Hexokinase 2 is a molecular bridge linking telomerase and autophagy

PLoS One. 2018 Feb 20;13(2):e0193182. doi: 10.1371/journal.pone.0193182. eCollection 2018.

Abstract

Autophagy is systematically regulated by upstream factors and nutrients. Recent studies reported that telomerase and hexokinase 2 [HK2) regulate autophagy through mTOR and that telomerase has the capacity to bind to the HK2 promoter. However, the molecular linkage among telomerase, HK2, and autophagy is not fully understood. Here, we show that HK2 connects telomerase to autophagy. HK2 inhibition in HepG2 cells suppressed TERT-induced autophagy activation and further enhancement by glucose deprivation. The HK2 downstream factor mTOR was responsible for the TERT-induced autophagy activation under glucose deprivation, implying that TERT promotes autophagy through an HK2-mTOR pathway. TERC played a role similar to that of TERT, and simultaneous expression of TERT and TERC synergistically enhanced HK2 expression and autophagy. At the gene level, TERT bound to the HK2 promoter at a specific region harboring the telomerase-responsive sequence 'TTGGG.' Mutagenesis of TERC and the TERT-responsive element in the HK2 promoter revealed that TERC is required for the binding of TERT to the HK2 promoter. We demonstrate the existence of a telomerase-HK2-mTOR-autophagy axis and suggest that inhibition of the interaction between telomerase and the HK2 promoter diminishes glucose starvation-induced autophagy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autophagy / physiology*
  • Glucose / metabolism
  • Glycolysis / physiology
  • HeLa Cells
  • Hep G2 Cells
  • Hexokinase / genetics
  • Hexokinase / metabolism*
  • Humans
  • Promoter Regions, Genetic
  • Telomerase / genetics
  • Telomerase / metabolism*

Substances

  • HK2 protein, human
  • Hexokinase
  • Telomerase
  • Glucose

Grants and funding

This work was supported by grants from the National Research Foundation of Korea (NRF; 2015R1A2A1A01003845, 2017R1A4A1015328) and The Yonsei University Yonsei-SNU Collaborative Research Fund of 2017 to HWL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.