164. INTEGRIN CLEAVAGE IS MEDIATED BY PROPROTEIN CONVERTASE 6 IN HUMAN ENDOMETRIAL EPITHELIAL CELLS FOR ENDOMETRIAL RECEPTIVITY AND IMPLANTATION

Abstract

Integrins are transmembrane glycoproteins composed of non-covalently associated α and β chains. Integrins participates in cell–cell interaction and binding to components of the extracellular matrix. Integrin expression changes during the establishment of receptivity for implantation. Integrins α₁β₁, α₄β1 and α_vβ₃ are expressed in the endometrium during the window of implantation [1, 2] and deficiency in integrin α_vβ₃ is associated with idiopathic infertility and delayed endometrial maturation [1, 3, 4]. Proprotein convertases (PCs) cleave proproteins at the basic amino acids consensus motif (K/R)-(X)n-(K/R)↓ (where n = 0, 2, 4 or 6 and X is any aa) for activation. Integrins require post-translational cleavage for activation and are known to be cleaved by PCs. PC6 plays a critical role in the establishment of endometrial receptivity. We hypothesized that PC6 cleaves integrins for its activation in the endometrial epithelium for implantation. The aim of this study was to investigate the functional importance of PC6 in integrin cleavage, using a stable PC6-knockdown in HEC1A cells (HEC1A-HP) by siRNA technology. Cells transfected with a scrambled siRNA sequence (HEC1A-control) were used as the control. To determine the amount of functional integrins on the cell surface, HEC1A-PC6 and HEC1A-control were subjected to an integrin monoclonal antibody array. The amount of functional integrins α₁, α₃, α₅, α_v, α_vβ₃, β₁, β₃, β₄ and α₅β₁ on the cell surface was much less in HEC1A-HP than HEC1A-control cells. Western blot analysis confirmed that cleavage of pro-integrin α₅ into disulfide-linked heavy chain (110kDa) and light chain (35kDa) was greater in HEC1A-control compared to HEC1A-HP cells, suggesting that knockdown of PC6 affects integrin cleavage. Our studies imply that integrin cleavage is mediated by PC6 in endometrial epithelial cells for the establishment of receptivity for embryo implantation.

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