Expression of profilin in Trypanosoma cruzi and identification of some of its ligands

• Profilin is expressed in insect and mammalian stages of Trypanosoma cruzi.
• Profilin interacts with trypanosomatid-specific proteins in vitro.
• Novel actin functions and regulatory pathways may be operating in T. cruzi.

The role and regulation of actin in Trypanosoma cruzi and other related parasites is largely unknown. Based on early genome analysis, it was proposed that there was a reduced dependency on the acto-myosin system in the trypanosomatid parasites. However, more recent studies have extended the set of potential actin regulatory proteins, particularly for T. cruzi. One of the identified actin-binding proteins in trypanosomatids is profilin. In other systems, it is capable of simultaneously binding both monomeric actin and several actin-regulatory factors. Hence, the study of profilin and its ligands may help to identify novel pathways in which actin is involved. In T. cruzi, profilin is encoded by a single copy gene. In this work, we demonstrated that this gene is constitutively expressed in both insect and mammalian stages of the parasite, and that the protein is diffusely distributed. Furthermore, we identified some of its potential ligands by LC-MS using GST-profilin pull-down assays of parasite's protein extracts. Many of them were trypanosomatid specific proteins with unknown functions, although proteins from the carbohydrate metabolism, and two metallopeptidases were also detected. As expected, known ligands of profilin in other organisms were identified, including actin, the microtubule components, and the elongation factor 1-alpha. Our work suggests that profilin and the actin system may be regulated by unknown factors and participate in novel biological processes.