The eEF2 kinase-induced STAT3 inactivation inhibits lung cancer cell proliferation by phosphorylation of PKM2

Abstract

Background: Eukaryotic elongation factor-2 kinase (eEF2K) is a Ca 2+ /calmodulin (CaM)-dependent protein kinase that inhibits protein synthesis. However, the role of eEF2K in cancer development was reported paradoxically and remains to be elucidated. Methods: Herein, A549 cells with eEF2K depletion or overexpression by stably transfected lentivirus plasmids were used in vitro and in vivo study. MTT and colony assays were used to detect cell proliferation and growth. Extracellular glucose and lactate concentration were measured using test kit. Immunoblot and co-immunoprecipitation assays were used to examine the molecular biology changes and molecular interaction in these cells. LC-MS/MS analysis and [γ-32 P] ATP kinase assay were used to identify combining protein and phosphorylation site. Nude mice was utilized to study the correlation of eEF2K and tumor growth in vivo. Results: We demonstrated that eEF2K inhibited lung cancer cells proliferation and affected the inhibitory effects of EGFR inhibitor gefitinib. Mechanistically, we showed that eEF2K formed a complex with PKM2 and STAT3, thereby phosphorylated PKM2 at T129, leading to reduced dimerization of PKM2. Subsequently, PKM2 impeded STAT3 phosphorylation and STAT3-dependent c-Myc expression. eEF2K depletion promoted the nuclear translocation of PKM2 and increased aerobic glycolysis reflected by increased lactate secretion and glucose. Conclusions: Our findings define a novel mechanism underlying the regulation of cancer cell proliferation by eEF2K independent of its role in protein synthesis, disclosing the diverse roles of eEF2K in cell biology, which lays foundation for the development of new anticancer therapeutic strategies.

eEF2K enhances expression of PD-L1 by promoting the translation of its mRNA

“…This is in line with the fact that the role of eEF2K in cancer development is complex as revealed by apparently conflicting reports, which suggest eEF2K may promote or impair tumour growth or survival. For example, we recently reported that depletion of eEF2K promotes growth of A549 xenografts in mice [37]. In direct contrast, eEF2K is also highly expressed in other cancers (see, e.g., [38,39] and is also activated under conditions (such as nutrient depletion or hypoxia [8]) which occur within solid tumours; this will permit the enhanced expression of PD-L1 increasing the resistance of the tumour cells to immune attack.…”

Development and validation of a novel epigenetic-related prognostic signature and candidate drugs for patients with lung adenocarcinoma

“…The M2 isoform of pyruvate kinase (PKM2) (also named PKM, PK3, THBP1), an essential enzyme involved in glycolysis, is known to mediate the conversion of glucose to lactate in cancer cells under normoxic conditions [ 27 , 28 ]. Jing Li reported that phosphorylation of PKM2 and inactivation of STAT3 inhibited lung cancer cell proliferation [ 29 ]. Inhibitors of PKM2 could moderately decelerate tumor cell proliferation [ 30 , 31 ].…”

TRPM7 Silencing Modulates Glucose Metabolic Reprogramming to Inhibit the Growth of Ovarian Cancer by Enhancing AMPK Activation to Promote HIF-1α Degradation.

“…The PKM2 is a speci c isoform of pyruvate kinase and a rate-limiting enzyme controlling the glycolysis process. The PKM2 is highly expressed in many types of tumors, including ovarian cancer [39][40][41][42][43]. Studies have shown that PKM2 can translocate to the nucleus, where it forms a complex with HIF-1α and acts as a transcription coactivator of HIF-1α to promote the transcription of HIF-1α targeted genes (such as glycolytic rate-limiting enzymes).…”