Human endometrial proteins with cyclic changes in the expression during the normal menstrual cycle: characterization by protein sequence analysis

Endometrial proteins showing cyclic expression during the normalmenstrual cycle were localized on twodimensional (2-D) electrophoresisgels separating proteins with isoelectric points (pi) rangingfrom 3.5 to 7 and relative molecular weights ranging from 10to 300 kDa. Menstrual cycle-related proteins were excised fromseveral 2-D gels, concentrated by one-dimensional (1-D) sodiumdodecyl sulphate (SDS)-polyacrylamide gel electrophoresis, andcleaved in situ by trypsin. The tryptic fragments were extractedand separated by reverse phase high performance liquid chromatography(RP-HPLC). Finally, the partial amino-terminal amino acid sequenceof selected tryptic fragments were determined for each protein.We aimed at characterizing the 21 menstrual cycle-related proteinsthat were visible on silver-stained 2-D electrophoresis gels.Of the proteins being maximally synthesized in the proliferativephase endometrium, we identified proteins associated mainlywith the cytoskeleton: vimentins, keratin, tropomyosin and tubulin,but also proteins such as proliferating cell nuclear antigenand -galactoside binding lectin. The partial amino acid sequencesfor another two proteins did not match any protein sequencein the Protein Identification Resource (PIR) and Swissprot databases.In the group of proteins having maximal synthesis in the secretoryphase endometrium, we identified creatine kinase chain B andan isocitrate dehydrogenase-homologous protein, both of whichare involved in energy metabolism. However, we also identifiedthe annexin IV precursor, the 14-3-3 protein homologue alsocalled stratifin or the epithelial cell marker protein 1 andthe 21K tumour protein. Finally, four of the proteins were presentin too low amounts to allow characterization. Interestingly,most of the identified proteins have not previously been describedas having a menstrual cycle-related synthesis in the human endometrium.It may be considered that the concentration of some of the cycle-relatedproteins may be used in clinical situations to reflect specificendometrial phases.