ABSTRACT
PFKP (phosphofructokinase, platelet), the major isoform of PFK1 expressed in T cell acute lymphoblastic leukemia (T-ALL), is predominantly expressed in the cytoplasm to carry out its glycolytic function. Our study showed that PFKP is a nucleocytoplasmic shuttling protein with functional nuclear export and nuclear localization sequences (NLSs). Cyclin D3/CDK6 facilitated PFKP nuclear translocation by dimerization and by exposing the NLS of PFKP to induce the interaction between PFKP and importin 9. Nuclear PFKP stimulated the expression of C-X-C chemokine receptor type 4 (CXCR4), a chemokine receptor regulating leukemia homing/infiltration, to promote T-ALL cell invasion, which depended on the activity of c-Myc. In vivo experiments showed that nuclear PFKP promoted leukemia homing/infiltration into the bone marrow, spleen, and liver, which could be blocked with CXCR4 antagonists. Immunohistochemical staining of tissues from a clinically well-annotated cohort of T cell lymphoma/leukemia patients showed nuclear PFKP localization in invasive cancers, but not in nonmalignant T lymph node or reactive hyperplasia. The presence of nuclear PFKP in these specimens correlated with poor survival in patients with T cell malignancy, suggesting the potential utility of nuclear PFKP as a diagnostic marker.
Subject(s)
Phosphofructokinase-1, Type C/metabolism , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/metabolism , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/pathology , Receptors, CXCR4/metabolism , Active Transport, Cell Nucleus , Animals , Biomarkers, Tumor/metabolism , Cyclin-Dependent Kinase 6/metabolism , Female , Humans , Karyopherins/metabolism , Lymphocytes, Tumor-Infiltrating/metabolism , Lymphocytes, Tumor-Infiltrating/pathology , Male , Mice , Mice, Inbred NOD , Mice, SCID , Middle Aged , Models, Molecular , Neoplasm Invasiveness/pathology , Neoplasm Invasiveness/physiopathology , Phosphofructokinase-1, Type C/chemistry , Phosphofructokinase-1, Type C/genetics , Prognosis , Protein Interaction Domains and Motifs , Proto-Oncogene Proteins c-myc/metabolism , Tumor Cells, CulturedABSTRACT
Two phosphofructokinase (PFK) chimeras were constructed by exchanging the N- and C-terminal halves of the mammalian M- and C-type isozymes, to investigate the contribution of each terminus to the catalytic site and the fructose-2,6-P(2)/fructose-1,6-P(2) allosteric site. The homogeneously-purified chimeric enzymes organized into tetramers, and exhibited kinetic properties for fructose-6-P and MgATP similar to those of the native enzyme that furnished the N-terminal domain in each case, whereas their fructose-2,6-P(2) activatory characteristics coincided with those of the isozyme that provided the C-terminal half. This reflected the role of each domain in the formation of the corresponding binding site. Grafting the N-terminus of PFK-M onto the C-terminus of the fructose-1,6-P(2) insensitive PFK-C restored transduction of this signal to the catalytic site, which significance is also discussed.
