Alternative trans‐splicing of the Trypanosoma cruzi LYT1 gene transcript results in compartmental and functional switch for the encoded protein

Abstract

SummaryTrypanosma cruzi has a complex life cycle that includes infective and non-infective stages in distinct hosts. Control of gene expression by the parasite must adjust to rather diverse circumstances. Through stage-regulated, alternative trans-splicing of the primary transcript, the T. cruzi LYT1 gene generates two protein products differing in the presence or absence of 28 amino acids at their amino end. We find that the shorter protein, kLYT1, is located at two spots in the mitochondrial kinetoflagellar zone and its expression reverts the 'accelerated stage development' phenotype of the LYT1-null mutant. The larger product, mLYT1, localizes on the plasma membrane. The signal for membrane localization presents characteristics of a type II anchor including the possibility of cleavage. Expression of mLYT1 reverts the 'loss of virulence' phenotype associated to diminished haemolytic activity at acid pH, but stage development still progresses at an accelerated rate. This compartmentalization switch of LYT1 results in two surprisingly different functions: haemolytic activity at acid pH for mLYT1, and a putative involvement in mitochondrial metabolism for kLYT1. We conclude that alternative trans-splicing plays an important role in stage-regulated control of gene expression in trypanosomatids.

Spliced Leader Trapping Reveals Widespread Alternative Splicing Patterns in the Highly Dynamic Transcriptome of Trypanosoma brucei

“…About half of the major splice sites in the different life stages could not be predicted using our current splice site recognition model, although the majority contained the signals that conform to our current understanding of splice sites. An obvious consequence of alternative splicing would be the change of N-terminal targeting sequences as has been shown for T. cruzi (LYT1) and for alternative cis -splicing in other systems [48], [49], [50], [51]. Our analysis indicated this likely to be the case for several AARS that are essential in the cytosol and mitochondrion [35], [36] thus providing evidence that alternative splicing is a potential mechanism for dual localization of proteins similar to what has been reported for the LYT1 gene in T. cruzi [48].…”

Dual targeting of isoleucyl-tRNA synthetase in Trypanosoma brucei is mediated through alternative trans-splicing

“…In trypanosomatids only a few examples of dually targeted proteins are known. They include the phosphodiesterase TbrPDEB2, which localizes to the cytosol and flagellum (14), the LYT1 protein in Trypanosoma cruzi , which localizes to the plasma membrane and to the base of the flagellum (15) and glutaminyl- and glutamyl-tRNA synthetases whose cytosolic and mitochondrial activities are encoded by a single gene (16). In all cases, however the mechanism of dual localization is not well understood.…”

Impairment of Infectivity and Immunoprotective Effect of a LYT1 Null Mutant of Trypanosoma cruzi

“…The trans-splicing processing was developmentally regulated, since the complete form was expressed mostly in the mammalian stages and the shorter one in epimastigotes (23). Recently, Benabdellah et al (9) revealed how these two proteins can be involved in processes so different as developmental regulation and cell invasion. The researchers found that the shorter form, named kLYT1, localizes in the kinetoflagellar zone and is responsible for the accelerated-stage development phenotype, while the full-size LYT1, named mLYT1, was associated with impaired infectivity.…”

“…The latter is a type II membrane-anchored protein, whose mature active form is released by cleavage of the signal sequence resident in the amino-terminal end. Hemolytic activity has been correlated with infectivity, and this behavior was shown to be displayed only by the parasites expressing LYT1 on their surfaces (9).…”