TFEB, un factor de transcripción maestro para cestodes.

NIETO, SABINA; FRANCO, MICAELA; BLANCO, SOFÍA; CUMINO, ANDREA C.; LOOS, JULIA A.

La Pampa

Congreso; II Congreso Iberoamericano de Echinococcosis, XLIV Jornadas Internacionales de Hidatidología y XXXIX Jornadas Nacionales de Hidatidología.; 2023

Asociación Parasitológica Argentina

Stress response and adaptation are critical for the survival of Echinococcus larval stages. The regulation of the transcriptional machinery involved in lysosome generation is an important aspect of these processes due to the role they play in the metabolism of cestodes, which lack excretory and digestive systems. The TFEB transcription factor, a member of the structurally related and conserved MiT/TFE family, has been demonstrated to be a crucial controller of the autophagy–lysosomal biogenesis and emerges as a key player in a wide range of cellular functions in response to internal and external stresses. In vertebrates, TOR (Target Of Rapamycin) kinase phosphorylates TFEB at the conserved serine (S211) to regulate its activity and mediate its retention in the cytoplasm by binding to the cytosolic chaperone protein 14-3-3. In this work we identified a putative orthologous gene of TFEB in the E. granulosus genome (Eg-TFEB). The full-length open reading frame of Eg-TFEB predicts a protein of 514 amino acids with a conserved domain structure containing a bHLH/ZIP domain for DNA binding (residues 220-300), which include a nuclear localization signal (229RRRR232) and it is preceded by the conserved Ser199 phosphorylatable by TOR (equivalent to Ser211 of Homo sapiens TFEB), and a second C-terminal proline-rich domain. N-terminal region of Eg-TFEB (residues 2–108) is conserved and contains the glutamine and proline-rich loops (residues 38-80), Rag binding (residues 76-83) and lysosomal localization sites. By in toto immunolocalization assays, the expression and cellular localization of Eg-TFEB were detected in the germinal layer of metacestodes and cells of protoscoleces. Eg-TFEB was shown to be highly expressed and constitutively activated under basal conditions. Furthermore, it was relocated from the cytoplasm to the nucleus in response to different pharmacological stimuli. Our results demonstrated activation of Eg-TFEB in presence of rapamycin and metformin due to direct and indirect suppression of Eg-TOR, respectively. The increase in the level of active Eg-TOR in response to exogenous insulin suggest that Eg-TFEB is part of the parasite’s insulin-TOR signaling pathway, and that Eg-TORC1 probably phosphorylates Eg-TFEB, independently of Rheb. The induction of the autophagy process was concomitant with the nuclear localization of Eg-TFEB, which could be correlated with the transcriptional regulation of this pathway.