Abstract
To assess responses to low-dose ionizing radiation (LD-IR) exposures potentially encountered during medical diagnostic procedures, nuclear accidents or terrorist acts, a quantitative proteomic approach was used to identify changes in protein abundance in a reconstituted human skin tissue model treated with 0.1 Gy of ionizing radiation. To improve the dynamic range of the assay, subcellular fractionation was employed to remove highly abundant structural proteins and to provide insight into radiation-induced alterations in protein localization. Relative peptide quantification across cellular fractions, control and irradiated samples was performing using 8-plex iTRAQ labeling followed by online two-dimensional nano-scale liquid chromatography and high resolution MS/MS analysis. A total of 107 proteins were detected with statistically significant radiation-induced change in abundance (>1.5 fold) and/or subcellular localization compared to controls. The top biological pathways identified using bioinformatics include organ development, anatomical structure formation and the regulation of actin cytoskeleton. From the proteomic data, a change in proteolytic processing and subcellular localization of the skin barrier protein, filaggrin, was identified, and the results were confirmed by western blotting. This data indicate post-transcriptional regulation of protein abundance, localization and proteolytic processing playing an important role in regulating radiation response in human tissues.
Highlights
Humans are exposed to low levels of ionizing radiation on a daily basis due to naturally occurring background radiation, medical diagnostic procedures and occupational exposures [1,2]
Our laboratory recently completed a phosphoproteomic study on a full-thickness human skin tissue model exposed to both high (2 Gy) and low (0.03 and 0.1 Gy) doses of radiation and identified multiple proteins that were affected at the post-translational level [16]
Proteomic analysis of skin tissue is complicated by the highly abundant structural proteins that comprise the extracellular matrix in the dermis and cornified layer of the epidermis [16]
Summary
Humans are exposed to low levels of ionizing radiation on a daily basis due to naturally occurring background radiation, medical diagnostic procedures and occupational exposures [1,2]. With a high background of naturally occurring cancers, epidemiological studies of exposed individuals provide inconclusive data on the health effects of LD-IR [5], which are currently extrapolated using high dose data and a predicted linear response [6]. This model remains contentious in the radiation research field [5,7]. Our laboratory recently completed a phosphoproteomic study on a full-thickness human skin tissue model exposed to both high (2 Gy) and low (0.03 and 0.1 Gy) doses of radiation and identified multiple proteins that were affected at the post-translational level [16]. Post-transcriptional regulation, including altered proteolytic processing and changes in subcellular localization, contributed to alterations in observed protein abundance
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