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Cubilin, a binding partner for galectin-3 in the murine utero-placental complex
Sunday Crider-Pirkle1, Peggy Billingsley, Charles Faust
1Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
Insights
Galectin-3 binds to cubilin at the maternal-fetal interface. Yolk sac cubilin is endocytosed by uterine NK cells via galectin-3, suggesting a role in NK cell function.
Area of Science:
- Reproductive biology
- Immunology
- Molecular biology
Background:
- Galectin-3 is a lectin crucial for animal development and regulation.
- It is specifically located at the mouse embryo implantation site.
- Its precise role at the maternal-fetal interface requires further investigation.
Purpose of the Study:
- To identify and characterize binding partners of galectin-3 at the maternal-fetal interface.
- To elucidate the functional relationship between galectin-3 and its binding partner in uterine natural killer (uNK) cells.
Main Methods:
- Affinity chromatography using immobilized recombinant galectin-3 to isolate binding proteins from uteroplacental tissue homogenates.
- Protein identification through SDS-PAGE and peptide sequencing.
- Immunohistochemistry and in situ hybridization to determine tissue distribution and cellular localization of proteins and mRNA.
Main Results:
- A 400,000 M(r) protein, p400, was identified as the murine ortholog of cubilin.
- Cubilin is expressed in yolk sac epithelium throughout pregnancy, while galectin-3 is present during the last week.
- Cubilin is localized in perforin-containing granules of uNK cells, and its mRNA is found in yolk sac epithelium but not uNK cells.
Conclusions:
- Yolk sac-derived cubilin is endocytosed by uNK cells mediated by galectin-3.
- Cubilin is an endogenous binding partner of galectin-3 at the maternal-fetal interface.
- This interaction suggests a significant role for cubilin in uNK cell function during pregnancy.
Abstract:
Galectin-3 is a lectin important in animal development and regulatory processes and is found selectively localized at the implantation site of the mouse embryo. To better understand the role of galectin-3 at the maternal-fetal interface, a binding partner was isolated and characterized. Homogenates of uteroplacental tissue were incubated with immobilized recombinant galectin-3, and specifically bound proteins were eluted using lactose. The principal protein, p400, had an M(r) of 400,000 in SDS-PAGE. Physical properties of p400 and amino acid sequences of seven tryptic peptides were similar to cubilin from rats, humans, and dogs, identifying p400 as the murine ortholog of cubilin. This was further supported by the tissue distribution observed only in yolk sac, kidney, and ileum with monospecific antiserum for p400. Cubilin occurred in yolk sac epithelium throughout pregnancy, but galectin-3 was there only during the last week. Unexpectedly, cubilin was found only in perforin-containing granules of uterine natural killer (uNK) cells, although galectin-3 occurred throughout the cell cytoplasm. In situ hybridization revealed cubilin mRNA in yolk sac epithelium but not uNK cells, implying that yolk sac-derived cubilin is endocytosed by uNK cells via galectin-3. This is consistent with cubilin being an endogenous partner of galectin-3 at the maternal-fetal interface and suggests an important role for cubilin in uNK cell function.