Influence on immunoreactive folate-binding proteins of extracellular folate concentration in cultured human cells.

M. A. Kane, P. C. Elwood, R. M. Portillo, Asok Antony, V. Najfeld, A. Finley, S. Waxman, J. F. Kolhouse

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Abstract

The influence of extracellular folate concentration on cellular levels of the folate transport protein and its soluble product was studied directly in cultured human nasopharyngeal carcinoma (KB) cells. As determined by radioimmunoassay, levels of the folate transport protein and the soluble folate-binding protein were 58 +/- 17 (mean +/- SD) and 5 +/- 2 pmol/mg cell protein, respectively, in KB cells maintained in standard medium (containing 2,300 nM folic acid). These levels significantly increased to 182 +/- 34 and 26 +/- 6 pmol/mg cell protein, respectively, in KB cells serially passaged in low folate medium (containing 2-10 nM 5-methyltetrahydrofolate). Increases in folate-binding protein levels occurred more rapidly in KB cells serially passaged in very low folate medium containing less than 2 nM folate and were prevented by the addition of 100 nM 5-methyltetrahydrofolate or 0.1-1 microM 5-formyltetrahydrofolate to this medium. When KB cells which had been passaged in low folate medium were passaged back into either standard medium or low folate medium supplemented with reduced folates, the levels of both folate-binding proteins fell linearly towards the levels in KB cells continuously maintained in standard medium. The folate transport protein was identified in and underwent similar changes in human and mouse mammary tumor cells. These studies indicate that the folate transport system is probably regulated by the extracellular folate concentration through changes in intracellular metabolite levels.

Original languageEnglish (US)
Pages (from-to)1398-1406
Number of pages9
JournalJournal of Clinical Investigation
Volume81
Issue number5
StatePublished - May 1988
Externally publishedYes

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Folic Acid
Cultured Cells
Carrier Proteins
KB Cells
Folic Acid Transporters
Leucovorin
Radioimmunoassay
Proteins
Breast Neoplasms

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Kane, M. A., Elwood, P. C., Portillo, R. M., Antony, A., Najfeld, V., Finley, A., ... Kolhouse, J. F. (1988). Influence on immunoreactive folate-binding proteins of extracellular folate concentration in cultured human cells. Journal of Clinical Investigation, 81(5), 1398-1406.

Influence on immunoreactive folate-binding proteins of extracellular folate concentration in cultured human cells. / Kane, M. A.; Elwood, P. C.; Portillo, R. M.; Antony, Asok; Najfeld, V.; Finley, A.; Waxman, S.; Kolhouse, J. F.

In: Journal of Clinical Investigation, Vol. 81, No. 5, 05.1988, p. 1398-1406.

Research output: Contribution to journalArticle

Kane, MA, Elwood, PC, Portillo, RM, Antony, A, Najfeld, V, Finley, A, Waxman, S & Kolhouse, JF 1988, 'Influence on immunoreactive folate-binding proteins of extracellular folate concentration in cultured human cells.', Journal of Clinical Investigation, vol. 81, no. 5, pp. 1398-1406.
Kane, M. A. ; Elwood, P. C. ; Portillo, R. M. ; Antony, Asok ; Najfeld, V. ; Finley, A. ; Waxman, S. ; Kolhouse, J. F. / Influence on immunoreactive folate-binding proteins of extracellular folate concentration in cultured human cells. In: Journal of Clinical Investigation. 1988 ; Vol. 81, No. 5. pp. 1398-1406.
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