametocyte) stage parasites. The hsp90 protein is homologous to a previously identified 90-kDa antigen strongly recognised by both sera from vaccinated monkeys and monoclonal antibody XIV/7.
Assuntos
Proteínas de Choque Térmico HSP90/genética , Plasmodium falciparum/genética , Trifosfato de Adenosina/metabolismo , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais , Sequência de Bases , Proteínas de Ligação ao Cálcio/genética , Calreticulina , Proteínas de Transporte/genética , Clonagem Molecular , Sequência Consenso , Primers do DNA/genética , DNA Complementar/genética , DNA de Protozoário/genética , Genes de Protozoários , Proteínas de Choque Térmico HSP90/imunologia , Humanos , Íntrons , Dados de Sequência Molecular , Plasmodium falciparum/crescimento & desenvolvimento , Ribonucleoproteínas/genética , Homologia de Sequência de Aminoácidos , Especificidade da EspécieRESUMO
Mutants of poliovirus (PV) with highly modified biological properties can be selected in vitro in cells of neural origin. Mutations accumulate in the genome of type 1 PV strains selected in human neuroblastoma cells, modifying cell specificity and conferring to the virus the ability to persist in such nonneural cells as HEp-2c (Pelletier et al., Virology 180, 729 1991). With this cell system, we have both parent lytic strains and persistent PV mutants; these were used to study the mechanisms of the establishment and maintenance of the persistent infection. We found that a persistent infection was established when the lytic potential of the virus was reduced; this involved both an early and a late event of the virus cycle for the type 1 mutants. In contrast, maintenance of the infection did not correlate with the reduced lytic potential of the viruses, but rather with the selection of mutant cell populations of various phenotypes. Two cell lines, representative of two phenotypes, were studied in greater detail. In the first one, HEp-S32 (cl7), the PV receptor was not detected by cytofluorometry and viral genomes were detected by in situ hybridization in 2% of the cells. In the second cell line, HEp-S31 (cl18), 97% of the cells expressed the PV receptor, viral genomes were detected in 9-10% of the cells, and viral antigens in 5-10% of the cells. With this cell line, the cure of the culture or, alternatively, the lysis of the majority of cells, could be induced under specific culture conditions. We propose a model involving an equilibrium between an abortive and a lytic infection to explain the properties of cells persistently infected with PV.