ABSTRACT
DNA repair pathways are aberrant in cancer, enabling tumor cells to survive standard therapies-chemotherapy and radiotherapy. Our group previously reported that, upon irradiation, the membrane-bound tyrosine kinase receptor TIE2 translocates into the nucleus and phosphorylates histone H4 at Tyr51, recruiting ABL1 to the DNA repair complexes that participate in the nonhomologous end-joining pathway. However, no specific molecular mechanisms of TIE2 endocytosis have been reported. Here, we show that irradiation or ligand-induced TIE2 trafficking is dependent on caveolin-1, the main component of caveolae. Subcellular fractionation and confocal microscopy demonstrated TIE2/caveolin-1 complexes in the nucleus, and using inhibitor or small interfering RNAs (siRNAs) against caveolin-1 or Tie2 inhibited their trafficking. TIE2 was found in caveolae and directly phosphorylated caveolin-1 at Tyr14 in vitro and in vivo This modification regulated the generation of TIE2/caveolin-1 complexes and was essential for TIE2/caveolin-1 nuclear translocation. Our data further demonstrate that the combination of TIE2 and caveolin-1 inhibitors resulted in significant radiosensitization of malignant glioma cells, which will guide the development of combinatorial treatment with radiotherapy for patients with glioblastoma.
Subject(s)
Caveolae/metabolism , Caveolin 1/metabolism , Cell Nucleus/metabolism , Glioma/metabolism , Receptor, TIE-2/metabolism , Animals , Cell Line, Tumor , Gene Expression Regulation, Neoplastic/radiation effects , HEK293 Cells , HeLa Cells , Human Umbilical Vein Endothelial Cells , Humans , Phosphorylation/radiation effects , Protein Transport/radiation effects , Up-Regulation/radiation effectsABSTRACT
DNA repair pathways enable cancer cells to survive DNA damage induced after genotoxic therapies. Tyrosine kinase receptors (TKRs) have been reported as regulators of the DNA repair machinery. TIE2 is a TKR overexpressed in human gliomas at levels that correlate with the degree of increasing malignancy. Following ionizing radiation, TIE2 translocates to the nucleus, conferring cells with an enhanced nonhomologous end-joining mechanism of DNA repair that results in a radioresistant phenotype. Nuclear TIE2 binds to key components of DNA repair and phosphorylates H4 at tyrosine 51, which, in turn, is recognized by the proto-oncogene ABL1, indicating a role for nuclear TIE2 as a sensor for genotoxic stress by action as a histone modifier. H4Y51 constitutes the first tyrosine phosphorylation of core histones recognized by ABL1, defining this histone modification as a direct signal to couple genotoxic stress with the DNA repair machinery.
Subject(s)
DNA Damage , Histones/metabolism , Proto-Oncogene Proteins c-abl/metabolism , Receptor, TIE-2/metabolism , Tyrosine/metabolism , Angiotensin I/metabolism , Cell Line, Tumor , DNA End-Joining Repair , Humans , Protein Binding , Protein Transport , Proto-Oncogene Mas , Radiation Tolerance/genetics , Radiation, Ionizing , Receptor, TIE-2/geneticsABSTRACT
The Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) was applied to analyze the genetic variation of the Hilsa shad, Tenualosa ilisha Ham., from the two major inland rivers (Padma and Meghna) in Bangladesh. Twenty-eight random 10-mer primers were primarily scored in 8 individuals from each of the two locations. Fifteen primers, which gave polymorphism, were selected and used in the final analysis of 34 individuals from the two sites. Using these primers, 480 scorable DNA fragments were found, of which 98 (20.41%) were polymorphic. By comparing the RAPD banding patterns, variations were found between and within the populations. A dendrogram was constructed with the polymorphic fragments to analyze the genetic distances between the Hilsa shad populations. The results show two major clusters of Padma and Meghna, assuming different spawning populations with different stocks or races of Hilsa shad in the major Bangladesh rivers.
