Molecular and Structural Characterization of an Immunopurified Telomerase from Leishmania major and the Effect of Telomerase Inhibitors

<i>Leishmania major</i> is the etiological agent of cutaneous leishmaniasis (CL) in several countries in Asia and Northern Africa. The disease is considered a zoonotic infection where rodents are the reservoirs and phlebotomine sandflies are the vectors. Once inside the human body, the parasite multiplies inside the macrophages of infected patients, but the disease eventually cures spontaneously, leaving scars where the phlebotomine bites occurred. Given the importance of the replicative forms in the parasite's cell cycle, here, we decided to study the enzyme telomerase, which has the critical role of replenishing the chromosomal telomeric ends during cell replication. To this aim, we first conducted partial purification using Sephacryl-300 HR gel filtration, which allowed us to determine that the telomerase activity eluted as a 600 KDa complex. Second, we characterized an immunopurified <i>L. major</i> telomerase, and to try to explain some of our findings, we performed modeling studies using Alfa fold 3, Pyre2, and Swiss Protein Model. Finally, considering the similarity between the catalytic site of <i>Leishmania</i> and <i>Homo sapiens</i> telomerase, we decided to test typical inhibitors of human telomerase on the purified enzyme and promastigote cell forms, confirming that MST-312 and TMPYP4 efficiently inhibited <i>L. major</i> activity and arrested cell growth in <i>Leishmania</i> promastigotes. Our findings confirm the importance of telomerase activity in <i>L. major</i>'s replicative forms and suggest the possibility of using drugs previously tested on human telomerase to treat CL.