Cubilin, a Binding Partner for Galectin-3 in the Murine Utero-Placental Complex

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. 1 is one of at least 10 members of a lectin family, which share a conserved carbohydrate recognition domain and which exert their varied biological effects through interaction with complementary ␤-galactoside ligands of glycoprotein or glycolipid "counterreceptors." Since galectins are divalent and are able to form multivalent aggregates, they can cross-link counterreceptors, effecting cell-cell, cell-matrix, or matrix-matrix interactions, thus possibly initiating signal transduction. Isolation of several membrane or matrix counterreceptors by affinity chromatography has revealed that galectins are linked to a variety of important processes including neoplastic transformation, cell adhesion, tumor invasiveness and metastasis, cellular proliferation, and localized immunomodulation (see Ref. 1). gal-3 and its mRNA are expressed in trophoblast cells of placenta as well as in the granular uNK cells of the metrial gland and decidualized endometrium of the murine implantation site (2-4). That finding, along with the additional observation that gal-3 is absent from nondecidualized endometrium between implantation sites and is not present in uteri of nonpregnant females (3), strongly suggests that this lectin has a pregnancy-related function at the maternalfetal interface. Although a role for gal-3 at the maternal-fetal interface is not yet known, it may contribute in some fashion to cell adhesion, proliferation, or immunomodulation, all of which occur in other contexts. Therefore, to gain more insight into a role for this lectin at the maternal-fetal interface, we isolated and characterized a counte...

Amnionless function is required for cubilin brush-border expression and intrinsic factor-cobalamin (vitamin B12) absorption in vivo

“…Additionally intriguing is the apparent expression of AMN in tissues where CUBN is not, suggesting that there are as yet unsuspected AMN functions. However, despite demonstration here and elsewhere of CUBN or AMN expression in those tissues, [34][35][36][37] no aspect of the I-GS phenotype in humans or dogs has yet been attributed to malfunction of cubilin or AMN in any tissue other than intestine and kidney.…”

“…Additionally intriguing is the apparent expression of AMN in tissues where CUBN is not, suggesting that there are as yet unsuspected AMN functions. However, despite demonstration here and elsewhere of CUBN or AMN expression in those tissues, [34][35][36][37] no aspect of the I-GS phenotype in humans or dogs has yet been attributed to malfunction of cubilin or AMN in any tissue other than intestine and kidney.In mice, tissue expression of AMN includes the extraembryonic visceral endoderm, and AMN knockout mutations cause early embryonic malformation and death. 9 Cubilin is expressed in the same early embryonic structure of mice, 37 and exposure of developing rat embryos to anticubilin antibodies causes embryonic malformations and lethality.…”

Deletion of galectin-3 in the host attenuates metastasis of murine melanoma by modulating tumor adhesion and NK cell activity

“…T cells and promotes tumor growth in a mouse model of colorectal cancer [24]. Although, the expression of Galectin-3 on uterine NK cells has been suggested to downregulate their function [25,26], little is known about the role of Galectin-3 on NK cells, in general. This is of potential importance because NK cells provide effective anti-melanoma activity, leading to reduced number of metastasis [27,28].…”

REVIEW ARTICLE: Governing the Invasive Trophoblast: Current Aspects on Intra‐ and Extracellular Regulation

“…34 Up-regulation of Gal-3 in both pre-eclamptic and Hemolytic anemia Elevated Liver enzymes and Low Platelet count extravillous trophoblast (EVT) may compensate for the reduced trophoblast invasion observed in both types of pathologic pregnancies. [35][36][37][38][39] Gal-4 binds to glycosphingolipids. 40,41 Furthermore, Gal-4 promotes adhesion of human colon adenocarcinoma cells.…”