Genomic Analyses, Gene Expression and Antigenic Profile of the Trans-Sialidase Superfamily of Trypanosoma cruzi Reveal an Undetected Level of Complexity

Abstract

The protozoan parasite Trypanosoma cruzi is the etiologic agent of Chagas disease, a highly debilitating human pathology that affects millions of people in the Americas. The sequencing of this parasite's genome reveals that trans-sialidase/trans-sialidase-like (TcS), a polymorphic protein family known to be involved in several aspects of T. cruzi biology, is the largest T. cruzi gene family, encoding more than 1,400 genes. Despite the fact that four TcS groups are well characterized and only one of the groups contains active trans-sialidases, all members of the family are annotated in the T. cruzi genome database as trans-sialidase. After performing sequence clustering analysis with all TcS complete genes, we identified four additional groups, demonstrating that the TcS family is even more heterogeneous than previously thought. Interestingly, members of distinct TcS groups show distinctive patterns of chromosome localization. Members of the TcSgroupII, which harbor proteins involved in host cell attachment/invasion, are preferentially located in subtelomeric regions, whereas members of the largest and new TcSgroupV have internal chromosomal locations. Real-time RT-PCR confirms the expression of genes derived from new groups and shows that the pattern of expression is not similar within and between groups. We also performed B-cell epitope prediction on the family and constructed a TcS specific peptide array, which was screened with sera from T. cruzi-infected mice. We demonstrated that all seven groups represented in the array are antigenic. A highly reactive peptide occurs in sixty TcS proteins including members of two new groups and may contribute to the known cross-reactivity of T. cruzi epitopes during infection. Taken together, our results contribute to a better understanding of the real complexity of the TcS family and open new avenues for investigating novel roles of this family during T. cruzi infection.

Multigene Families in Trypanosoma cruzi and Their Role in Infectivity

“…These UTRs could cause expression efficiency to differ between the various stages, with greater expression efficiency in the trypomastigote blood forms resulting from intracellular replication, although it has been recently shown that expression levels are not homogeneous among genes belonging to different groups of TSs (34,38).…”

Reconhecimento molecular na doença de chagas do ponto de vista do parasita e do hospedeiro

“…Células epiteliais de Macaca mulata da linhagem de LLC-MK2 (ATCC CCL-7) (macaco rhesus) foram utilizadas para o cultivo do T. cruzi e os ensaios de infecção. As células foram mantidas em meio mínimo essencial das gp85/trans-sialidases foram obtidas no banco de dados TriTrypDB (ASLETT et al, 2010) utilizando listas de genes publicadas por FREITAS et al (2011). As sequências pertencentes ao grupo II das gp85/trans-sialidases foram então alinhadas utilizando o software "Clustal Ômega" (SIEVERS et al, 2011).…”

“…Com base na similaridade de sequências, as proteínas codificadas por esta família de genes foram ainda subdivididas em oito grupos (FREITAS et al, 2011). As proteínas pertencentes ao grupo I são as únicas proteínas que possuem domínios trans-sialidase enzimaticamente ativos, podendo remover resíduos de ácido siálico das glicoproteínas presentes na superfície celular dos mamíferos e transferí-los para glicoproteínas na membrana celular do parasita.…”

Interação parasita-célula hospedeira: modificação de proteínas de Tripanosoma cruzi durante adesão à matriz extracelular

“…A superfamília gp85/TS foi inicialmente dividida em quatro grupos de acordo com a presença de domínios ou motivos estruturais conservados (Asp Box, SAPA, VTxNVxLYNR, também denominado VTV ou FLY) (Pereira, et al, 1991, Colli, 1993, Cross & Takle, 1993, Frasch, 1994, Schenkman & Eichinger, 1994 Sayed, et al, 2005) e uma nova distribuição em 8 grupos foi proposta, sendo os grupos I a IV idênticos à distribuição anterior (Freitas, et al, 2011). O grupo I é o único formado por proteínas com atividade de trans-sialidase.…”

“…Grupo II é constitudo pelas glicoproteínas localizadas na superfície do parasita, como Tc85. Grupo III apresenta as proteínas de superfície associadas ao flagelo do parasita e os demais grupos (IV a VIII) apresentam os membros cuja função ainda não foi evidenciada (Freitas, et al, 2011. Na análise desses oito novos grupos, 328…”