Synthesis and secretion of the human vitamin B12-binding protein, transcobalamin II, by cultured skin fibroblasts and by bone marrow cells

Fràter‐Schröder, Marijke; Porck, H. J.; Erten, Jale; Müller, Martin; Steinmann, Beat; Kierat, L.; Arwert, Fré

doi:10.1016/0167-4889(85)90207-1

Cited by 33 publications

(13 citation statements)

References 22 publications

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“…This finding is in line with previous observations that many cell types have the capacity to secrete TC and that this correlates with the rate of cellular proliferation [3, 36, 37]. This is consistent with our observations in the present study where HT1080 cells secrete significant amounts of TC and have a reported doubling time of 20 to 24 h [26], whereas AG01518 cells did not secrete TC at levels that are detectable by western blotting and they have a reported doubling time of 3 to 4 days [27].…”

Section: Discussionsupporting

confidence: 93%

Cell Type-Specific Modulation of Cobalamin Uptake by Bovine Serum

Zhao

Ruberu

et al. 2016

PLoS ONE

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Tracking cellular 57Co-labelled cobalamin (57Co-Cbl) uptake is a well-established method for studying Cbl homeostasis. Previous studies established that bovine serum is not generally permissive for cellular Cbl uptake when used as a supplement in cell culture medium, whereas supplementation with human serum promotes cellular Cbl uptake. The underlying reasons for these differences are not fully defined. In the current study we address this question. We extend earlier observations by showing that fetal calf serum inhibits cellular 57Co-Cbl uptake by HT1080 cells (a fibrosarcoma-derived fibroblast cell line). Furthermore, we discovered that a simple heat-treatment protocol (95°C for 10 min) ameliorates this inhibitory activity for HT1080 cell 57Co-Cbl uptake. We provide evidence that the very high level of haptocorrin in bovine serum (as compared to human serum) is responsible for this inhibitory activity. We suggest that bovine haptocorrin competes with cell-derived transcobalamin for Cbl binding, and that cellular Cbl uptake may be minimised in the presence of large amounts of bovine haptocorrin that are present under routine in vitro cell culture conditions. In experiments conducted with AG01518 cells (a neonatal foreskin-derived fibroblast cell line), overall cellular 57Co-Cbl uptake was 86% lower than for HT1080 cells, cellular TC production was below levels detectable by western blotting, and heat treatment of fetal calf serum resulted in only a modest increase in cellular 57Co-Cbl uptake. We recommend a careful assessment of cell culture protocols should be conducted in order to determine the potential benefits that heat-treated bovine serum may provide for in vitro studies of mammalian cell lines.

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Section: Discussionsupporting

confidence: 93%

Cell Type-Specific Modulation of Cobalamin Uptake by Bovine Serum

Zhao

Ruberu

et al. 2016

PLoS ONE

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“…At the start, after 20 additional doublings and again after 26 more, a subculture was set up for sampling on days 0,1, 3, and 6 as in the main study. Measured in each subculture were cell number, binding of TC 11-Cbl, and lysed cell MS. Human fibroblasts release apo TC I1 (Frater-Schroeder et al, 1985) and the TC I1 was measured at the three ages of culture by gel filtration (apo form) and by radioimmunoassay (total) (Begley, 1983;Frater-Schroeder et al, 1985).…”

Section: Materials and Methods Cells And Culturingmentioning

confidence: 99%

Cyclic activity of the receptors of cobalamin bound to transcobalamin II

Hall

Colligan

Begley

1987

Journal Cellular Physiology

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The activity of receptors specific for human transcobalamin II-Cobalamin (TC II-Cbl) were measured in virus-transformed lymphoblasts, hepatocytes (hepatoma) and diploid fibro lasts. In all three types of human cells the receptor activity increased as cells went from a resting phase to the most actively dividing phase. Receptor activity declined as cell division slowed. The changes in activity of lymphoblasts and hepatocytes were produced by changes in receptor number and not by changes in affinity between receptors and TC II-Cbl. The basis of the change in fibroblasts was not clear. The Cbl-dependent methionine synthetase activity of fibroblasts, in contrast, tended to be greatest when the cultures were confluent and replication had slowed. As the fibroblasts became senescent the receptor activity for TC II-Cbl declined and the fluctuations with the phase of the cell were blunted. However, the release of apo TC II from the cells was maintained. These observations must be taken into consideration when the respective cells are used as models. Even more important are the implications of the observations of the changes in receptor activity for TC II-Cbl for the regulation of the entry of Cbl into cells.

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“…This notion was soon dismissed when studies showed that total hepatectomy did not affect TC level in blood (35). TC synthesis in vitro by primary and established cell lines in culture suggested that most cell types could contribute to TC in circulation (36). We were the first to conduct a detailed study of TC synthesis in human umbilical vein endothelial cells (HUVEC) in culture and show that copious amounts of TC is secreted by these cells in culture.…”

Section: Introductionmentioning

confidence: 99%

Cellular uptake of cobalamin: Transcobalamin and the TCblR/CD320 receptor

Quadros

Sequeira

2013

Biochimie

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Cellular uptake of cobalamin is facilitated by a receptor mediated endocytosis process involving transcobalamin, a plasma protein that binds cobalamin and a cell surface receptor that specifically binds transcobalamin saturated with cobalamin. Intracellular Cbl concentration is maintained by modulating the expression of the receptor, which is cell cycle associated with highest expression in actively proliferating cells and an efflux system that shunts the excess cobalamin out of the cells for mobilization to other tissues where it is most needed. This review describes the process, proteins involved and genes encoding these proteins.

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Synthesis and secretion of the human vitamin B12-binding protein, transcobalamin II, by cultured skin fibroblasts and by bone marrow cells

Cited by 33 publications

References 22 publications

Cell Type-Specific Modulation of Cobalamin Uptake by Bovine Serum

Cell Type-Specific Modulation of Cobalamin Uptake by Bovine Serum

Cyclic activity of the receptors of cobalamin bound to transcobalamin II

Cellular uptake of cobalamin: Transcobalamin and the TCblR/CD320 receptor

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