418. Proteomic analysis of proliferative and secretory phase endometrium

Abstract

The human endometrium undergoes marked proliferation and differentiation between the proliferative and secretory phases of the menstrual cycle; however the underlying biology is poorly understood. This aims of this study were to identify proteins differentially expressed in the human endometrium between the proliferative and secretory phases of normal menstrual cycles. 2D SDS–PAGE analysis with differential fluorescent Cydye labelling was conducted across the pH range 4–7 on endometrial tissue extracts from mid-proliferative and mid-secretory phases (n = 4/group). Profiles were quantitatively assessed using SameSpots image analysis software. Differentially expressed proteins were identified using MALDI-TOF MS and were used to generate biological network by Ingenuity Pathways Analysis. Protein expression changes for three of the proteins were validated by immunohistochemistry. Of 1017 protein spots detected in the proteome of endometrial tissue, 196 were significantly differentially expressed (P < 0.05) between the proliferative and secretory phases. 157 proteins increased in expression, whilst 39 were decreased compared with the proliferative endometrium. Mass spectrometry identified 76 proteins representing 42 unique gene products. The identity and expression change for 3 proteins (Rho-GD1α, CLIC1, PGRMC-1) was confirmed using immunohistochemical staining of tissue section. Using pathway profiling software, the identified proteins were broadly grouped into seven major functional categories (cell architecture, transcription regulation, transport, membranes, enzymes and regulatory proteins), with the majority showing clear dependence on the Jnk signalling pathway. Comparison of the proteomic data with published mRNA expression array data clearly demonstrated discrepancies between the protein changes and gene expression, suggesting that a large majority of proteomic changes occurring at the transition of proliferative to secretory phase were due to post-translational modifications. These studies enable the understanding of the complex dynamics of protein expression and the possible involvement of post-translational modifications in cyclic changes of human endometrium.