Identification of cellular isoform of oviduct-specific glycoprotein: role in oviduct tissue remodeling?

Abstract

The oviduct is known to secrete mucins (MUC1 and MUC9) under the influence of ovarian steroids. The secreted form of MUC1 binds gametes in the oviduct, whereas the cellular form seen in breast cancers has been implicated in cell adhesion and morphogenesis. The secreted MUC9 or oviduct-specific glycoprotein (OGP), in addition to being a mucin, belongs to family 18 glycosylhydrolases and is known to bind gametes and embryos in the oviduct. Studies in our laboratory have identified non-muscle myosin IIA (involved in cell shape, polarity, and morphogenesis) as the protein partner to OGP in gametes. In view of the crucial role of the cortical cytoskeleton in the selective internalization of tight junctions (TJs) /adherent junctions (AJs) or apical junctional complex (AJC) in simple epithelial cells during tissue remodeling, the present study has been undertaken to evaluate the existence of a cellular form of OGP in oviductal tissue, which itself undergoes cyclic tissue remodeling. In silico analysis of the deduced amino-acid sequence of OGP has revealed the presence of several conserved motifs; these imply that OGP is a component of multi-protein complexes such as TJs. Corroborative immunoelectron-microscopic analysis in peri-ovulatory oviduct epithelia in the bonnet monkey has revealed the presence of OGP at the TJ. Co-localization studies of OGP and cadherin demonstrate that, whereas OGP is localized at the tonofilaments of the TJs, cadherin is localized at the intercellular space of the AJ. The possible role of OGP in oviductal tissue remodeling is discussed in light of the present findings and those reported in the literature.

The C-terminal region of OVGP1 remodels the zona pellucida and modifies fertility parameters

“…These data suggest that region A contains a ZP-binding domain, perhaps based on its chitinase-like domain that may retain sugar-binding properties to associate with gametes21. In addition, such region could be involved in molecular interactions with other oviductal proteins1322, generating the microenvironment necessary to facilitate fertilization and early embryo development.…”

“…The N-terminal region of mature OVGP1 shows a high degree of identity (77–84%) and similarity (86–90%) to that of other species. It contain a signal peptide, several post-translational modifications sites involved in secretion12 as well as a clathrin box associated with endocytosis13. Hamster OVGP1 has been reported to be endocytosed by developing blastocysts and has been hypothesized to undergo degradation through the ubiquitin-proteasome pathway14.…”

“…Hamster OVGP1 has six repeats of 15 aminoacids; human, baboon and rhesus monkey contain only 4, whereas and cattle, sheep and pig have incomplete or no tandem-repeat sequences. In silico analysis of deduced amino acid sequences identified a Class III PDZ-binding domain in human, baboon, porcine and bonnet OVGP1 glycoproteins, suggesting that OVGP1 is a component of a multi-protein complex13. Recently, comparison of mammalian OVGP1 amino acid sequences defined five distinct regions (A-E) that are differentially conserved among mammalian groups.…”

In Vitro Mimicking of Estrous Cycle Stages in Porcine Oviduct Epithelium Cells: Estradiol and Progesterone Regulate Differentiation, Gene Expression, and Cellular Function1

“…OVGP1 (MUC9) and MUC16 are the major mucins secreted by oviduct epithelium cells [33], whereas HSP90B1 regulates protein secretion and protein folding. The elevated expression of these genes might reflect activated secretion in simulated estrus.…”

Oviductal Glycoprotein (OVGP1, MUC9)

“…In addition to the secreted form of OVGP1, an intracellular isoform has recently been discovered in oviductal epithelium. 18 This cellular form is localized at tight junctions, interacts with the cytoskeleton, and may be involved in the regulation of polarity and cell shapes. Whether this form plays a role in carcinogenesis is presently unknown.…”