Hexokinase 2 displacement from mitochondria-associated membranes prompts Ca²⁺-dependent death of cancer cells

Abstract

Cancer cells undergo changes in metabolic and survival pathways that increase their malignancy.Isoform 2 of the glycolytic enzyme hexokinase (HK2) enhances both glucose metabolism and resistance to death stimuli in many neoplastic cell types. Here we observe that HK2 locates at mitochondria-endoplasmic reticulum (ER) contact sites called MAMs (Mitochondria-Associated Membranes). HK2 displacement from MAMs with a selective peptide triggers mitochondrial Ca 2+ overload caused by Ca 2+ release from ER via inositol-3-phosphate receptors (IP3Rs) and by Ca 2+ entry through plasma membrane. This results in Ca 2+ -dependent calpain activation, mitochondrial depolarization and cell death. The HK2-targeting peptide causes massive death of chronic lymphocytic leukemia B cells freshly isolated from patients, and an actionable form of the peptide reduces growth of breast and colon cancer cells allografted in mice without noxious effects on healthy tissues. These results identify a signalling pathway primed by HK2 displacement from MAMs that can be activated as anti-neoplastic strategy.

Chemical Modulation of Mitochondria–Endoplasmic Reticulum Contact Sites

“…Such molecules include antimycotic drug clotrimazole [ 83 ], pyruvate analogue 3-bromopyruvate [ 84 ], and the plant stress hormone methyl jasmonate, which all induce detachment of HK from VDAC and stimulate apoptosis [ 85 ]. In addition, a selective peptide was shown to dislocate HK from MAMs in colon and breast cancer cells, and consequently to induce mitochondria Ca 2+ overload [ 86 ]. With respect to ANT, its association with VDAC is disrupted by arsenites, ionidamine, and steroid analogs [ 87 ].…”

ER-mitochondria contact sites; a multifaceted factory for Ca2+ signaling and lipid transport

“…Frontiers in Cell and Developmental Biology frontiersin.org B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia (CLL) cells, through mitochondria Ca 2+ overload driving mitochondrial transition pore opening (mPTP) (Kerkhofs et al, 2021). The mechanistic target of Rapamycin complex 2 (mTORC2)-Akt axis controls the phosphorylation-mediated inhibition of IP 3 R, which by preventing the transfer of Ca 2+ from the ER to the mitochondria attenuates mitochondrial apoptosis, while it favors cancer cell's aerobic glycolysis (Warburg effect) by phosphorylating hexokinase 2 (HK2), recently found as an essential component of EMCS in cancer cells (Betz et al, 2013;Ciscato et al, 2020). This oncogenic mechanism is counterbalanced by a transcriptional independent function of p53.…”

Mitochondrial Dysfunction Pathway Alterations Offer Potential Biomarkers and Therapeutic Targets for Ovarian Cancer

“…Mitochondria, as the core component of intracellular calcium pool regulation, can regulate intracellular calcium homeostasis through a variety of calcium transport systems on mitochondrial membranes. Abnormalities in mitochondrial calcium homeostasis are closely related to mitochondrial dysfunction and the development of tumors [ 7 ]. Mitophagy, as selective autophagy targeting mitochondria, is one of the important regulatory mechanisms to maintain mitochondrial homeostasis [ 8 , 9 ].…”