Calbindin-D9k (CaBP9k) localization and levels of expression in trophoblast cells from human term placenta

Abstract

During pregnancy, the calcium (Ca(2+)) transport machinery of the placenta is solely responsible for the nutrient supply to the developing fetus, where active Ca(2+) transport occurs from the mother to the fetus. As part of a larger study to determine the role of Ca(2+) in placental transport in vivo, we questioned whether calbindin-D9k (CaBP9k), which is mainly expressed in duodenum, uterus, and placenta of several mammals, is present in cytotrophoblast cells and syncytiotrophoblasts of human term placenta. We were interested in this protein because of its potential importance in serving as an indicator of Ca(2+) availability and utilization in the placenta. Here, we demonstrated that CaBP9k transcript is present in both cell types, with a lower expression in cytotrophoblast cells as compared to syncytiotrophoblasts. Moreover, we showed by immunochemistry that CaBP9k protein was present in cytotrophoblast and syncytiotrophoblast placental tissue sections as well as in cultured cells. The occurrence of CaBP9k protein in trophoblast cells was further confirmed by Western blot analysis. Thus, these results indicate for the first time that CaBP9k is unequivocally expressed by trophoblast cells from human term placenta.

Effects of calcitriol on calbindins gene expression and lipid peroxidation in human placenta

“…In the present study, cultured syncytiotrophoblast cells expressed the mRNAs of calbindin-D 9k and calbindin-D 28k , which confirm the results obtained by Belkacemi et al [12,13], who have reported the presence of the mRNA and protein of both calbindins in cultured human placenta cells. The effects of calcitriol on calbindins gene expression have not been evaluated in human placenta.…”

“…Regarding calbindin-D 9k , we did not find information about its relation with lipid peroxidation. Interestingly, calbindin-D 9k and calbindin-D 28k have been found in cultured trophoblast cells [12,13]. In addition, it has been reported that calcitriol stimulates calbindin-D 28k mRNA and protein in human choriocarcinoma cell line JEG-3 [14].…”

Placental nutrient supply and fetal growth

“…Over the last third of gestation, gene and protein expression for calbindin-D 9K increases markedly in both mouse and rat placenta Glazier et al, 1992;Hamilton et al, 2000;Mathieu et al, 1989) and correlates with the increase in unidirectional maternofetal 45 Ca clearance measured over the same period (Glazier et al, 1992), suggesting that transcytosolic transfer on this protein and the dynamic equilibrium between bound and free Ca 2+ in the syncytiotrophoblast might be the rate limiting step of transfer in these species. The situation may well be quite different in the human placenta where it has proved difficult to show the expression of calbindin-D 9K (Belkacemi et al, 2004), or to determine if another protein is involved instead. Interestingly, the activity, but not expression, of PMCA in the BM of human placenta increases linearly over the last third of gestation (Strid and Powell, 2000).…”

The Translationally Controlled Tumor Protein Is a Novel Calcium Binding Protein of the Human Placenta and Regulates Calcium Handling in Trophoblast Cells1

“…Among these, the calbindin proteins, a family of cytoplasmic CBPs containing an EF-hand motif, have been extensively investigated. Thus, S100 calcium binding protein G (S100G), calbindin 1 (CALB1), and calbindin-57K (CaBP57K) have been detected in the human and murine trophoblasts [18,[21][22][23]. Furthermore, an increase in calbindins expression at term, as well as during trophoblastic differentiation, has been reported [18,21,23].…”