ABSTRACT
Many tumor cells rely on aerobic glycolysis instead of oxidative phosphorylation for their continued proliferation and survival. Myc and HIF-1 are believed to promote such a metabolic switch by, in part, upregulating gene expression of pyruvate dehydrogenase (PDH) kinase 1 (PDHK1), which phosphorylates and inactivates mitochondrial PDH and consequently pyruvate dehydrogenase complex (PDC). Here we report that tyrosine phosphorylation enhances PDHK1 kinase activity by promoting ATP and PDC binding. Functional PDC can form in mitochondria outside of the matrix in some cancer cells and PDHK1 is commonly tyrosine phosphorylated in human cancers by diverse oncogenic tyrosine kinases localized to different mitochondrial compartments. Expression of phosphorylation-deficient, catalytic hypomorph PDHK1 mutants in cancer cells leads to decreased cell proliferation under hypoxia and increased oxidative phosphorylation with enhanced mitochondrial utilization of pyruvate and reduced tumor growth in xenograft nude mice. Together, tyrosine phosphorylation activates PDHK1 to promote the Warburg effect and tumor growth.
Subject(s)
Mitochondria/enzymology , Neoplasms/metabolism , Protein Serine-Threonine Kinases/metabolism , Tyrosine/metabolism , Animals , Female , Mice , Mice, Nude , Mitochondria/metabolism , Neoplasm Transplantation , Neoplasms/pathology , Phosphorylation , Pyruvate Dehydrogenase Acetyl-Transferring Kinase , Transplantation, HeterologousABSTRACT
The Warburg effect describes a pro-oncogenic metabolism switch such that cancer cells take up more glucose than normal tissue and favor incomplete oxidation of glucose even in the presence of oxygen. To better understand how tyrosine kinase signaling, which is commonly increased in tumors, regulates the Warburg effect, we performed phosphoproteomic studies. We found that oncogenic forms of fibroblast growth factor receptor type 1 inhibit the pyruvate kinase M2 (PKM2) isoform by direct phosphorylation of PKM2 tyrosine residue 105 (Y(105)). This inhibits the formation of active, tetrameric PKM2 by disrupting binding of the PKM2 cofactor fructose-1,6-bisphosphate. Furthermore, we found that phosphorylation of PKM2 Y(105) is common in human cancers. The presence of a PKM2 mutant in which phenylalanine is substituted for Y(105) (Y105F) in cancer cells leads to decreased cell proliferation under hypoxic conditions, increased oxidative phosphorylation with reduced lactate production, and reduced tumor growth in xenografts in nude mice. Our findings suggest that tyrosine phosphorylation regulates PKM2 to provide a metabolic advantage to tumor cells, thereby promoting tumor growth.
Subject(s)
Glycolysis/physiology , Neoplasms/metabolism , Pyruvate Kinase/metabolism , Tyrosine/metabolism , Adenosine Triphosphate/metabolism , Animals , Cell Line , Cell Line, Tumor , Cell Proliferation , Fructosediphosphates/metabolism , Glucose/metabolism , Humans , Immunoblotting , K562 Cells , Male , Mice , Mice, Nude , Mutation , Neoplasms/genetics , Neoplasms/pathology , Neoplasms, Experimental/genetics , Neoplasms, Experimental/metabolism , Neoplasms, Experimental/pathology , Oxygen Consumption , Phosphorylation , Proteomics/methods , Pyruvate Kinase/genetics , Receptor, Fibroblast Growth Factor, Type 1/genetics , Receptor, Fibroblast Growth Factor, Type 1/metabolism , Transplantation, Heterologous , Tumor BurdenABSTRACT
Dysregulation of the receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) plays a pathogenic role in a number of human hematopoietic malignancies and solid tumors. These include t(4;14) multiple myeloma associated with ectopic expression of FGFR3 and t(4;12)(p16;p13) acute myeloid leukemia associated with expression of a constitutively activated fusion tyrosine kinase, TEL-FGFR3. We recently reported that FGFR3 directly tyrosine phosphorylates RSK2 at Y529, which consequently regulates RSK2 activation. Here we identified Y707 as an additional tyrosine in RSK2 that is phosphorylated by FGFR3. Phosphorylation at Y707 contributes to RSK2 activation, through a putative disruption of the autoinhibitory alphaL-helix on the C terminus of RSK2, unlike Y529 phosphorylation, which facilitates ERK binding. Moreover, we found that FGFR3 interacts with RSK2 through residue W332 in the linker region of RSK2 and that this association is required for FGFR3-dependent phosphorylation of RSK2 at Y529 and Y707, as well as the subsequent RSK2 activation. Furthermore, in a murine bone marrow transplant assay, genetic deficiency in RSK2 resulted in a significantly delayed and attenuated myeloproliferative syndrome induced by TEL-FGFR3 as compared with wild-type cells, suggesting a critical role of RSK2 in FGFR3-induced hematopoietic transformation. Our current and previous findings represent a paradigm for tyrosine phosphorylation-dependent regulation of serine-threonine kinases.
