The absence of the Leishmania major telomerase TERT component links telomeres and cell homeostasis with infectivity

We studied the impacts of deleting the telomerase reverse transcriptase component of the Leishmania major (LmTERT) telomerase complex. The Leishmania genus comprises species that cause leishmaniasis, a neglected disease that lacks effective treatment and control options, highlighting the need for alternative therapeutics. Telomerase plays a crucial role in maintaining the integrity of eukaryotic genomes by synthesizing telomeres through its TERT and telomerase RNA components. Here, we show that the absence of TERT in L. major has a pleiotropic effect on parasite homeostasis, causing growth and proliferation alterations, progressive telomere shortening, increased TERRA expression, and γH2A signaling, besides the early onset of autophagosomes and mitochondrial insults. The proteomic analysis of LmTERT knockout promastigotes compared with the parental lineage confirmed some of these alterations, showing an imbalance in constituents of chromatin, plasma membrane, mitochondria, and cytoskeleton, and the unexpected presence of proteins involved in autophagy and virulence at this parasite life stage. Inactivating LmTERT also impaired metacyclogenesis, abolishing the parasite's infectivity. These results establish a strong link between telomeres, cell homeostasis, and the parasite's infective capability, highlighting LmTERT as a promising target for antiparasitic strategies.