Semen modulated secretory activity of oviductal epithelial cells is linked to cellular proteostasis network remodeling: Proteomic insights into the early phase of interaction in the oviduct in vivo

Abstract

The oviductal epithelium is crucial for the integrity of the female organ. Previously we got evidence that the surface proteome of oviductal epithelial cells (Oecs) is promptly altered in response to insemination and thus suggested that this early phase plays a notable regulatory role in maintaining cellular function. This study further aimed to assess the effect of semen on the cellular and molecular mechanisms in rabbit Oecs. A quantitative gel-based proteomic approach was applied to analyze changes at three time points (0h, 1h, 2h) after intrauterine insemination (IUI) compared to time matched controls. Within two hours the abundance of 22 protein species was evidently altered in the intracellular fraction. Functional analysis revealed that the proteins were primarily involved in proteostasis as well as metabolic processes. The analysis of phosphoproteins specified a role of mitogen-activated protein kinase (MAPK) signaling molecules. Concurrently, semen increased oviduct-specific glycoprotein (OVGP1) secretion. A correlation between OVGP1 abundance and microtubule-associated proteins 1A/1B-light chain 3 lipidation was observed. The localization and changes in abundance of selected proteins were corroborated by antibody-based methods. These results clearly show that the early phase of interaction acts as a trigger for cellular adaptation to meet an altered demand in the female organ.

Significance: The oviductal epithelium and its secreted proteins exert a pivotal role in reproductive processes, including the final maturation of male gametes. Thereby, the regulation and subsequently the functionality of the oviductal epithelial cell layer are important factors for the establishment of the appropriate milieu in the female reproductive tract. Notably, male gametes themselves have been shown to be an extrinsic modulatory factor of the oviductal epithelium. Accordingly a comprehensive knowledge about the underlying cellular and molecular mechanisms in the epithelial cells is of interest, also with regard to in vitro purposes. So far, the role of the early phase of interaction in the female organ has not been considered in detail. To get a further insight into the underlying cellular and molecular mechanisms, herein we analyzed the effect of semen on oviductal epithelial cells (Oecs) on the intracellular proteome level within the first two hours after insemination. The present study revealed a directed response of Oecs in vivo and disclosed intracellular pathways that are affected by the interplay between semen and the female reproductive tract. The prompt adaptation of the secretory activity and remodeling of the oviductal epithelium was accompanied by the concerted alterations of protein species that are primarily involved in the maintenance of cellular homeostasis. Besides emphasizing the importance of the early interaction phase for subsequent reproductive processes, the gained knowledge might further be implemented for in vitro applications as well.

Keywords: MAPK molecules; Oviduct-specific glycoprotein; Oviductal epithelial cells; Proteostasis; Secretion; Semen.