Mitochondrial PKM2 regulates oxidative stress-induced apoptosis by stabilizing Bcl2

Abstract

Pyruvate kinase M2 isoform (PKM2) catalyzes the last step of glycolysis and plays an important role in tumor cell proliferation. Recent studies have reported that PKM2 also regulates apoptosis. However, the mechanisms underlying such a role of PKM2 remain elusive. Here we show that PKM2 translocates to mitochondria under oxidative stress. In the mitochondria, PKM2 interacts with and phosphorylates Bcl2 at threonine (T) 69. This phosphorylation prevents the binding of Cul3-based E3 ligase to Bcl2 and subsequent degradation of Bcl2. A chaperone protein, HSP90α1, is required for this function of PKM2. HSP90α1's ATPase activity launches a conformational change of PKM2 and facilitates interaction between PKM2 and Bcl2. Replacement of wild-type Bcl2 with phosphorylation-deficient Bcl2 T69A mutant sensitizes glioma cells to oxidative stress-induced apoptosis and impairs brain tumor formation in an orthotopic xenograft model. Notably, a peptide that is composed of the amino acid residues from 389 to 405 of PKM2, through which PKM2 binds to Bcl2, disrupts PKM2-Bcl2 interaction, promotes Bcl2 degradation and impairs brain tumor growth. In addition, levels of Bcl2 T69 phosphorylation, conformation-altered PKM2 and Bcl2 protein correlate with one another in specimens of human glioblastoma patients. Moreover, levels of Bcl2 T69 phosphorylation and conformation-altered PKM2 correlate with both grades and prognosis of glioma malignancy. Our findings uncover a novel mechanism through which mitochondrial PKM2 phosphorylates Bcl2 and inhibits apoptosis directly, highlight the essential role of PKM2 in ROS adaptation of cancer cells, and implicate HSP90-PKM2-Bcl2 axis as a potential target for therapeutic intervention in glioblastoma.

Targeting cancer stem cell pathways for cancer therapy

“…138,139 GSK3 genes are critical for β-catenin regulation; therefore, many researchers expect the occurrence of GSK3 mutations, but GSK3 mutations are not correlated with cancer occurrence. In addition, some genes (pyruvate kinase isozyme M2 (PKM2) in breast cancer 140 and telomerase reverse transcriptase (TERT) in prostate cancer 141 ) and microRNAs (miR-164a in colorectal cancer 142 and miR-582-3p in non-small-cell lung cancer 143 ) inhibit the activity of APC, Axin, and GSK3β to promote the accumulation of β-catenin in the cytoplasm.…”

“…135 PKM2 catalyzes the last step of glycolysis and plays an essential role in the proliferation of breast CSCs by associating with increased β-catenin levels at regions "−410 to 180 and −2250 to 2000". 140,145,149 Enhancer of zeste homolog 2 (EZH2), a key component of the polycomb PRC2 complex, promotes selfrenewal of CSCs by activating β-catenin. 150 Moreover, TERT, an RNA-dependent DNA polymerase, acts as a cofactor and forms a complex with β-catenin to activate Wnt downstream targets in In the absence of Wnt signaling, β-catenin is bound to the Axin complex, which contains APC and GSK3β, and is phosphorylated, leading to ubiquitination and proteasomal degradation through the β-Trcp pathway.…”

Down‐regulation of PKM2 decreases FASN expression in bladder cancer cells through AKT/mTOR/SREBP‐1c axis

“…PKM2 also can phosphorylate the spindle checkpoint protein Bub3, and regulate correct chromosome segregation of tumor cells (Jiang et al, ). Besides, mitochondrial PKM2 is capable to phosphorylate Bcl‐2, prevents Bcl‐2 degradation, and thus inhibits apoptosis in glioblastoma (Lian et al, ).…”

Hsp90 Relieves Heat Stress-Induced Damage in Mouse Kidneys: Involvement of Antiapoptotic PKM2-AKT and Autophagic HIF-1α Signaling

“…Intracellular HSPs can function to inhibit apoptosis and facilitate cell proliferation, preserving renal tubule viability after acute injury [24,29]. Although PKM2, Akt, and HIF-1α are well-known client proteins of Hsp90 in kinds of cancer cells [30][31][32], little is known about the role of Hsp90 in autophagy and its relationship with apoptosis in heat stress-induced AKI pathogenesis.Our previous study in myocardial cells showed that aspirin (ASA), a nonsteroidal antipyretic drug, increased Hsp90 expression, contributing to the resistance to heat stress-induced apoptosis, and that geldanamycin (GA) treatment effectively inhibited its function as a molecular chaperone [20]. In this in vivo study, mice were treated with ASA, GA, and TR (triciribine, the inhibitor of Akt activation) without or with heat stress, for evaluating our hypothesis that heat stress-induced acute kidney injury originated from peroxidation, and that Hsp90 enhanced cellular protection by restricting apoptosis and inducing autophagy-mediated survival by two separate signaling pathways, Hsp90-PKM2-Akt and Hsp90-HIF-1α-BNIP3/BNIP3L.…”

“…Intracellular HSPs can function to inhibit apoptosis and facilitate cell proliferation, preserving renal tubule viability after acute injury [24,29]. Although PKM2, Akt, and HIF-1α are well-known client proteins of Hsp90 in kinds of cancer cells [30][31][32], little is known about the role of Hsp90 in autophagy and its relationship with apoptosis in heat stress-induced AKI pathogenesis.…”