Expression and activation of the membrane-cytoskeleton protein ezrin during the normal endometrial cycle

Capsule:
Ezrin/phospho-ezrin immunoreactivity are present on apical surfaces of the luminal epithelium, around secretory vacuoles and in luminal secretions during the secretory phase. These findings have functional implications for implantation biology.

Authors:
Orkun Tan, M.D., Turkan Ornek, M.D., Ahmed Fadiel, Ph.D., Kelley S. Carrick, M.D., Aydin Arici, M.D., Kevin Doody, M.D., Bruce R. Carr, M.D., Frederick Naftolin, M.D., Ph.D.
Volume 97, Issue 1 , Pages 192-199.e2, January 2012

Objective:
To examine total ezrin expression (ezrin and phospho-ezrin) through the normal endometrial cycle and to correlate ezrin activation and localization with cytologic changes.

Design:
Experimental laboratory study.

Setting:
University medical centers.

Patient(s):
Reproductive-age women.

Intervention(s):
A total of 36 samples of normal early, mid-, and late proliferative- and secretory-phase endometrium were studied for immunoreactive total ezrin (ir-T-ezrin) and phospho-ezrin (ir-p-ezrin) expression by histology, immunohistochemistry, and Western blotting.

Main Outcome Measure(s):
Total ezrin and phospho-ezrin expressions through the normal endometrial cycle.

Result(s):
Throughout the cycle ir-T-ezrin is present in the epithelium. The intensity and localization of both ir-ezrin and ir-p-ezrin vary greatly throughout the cycle. The main findings include the following: lateral localization of ir-ezrin/ir-p-ezrin in association with membrane specializations; dense staining around secretory vacuoles (secretory phase); dense staining of the apical surfaces, including microvilli and pinopodes of epithelial cells, especially during the mid- to late secretory phases; and the presence of ezrin in the glandular secretions. Immunoreactive total ezrin and ir-p-ezrin were not expressed by stromal fibroblasts.

Conclusion(s):
Ezrin is a prominent protein in the cycling endometrium. The most striking findings were the gravitation of ir-ezrin/ir-p-ezrin to the periphery of secretory vacuoles, localization on apical surfaces of the luminal epithelium, dense ezrin staining in secretory-phase epithelial cell plumes, and the presence of ir-ezrin/ir-p-ezrin in secretory-phase luminal secretions. These findings may have functional implications, especially for implantation biology.

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