iTRAQ‐based proteomic analysis of 17β‐Estradiol‐induced anti‐proliferation and apoptosis in mouse thymic epithelial cells by disturbing ribosomal biogenesis

Many evidences have suggested that estrogen was associated with thymic atrophy and suppressed thymocyte functions. Thymic epithelial cells (TECs), as a crucial constituent of thymic stroma support a unique microenvironment for thymocyte maturation, but the effects of estrogen on TECs were poorly understood. In our study, we found that 17β-Estradiol (17β-E2), one of the primary estrogens, could significantly inhibit cell proliferation, and cause cell cycle arrest in G2/M phase and apoptosis in mouse thymic epithelial cell line 1 (MTEC1 cells) with time- and dose- dependent. Above all, we provided the systemic and sufficient proteomic profiling of 17β-E2 (50 nmol/L) acting on MTEC1 cells through isobaric tags for relative and absolute quantitation and LC-MS/MS (Liquid Chromatography Mass Spectrometry/Mass Spectrometry). A total of 71 differentially expressed proteins were identified, of which 61 were up-regulated and 10 were down-regulated. Particularly, the differential expression of abundant ribosomal proteins (RPs) was drawing our attention, including RPL3, RPL4, RPS11, RPL17, RPL5, RPS9, RPL13, RPL23A, RPLP2, RPS15A, and RPL29. Most of these proteins have been widely reported exerting extra-ribosomal function associated with the proliferation and apoptosis of distinct cell types, but not yet observed in TECs. Moreover, bioinformatics analysis revealed that disturbance of ribosomal biogenesis was closely related to the anti-proliferation and apoptosis in MTEC1 cells upon 17β-E2. These data highlighted the possible mechanisms of 17β-E2 on MTEC1 cells through showing adequate differential protein expression profiles. We inferred that 17β-E2 induced anti-proliferation and apoptosis in MTEC1 cells in response to alterations of ribosome biogenesis and RPs expression, which will contribute to gaining insight into the internal mechanism of thymic degeneration and exploiting to treat autoimmune diseases in the future.