title: Accumulation of cyclophilin A isoforms in conditioned medium of irradiated breast cancer cells.
abstract: Secreted proteins play a key role in cell signaling and communication. We recently showed that ionizing radiations induced a delayed cell death of breast cancer cells, mediated by the death receptor pathways through the expression of soluble forms of "death ligands." Using the same cell model, the objective of our work was the identification of diffusible factors, secreted following cell irradiation, potentially involved in cell death signaling. Differential proteomic analysis of conditioned media using 2DE resulted in detection of numerous spots that were significantly modulated following cell irradiation. The corresponding proteins were identified using MALDI-TOF MS and LC-MS/MS approaches. Interestingly, five isoforms of cyclophilin A were observed as increased in conditioned medium of irradiated cells. These isoforms differed in isoelectric points and in accumulation levels. An increase of cyclophilin A secretion was confirmed by Western blotting of conditioned media of irradiated or radiosentive mammary cells. These isoforms displayed an interesting pattern of protein maturation and post-translational modifications, including an alternating removal of N-terminal methionine, associated with a combination of acetylations and methylations. The role of the protein is discussed in relation with its potential involvement in the mechanisms of intercells relationships and radiosensitivity.
authors.affiliation: CEA, DSV, iRCM, Plateforme de Protéomique, Fontenay-aux-Roses, France. francois.chevalier@cea.fr
authors.forename: François
authors.initials: F
authors.lastname: Chevalier
authors.forename: Jordane
authors.initials: J
authors.lastname: Depagne
authors.forename: Sonia
authors.initials: S
authors.lastname: Hem
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chevillard
authors.forename: Julie
authors.initials: J
authors.lastname: Bensimon
authors.forename: Pascale
authors.initials: P
authors.lastname: Bertrand
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lebeau
mesh_terms: D000107:Acetylation; D001943:Breast Neoplasms / Q000378:metabolism* / Q000532:radiotherapy; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000737:chemistry*; D021984:Cyclophilin A / Q000378:metabolism*; D005260:Female; D006801:Humans; D008745:Methylation; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D040901:Proteomics; D011839:Radiation, Ionizing; D015398:Signal Transduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D017077:Culture Media, Conditioned; D020033:Protein Isoforms; D021984:Cyclophilin A