A Calcium- and GTP-Dependent Transglutaminase in Leishmania infantum

SIMPLE SUMMARY: Protozoan parasites of the Leishmania genus (Kinetoplastida: Trypanosomatidae) are responsible for human and animal leishmaniasis, pathologies mainly spread in the tropical and subtropical regions of the Americas and Afro-Eurasia, with several millions of people affected worldwide. Antileishmanial drugs present problems associated with drug toxicity and increasing parasite resistance. Therefore, the acquirement of further knowledge of these parasites with a focus on new potential drug targets is extremely useful. While transglutaminases are known to be involved in cell death and autophagy, it appears that these functions are very important for parasites’ virulence. Transglutaminase activity has been reported in Leishmania, where it was shown to be important for the proliferation of the insect promastigote stage. However, the enzyme has never been purified or well characterized. This study aimed to fill this knowledge gap by isolating and characterizing TGase from L. infantum promastigotes. For the first time, we showed a Ca(2+)- and GTP-dependent TGase in Leishmania corresponding to a 54 kDa protein, which was purified to homogeneity through two chromatographic steps: DEAE-Sepharose and Heparin-Sepharose. These results might allow for the exploration of the potential of this enzyme in fighting leishmaniasis. ABSTRACT: While human and animal leishmaniasis affect several millions of people worldwide, L. infantum is the species responsible for visceral leishmaniasis in Europe, Middle East, and America. Antileishmanial drugs present issues associated with drug toxicity and increasing parasite resistance. Therefore, the study of this parasite with a focus on new potential drug targets is extremely useful. Accordingly, we purified and characterized a transglutaminase (TGase) from L. infantum promastigotes. While Tgases are known to be involved in cell death and autophagy, it appears that these functions are very important for parasites’ virulence. For the first time, we showed a Ca(2+)- and GTP-dependent TGase in Leishmania corresponding to a 54 kDa protein, which was purified by two chromatographic steps: DEAE-Sepharose and Heparin-Sepharose. Using polyclonal antibodies against a 50-amino-acid conserved region of the catalytic core of human TGase 2, we revealed two other bands of 66 and 75 kDa. The 54 kDa band appears to be different from the previously reported TGase, which was shown to be Ca(2+)- independent. Future research should address the identification of the purified enzyme sequence and, subsequently, its cloning to more comprehensively investigate its pathophysiological function and possible differences from mammal enzymes.