Tetrandrine blocks autophagic flux and induces apoptosis via energetic impairment in cancer cells.

Abstract

Lysosomes are acidic organelles that have a crucial role in degrading intracellular macromolecules and organelles during the final stage of autophagy. Tetrandrine (Tet), a bisbenzylisoquinoline alkaloid, was reported as an autophagy activator. Here, in contrast with previous studies, we show that Tet is a potent lysosomal deacidification agent and is able to block autophagic flux in the degradation stage. Single-agent Tet induces significant apoptosis both in vitro and in xenograft models. In the presence of Tet, apoptosis was preceded by a robust accumulation of autophagosomes and an increased level of microtubule-associated protein 1 light chain 3, type II (LC3-II). However, Tet increased the level of sequestosome 1 and decreased the turnover of LC3, indicating the blockade of autophagic flux in the degradation stage. As blockade of autophagic flux decreases the recycling of cellular fuels, Tet reduces the uptake of glucose in cancer cells. These effects lead to insufficient substrates for tricarboxylic acid (TCA) cycle and impaired oxidative phosphorylation. Blunting autophagosome formation using 3-methyladenine or genetic knockdown of Beclin-1 failed to rescue cells upon Tet treatment. By contrast, addition of methyl pyruvate to supplement TCA substrates protected Tet-treated tumor cells. These results demonstrate that energetic impairment is required in Tet-induced apoptosis. Tet, as a potent lysosomal inhibitor, is translatable to the treatment of malignant tumor patients.

• Authors: W Qiu, M Su, F Xie, J Ai, Y Ren, J Zhang, R Guan, W He, Y Gong, Y Guo
• Journal: Cell death & disease (Cell Death Dis) Vol. 5 Pg. e1123 (Mar 13 2014) ISSN: 2041-4889 [Electronic] England
• PMID: 24625982 (Publication Type: Journal Article)

Chemical References

• Adaptor Proteins, Signal Transducing
• Antineoplastic Agents, Phytogenic
• Apoptosis Regulatory Proteins
• BECN1 protein, human
• Beclin-1
• Benzylisoquinolines
• MAP1LC3A protein, human
• Membrane Proteins
• Microtubule-Associated Proteins
• SQSTM1 protein, human
• Sequestosome-1 Protein
• tetrandrine
• CASP3 protein, human
• Caspase 3
• Glucose

Topics

• Adaptor Proteins, Signal Transducing (metabolism)
• Animals
• Antineoplastic Agents, Phytogenic (pharmacology)
• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins (genetics, metabolism)
• Autophagy (drug effects)
• Beclin-1
• Benzylisoquinolines (pharmacology)
• Caspase 3 (metabolism)
• Citric Acid Cycle (drug effects)
• Energy Metabolism (drug effects)
• Female
• Glucose (metabolism)
• HeLa Cells
• Hep G2 Cells
• Humans
• Hydrogen-Ion Concentration
• Lysosomes (drug effects, metabolism, pathology)
• Male
• Membrane Proteins (genetics, metabolism)
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• Microtubule-Associated Proteins (genetics, metabolism)
• Neoplasms (drug therapy, genetics, metabolism, pathology)
• Oxidative Phosphorylation (drug effects)
• RNA Interference
• Sequestosome-1 Protein
• Signal Transduction (drug effects)
• Time Factors
• Transfection
• Tumor Cells, Cultured
• Xenograft Model Antitumor Assays